Journal articles on the topic 'Photon beam position detector'
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1
Shu, Deming, Tuncer M. Kuzay, Yue Fang, Juan Barraza, and Tim Cundiff. "Synthetic diamond-based position-sensitive photoconductive detector development for the Advanced Photon Source." Journal of Synchrotron Radiation 5, no. 3 (May 1, 1998): 636–38. http://dx.doi.org/10.1107/s0909049597019778.
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A novel X-ray beam-position detection device that we call a position-sensitive photoconductive detector (PSPCD) is designed to have synthetic diamond as its substrate material. We proved that it is feasible to use synthetic diamond to make a hard X-ray position-sensitive detector based on the photoconductivity principle and that it acts as a solid-state ion chamber. Experiments on different PSPCD samples using synthetic diamond with a high-heat-flux white undulator beam, as well as with monochromatic hard X-ray beams, have been performed at the Advanced Photon Source. Recent test results with the PSPCD in the quadrant configuration as an X-ray beam-position monitor and in a multipixel array as an X-ray beam profiler are presented in this paper.
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Dhoska, Klodian, Helmuth Hofer, Marco López, Toomas Kübarsepp, and Stefan Kück. "Alignment position method for SPAD detector calibration and homogeneity." International Journal of Scientific Reports 1, no. 7 (November 29, 2015): 271. http://dx.doi.org/10.18203/issn.2454-2156.intjscirep20151253.
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<p><strong>Background:</strong> Over the last decade have seen a drastically increase of interest in the Single photon avalanche diode (SPAD) detectors applications at many variety of quantum experiments where the detection efficiency at single-photon level is required. The calibration of such detectors involves predominantly the determination of the detection efficiency.</p><p><strong>Methods:</strong> The present study was carried out at Department of Photometry and Applied Radiometry, Physikalisch-Technische Bundesanstalt (PTB), National Metrology Institute of Germany. This work is focused in a reproducible and close-to-ideal alignment position method of the SPAD detectors to the incident beam for achieving low measurement uncertainty.</p><p><strong>Results:</strong> A dominantly Gaussian profile is obtained when the diameter of the detector is smaller than the beam diameter, whereas in case then the detector is larger than the beam, a dominantly rectangular scan is obtained. The optimal position (X/Y/Z) for setting the SPAD detector correspond to X<sub>center</sub> = 235.11 mm, Y<sub>center</sub><em> </em>= 6.28 mm and Z<sub>position</sub> = 14.6 mm. Homogeneity of the detection efficiency depends on the beam size and evaluated regions.</p><p><strong>Conclusions:</strong> The experimental set-up and experimental results needed for optimization of the SPAD detector position were described. This analysis gives important information in how to carry out the optimization of the detector position for the calibration of the SPAD and analysis of quantum detection homogeneity.</p>
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Samadi, Nazanin, Bassey Bassey, Mercedes Martinson, George Belev, Les Dallin, Mark de Jong, and Dean Chapman. "A phase-space beam position monitor for synchrotron radiation." Journal of Synchrotron Radiation 22, no. 4 (June 25, 2015): 946–55. http://dx.doi.org/10.1107/s1600577515007390.
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The stability of the photon beam position on synchrotron beamlines is critical for most if not all synchrotron radiation experiments. The position of the beam at the experiment or optical element location is set by the position and angle of the electron beam source as it traverses the magnetic field of the bend-magnet or insertion device. Thus an ideal photon beam monitor would be able to simultaneously measure the photon beam's position and angle, and thus infer the electron beam's position in phase space. X-ray diffraction is commonly used to prepare monochromatic beams on X-ray beamlines usually in the form of a double-crystal monochromator. Diffraction couples the photon wavelength or energy to the incident angle on the lattice planes within the crystal. The beam from such a monochromator will contain a spread of energies due to the vertical divergence of the photon beam from the source. This range of energies can easily cover the absorption edge of a filter element such as iodine at 33.17 keV. A vertical profile measurement of the photon beam footprint with and without the filter can be used to determine the vertical centroid position and angle of the photon beam. In the measurements described here an imaging detector is used to measure these vertical profiles with an iodine filter that horizontally covers part of the monochromatic beam. The goal was to investigate the use of a combined monochromator, filter and detector as a phase-space beam position monitor. The system was tested for sensitivity to position and angle under a number of synchrotron operating conditions, such as normal operations and special operating modes where the photon beam is intentionally altered in position and angle at the source point. The results are comparable with other methods of beam position measurement and indicate that such a system is feasible in situations where part of the synchrotron beam can be used for the phase-space measurement.
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Lelyukhin, A. S., and D. A. Muslimov. "APPLICATION OF POSITION-SENSITIVE DETECTORS FOR ANALYZING THE ENERGY SPECTRA OF PHOTON RADIATION." Kontrol'. Diagnostika, no. 270 (December 2020): 44–48. http://dx.doi.org/10.14489/td.2020.12.pp.044-048.
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Monitoring the spectral composition of photon radiation from generating sources and emitting objects is the most informative way to analyze the radiation fields created by them. However, it is impossible to study the radiation characteristics of radiation fields of ultra short duration and high intensity using direct measurement methods. This work considers a method for reconstructing the spectral distributions of photon radiation from the profile of the secondary radiation fields recorded by a position-sensitive detector. To implement a new method of measurement in the primary beam of radiation is an extended scattering body of homogeneous material. Outside the field of the primary beam, a position-sensitive detector is placed along the generatrix of the scattering body, which records the photons of the secondary radiation and the coordinates of their emission. The spectral composition of the primary radiation beam is restored from the shape of the spatial distribution obtained. To find a quasi-solution describing the energy spectrum of the primary radiation beam, it is proposed to use the maximum likelihood expectation maximization method. The possibility of switching to measurements in secondary radiation fields having a lower intensity is confirmed by the experimental results. To form secondary radiation fields, we used a composite phantom containing three scattering bodies in the form of rectangular parallelepipeds made of graphite, aluminum, and titanium. The secondary radiation fields were recorded by a radiographic sensor. Using an X-ray source operating in a pulsed mode, images were obtained and profiles of the secondary radiation fields were formed. It is experimentally shown that the secondary radiation fields have a gradient structure and can be used to analyze the energy spectra of the radiation beams generating them. The method for reconstructing spectral distributions proposed in this work allows one to measure the energy spectra of photons using position-sensitive detectors and can be used in solving problems of diagnostics of pulsed high-intensity radiation beams.
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Khalil, Mohamad, Erik Schou Dreier, Jan Kehres, Jan Jakubek, and Ulrik Lund Olsen. "Subpixel resolution in CdTe Timepix3 pixel detectors." Journal of Synchrotron Radiation 25, no. 6 (October 26, 2018): 1650–57. http://dx.doi.org/10.1107/s1600577518013838.
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Timepix3 (256 × 256 pixels with a pitch of 55 µm) is a hybrid-pixel-detector readout chip that implements a data-driven architecture and is capable of simultaneous time-of-arrival (ToA) and energy (ToT: time-over-threshold) measurements. The ToA information allows the unambiguous identification of pixel clusters belonging to the same X-ray interaction, which allows for full one-by-one detection of photons. The weighted mean of the pixel clusters can be used to measure the subpixel position of an X-ray interaction. An experiment was performed at the European Synchrotron Radiation Facility in Grenoble, France, using a 5 µm × 5 µm pencil beam to scan a CdTe-ADVAPIX-Timepix3 pixel (55 µm × 55 µm) at 8 × 8 matrix positions with a step size of 5 µm. The head-on scan was carried out at four monochromatic energies: 24, 35, 70 and 120 keV. The subpixel position of every single photon in the beam was constructed using the weighted average of the charge spread of single interactions. Then the subpixel position of the total beam was found by calculating the mean position of all photons. This was carried out for all points in the 8 × 8 matrix of beam positions within a single pixel. The optimum conditions for the subpixel measurements are presented with regards to the cluster sizes and beam subpixel position, and the improvement of this technique is evaluated (using the charge sharing of each individual photon to achieve subpixel resolution) versus alternative techniques which compare the intensity ratio between pixels. The best result is achieved at 120 keV, where a beam step of 4.4 µm ± 0.86 µm was measured.
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Smallwood, J. C., S. Bhasin, T. Blake, N. H. Brook, M. F. Cicala, T. Conneely, D. Cussans, et al. "Test-beam demonstration of a TORCH prototype module." Journal of Physics: Conference Series 2374, no. 1 (November 1, 2022): 012004. http://dx.doi.org/10.1088/1742-6596/2374/1/012004.
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The TORCH time-of-flight detector is designed to provide a 15 ps timing resolution for charged particles, resulting in π/K particle identification up to 10 GeV/c momentum over a 10 m flight path. Cherenkov photons, produced in a quartz plate of 10 mm thickness, are focused onto an array of micro-channel plate photomultipliers (MCP-PMTs) which measure the photon arrival times and spatial positions. A half-scale (660 × 1250 × 10 mm3) TORCH demonstrator module has been tested in an 8 GeV/c mixed proton-pion beam at CERN. Customised square MCP-PMTs of active area 53 × 53 mm2 and granularity 64 × 64 pixels have been employed, which have been developed in collaboration with an industrial partner. The single-photon timing performance and photon yields have been measured as a function of beam position in the radiator, giving measurements which are consistent with expectations. The expected performance of TORCH for high luminosity running of the LHCb Upgrade II has been simulated.
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Huang, J. Y., and I. S. Ko. "Spatio-temporal measurement of beam properties in the PLS diagnostic beamline." Journal of Synchrotron Radiation 5, no. 3 (May 1, 1998): 642–44. http://dx.doi.org/10.1107/s090904959702013x.
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A diagnostic beamline is being constructed in the PLS storage ring for measurement of electron- and photon-beam properties. It consists of two 1:1 imaging systems: a visible-light imaging system and a soft X-ray imaging system. In the visible-light imaging system, the transverse beam size and beam position are measured with various detectors: a CCD camera, two photodiode arrays and a photon-beam position monitor. Longitudinal bunch structure is also investigated with a fast photodiode detector and a picosecond streak camera. On the other hand, the soft X-ray imaging system is under construction to measure beam sizes with negligible diffraction-limited error. The X-ray image optics consist of a flat cooled mirror and two spherical focusing mirrors.
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Gu Liming, 顾黎明, 孙葆根 Sun Baogen, 申超波 Shen Chaobo, 卢平 Lu Ping, 王季刚 Wang Jigang, 王晓辉 Wang Xiaohui, 唐雷雷 Tang Leilei, and 肖云云 Xiao Yunyun. "Photon beam position measurement system based on four-quadrant detector." High Power Laser and Particle Beams 22, no. 12 (2010): 2964–68. http://dx.doi.org/10.3788/hplpb20102212.2964.
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Gallin-Martel, M. L., L. Abbassi, A. Bes, G. Bosson, J. Collot, T. Crozes, S. Curtoni, et al. "A large area diamond-based beam tagging hodoscope for ion therapy monitoring." EPJ Web of Conferences 170 (2018): 09005. http://dx.doi.org/10.1051/epjconf/201817009005.
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The MoniDiam project is part of the French national collaboration CLaRyS (Contrôle en Ligne de l’hAdronthérapie par RaYonnements Secondaires) for on-line monitoring of hadron therapy. It relies on the imaging of nuclear reaction products that is related to the ion range. The goal here is to provide large area beam detectors with a high detection efficiency for carbon or proton beams giving time and position measurement at 100 MHz count rates (beam tagging hodoscope). High radiation hardness and intrinsic electronic properties make diamonds reliable and very fast detectors with a good signal to noise ratio. Commercial Chemical Vapor Deposited (CVD) poly-crystalline, heteroepitaxial and monocrystalline diamonds were studied. Their applicability as a particle detector was investigated using α and β radioactive sources, 95 MeV/u carbon ion beams at GANIL and 8.5 keV X-ray photon bunches from ESRF. This facility offers the unique capability of providing a focused (~1 μm) beam in bunches of 100 ps duration, with an almost uniform energy deposition in the irradiated detector volume, therefore mimicking the interaction of single ions. A signal rise time resolution ranging from 20 to 90 ps rms and an energy resolution of 7 to 9% were measured using diamonds with aluminum disk shaped surface metallization. This enabled us to conclude that polycrystalline CVD diamond detectors are good candidates for our beam tagging hodoscope development. Recently, double-side stripped metallized diamonds were tested using the XBIC (X Rays Beam Induced Current) set-up of the ID21 beamline at ESRF which permits us to evaluate the capability of diamond to be used as position sensitive detector. The final detector will consist in a mosaic arrangement of double-side stripped diamond sensors read out by a dedicated fast-integrated electronics of several hundreds of channels.
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Albicocco, P., R. Assiro, F. Bossi, P. Branchini, B. Buonomo, V. Capirossi, E. Capitolo, et al. "Commissioning of the PADME experiment with a positron beam." Journal of Instrumentation 17, no. 08 (August 1, 2022): P08032. http://dx.doi.org/10.1088/1748-0221/17/08/p08032.
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Abstract The PADME experiment is designed to search for a hypothetical dark photon A' produced in positron-electron annihilation using a bunched positron beam at the Beam Test Facility of the INFN Laboratori Nazionali di Frascati. The expected sensitivity to the A' -photon mixing parameter ϵ is 10-3, for A' mass ≤ 23.5 MeV/c 2 after collecting ∼ 1013 positrons-on-target. This paper presents the PADME detector status after commissioning in July 2019. In addition, the software algorithms employed to reconstruct physics objects, such as photons and charged particles, and the calibration procedures adopted are illustrated in detail. The results show that the experimental apparatus reaches the design performance, and is able to identify and measure standard electromagnetic processes, such as positron bremsstrahlung and electron-positron annihilation into two photons.
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Gianotti, Paola. "The PADME Detector." EPJ Web of Conferences 170 (2018): 01007. http://dx.doi.org/10.1051/epjconf/201817001007.
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The PADME experiment, by using the positron beam of the Frascati laboratory, aims at searching for signals of a dark photon, A′ . It will evaluate the final state missing mass of the process e+ e- → A′ γ by knowing the beam energy and measuring the four-momentum of the ordinary recoil photon. The precise determination of this quantity, and the capability to reject background events, are the key points for the success of the experiment. In this paper a description of each component of the PADME detector is given.
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Peng, X., J. Zhu, L. He, W. Xiao, F. Luo, M. Xiao, and X. Wang. "Simulation study on optical transmission performance and time resolution of Shashlik tower." Journal of Instrumentation 18, no. 02 (February 1, 2023): P02018. http://dx.doi.org/10.1088/1748-0221/18/02/p02018.
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Abstract The Shashlik tower is a significant component to measure the energy, time, and position of photons and electrons in the Electromagnetic Calorimeter (ECal), a vital detector of the Multi-Purpose Detector (MPD) in the Nuclotron-based lon Collider fAcility (NICA), Dubna, Russia. Based on the GEANT4 simulation toolkit, a variation of physical behavior in the tower was simulated, including the changes of photons during transmission, and used the rising edge detection method to measure the time-resolving ability of the module for natural muons and electron beams. Results show that 3 GeV electrons enter the tower, photons emitted by the scintillator are transmitted, 10665 photoelectrons are collected on Silicon Multipliers (SiPMs), yield is 3555 pe/GeV, and the light output is 0.16%. The time resolution of the module for muons is better than 160 ps, but the value of each tower is different. In addition, by changing the electron beam energy in the simulation, we observed that a larger number of photoelectrons collected by SiPMs leads to a better time resolution. At an electron beam energy of 1 GeV, the time resolution of the tower could be better than 101 ps. The simulated measuring results, and the methods of the tower photon transmission performance and the time resolution, will provide references and new optimum methods for subsequent experiential tests.
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Sorokin, Andrey A., Yilmaz Bican, Susanne Bonfigt, Maciej Brachmanski, Markus Braune, Ulf Fini Jastrow, Alexander Gottwald, Hendrik Kaser, Mathias Richter, and Kai Tiedtke. "An X-ray gas monitor for free-electron lasers." Journal of Synchrotron Radiation 26, no. 4 (June 12, 2019): 1092–100. http://dx.doi.org/10.1107/s1600577519005174.
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A novel X-ray gas monitor (XGM) has been developed which allows the measurement of absolute photon pulse energy and photon beam position at all existing and upcoming free-electron lasers (FELs) over a broad spectral range covering vacuum ultraviolet (VUV), extreme ultraviolet (EUV) and soft and hard X-rays. The XGM covers a wide dynamic range from spontaneous undulator radiation to FEL radiation and provides a temporal resolution of better than 200 ns. The XGM consists of two X-ray gas-monitor detectors (XGMDs) and two huge-aperture open electron multipliers (HAMPs). The HAMP enhances the detection efficiency of the XGM for low-intensity radiation down to 105 photons per pulse and for FEL radiation in the hard X-ray spectral range, while the XGMD operates in higher-intensity regimes. The relative standard uncertainty for measurements of the absolute photon pulse energy is well below 10%, and down to 1% for measurements of relative pulse-to-pulse intensity on pulses with more than 1010 photons per pulse. The accuracy of beam-position monitoring in the vertical and horizontal directions is of the order of 10 µm.
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Galimberti, A., C. J. Bocchetta, C. Fava, A. Gambitta, G. Paolucci, R. Presacco, G. Paolicelli, and G. Stefani. "A new detector for photon beam position monitoring designed for synchrotron radiation beamlines." Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment 477, no. 1-3 (January 2002): 317–22. http://dx.doi.org/10.1016/s0168-9002(01)01845-9.
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Gallice, N. "Xenon doping of liquid argon in ProtoDUNE single phase." Journal of Instrumentation 17, no. 01 (January 1, 2022): C01034. http://dx.doi.org/10.1088/1748-0221/17/01/c01034.
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Abstract The Deep Underground Neutrino Experiment (DUNE) will be the next generation long-baseline neutrino experiment. The far detector is designed as a complex of four LAr-TPC (Liquid Argon Time Projection Chamber) modules with 17 kt of liquid argon each. The development and validation of the first far detector technology is pursued through ProtoDUNE Single Phase (ProtoDUNE-SP), a 770 t LAr-TPC at CERN Neutrino Platform. Crucial in DUNE is the photon detection system that will ensure the trigger of non-beam events — proton decay, supernova neutrino burst and BSM searches — and will improve the timing and calorimetry for neutrino beam events. Doping liquid argon with xenon is a known technique to shift the light emitted by argon (128 nm) to a longer wavelength (178 nm) to ease its detection. The largest xenon doping test ever performed in a LAr-TPC was carried out in ProtoDUNE-SP. From February to May 2020, a gradually increasing amount of xenon was injected to also compensate for the light loss due to air contamination. The response of such a large TPC has been studied using the ProtoDUNE-SP Photon Detection System (PDS) and a dedicated setup installed before the run. With the first it was possible to study the light collection efficiency with respect to the track position, while with the second it was possible to distinguish the xenon light (178 nm) from the LAr light (128 nm). The light shifting mechanism proved to be highly efficient even at small xenon concentrations (<20 ppm in mass) furthermore it allowed recovering the light quenched by pollutants. The light collection improved far from the detection plane, enhancing the photon detector response uniformity along the drift direction and confirming a longer Rayleigh scattering length for 178 nm photons, with respect to 128 nm ones. The charge collection by the TPC was monitored proving that xenon up to 20 ppm does not impact its performance.
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Yamaguchi, Mitsutaka, Yuto Nagao, Naoki Kawachi, Takahiro Satoh, Shu Fujimaki, Tomihiro Kamiya, Kota Torikai, et al. "Detection of a gas region in a human body across a therapeutic carbon beam by measuring low-energy photons." International Journal of PIXE 26, no. 01n02 (January 2016): 61–72. http://dx.doi.org/10.1142/s0129083516500078.
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We studied feasibility of detection of a gap which is located across a beam track by measuring low-energy (63–68 keV) photons generated by beam irradiation. An experiment was performed with the Heavy Ion Medical Accelerator in Chiba (HIMAC). A 12C beam having 290 MeV/u was injected on a target consisting of two acrylic blocks. These two blocks were placed with a 10 mm gap along the beam axis. A detection system consisting of a semiconductor detector, a lead collimator having a slit, and borated polyethylene blocks was placed on a movable stage to detect low-energy photons emitted perpendicularly to the beam axis. The position of the detection system was moved at 2 mm intervals along the beam axis. It was found that the yield of 63–68 keV photons was clearly correlated with the position of the detection system. The position at which the yield curve had the lowest value agreed with the gap position. We also confirmed that the experimental result was well reproduced by a Monte Carlo simulation that includes generation of secondary electron bremsstrahlung.
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Sharma, S., J. Baran, R. S. Brusa, R. Caravita, N. Chug, A. Coussat, C. Curceanu, et al. "J-PET detection modules based on plastic scintillators for performing studies with positron and positronium beams." Journal of Instrumentation 18, no. 02 (February 1, 2023): C02027. http://dx.doi.org/10.1088/1748-0221/18/02/c02027.
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Abstract The J-PET detector, which consists of inexpensive plastic scintillators, has demonstrated its potential in the study of fundamental physics. In recent years, a prototype with 192 plastic scintillators arranged in 3 layers has been optimized for the study of positronium decays. This allows performing precision tests of discrete symmetries (C, P, T) in the decays of positronium atoms. Moreover, thanks to the possibility of measuring the polarization direction of the photon based on Compton scattering, the predicted entanglement between the linear polarization of annihilation photons in positronium decays can also be studied. Recently, a new J-PET prototype was commissioned, based on a modular design of detection units. Each module consists of 13 plastic scintillators and can be used as a stand-alone, compact and portable detection unit. In this paper, the main features of the J-PET detector, the modular prototype and their applications for possible studies with positron and positronium beams are discussed. Preliminary results of the first test experiment performed on two detection units in the continuous positron beam recently developed at the Antimatter Laboratory (AML) of Trento are also reported.
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Liu, D. G., C. H. Chang, L. C. Chiang, M. H. Lee, C. F. Chang, C. Y. Lin, C. C. Liang, et al. "Optical design and performance of the biological small-angle X-ray scattering beamline at the Taiwan Photon Source." Journal of Synchrotron Radiation 28, no. 6 (October 18, 2021): 1954–65. http://dx.doi.org/10.1107/s1600577521009565.
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The optical design and performance of the recently opened 13A biological small-angle X-ray scattering (SAXS) beamline at the 3.0 GeV Taiwan Photon Source of the National Synchrotron Radiation Research Center are reported. The beamline is designed for studies of biological structures and kinetics in a wide range of length and time scales, from angstrom to micrometre and from microsecond to minutes. A 4 m IU24 undulator of the beamline provides high-flux X-rays in the energy range 4.0–23.0 keV. MoB4C double-multilayer and Si(111) double-crystal monochromators (DMM/DCM) are combined on the same rotating platform for a smooth rotation transition from a high-flux beam of ∼4 × 1014 photons s−1 to a high-energy-resolution beam of ΔE/E ≃ 1.5 × 10−4; both modes share a constant beam exit. With a set of Kirkpatrick–Baez (KB) mirrors, the X-ray beam is focused to the farthest SAXS detector position, 52 m from the source. A downstream four-bounce crystal collimator, comprising two sets of Si(311) double crystals arranged in a dispersive configuration, optionally collimate the DCM (vertically diffracted) beam in the horizontal direction for ultra-SAXS with a minimum scattering vector q down to 0.0004 Å−1, which allows resolving ordered d-spacing up to 1 µm. A microbeam, of 10–50 µm beam size, is tailored by a combined set of high-heat-load slits followed by micrometre-precision slits situated at the front-end 15.5 m position. The second set of KB mirrors then focus the beam to the 40 m sample position, with a demagnification ratio of ∼1.5. A detecting system comprising two in-vacuum X-ray pixel detectors is installed to perform synchronized small- and wide-angle X-ray scattering data collections. The observed beamline performance proves the feasibility of having compound features of high flux, microbeam and ultra-SAXS in one beamline.
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Samadi, Nazanin, Xianbo Shi, and Dean Chapman. "Optimization of a phase-space beam position and size monitor for low-emittance light sources." Journal of Synchrotron Radiation 26, no. 6 (September 11, 2019): 1863–71. http://dx.doi.org/10.1107/s1600577519010658.
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The recently developed vertical phase-space beam position and size monitor (ps-BPM) system has proven to be able to measure the electron-source position, angle, size and divergence simultaneously in the vertical plane at a single location of a beamline. The optimization of the ps-BPM system is performed by ray-tracing simulation to maximize the instrument sensitivity and resolution. The contribution of each element is studied, including the monochromator, the K-edge filter, the detector and the source-to-detector distance. An optimized system is proposed for diffraction-limited storage rings, such as the Advanced Photon Source Upgrade project. The simulation results show that the ps-BPM system can precisely monitor the source position and angle at high speed. Precise measurements of the source size and divergence will require adequate resolution with relatively longer integration time.
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Dragoi, Danut. "Computational (ω, φ) X-ray Diffractometry for Single Crystal Analysis." Advances in X-ray Analysis 38 (1994): 277–82. http://dx.doi.org/10.1154/s0376030800017894.
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Abstract (ω, φ) X-ray Diffraetometry is a method of XRD based on two independent variables, ω–the rotation of the sample around an axis contained in the plane of the sample and normal to the incident beam, and-the rotation of the sample in its own plane. Each crystallographic plane has an φ peak position, i.e. diffracted intensity is a maximum at a particular ω position for a given φ position. The incident X-ray beam is considered to be parallel, (a divergence of 0.1 degrees or less is accepted), very narrow (the width of the beam is not critical, a width of 0.1 mm or less is accepted), and monochromatic. The position of the detector is not a necessary variable in this system. Its open X-ray sensitive area collects the photons from the diffracting planes at different positions on that sensitive area. Using the method, the diffraction angles 2θ of different crystallographic planes can be determined without the need for knowing the position of the detector, which is a large area detector, free of slits between the sample and the area sensitive to the X-ray photons. Consequently the detector can be placed in a favorable position such as close to the sample. The method can be applied to any crystal symmetry. If the symmetry of the crystal is known then a theoretical ω(φ) curve can be generated and compared with the experimental data. The difference between these two curves can be easily computed and attributed to the crystallographic lattice distortions of the sample.
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Mahani, Hojjat, Ali Taheri, and Mojtaba Askari. "Detection performance of pixelated lutetium–yttrium oxyorthosilicate (LYSO) scintillators for high-resolution photon-counting CT imaging." Review of Scientific Instruments 94, no. 2 (February 1, 2023): 023308. http://dx.doi.org/10.1063/5.0125952.
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High-resolution photon-counting detector (PCD) computed tomography (CT) imaging is increasingly used for several applications. Recent technological advances in CT instrumentation have introduced various types of radiation detectors. Therefore, this work aims at evaluating the lutetium–yttrium oxyorthosilicate (LYSO) scintillator for use in PCD CT from a detector point of view. To do so, a mini-CT prototype was designed and constructed based on the pixelated LYSO blocks. The detector comprises four 10 × 10 linearly arranged LYSO blocks coupled with four position-sensitive photomultiplier tubes. The prototype utilizes a point gamma-ray source along with a cone-beam collimator. An in-home MATLAB-based data processing software package was also developed for storing the list-mode data, event positioning, and energy windowing. A set of experiments were conducted to assess the performance of the constructed energy-resolved LYSO:Ce detector for mini-CT imaging. The results show good crystal identification for all blocks with a maximum peak-to-valley ratio of 3.48. In addition, the findings confirm that the developed detector is position-sensitive. The 20% energy window provides an optimal performance by simultaneously providing good crystal identification and a scatter removal factor of 0.71. A 96% uniformity was also observed when the detector was irradiated with a uniform flood. The spatial resolution of the mini-CT prototype in the x- and y-directions was calculated to be 0.9 and 0.93 mm, respectively, corrected for a magnification factor of 2.5. It is concluded that the pixelated LYSO crystal is a promising alternative to the current detectors and would be the scintillator of choice for high-resolution PCD CT imaging tasks.
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Peng, X., K. Zhu, X. Ji, M. Xiao, F. Luo, Y. Huang, J. Zhu, et al. "Simulation study on photon generation and collection of tower applied to NICA-MPD electromagnetic calorimeter." Journal of Instrumentation 17, no. 01 (January 1, 2022): T01004. http://dx.doi.org/10.1088/1748-0221/17/01/t01004.
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Abstract Shashlik tower, which is composed of absorbers and scintillators alternately, surrounded by reflector and coupled with Silicon Photomultiplier (SiPM) by Wavelength-Shifting (WLS) fibers, is a significant component to measure the energy and position of photons and electrons in Electromagnetic Calorimeter (ECal), a key detector of the Multi Purpose Detector (MPD) at the Nuclotron-based Ion Collider facility (NICA) in Russia. In this paper, the effect of materials adopted for absorber, reflector and WLS fiber, the length and curvature of fibers and the electrons incident position on photons transmission performance of tower is simulated based on GEANT4 software. The impact of Gaussian deviation's electron beam energy and spread of 10% in the energy range on the energy resolution of tower is also studied. Results show that the low polishing degree absorber, the high polishing degree TiO_2 reflector and the type of Y-11 WLS fibers bent with a curvature radius of greater than 11 cm can significantly improve the light output. In addition, electrons injected along the centre of tower can make photons position distribution in SiPM more uniform. The generation time of photons in scintillators and time of arrival at the SiPM both obey the Landau distribution. Finally, the energy resolution of tower can be better than 3.8%/√(E) (GeV) for a Gaussian deviation's electron beam with an average energy of 3 GeV and spread of 10% in the energy range.
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Ying, Andrew, Braxton Osting, I. C. Noyan, Conal E. Murray, Martin Holt, and Jörg Maser. "Modeling of kinematic diffraction from a thin silicon film illuminated by a coherent, focused X-ray nanobeam." Journal of Applied Crystallography 43, no. 3 (April 15, 2010): 587–95. http://dx.doi.org/10.1107/s0021889810008459.
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A rigorous model of a diffraction experiment utilizing a coherent, monochromatic, X-ray beam, focused by a Fresnel zone plate onto a thin, perfect, single-crystal layer is presented. In this model, first the coherent wave emanating from an ideal zone plate equipped with a direct-beam stop and order-sorting aperture is computed. Then, diffraction of the focused wavefront by a thin silicon film positioned at the primary focal spot is calculated. This diffracted wavefront is propagated to the detector position, and the intensity distribution at the detector plane is extracted. The predictions of this model agree quite well with experimental data measured at the Center for Nanoscale Materials nanoprobe instrument at Sector 26 of the Advanced Photon Source.
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Dimitrova, Kalina. "Using Artificial Intelligence in the Reconstruction of Signals from the PADME Electromagnetic Calorimeter." Instruments 6, no. 4 (September 21, 2022): 46. http://dx.doi.org/10.3390/instruments6040046.
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The PADME apparatus was built at the Frascati National Laboratory of INFN to search for a dark photon (A′) produced via the process e+e−→A′γ. The central component of the PADME detector is an electromagnetic calorimeter composed of 616 BGO crystals dedicated to the measurement of the energy and position of the final state photons. The high beam particle multiplicity over a short bunch duration requires reliable identification and measurement of overlapping signals. A regression machine-learning-based algorithm has been developed to disentangle with high efficiency close-in-time events and precisely reconstruct the amplitude of the hits and the time with sub-nanosecond resolution. The performance of the algorithm and the sequence of improvements leading to the achieved results are presented and discussed.
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Rossington, C., J. Jaklevic, J. Reid, C. Haber, and H. Spieler. "Evaluation of the X-ray Response of a Position-Sensitive Microstrip Detector with an Integrated Readout Chip." Advances in X-ray Analysis 34 (1990): 337–47. http://dx.doi.org/10.1154/s0376030800014646.
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Many of the scientific programs proposed for implementation at existing and future synchrotron radiation sources involve measurement of the spatial distribution of transmitted or diffracted x-ray beams. The design of a general purpose position-sensitive detector for use in such experiments must address several conflicting requirements. Ideally, such a detector would meet the following criteria: high detection efficiency over a wide energy range, large dynamic range in measured photon intensities and response to a wide range of measurement intervals. Existing detector systems only partially meet these requirements, although much work has gone into improving the current technology.
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Juanhuix, Jordi, Fernando Gil-Ortiz, Guifré Cuní, Carles Colldelram, Josep Nicolás, Julio Lidón, Eva Boter, Claude Ruget, Salvador Ferrer, and Jordi Benach. "Developments in optics and performance at BL13-XALOC, the macromolecular crystallography beamline at the Alba Synchrotron." Journal of Synchrotron Radiation 21, no. 4 (May 20, 2014): 679–89. http://dx.doi.org/10.1107/s160057751400825x.
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BL13-XALOC is currently the only macromolecular crystallography beamline at the 3 GeV ALBA synchrotron near Barcelona, Spain. The optics design is based on an in-vacuum undulator, a Si(111) channel-cut crystal monochromator and a pair of KB mirrors. It allows three main operation modes: a focused configuration, where both mirrors can focus the beam at the sample position to 52 µm × 5.5 µm FWHM (H × V); a defocused configuration that can match the size of the beam to the dimensions of the crystals or to focus the beam at the detector; and an unfocused configuration, where one or both mirrors are removed from the photon beam path. To achieve a uniform defocused beam, the slope errors of the mirrors were reduced down to 55 nrad RMS by employing a novel method that has been developed at the ALBA high-accuracy metrology laboratory. Thorough commissioning with X-ray beam and user operation has demonstrated an excellent energy and spatial stability of the beamline. The end-station includes a high-accuracy single-axis diffractometer, a removable mini-kappa stage, an automated sample-mounting robot and a photon-counting detector that allows shutterless operation. The positioning tables of the diffractometer and the detector are based on a novel and highly stable design. This equipment, together with the operation flexibility of the beamline, allows a large variety of types of crystals to be tackled, from medium-sized crystals with large unit-cell parameters to microcrystals. Several examples of data collections measured during beamline commissioning are described. The beamline started user operation on 18 July 2012.
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Di Fraia, Michele, Antonio De Sio, Matias Antonelli, Renzo Nesti, Dario Panella, Ralf H. Menk, Giuseppe Cautero, et al. "Fast beam monitor diamond-based devices for VUV and X-ray synchrotron radiation applications." Journal of Synchrotron Radiation 26, no. 2 (February 13, 2019): 386–92. http://dx.doi.org/10.1107/s1600577519000791.
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The improved performance of third-generation light sources and the advent of next-generation synchrotron radiation facilities require the use of extremely precise monitoring of the main photon-beam parameters, such as position, absolute and relative intensity, and temporal structure. These parameters, and associated real-time feedbacks, are fundamental at the beamline control level and at the machine control level, to improve the stability of the photon beams and to provide bunch-to-bunch quantitative information. Fast response time, high radiation hardness and visible–blind response are main features of photon-beam monitors for VUV and X-ray synchrotron radiation beamlines; hence diamond-based detectors are outstanding candidates. Here, results are presented of an extensive measurement campaign aiming at optimizing the capabilities of diamond detectors to discern time structures below the 100 ps timescale. A custom-built device has been fabricated and tested at the Italian Synchrotron Radiation Laboratory Elettra in Trieste. The results obtained show that diamond is an excellent material for ultra-fast photon pulses with picosecond time resolution; finally the possibilities for application at free-electron laser sources are discussed.
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Yang, Junliang, Tang Li, Ye Zhu, Xiaowei Zhang, Atsushi Waseda, and Hiroyuki Fujimoto. "High-efficiency ultra-precision comparator for d-spacing mapping measurement of silicon." Journal of Synchrotron Radiation 27, no. 3 (March 13, 2020): 577–82. http://dx.doi.org/10.1107/s1600577520001496.
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This article describes a high-efficiency experimental configuration for a self-referenced lattice comparator with a `brush beam' of synchrotron radiation from a bending magnet and two linear position-sensitive photon-counting-type X-ray detectors. The efficiency is more than ten times greater compared with the `pencil-beam' configuration and a pair of zero-dimensional detectors. A solution for correcting the systematic deviation of d-spacing measurements caused by the horizontal non-uniformity of the brush beam is provided. Also, the use of photon-counting-type one-dimensional detectors not only improves the spatial resolution of the measurements remarkably but can also adjust the sample's attitude angles easily.
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Zhao, F., G. Lo Curto, L. Pasquini, J. I. González Hernández, J. R. De Medeiros, B. L. Canto Martins, I. C. Leão, et al. "Measuring and characterizing the line profile of HARPS with a laser frequency comb." Astronomy & Astrophysics 645 (December 22, 2020): A23. http://dx.doi.org/10.1051/0004-6361/201937370.
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Aims. We study the 2D spectral line profile of the High Accuracy Radial Velocity Planet Searcher (HARPS), measuring its variation with position across the detector and with changing line intensity. The characterization of the line profile and its variations are important for achieving the precision of the wavelength scales of 10−10 or 3.0 cm s−1 necessary to detect Earth-twins in the habitable zone around solar-like stars. Methods. We used a laser frequency comb (LFC) with unresolved and unblended lines to probe the instrument line profile. We injected the LFC light – attenuated by various neutral density filters – into both the object and the reference fibres of HARPS, and we studied the variations of the line profiles with the line intensities. We applied moment analysis to measure the line positions, widths, and skewness as well as to characterize the line profile distortions induced by the spectrograph and detectors. Based on this, we established a model to correct for point spread function distortions by tracking the beam profiles in both fibres. Results. We demonstrate that the line profile varies with the position on the detector and as a function of line intensities. This is consistent with a charge transfer inefficiency effect on the HARPS detector. The estimate of the line position depends critically on the line profile, and therefore a change in the line amplitude effectively changes the measured position of the lines, affecting the stability of the wavelength scale of the instrument. We deduce and apply the correcting functions to re-calibrate and mitigate this effect, reducing it to a level consistent with photon noise.
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Ellis, Malcolm. "A Scintillating Fibre Tracker for MICE." International Journal of Modern Physics A 20, no. 16 (June 30, 2005): 3815–19. http://dx.doi.org/10.1142/s0217751x05027709.
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The provision of intense stored muon beams would allow the properties of neutrinos to be measured precisely and provide a route to multi-TeV lepton-anti-lepton collisions. The short muon lifetime makes it impossible to employ traditional cooling techniques while maintaining the muon-beam intensity. Ionisation cooling, a process in which the muon beam is passed through a series of liquid hydrogen absorbers followed by accelerating RF-cavities, is the proposed cooling technique. The international Muon Ionisation Cooling Experiment (MICE) collaboration has been approved at the Rutherford Appleton Laboratory and proposes to perform an engineering demonstration of ionisation cooling. The MICE experiment will require the measurement of the momentum and position of muons entering and leaving a section of ionisation cooling channel with high precision and purity in the presence of a large background. The technology chosen to meet this challenge is scintillating fibres readout with Visible Light Photon Detectors. The design, construction and operation of a prototype detector is described, as well as a summary of ongoing research and development activities in preparation for supplying the trackers needed for the MICE experiment.
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Shekhtman, L., F. Ignatov, and V. Tayursky. "Simulation of physics background in Super c-tau factory detector." EPJ Web of Conferences 212 (2019): 01009. http://dx.doi.org/10.1051/epjconf/201921201009.
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Simulation of background particle fluxes generated by colliding beams is performed with FLUKA package for the Super C-Tau factory Detector (SCTD). Two processes are considered as main sources of luminosity generated background: two-photon production of electron-positron pairs and Bha-Bha scattering with bremsstrahlung photon emission (radiative Bha-Bha). The SCTD geometry is described corresponding to the last version of the Conceptual Design Report. The magnetic field based on the calculation in ANSYS is introduced in the model. Main results of the simulation for beam energy of 3 GeV, luminosity of 1035 cm−2s−1 and 1.5 T magnetic field are the following: charged particle fluence in the region of the Inner Tracker (radius 5cm -20 cm, Z between -30cm and 30 cm) is between 105 particles/(cm2s) and ∼103 particles/(cm2s); 1-MeV neutron equivalent fluence for Si in the regions corresponding to electronics of the Inner Tracker and the Drift Chamber is below 1011 n/(cm2y) and absorbed dose is below 100 Gy/y in the hottest regions of the detector.
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Wacha, András. "Optimized pinhole geometry for small-angle scattering." Journal of Applied Crystallography 48, no. 6 (November 19, 2015): 1843–48. http://dx.doi.org/10.1107/s1600576715018932.
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In order to make the most of the low photon flux in laboratory small-angle X-ray scattering instruments, the experimental geometry has to be chosen carefully, with special stress on the beam-shaping system. The optimum collimation scheme should enable accurate measurements over the desired range of the scattering variable, while yielding the highest flux and the lowest possible instrumental background. In order to identify the best setting, a phase-space optimization of the collimating scheme is carried out in the present work, including constraints on the beam size at the sample position and on the detector surface. The resulting formulae are implemented in a Python script with a graphical user interface, to aid the planning, construction and daily operation of pinhole small-angle scattering cameras.
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Kuvvetli, Irfan, Carl Budtz-Jørgensen, Natalia Auricchio, John Stephen, Ezio Caroli, Giacomo Benassi, Nicola Zambelli, and Andrea Zappettini. "A 3D CZT High Resolution Detector for X-and gamma-ray applications." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C683. http://dx.doi.org/10.1107/s2053273314093164.
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A high resolution three dimensional (3D) position sensitive CdZnTe-based detector was developed to detect high energy photons (10 keV-1MeV). The design of the 3D CZT detector, developed at DTU Space, is based on the CZT Drift Strip detector principle. The prototype detector contains 12 drift cells, each comprising one collecting anode strip with 3 drift strips, biased such that the electrons are focused and collected by the anode strips. The anode pitch is 1.6mm. The position determination perpendicular to the anodes, the X-direction, is performed using a novel interpolating technique. The position determination along the detector depth direction, Y-direction, is made using the depth sensing technique. The position determination along the anode strips, Z-direction is made with the help of 10 cathode strips orthogonal to the anode strips. REDLEN CZT crystals (20 mm x 20 mm x 5 mm) were used for the proto type detectors. IMEM-CNR fabricated the proto type detectors using a special surface treatment method and electrode attachment process. A novel method was applied to reduce the surface leakage current between the strips. The proto type detector was investigated at the European Synchrotron Radiation Facility, Grenoble which provided a fine 50 x 50 μm2 collimated X-ray beam covering an energy band up to 600 keV. At 400 keV we measured position resolutions of 0.2 mm FWHM in the X- and Y-direction and 0.6 mm FWHM in the Z-direction. The measured energy resolution of the detector was ~5.5 keV FWHM at 400 keV. The electronic noise contribution of the detector setup was 3.7 keV FWHM . The detector provides 3D position with very good spatial resolution as well as high resolution energy information and is therefore a well suited candidate e.g. as a Compton telescope detector, or for any application fields (medicine, security, science) where imaging and spectroscopy of high energy photons in the 10keV-1MeV range are required.
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Bacchi, C., A. Dawiec, and F. Orsini. "Pragmatic method for fast programming of hybrid photon counting detectors." Journal of Instrumentation 17, no. 01 (January 1, 2022): C01026. http://dx.doi.org/10.1088/1748-0221/17/01/c01026.
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Abstract It is now been over 15 years since Hybrid Photon Counting Detectors (HPCD) became one of the standard position-sensitive detectors for synchrotron light sources and X-ray detection applications. This is mainly due to their single-photon sensitivity over a high dynamic energy range and electronic noise suppression thanks to energy thresholding. To reach those performances, all HPCD pixels must feature the same electrical response against photons of the same energy. From the analysis of a monochromatic beam, in case of an ideal HPCD detector, it would be sufficient to apply a fixed voltage threshold among all pixels, positioned at half of the mean pulse amplitude to count every photon above the threshold. However, in practical cases, it must be considered that noise baselines from all pixels are not always strictly located at the same voltage level but can be spread over some voltage ranges. To address this kind of issue, most of all HPCDs apply a conventional threshold equalization method, that mainly relies on three steps; the setting of a global threshold at an arbitrary value, the identification of pixels noise baseline around that global threshold through an in-pixel threshold trimmer, and the computation of the required threshold offsets for setting all pixels at their own noise baseline at the same time. However, in case of a first-time use of an HPCD prototype, the threshold equalization might be biased by parameters that are wrongly set. Those biases can sometimes be characterized by the inability to localize some pixel noise baselines, which could be outside the voltage range of the threshold trimmer. The recovery of those biased pixels could be performed by changing the position of the global threshold, or by increasing the voltage range of the threshold trimmer. Unfortunately, both solutions could be time consuming due to the lack of information on the required steps for recovering all noise baselines. In order to overcome this issue in a reasonable time, this work introduces a pragmatic method that can be applied to HPCDs for an early and effective identification of appropriate pixels’ parameters, avoiding the need to test a high number of pixels configurations. The application of this method, at the early stage of the HPCD calibration, may drastically reduce the investigation time for finding the optimal operating parameters of HPCD prototypes.
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Pritchard, J. L., J. J. Velthuis, L. Beck, Y. Li, C. De Sio, L. Ballisat, J. Duan, Y. Shi, and R. P. Hugtenburg. "Complex field verification using a large area CMOS MAPS upstream in radiotherapy." Journal of Instrumentation 17, no. 08 (August 1, 2022): C08018. http://dx.doi.org/10.1088/1748-0221/17/08/c08018.
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Abstract A multileaf collimator (MLC) is an integral component in modern radiotherapy machines as it dynamically shapes the photon field used for patient treatment. Currently, the MLC leaves which collimate the treatment field are mechanically calibrated to ±1 mm every 3 months and during pre-treatment calibration are calibrated to the mechanically set leaf positions. Leaf drift can occur between calibration dates and hence exceed the ±1 mm tolerance. Pre-treatment verification, increases LINAC usage time so is seldom performed for each individual patient treatment, but instead for an acceptable sample of patients and/or treatment fractions. Independent real-time treatment verification is therefore desirable. We are developing a large area CMOS MAPS upstream of the patient to monitor MLC leaf positions for real-time treatment verification. CMOS MAPS are radiation hard for photon and electron irradiation, have high readout speeds and low attenuation which makes them an ideal upstream radiation detector for radiotherapy. Previously, we reported on leaf position reconstruction for single leaves using the Lassena, a 12 × 14 cm2, three side buttable MAPS suitable for clinical deployment. Sobel operator based methods were used for edge reconstruction. It was shown that the correspondence between reconstructed and set leaf position was excellent and resolutions ranged between 60.6 ± 8 and 109 ± 12 μm for a single central leaf with leaf extensions ranging from 1 to 35 mm using 0.3 sec of treatment beam time at 400 MU/min. Here, we report on leaf edge reconstruction using updated methods for complex leaf configurations, as occur in clinical use. Results show that leaf positions can be reconstructed with resolutions of 62 ± 6 μm for single leaves and 86 ± 16 μm for adjacent leaves at the isocenter using 0.15 sec at 400 MU/min of treatment beam. These resolutions are significantly better than current calibration standards.
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Juanhuix, Jordi, Josep Nicolás, Guifré Cuní, Carles Colldelram, Alberto Rubio, Jose Ávila, Nahikari González, et al. "New developments and operation of the MX beamline XALOC at ALBA synchrotron." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1744. http://dx.doi.org/10.1107/s2053273314082552.
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BL13-XALOC is a Macromolecular Crystallography beamline at the 3-GeV ALBA synchrotron near Barcelona, and is operating with users since 2012. Currently being the only MX beamline at the site, XALOC has been designed to deal not only with easily automatable x-ray diffraction experiments of medium-sized crystals, but also with more complex ones that include a variety of crystal sizes and unit-cell length dimensions, crystals with high mosaic spread, and/or poorly diffracting crystals. The aim for a reliable all-in-one beamline contrasts with the trend observed lately, i.e. MX beamlines target specific characteristics of the crystals (microcrystals, large unit cells), techniques (tunability, small or large wavelengths), or to the status of the MX projects (crystal screening). The flexibility of the beamline is achieved by providing a very stable photon beam in an enery range of 5-22 keV and by changing the beam size at the sample position without loosing flux through defocusing to accomodate the dimensions of the beam to those of the sample. The beam dimensions at the sample position range from 57×5.5 µm2 FWHM (H×V) when focused to ~300×300 µm2. The dimensions of the beam are changed without varying the beam path. The beamline optics that allows this flexibility is based on an in-vacuum undulator, a Si(111) channel-cut monochromator, and a pair of KB mirrors. The defocused beam is severely affected by the slope errors of the mirrors, which produce striations on the beam profile at the sample position, mainly in the vertical direction. To minimize these striations, we have developed a new method that corrects mirror profiles by using spring actuators. The process resulted in a 4-fold reduction of the mirror slope errors, and in striations of the beam that amount only for ~10% of the nominal defocused beam profile. We expect that this uniform, tailored beam will improve the estimation of the radiation dose onto the sample, and will help in establishing a better data collection strategy. The end station includes a high accuracy single-axis diffractometer, a removable mini-kappa stage, an automated sample mounting robot, and a Pilatus6M, photon-counting detector. A new TANGO-based beamline control system (Sardana) has also been developed. Statistics of usage of the beamline and some relevant examples will be given.
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Iramina, Hiraku, Mitsuhiro Nakamura, Yuki Miyabe, Nobutaka Mukumoto, Tomohiro Ono, Hideaki Hirashima, and Takashi Mizowaki. "Quantification and correction of the scattered X-rays from a megavoltage photon beam to a linac-mounted kilovoltage imaging subsystem." BJR|Open 2, no. 1 (November 2020): 20190048. http://dx.doi.org/10.1259/bjro.20190048.
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Objective: To quantify and correct megavoltage (MV) scattered X-rays (MV-scatter) on an image acquired using a linac-mounted kilovoltage (kV) imaging subsystem. Methods and materials: A linac-mounted flat-panel detector (FPD) was used to acquire an image containing MV-scatter by activating the FPD only during MV beam irradiation. 6-, 10-, and 15 MV with a flattening-filter (FF; 6X-FF, 10X-FF, 15X-FF), and 6- and 10 MV without an FF (6X-FFF, 10X-FFF) were used. The maps were acquired by changing one of the irradiation parameters while the others remained fixed. The mean pixel values of the MV-scatter were normalized to the 6X-FF reference condition (MV-scatter value). An MV-scatter database was constructed using these values. An MV-scatter correction experiment with one full arc image acquisition and two square field sizes (FSs) was conducted. Measurement- and estimation-based corrections were performed using the database. The image contrast was calculated at each angle. Results: The MV-scatter increased with a larger FS and dose rate. The MV-scatter value factor varied substantially depending on the FPD position or collimator rotation. The median relative error ranges of the contrast for the image without, and with the measurement- and estimation-based correction were −10.9 to −2.9, and −1.5 to 4.8 and −7.4 to 2.6, respectively, for an FS of 10.0 × 10.0 cm2. Conclusions: The MV-scatter was strongly dependent on the FS, dose rate, and FPD position. The MV-scatter correction improved the image contrast. Advances in knowledge: The MV-scatters on the TrueBeam linac kV imaging subsystem were quantified with various MV beam parameters, and strongly depended on the fieldsize, dose rate, and flat panel detector position. The MV-scatter correction using the constructed database improved the image quality.
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Kowalik, Anna Natalia, Tomasz Koper, Sebastian Adamczyk, and Julian Malicki. "Comparison of dose distributions for 6MV and 15MV energy for Total Body Irradiation (TBI)." Letters in Oncology Science 16, no. 1 (March 12, 2019): 1–5. http://dx.doi.org/10.21641/los.16.1.90.
Full textAbstract:
Introduction Contemporary radiotherapy uses a number of highly specialized irradiation techniques dedicated to well-defined clinical diagnoses. Among these methods are techniques to irradiate the skin (TSEI), bone marrow (TMI) or the whole body of the patient (TBI). TBI has over the last century been used in the treatment of a variety of conditions, both benign and malignant. However, its importance has increased with the development of knowledge about the impact of ionizing radiation on the human body and the development of clinical dosimetry techniques. At present, however, this method is primarily used in the treatment of hyperplasia.
Aim The general aim of the study is to compare dose distributions at selected points of the anthropomorphic phantom under full body radiation conditions for X: 6MV and 15MV radiation. Specific objectives are defined: comparison of percent depth and function of photon emission profiles: 6MV and 15MV measured with radiofrequency hydrophobic films; measurement of doses in selected cross sections of the anthropomorphic phantom.
Material and method
A number of measuring devices and materials used in daily work by staff of the Medical Physics Department of the Greater Poland Cancer Centre were used to carry out the study part, but Alderson's anthropomorphic phantom and the radiochromic films in the form of point detectors were essential. In addition to each step of the research part, a special measuring system was prepared to reproduce the conditions prevailing during the TBI session as closely as possible. The research was carried out in three stages: Calibration of radiochromic films; PDD and OCR measurement for: 6MV and 15MV photon beam under TBI conditions; Measurement of dose distribution in selected anthropomorphic phantom's cross sections using radiochromic films in the form of point detectors.
Results For the lateral field irradiated with 6MV photon beam, the maximum compliance (less than 2%) was obtained for the elbows at the entrance and in the center of the phantom; abdomen for the detector positioned in the center of the phantom, the lungs at the entrance and the arms in the middle, and the neck at the position of the film at the entrance. In the case of the lateral field X 15MV, the highest correspondence occurred for the points: the head and the PC in the position of the film in the center of the phantom and the entrance neck. In the case of AP/PA fields for 6MV energy, the highest compatibility was obtained for the mediastinum in all positions of the film. A small difference was also obtained for the points: head in the middle and at the output of the beam; as well as PC on the output. For AP/PA X 15MV fields, the highest dose compliance not exceeding 1% was obtained for the location of the neck - at the beam entrance, and the lung and mediastinum at the detector position at the center of the phantom.
Conclusions On the basis of measurements of dose distribution at selected points of the patient's body for radiation X: 6MV and 15MV in the TBI procedure, the following conclusions can be made: Gafchromic EBT (radiochromic type film) can be successfully used for dosimetric measurements, among others. Due to their properties, such as the ability to cut from the sheet of film spot detectors of any shape and size, flexibility, low sensitivity to daylight, resistance to humidity, etc.; Their main drawback is the high cost of buying films and the long time required to prepare the detectors and then read the measured doses. Because of the low popularity of point-based EBTs in point dosing, further research is needed to improve their response to ionizing radiation. There is a noticeable increase in the difference between the dose calculated and measured as the distance between the position of individual detectors increases from the center point. The difference between the dose measured and planned in any of the cases examined does not exceed 9%. The measurements show that the method used is fast, accurate, and can be successfully used as a validation tool not only for the TBI procedure but also for other methods of cancer radiotherapy.
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Favia, Paola, John Hunt, David Joyce, Paul Mooney, and Ming Pan. "New Ultra-High-Resolution TEM Cameras." Microscopy and Microanalysis 7, S2 (August 2001): 910–11. http://dx.doi.org/10.1017/s1431927600030622.
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TEM image acquisition is subject to limitations in resolution imposed by the physics of the position-sensitive detection process. in existing on-line digital cameras detection consists of scintillation, image transfer and photon detection by a CCD. Scintillator resolution is governed primarily by the incident beam energy. Material parameters affect the resolution only weakly. Some improvement can be made with a thin transmission scintillator. Still, backscatter of electrons from below can form a noisy background. Optical transfer resolution also has an important effect on overall camera system resolution. Leakage of light within scintillator, between fibers, at interfaces, and the inherent resolution loss due to binning into a finite pixel all contribute to optical resolution loss. This point spread function is narrower than the electron point spread function above 100kV but has an affect at all voltages. Long-range light leakage (psf tail) affects the background noise in diffraction work where there is often a 10e6 ratio between central peak and diffraction spot of interest. Thus, the number of resolved pixels in a TEM image detector is limited by the area of the detector, the effective thickness of the scintillator and the quality of the image transfer.Gatan has developed several improvements which will address both electron and lightoptical resolution loss.
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Houghton, C., C. Bloomer, and L. Alianelli. "Modelling the effects of optical vibrations on photon beam parameters using ray-tracing software." Journal of Synchrotron Radiation 28, no. 5 (August 12, 2021): 1357–63. http://dx.doi.org/10.1107/s1600577521007013.
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A method to simulate beam properties observed at the beamline sample-point in the presence of motion of optical components has been developed at Diamond Light Source. A series of stationary ray-tracing simulations are used to model the impact on the beam stability caused by dynamic motion of optical elements. Ray-tracing simulations using SHADOW3 in OASYS, completed over multiple iterations and stitched together, permit the modelling of a pseudo-dynamic beamline. As beamline detectors operating at higher frequencies become more common, beam stability is crucial. Synchrotron ring upgrades to low-emittance lattices require increased stability of beamlines in order to conserve beam brightness. By simulating the change in beam size and position, an estimate of the impact the motion of various components have on stability is possible. The results presented in this paper focus on modelling the physical vibration of optical elements. Multiple beam parameters can be analysed in succession without manual input. The simulation code is described and the initial results obtained are presented. This method can be applied during beamline design and operation for the identification of optical elements that may introduce large errors in the beam properties at the sample-point.
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Gu, Do-Heon, Cheolsoo Eo, Seung-A. Hwangbo, Sung-Chul Ha, Jin Hong Kim, Hyoyun Kim, Chae-Soon Lee, et al. "BL-11C Micro-MX: a high-flux microfocus macromolecular-crystallography beamline for micrometre-sized protein crystals at Pohang Light Source II." Journal of Synchrotron Radiation 28, no. 4 (June 1, 2021): 1210–15. http://dx.doi.org/10.1107/s1600577521004355.
Full textAbstract:
BL-11C, a new protein crystallography beamline, is an in-vacuum undulator-based microfocus beamline used for macromolecular crystallography at the Pohang Accelerator Laboratory and it was made available to users in June 2017. The beamline is energy tunable in the range 5.0–20 keV to support conventional single- and multi-wavelength anomalous-dispersion experiments against a wide range of heavy metals. At the standard working energy of 12.659 keV, the monochromated beam is focused to 4.1 µm (V) × 8.5 µm (H) full width at half-maximum at the sample position and the measured photon flux is 1.3 × 1012 photons s−1. The experimental station is equipped with a Pilatus3 6M detector, a micro-diffractometer (MD2S) incorporating a multi-axis goniometer, and a robotic sample exchanger (CATS) with a dewar capacity of 90 samples. This beamline is suitable for structural determination of weakly diffracting crystalline substances, such as biomaterials, including protein, nucleic acids and their complexes. In addition, serial crystallography experiments for determining crystal structures at room temperature are possible. Herein, the current beamline characteristics, technical information for users and some recent scientific highlights are described.
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Desjardins, Kewin, Michal Pomorski, and John Morse. "Ultra-thin optical grade scCVD diamond as X-ray beam position monitor." Journal of Synchrotron Radiation 21, no. 6 (October 4, 2014): 1217–23. http://dx.doi.org/10.1107/s1600577514016191.
Full textAbstract:
Results of measurements made at the SIRIUS beamline of the SOLEIL synchrotron for a new X-ray beam position monitor based on a super-thin single crystal of diamond grown by chemical vapor deposition (CVD) are presented. This detector is a quadrant electrode design processed on a 3 µm-thick membrane obtained by argon–oxygen plasma etching the central area of a CVD-grown diamond plate of 60 µm thickness. The membrane transmits more than 50% of the incident 1.3 keV energy X-ray beam. The diamond plate was of moderate purity (∼1 p.p.m. nitrogen), but the X-ray beam induced current (XBIC) measurements nevertheless showed a photo-charge collection efficiency approaching 100% for an electric field of 2 V µm−1, corresponding to an applied bias voltage of only 6 V. XBIC mapping of the membrane showed an inhomogeneity of more than 10% across the membrane, corresponding to the measured variation in the thickness of the diamond plate before the plasma etching process. The measured XBIC signal-to-dark-current ratio of the device was greater than 105, and the X-ray beam position resolution of the device was better than a micrometer for a 1 kHz sampling rate.
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Greiffenberg, Dominic, Marie Andrä, Rebecca Barten, Anna Bergamaschi, Martin Brückner, Paolo Busca, Sabina Chiriotti, et al. "Characterization of Chromium Compensated GaAs Sensors with the Charge-Integrating JUNGFRAU Readout Chip by Means of a Highly Collimated Pencil Beam." Sensors 21, no. 4 (February 23, 2021): 1550. http://dx.doi.org/10.3390/s21041550.
Full textAbstract:
Chromium compensated GaAs or GaAs:Cr sensors provided by the Tomsk State University (Russia) were characterized using the low noise, charge integrating readout chip JUNGFRAU with a pixel pitch of 75 × 75 µm2 regarding its application as an X-ray detector at synchrotrons sources or FELs. Sensor properties such as dark current, resistivity, noise performance, spectral resolution capability and charge transport properties were measured and compared with results from a previous batch of GaAs:Cr sensors which were produced from wafers obtained from a different supplier. The properties of the sample from the later batch of sensors from 2017 show a resistivity of 1.69 × 109 Ω/cm, which is 47% higher compared to the previous batch from 2016. Moreover, its noise performance is 14% lower with a value of (101.65 ± 0.04) e− ENC and the resolution of a monochromatic 60 keV photo peak is significantly improved by 38% to a FWHM of 4.3%. Likely, this is due to improvements in charge collection, lower noise, and more homogeneous effective pixel size. In a previous work, a hole lifetime of 1.4 ns for GaAs:Cr sensors was determined for the sensors of the 2016 sensor batch, explaining the so-called “crater effect” which describes the occurrence of negative signals in the pixels around a pixel with a photon hit due to the missing hole contribution to the overall signal causing an incomplete signal induction. In this publication, the “crater effect” is further elaborated by measuring GaAs:Cr sensors using the sensors from 2017. The hole lifetime of these sensors was 2.5 ns. A focused photon beam was used to illuminate well defined positions along the pixels in order to corroborate the findings from the previous work and to further characterize the consequences of the “crater effect” on the detector operation.
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Wagner, Andreas, Wolfgang Anwand, Maik Butterling, Thomas E. Cowan, Fine Fiedler, Mathias Kempe, and Reinhard Krause-Rehberg. "Annihilation Lifetime Spectroscopy Using Positrons from Bremsstrahlung Production." Defect and Diffusion Forum 331 (September 2012): 41–52. http://dx.doi.org/10.4028/www.scientific.net/ddf.331.41.
Full textAbstract:
A new type of a positron annihilation lifetime spectroscopy (PALS) system has been set up at the superconducting electron accelerator ELBE [ at Helmholtz-Zentrum Dresden-Rossendorf. In contrast to existing source-based PALS systems, the approach described here makes use of an intense photon beam from electron bremsstrahlung which converts through pair production into positrons inside the sample under study. The article focusses on the production of intense bremsstrahlung using a superconducting electron linear accelerator, the production of positrons inside the sample under study, the efficient detector setup which allows for annihilation lifetime and Doppler-broadening spectroscopy simultaneously. Selected examples of positron annihilation spectroscopy are presented.
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Stavek, Jiri. "Controlled Double-Jet Mixing of Light Speeds in the Trigonometric Realm." Applied Physics Research 10, no. 1 (January 30, 2018): 53. http://dx.doi.org/10.5539/apr.v10n1p53.
Full textAbstract:
We were inspired by three great concepts: 1. Pythagorean means, 2. Pierre de Fermat´s principle of the least time, 3. Michael Faraday´s concept of vibrating rays in longitudinal and transverse directions. We have formulated an extended Doppler formula for rectilinear motions in the absolute spacetime where both postulates of the special relativity are valid. The second postulate of the special relativity for rectilinear motions was derived as the harmonic mean speed based on the Pythagoras-Fermat-Faraday (PF2) model. The null result of the Michelson-Morley experiment is valid for the arms of that interferometer separated by the angle π/2. However, for the angles smaller than π/2 a predicted fringe shift should be observed. For the circular motions the Doppler formula combines the longitudinal and transverse speeds in such a way that the frequency of the rotating light beam is diluted by a factor [1-(v/c)2]0.5 and the wavelength of that light beam is extended by the same factor. The Doppler formula for light beams can be tested for the rotating source and the detector placed close to the rim of that rotating disk in a defined position. In order to obtain new experimental data we propose to construct the Michelson-Morley-Harress-Sagnac interferometer where rotating disks have being attached to both arms of the Michelson interferometer. In rotating disks we might prepare light beams with defined independent values of their longitudinal speeds and after the mixing of these two light beams on their return path to the detector we might observe predicted fringe shifts. In these circular paths the second postulate of the special relativity is not valid. The full composition of Doppler formula is given by the interplay of the macro Doppler effect (the relative motion of the source and observer) and the micro Doppler effect (the combination of the longitudinal and transverse vibration speeds of that oscillating particle – the elasticity of the photon wave).
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Saushin, Aleksandr S., Gennady M. Mikheev, Viatcheslav V. Vanyukov, and Yuri P. Svirko. "The Surface Photogalvanic and Photon Drag Effects in Ag/Pd Metal-Semiconductor Nanocomposite." Nanomaterials 11, no. 11 (October 25, 2021): 2827. http://dx.doi.org/10.3390/nano11112827.
Full textAbstract:
We performed the investigation of the polarization-sensitive photocurrent generated in silver-palladium metal-semiconductor nanocomposite films under irradiation with nanosecond laser pulses at the wavelength of 2600 nm. It is shown that in both the transverse and the longitudinal configuration, the surface photogalvanic (SPGE) and photon drag effects (PDE) contribute to the observed photocurrent. However, the temporal profile of the transverse photocurrent pulse is monopolar at any polarization and angle of incidence, while the temporal profile of the longitudinal photocurrent pulse depends on the polarization of the excitation beam. Specifically, the irradiation of the film with the s-polarized excitation beam produces a monopolar photoresponse, while at p-polarized excitation, the photoresponse is bipolar, having a short front and long tail. Obtained experimental results are in agreement with the developed phenomenological theory, which describes transverse and longitudinal photocurrents due to SPGE and PDE in terms of relevant second-order nonlinear susceptibilities and allows us to obtain their dependences on the angle of incidence and polarization of the excitation laser beam. The pronounced dependence of the photocurrent on the angle of incidence and polarization of the excitation beam opens avenues toward the development of polarization- and position-sensitive detectors for industrial and space applications.
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Qi, Baohua, and Yong Liu. "R&D of a Novel High Granularity Crystal Electromagnetic Calorimeter." Instruments 6, no. 3 (September 15, 2022): 40. http://dx.doi.org/10.3390/instruments6030040.
Full textAbstract:
Future electron-positron collider experiments aim at the precise measurement of the Higgs boson, electroweak physics and the top quark. Based on the particle-flow paradigm, a novel highly granular crystal electromagnetic calorimeter (ECAL) is proposed to address major challenges from jet reconstruction and to achieve the optimal EM energy resolution of around 2–3%/E(GeV) with the homogeneous structure. Extensive R&D efforts have been carried out to evaluate the requirements and potentials of the crystal calorimeter concept from sensitive detection units to a full sub-detector system. The requirements on crystal candidates, photon sensors as well as readout electronics are parameterized and quantified in Geant4 full simulation. Experiments including characterizations of crystals and silicon photomultipliers (SiPMs) are performed to validate and improve the simulation results. The physics performance of the crystal ECAL is been studied with the particle flow algorithm “ArborPFA” which is also being optimized. Furthermore, a small-scale detector module with a crystal matrix and SiPM arrays is under development for future beam tests to study the performance for EM showers.
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Liprandi, Silvia, Michael Mayerhofer, Saad Aldawood, Tim Binder, George Dedes, Agnese Miani, Dennis R. Schaart, Ingrid I. Valencia Lozano, Katia Parodi, and Peter G. Thirolf. "Sub-3mm spatial resolution from a large monolithic LaBr3 (Ce) scintillator." Current Directions in Biomedical Engineering 3, no. 2 (September 7, 2017): 655–59. http://dx.doi.org/10.1515/cdbme-2017-0138.
Full textAbstract:
AbstractA Compton camera prototype for ion beam range monitoring via prompt (< 1 ns) gamma detection in hadron therapy is being developed and characterized at the Medical Physics Department of LMU Munich. The system consists of a large (50x50x30 mm3) monolithic LaBr3(Ce) scintillation crystal as absorber component to detect the multi-MeV Compton scattered photons, together with a stack of 6 double-sided silicon strip detectors (DSSSD) acting as scatterer component. Key ingredient of the γ-source reconstruction is the determination of the γ-ray interaction position in the scintillator, which is read out by a 256-fold segmented multi-anode photomultiplier tube (PMT). From simulations an angular resolution of about 1.5o for the photon source reconstruction can be expected for the energy range around 3 – 5 MeV, provided that a spatial resolution of 3 mm can be reached in the absorbing scintillator [1]. Therefore, particular effort was dedicated to characterize this latter property as a function of the γ-ray energy. Intense, tightly collimated 137Cs and 60Co photon sources were used for 2D irradiation scans (step size 0.5 mm) as prerequisite for studying the performance of the “k-Nearest-Neighbors” algorithm developed at TU Delft [2] (together with its variant ”Categorical Average Pattern”, CAP) and extending its applicability into the energy range beyond the original 511 keV. In this paper we present our most recent interaction position analysis in the absorbing scintillator, leading to a considerably improved value for the spatial resolution: systematic studies were performed as a function of the k-NN parameters and the PMT segmentation. A trend of improving spatial resolution with increasing photon energy was confirmed, resulting in the realization of the presently optimum spatial resolution of 2.9(1) mm @1.3 MeV, thus reaching the design specifications of the Compton camera absorber. The specification goal was reached also for a reduced PMT segmentation of 8x8 anode segments (each with 6x6 mm2 active area), thus allowing to reduce the complexity of the signal processing while preserving the performance.
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Chiappini, Marco, Marco Francesconi, Satoru Kobayashi, Manuel Meucci, Rina Onda, and Patrick Schwendimann. "Towards a New μ→eγ Search with the MEG II Experiment: From Design to Commissioning." Universe 7, no. 12 (November 30, 2021): 466. http://dx.doi.org/10.3390/universe7120466.
Full textAbstract:
The MEG experiment represents the state of the art in the search for the Charged Lepton Flavour Violating μ+→e+γ decay. With its first phase of operations at the Paul Scherrer Institut (PSI), MEG set the most stringent upper limit on the BR (μ+→e+γ)≤4.2×10−13 at 90% confidence level, imposing one of the tightest constraints on models predicting LFV-enhancements through new physics beyond the Standard Model. An upgrade of the MEG experiment, MEG II, was designed and it is presently in the commissioning phase, aiming at a sensitivity level of 6×10−14. The MEG II experiment relies on a series of upgrades, which include an improvement of the photon detector resolutions, brand new detectors on the positron side with better acceptance, efficiency and performances and new and optimized trigger and DAQ electronics to exploit a muon beam intensity twice as high as that of MEG (7×107 μ+/s). This paper presents a complete overview of the MEG II experimental apparatus and the current status of the detector commissioning in view of the physics data taking in the upcoming three years.
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Mulichak, Anne, Kevin Battaile, Joe Digilio, J. Lewis Muir, Eric Zoellner, and Lisa Keefe. "Automated High-Throughput Data Collection at IMCA-CAT." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C1663. http://dx.doi.org/10.1107/s2053273314083363.
Full textAbstract:
The Industrial Macromolecular Crystallography Association Collaborative Access Team (IMCA-CAT) operates a data collection facility at the Advanced Photon Source for protein crystallography. IMCA-CAT meets the demands of IMCA member pharmaceutical companies for reliable, high-quality, high-throughput data collection, while ensuring a secure environment for proprietary research. The 17ID micro-focused high-flux insertion device beamline, equipped with a Pilatus 6M pixel array detector, allows for very fast data collection times. The focused beam size (30 μm x 70 μm) can be easily optimized for each sample using a GM/CA-CAT mini-beam quad collimator, with user-selectable beam sizes of 50, 20, 10 and 5 μm. An Alio goniometer has a small (1.2 μm) sphere of confusion, providing stable sample positioning, and X-ray beam position is maintained within 2 μm by custom software in real time. Automated sample mounting is performed with a Rigaku ACTOR robot, accepting both Rigaku and ALS/Unipuck style magazines, providing fast yet reliable sample exchanges and enabling remote access and unattended data collection. Rigaku JDirector software for robot control and data collection has been customized to incorporate additional tools, such as diffraction-based sample centering for both manual and unattended data collection modes, vector data collection and inverse beam anomalous data collection. While targeting the needs of industrial research, the automation and rapid data collection times at 17ID are also ideally suited for structural genomics and other research efforts requiring high-throughput experiments. Access is available to interested researchers through the APS General User Program and through subscription memberships for those needing regular and guaranteed proprietary beamtime.