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1
Bencheikh, Mohamed, Abdelmajid Maghnouj, Jaouad Tajmouati, Abdessamad Didi, and Abdesslam Lamrabet. "Detailed Monte Carlo analysis of the secondary photons coming out of the therapeutic X-ray beam of linear accelerator." Polish Journal of Medical Physics and Engineering 27, no. 2 (June 1, 2021): 151–56. http://dx.doi.org/10.2478/pjmpe-2021-0018.
Abstract:
Abstract External photon beam radiotherapy is often used in tumor treatment. The photons are generated from the target which had stricken by the primary electron beam (incident particles). The photon beam contains the primary photons coming directly from the target and secondary photons coming from the photon interactions with head component materials (scattered photons). Altogether is thereafter used in radiotherapy treatment. This Monte Carlo study aims to investigate and evaluate the secondary radiations (photons) in terms of fluence, energy fluence, spectral distribution, mean energy and angular spread distribution. The secondary photons, which contributed in radiotherapy treatment, are examined and evaluated in number (fluence) and energy. At the phantom surface, the secondary photons originated in the whole linac head are mainly coming from the primary collimator. In 0.45% of secondary photons coming from the whole linac head, the primary collimator contributes by 86% and they are more energetic. However, the flattening filter and the secondary collimator contribute together by less than 14% and their photons are less energetic and then can deteriorate the beam dosimetry quality. To improve the radiotherapy treatment quality, the number of photons of low energy should be as low as possible in the clinical beam. Our work can be a basic investigation to use in the improvement of linac head configuration and specially the beam modifiers.
2
Pickford Scienti, Oliver L. P. Pickford, and Dimitra G. Darambara. "Demonstrating a Novel, Hidden Source of Spectral Distortion in X-ray Photon Counting Detectors and Assessing Novel Trigger Schemes Proposed to Avoid It." Sensors 23, no. 9 (May 1, 2023): 4445. http://dx.doi.org/10.3390/s23094445.
Abstract:
X-ray photon counting spectral imaging (x-CSI) determines a detected photon’s energy by comparing the charge it induces with several thresholds, counting how many times each is crossed (the standard method, STD). This paper is the first to demonstrate that this approach can unexpectedly delete counts from the recorded energy spectrum under some clinically relevant conditions: a process we call negative counting. Four alternative counting schemes are proposed and simulated for a wide range of sensor geometries (pixel pitch 100–600 µm, sensor thickness 1–3 mm), number of thresholds (3, 5, 8, 24 and 130) and medically relevant X-ray fluxes (106–109 photons mm−2 s−1). Spectral efficiency and counting efficiency are calculated for each simulation. Performance gains are explained mechanistically and correlated well with the improved suppression of “negative counting”. The best performing scheme (Shift Register, SR) entirely eliminates negative counting, remaining close to an ideal scheme at fluxes of up to 108 photons mm−2 s−1. At the highest fluxes considered, the deviation from ideal behaviour is reduced by 2/3 in SR compared with STD. The results have significant implications both for generally improving spectral fidelity and as a possible path toward the 109 photons mm−2 s−1 goal in photon-counting CT.
3
Saá Hernández, Ángela, Diego González-Díaz, Pablo Villanueva, Carlos Azevedo, and Marcos Seoane. "A new imaging technology based on Compton X-ray scattering." Journal of Synchrotron Radiation 28, no. 5 (July 22, 2021): 1558–72. http://dx.doi.org/10.1107/s1600577521005919.
Abstract:
A feasible implementation of a novel X-ray detector for highly energetic X-ray photons with a large solid angle coverage, optimal for the detection of Compton X-ray scattered photons, is described. The device consists of a 20 cm-thick sensitive volume filled with xenon at atmospheric pressure. When the Compton-scattered photons interact with the xenon, the released photoelectrons create clouds of secondary ionization, which are imaged using the electroluminescence produced in a custom-made multi-hole acrylic structure. Photon-by-photon counting can be achieved by processing the resulting image, taken in a continuous readout mode. Based on Geant4 simulations, by considering a realistic detector design and response, it is shown that photon rates up to at least 1011 photons s−1 on-sample (5 µm water-equivalent cell) can be processed, limited by the spatial diffusion of the photoelectrons in the gas. Illustratively, if making use of the Rose criterion and assuming the dose partitioning theorem, it is shown how such a detector would allow obtaining 3D images of 5 µm-size unstained cells in their native environment in about 24 h, with a resolution of 36 nm.
4
Reusch, Tobias, Markus Osterhoff, Johannes Agricola, and Tim Salditt. "Pulse-resolved multi-photon X-ray detection at 31 MHz based on a quadrant avalanche photodiode." Journal of Synchrotron Radiation 21, no. 4 (June 3, 2014): 708–15. http://dx.doi.org/10.1107/s1600577514006730.
Abstract:
The technical realisation and the commissioning experiments of a high-speed X-ray detector based on a quadrant avalanche silicon photodiode and high-speed digitizers are described. The development is driven by the need for X-ray detectors dedicated to time-resolved diffraction and imaging experiments, ideally requiring pulse-resolved data processing at the synchrotron bunch repetition rate. By a novel multi-photon detection scheme, the exact number of X-ray photons within each X-ray pulse can be recorded. Commissioning experiments at beamlines P08 and P10 of the storage ring PETRA III, at DESY, Hamburg, Germany, have been used to validate the pulse-wise multi-photon counting scheme at bunch frequencies ≥31 MHz, enabling pulse-by-pulse readout during the PETRA III 240-bunch mode with single-photon detection capability. An X-ray flux of ≥3.7 × 109 photons s−1can be detected while still resolving individual photons at low count rates.
5
Zhao, Di, Pengxian You, Jing Yang, Junhong Yu, Hang Zhang, Min Liao, and Jianbo Hu. "A Highly Stable-Output Kilohertz Femtosecond Hard X-ray Pulse Source for Ultrafast X-ray Diffraction." Applied Sciences 12, no. 9 (May 7, 2022): 4723. http://dx.doi.org/10.3390/app12094723.
Abstract:
Femtosecond hard X-ray pulses generated by laser-driven plasma sources are eminently suitable to probe structural dynamics due to the angstrom spatial resolution and sub-picosecond time resolution. However, the insufficient flux of X-ray photons and high pulse-to-pulse instability compared with the large-scale ultrashort X-ray source, such as X-ray free-electron laser and synchrotrons, largely restricts its applications. In this work, we have optimized automation control and mechanical designs to significantly enhance the reliability and photon flux in our femtosecond laser plasma-induced X-ray source. Specifically, the optimized source provides a reliable pulse-to-pulse stability with a fluctuation of less than 1% (root-mean-square) and a total flux of Cu-Kα X-ray photons above 1011 photons/s. To confirm its functionality, ultrafast X-ray diffraction experiments are conducted on two different samples and the high consistency with previous results verifies the system’s superior performance.
6
Strnat, Sophia, Jonas Sommerfeldt, Vladimir Yerokhin, Wilko Middents, Thomas Stöhlker, and Andrey Surzhykov. "Circular Polarimetry of Hard X-rays with Rayleigh Scattering." Atoms 10, no. 4 (November 16, 2022): 140. http://dx.doi.org/10.3390/atoms10040140.
Abstract:
We present a theoretical investigation of the elastic Rayleigh scattering of X-rays by atomic targets. Special attention is paid to the question of how the polarization of the scattered photons is affected if the incident light is itself polarized. In particular, we found that the circular polarization of the incoming X-rays may lead to a remarkable modification of the linear polarization of the scattered photons. Based on this ’circular-to-linear-polarization-transfer’ and on the fact that the linear polarization of X-rays can be conveniently observed by solid-state Compton detectors, we argue that Rayleigh scattering may be used as a tool for circular polarimetry of hard X-rays. To illustrate our proposal, we performed detailed calculations of 145 and 500 keV circularly polarized photons scattered by lead atoms. Based on these calculations, we found that the photon scattering under large angles with respect to the incident beam direction is most favorable for the circular polarimetry of hard X-rays. In particular, for 500 keV photon energy and scattering angles around 70 deg we found a remarkable modification of the linear polarization of scattered light for the case when the incident radiation is circularly polarized.
7
Hu, Kun, Matthew G. Baring, Alice K. Harding, and Zorawar Wadiasingh. "High-energy Photon Opacity in the Twisted Magnetospheres of Magnetars." Astrophysical Journal 940, no. 1 (November 1, 2022): 91. http://dx.doi.org/10.3847/1538-4357/ac9611.
Abstract:
Abstract Magnetars are neutron stars characterized by strong surface magnetic fields generally exceeding the quantum critical value of 44.1 TG. High-energy photons propagating in their magnetospheres can be attenuated by QED processes like photon splitting and magnetic pair creation. In this paper, we compute the opacities due to photon splitting and pair creation by photons emitted anywhere in the magnetosphere of a magnetar. Axisymmetric, twisted dipole field configurations embedded in the Schwarzschild metric are treated. The paper computes the maximum energies for photon transparency that permit propagation to infinity in curved spacetime. Special emphasis is given to cases where photons are generated along magnetic field loops and/or in polar regions; these cases directly relate to resonant inverse Compton scattering models for the hard X-ray emission from magnetars and Comptonized soft gamma-ray emission from giant flares. We find that increases in magnetospheric twists raise or lower photon opacities, depending on both the emission locale and the competition between field-line straightening and field strength enhancement. Consequently, given the implicit spectral transparency of hard X-ray bursts and persistent “tail” emission of magnetars, photon splitting considerations constrain their emission region locales and the twist angle of the magnetosphere; these constraints can be probed by future soft gamma-ray telescopes such as COSI and AMEGO. The inclusion of twists generally increases the opaque volume of pair creation by photons above its threshold, except when photons are emitted in polar regions and approximately parallel to the field.
8
Shahmohammadi Beni, Mehrdad, Dragana Krstic, Dragoslav Nikezic, and Kwan Ngok Yu. "Realistic dosimetry for studies on biological responses to X-rays and γ-rays." Journal of Radiation Research 58, no. 5 (April 24, 2017): 729–36. http://dx.doi.org/10.1093/jrr/rrx019.
Abstract:
ABSTRACT A calibration coefficient R (= DA/DE) for photons was employed to characterize the photon dose in radiobiological experiments, where DA was the actual dose delivered to cells and DE was the dose recorded by an ionization chamber. R was determined using the Monte Carlo N-Particle version 5 (MCNP-5) code. Photons with (i) discrete energies, and (ii) continuous-energy distributions under different beam conditioning were considered. The four studied monoenergetic photons had energies E = 0.01, 0.1, 1 and 2 MeV. Photons with E = 0.01 MeV gave R values significantly different from unity, while those with E > 0.1 MeV gave R ≈ 1. Moreover, R decreased monotonically with increasing thickness of water medium above the cells for E = 0.01, 1 or 2 MeV due to energy loss of photons in the medium. For E = 0.1 MeV, the monotonic pattern no longer existed due to the dose delivered to the cells by electrons created through the photoelectric effect close to the medium–cell boundary. The continuous-energy distributions from the X-Rad 320 Biological Irradiator (voltage = 150 kV) were also studied under three different beam conditions: (a) F0: no filter used, (b) F1: using a 2 mm-thick Al filter, and (c) F2: using a filter made of (1.5 mm Al + 0.25 mm Cu + 0.75 mm Sn), giving mean output photon energies of 47.4, 57.3 and 102 keV, respectively. R varied from ~1.04 to ~1.28 for F0, from ~1.13 to ~1.21 for F1, and was very close to unity for F2.
9
Rinkel, Jean, Debora Magalhães, Franz Wagner, Florian Meneau, and Flavio Cesar Vicentin. "Detective quantum efficiency for photon-counting hybrid pixel detectors in the tender X-ray domain: application to Medipix3RX." Journal of Synchrotron Radiation 23, no. 1 (January 1, 2016): 206–13. http://dx.doi.org/10.1107/s1600577515020226.
Abstract:
Synchrotron-radiation-based X-ray imaging techniques using tender X-rays are facing a growing demand, in particular to probe theKabsorption edges of low-Zelements. Here, a mathematical model has been developed for estimating the detective quantum efficiency (DQE) at zero spatial frequency in the tender X-ray energy range for photon-counting detectors by taking into account the influence of electronic noise. The experiments were carried out with a Medipix3RX ASIC bump-bonded to a 300 µm silicon sensor at the Soft X-ray Spectroscopy beamline (D04A-SXS) of the Brazilian Synchrotron Light Laboratory (LNLS, Campinas, Brazil). The results show that Medipix3RX can be used to develop new imaging modalities in the tender X-ray range for energies down to 2 keV. The efficiency and optimal DQE depend on the energy and flux of the photons. The optimal DQE values were found in the 7.9–8.6 keV photon energy range. The DQE deterioration for higher energies due to the lower absorption efficiency of the sensor and for lower energies due to the electronic noise has been quantified. The DQE for 3 keV photons and 1 × 104 photons pixel−1s−1is similar to that obtained with 19 keV photons. Based on our model, the use of Medipix3RX could be extended down to 2 keV which is crucial for coming applications in imaging techniques at modern synchrotron sources.
10
Carvalho, A. M. G., D. H. C. Araújo, H. F. Canova, C. B. Rodella, D. H. Barrett, S. L. Cuffini, R. N. Costa, and R. S. Nunes. "X-ray powder diffraction at the XRD1 beamline at LNLS." Journal of Synchrotron Radiation 23, no. 6 (October 6, 2016): 1501–6. http://dx.doi.org/10.1107/s1600577516012686.
Abstract:
Various upgrades have been completed at the XRD1 beamline at the Brazilian synchrotron light source (LNLS). The upgrades are comprehensive, with changes to both hardware and software, now allowing users of the beamline to conduct X-ray powder diffraction experiments with faster data acquisition times and improved quality. The main beamline parameters and the results obtained for different standards are presented, showing the beamline ability of performing high-quality experiments in transmission geometry. XRD1 operates in the 5.5–14 keV range and has a photon flux of 7.8 × 109 photons s−1(with 100 mA) at 12 keV, which is one of the typical working energies. At 8 keV (the other typical working energy) the photon flux at the sample position is 3.4 × 1010 photons s−1and the energy resolution ΔE/E= 3 × 10−4.
11
Feranchuk, Ilya D., Oleg D. Skoromnik, and Quang San Nguyen. "Method of the equivalent photons for modulated electron beam." Journal of the Belarusian State University. Physics, no. 3 (October 7, 2020): 24–31. http://dx.doi.org/10.33581/2520-2243-2020-3-24-31.
Abstract:
It is shown in this work that electromagnetic self-field of the periodically density modulated electron bunch can be considered as the beam of the equivalent photons (pseudo-photons), collimated along the electron velocity. Pseudo-photon spectrum includes both the incoherent contribution being proportional to number of electrons in the bunch and the coherent part with the sharp maximum corresponding the modulation frequency. Method of the equivalent photons can be applied for description of the interaction between the electron bunch and a crystal that leads to generation of the coherent parametric X-ray radiation by the modulated bunches exited from the undulator of the X-ray free electron laser. It provides the possibility to obtain the X-ray pulses directed at the large angle to the electron velocity where intensity of the background radiation essentially decreased. It is defined the conditions when the spectral and angular distributions of the coherent pseudo-photons can be compared with the analogous values for the pulses of the X-ray laser.
12
John, R. W. "Brilliance of X rays and gamma rays produced by Compton backscattering of laser light from high-energy electrons." Laser and Particle Beams 16, no. 1 (March 1998): 115–27. http://dx.doi.org/10.1017/s0263034600011824.
Abstract:
In the Compton backscattering of laser light from a high-energy electron beam, the scattered photons are, as is well known, much harder than the incident photons. In connection with the inverse Compton effect, the spectral brightness, the brilliance of the backscattered radiation is theoretically investigated. For the brilliance B [photons/(sec × mm2 × sr × 0.1% bandwidth)] of the scattered radiation a defining relation is given. Then, the intensity I0 and the wavelength λ 0 of the incident laser light are assumed such that the intensity parameter η is sufficiently smaller than 1, so that with regard to the scattering process, multiphoton effects need not be considered, and the backscattered photon energy hν and the differential cross section dσ/dω approximately do not depend on η. In this case, the brilliance B linearly scales with I0. Furthermore, it is assumed that the primary electron and the incident laser photon are counterpropagating along a straight line, the head-on incidence of the laser photon. On these assumptions, for the brilliance B of the backscattered radiation, B depending on the back-scattered photon energy hν, an explicit formula is derived; from it, by approximations, a shorter formula for B is obtained.
13
Song, Sanghoon, Roberto Alonso-Mori, Matthieu Chollet, Yiping Feng, James M. Glownia, Henrik T. Lemke, Marcin Sikorski, et al. "Measurement of the absolute number of photons of the hard X-ray beamline at the Linac Coherent Light Source." Journal of Synchrotron Radiation 26, no. 2 (February 11, 2019): 320–27. http://dx.doi.org/10.1107/s1600577519000250.
Abstract:
X-ray free-electron lasers provide intense pulses of coherent X-rays with a short pulse duration. These sources are chaotic by nature and therefore, to be used at their full potential, require that every X-ray pulse is characterized in terms of various relevant properties such as intensity, photon energy, position and timing. Diagnostics are for example installed on an X-ray beamline to specifically monitor the intensity of individual X-ray pulses. To date, these can however only provide a single-shot value of the relative number of photons per shot. Here are reported measurements made in January 2015 of the absolute number of photons in the hard X-ray regime at LCLS which is typically 3.5 × 1011 photons shot−1 between 6 and 9.5 keV at the X-ray Pump–Probe instrument. Moreover, an average transmission of ≈62% of the hard X-ray beamline over this energy range is measured and the third-harmonic content of ≈0.47% below 9 keV is characterized.
14
Lewis, Cale E., and Mini Das. "Spectral Signatures of X-ray Scatter Using Energy-Resolving Photon-Counting Detectors." Sensors 19, no. 22 (November 18, 2019): 5022. http://dx.doi.org/10.3390/s19225022.
Abstract:
Energy-resolving photon-counting detectors (PCDs) separate photons from a polychromatic X-ray source into a number of separate energy bins. This spectral information from PCDs would allow advancements in X-ray imaging, such as improving image contrast, quantitative imaging, and material identification and characterization. However, aspects like detector spectral distortions and scattered photons from the object can impede these advantages if left unaccounted for. Scattered X-ray photons act as noise in an image and reduce image contrast, thereby significantly hindering PCD utility. In this paper, we explore and outline several important characteristics of spectral X-ray scatter with examples of soft-material imaging (such as cancer imaging in mammography or explosives detection in airport security). Our results showed critical spectral signatures of scattered photons that depend on a few adjustable experimental factors. Additionally, energy bins over a large portion of the spectrum exhibit lower scatter-to-primary ratio in comparison to what would be expected when using a conventional energy-integrating detector. These important findings allow flexible choice of scatter-correction methods and energy-bin utilization when using PCDs. Our findings also propel the development of efficient spectral X-ray scatter correction methods for a wide range of PCD-based applications.
15
Liguori, Antonio, Rebecca Barten, Filippo Baruffaldi, Anna Bergamaschi, Giacomo Borghi, Maurizio Boscardin, Martin Brückner, et al. "Characterization of iLGADs using soft X-rays." Journal of Instrumentation 18, no. 12 (December 1, 2023): P12006. http://dx.doi.org/10.1088/1748-0221/18/12/p12006.
Abstract:
Abstract Experiments at synchrotron radiation sources and X-ray Free-Electron Lasers in the soft X-ray energy range (250 eV–2 keV) stand to benefit from the adaptation of the hybrid silicon detector technology for low energy photons. Inverse Low Gain Avalanche Diode (iLGAD) sensors provide an internal gain, enhancing the signal-to-noise ratio and allowing single photon detection below 1 keV using hybrid detectors. In addition, an optimization of the entrance window of these sensors enhances their quantum efficiency (QE). In this work, the QE and the gain of a batch of different iLGAD diodes with optimized entrance windows were characterized using soft X-rays at the Surface/Interface:Microscopy beamline of the Swiss Light Source synchrotron. Above 250 eV, the QE is larger than 55% for all sensor variations, while the charge collection efficiency is close to 100%. The average gain depends on the gain layer design of the iLGADs and increases with photon energy. A fitting procedure is introduced to extract the multiplication factor as a function of the absorption depth of X-ray photons inside the sensors. In particular, the multiplication factors for electron- and hole-triggered avalanches are estimated, corresponding to photon absorption beyond or before the gain layer, respectively.
16
Kutukova, Kristina, Bartlomiej Lechowski, Joerg Grenzer, Peter Krueger, André Clausner, and Ehrenfried Zschech. "Laboratory High-Contrast X-ray Microscopy of Copper Nanostructures Enabled by a Liquid-Metal-Jet X-ray Source." Nanomaterials 14, no. 5 (February 29, 2024): 448. http://dx.doi.org/10.3390/nano14050448.
Abstract:
High-resolution imaging of Cu/low-k on-chip interconnect stacks in advanced microelectronic products is demonstrated using full-field transmission X-ray microscopy (TXM). The comparison of two lens-based laboratory X-ray microscopes that are operated at two different photon energies, 8.0 keV and 9.2 keV, shows a contrast enhancement for imaging of copper nanostructures embedded in insulating organosilicate glass of a factor of 5 if 9.2 keV photons are used. Photons with this energy (Ga-Kα radiation) are generated from a Ga-containing target of a laboratory X-ray source applying the liquid-metal-jet technology. The 5 times higher contrast compared to the use of Cu-Kα radiation (8.0 keV photon energy) from a rotating anode X-ray source is caused by the fact that the energy of the Ga-Kα emission line is slightly higher than that of the Cu-K absorption edge (9.0 keV photon energy). The use of Ga-Kα radiation is of particular advantage for imaging of copper interconnects with dimensions from several 100 nm down to several 10 nm in a Cu/SiO2 or Cu/low-k backend-of-line stack. Physical failure analysis and reliability engineering in the semiconductor industry will benefit from high-contrast X-ray images of sub-μm copper structures in microchips.
17
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.
Abstract:
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.
18
Tan, Fang, Xiao Hui Zhang, Bin Zhu, Gang Li, Yu Chi Wu, Ming Hai Yu, Yue Yang, et al. "Compact Thomson Scattering Source Based on a Mixed Injection Assisted Laser Wakefield Accelerator." Laser and Particle Beams 2022 (September 17, 2022): 1–7. http://dx.doi.org/10.1155/2022/4132792.
Abstract:
In order to establish a compact all-optical Thomson scattering source, experimental studies were conducted on the 45 TW Ti: sapphire laser facility. By including a steel wafer, mixed gas, and plasma mirror into a double-exit jet, several mechanisms, such as shock-assisted ionization injection, ionization injection, and driving laser reflection, were integrated into one source. So, the source of complexity was remarkably reduced. Electron bunches with central energy fluctuating from 90 to 160 MeV can be produced. Plasma mirrors were used to reflect the driving laser. The scattering of the reflected laser on the electron bunches led to the generation of X-ray photons. Through comparing the X-ray spots under different experimental conditions, it is confirmed that the X-ray photons are generated by Thomson scattering. For further application, the energy spectra and source size of the Thomson scattering source were measured. The unfolded spectrum contains a large amount of low-energy photons besides a peak near 67 keV. Through importing the electron energy spectrum into the Monte Carlo simulation code, the different contributions of the photons with small and large emitting angles can be used to explain the origin of the unfolded spectrum. The maximum photon energy extended to about 500 keV. The total photon production was 107/pulse. The FWHM source size was about 12 μm.
19
Jirsa, J., J. Gecnuk, Z. Janoska, J. Jakovenko, V. Kafka, M. Marcisovsky, M. Marcisovska, P. Stanek, L. Tomasek, and P. Vancura. "Monte-Carlo simulation of charge sharing in 2 mm thick pixelated CdTe sensor." Journal of Instrumentation 18, no. 02 (February 1, 2023): C02033. http://dx.doi.org/10.1088/1748-0221/18/02/c02033.
Abstract:
Abstract Precise physical models of sensors are essential for developing high precision pixelated detectors. Advanced technologies allowed pixel electronics to be integrated in tens of micrometers pixel pitch. Such fine pixelated detectors suffer from charge sharing effect and, in high-Z materials, also from fluorescent photons traversing one or more pixels. This work presents a Monte-Carlo model of a 2 mm thick 70 μm pitch pixelated CdTe sensor designed for simulation of the absorption of X-ray photons from monochromatic X-ray photon beams. Charge diffusion across a pixel matrix was computed using a drift-diffusion model for each photon generating free electron-hole pairs. Based on the simulation outcome, we estimated the dependence of cluster size on photon energy and total charge distribution between neighboring pixels.
20
Lipp, Vladimir, Ichiro Inoue, and Beata Ziaja. "Advantages of Using Hard X-ray Photons for Ultrafast Diffraction Measurements." Photonics 10, no. 8 (August 18, 2023): 948. http://dx.doi.org/10.3390/photonics10080948.
Abstract:
We present a comparative theoretical study of silicon crystals irradiated with X-ray free-electron laser pulses, using hard X-ray photons of various energies. Simulations are performed with our in-house hybrid code XTANT based on Monte Carlo, Tight Binding and Molecular Dynamics simulation techniques. By comparing the strength of the coherently scattered signal and the corresponding electronic radiation damage for three X-ray photon energies available at the SACLA free-electron laser facility, we conclude that it would be beneficial to use higher photon energies for “diffraction-before-destruction” experiments.
21
Lee, Eldred, Kaitlin M. Anagnost, Zhehui Wang, Michael R. James, Eric R. Fossum, and Jifeng Liu. "Monte Carlo Modeling and Design of Photon Energy Attenuation Layers for >10× Quantum Yield Enhancement in Si-Based Hard X-ray Detectors." Instruments 5, no. 2 (April 30, 2021): 17. http://dx.doi.org/10.3390/instruments5020017.
Abstract:
High-energy (>20 keV) X-ray photon detection at high quantum yield, high spatial resolution, and short response time has long been an important area of study in physics. Scintillation is a prevalent method but limited in various ways. Directly detecting high-energy X-ray photons has been a challenge to this day, mainly due to low photon-to-photoelectron conversion efficiencies. Commercially available state-of-the-art Si direct detection products such as the Si charge-coupled device (CCD) are inefficient for >10 keV photons. Here, we present Monte Carlo simulation results and analyses to introduce a highly effective yet simple high-energy X-ray detection concept with significantly enhanced photon-to-electron conversion efficiencies composed of two layers: a top high-Z photon energy attenuation layer (PAL) and a bottom Si detector. We use the principle of photon energy down conversion, where high-energy X-ray photon energies are attenuated down to ≤10 keV via inelastic scattering suitable for efficient photoelectric absorption by Si. Our Monte Carlo simulation results demonstrate that a 10–30× increase in quantum yield can be achieved using PbTe PAL on Si, potentially advancing high-resolution, high-efficiency X-ray detection using PAL-enhanced Si CMOS image sensors.
22
Wittry, D. B. "Focusing x rays for microprobe x-ray fluorescence analysis." Proceedings, annual meeting, Electron Microscopy Society of America 50, no. 2 (August 1992): 1730–31. http://dx.doi.org/10.1017/s042482010013328x.
Abstract:
X-ray microprobes that use focused monochromatic x rays for fluorescence excitation have four significant advantages over electron microprobes that use focused electrons for direct excitation, namely: 1) less background radiation is produced, 2) there is little or no charging of insulating specimens, 3) less damage is caused to the specimen, and 4) the specimen often does not need a high vacuum environment. These advantages result from the difference in interaction of photon and electron beams with matter. In the first place, because the x-ray photon is uncharged, bremsstrahlung which is always obtained with electron bombardment, is not produced by photon bombardment; this results in higher signal/background ratio and can yield lower detection limits by a factor of about 10−2 of those obtained with electron microprobes. Also because the photon is uncharged, the only charging of insulating specimens is due to secondary effects. Second, x-ray photons preferentially excite inner shell electrons as is well known from the large increase in absorption coefficient when the photon energy exceeds the critical excitation energy; this results in less damage for a given number of characteristic x-rays produced in the specimen.
23
Andreossi, V., Z. Balmforth, A. A. Bergamini Machado, G. Botogoske, N. Canci, F. Di Capua, G. Fiorillo, et al. "X-Arapuca long term test." Journal of Instrumentation 19, no. 02 (February 1, 2024): C02021. http://dx.doi.org/10.1088/1748-0221/19/02/c02021.
Abstract:
Abstract The photon detection system of the DUNE experiment is based on the X-ARAPUCA light trap. The basic elements of the X-ARAPUCA are the dichroic filters coated with wavelength shifter (para-Therphenyl), a waveshifting plate and an array of SiPMs which detects the trapped photons. A small scale prototype of the X-ARAPUCA has been installed in liquid argon in a dedicated facility at INFN-Napoli and exposed to alpha particles from a source. In order to test the stability of the overall device response the X-ARAPUCA was kept for 10 days in continuously purified liquid argon. The performed tests allowed for a preliminary estimation of the X-ARAPUCA absolute photon detection efficiency.
24
SAKAI, FUMIO, TERUNOBU NAKAJYO, TATSUYA YANAGIDA, and SHINJI ITO. "A COMPACT THOMSON X-RAY SOURCE AT SHI." International Journal of Modern Physics B 21, no. 03n04 (February 10, 2007): 465–72. http://dx.doi.org/10.1142/s0217979207042252.
Abstract:
A compact, high-brightness x-ray source has been developed through Thomson scattering between photons and relativistic electrons. 33keV energy photons (maximum) were generated in a 165-degree interaction configuration with 38MeV electrons and 800nm-wavelength Ti :sapphire laser light. The number of total photons generated at an interaction point was 106 photons/pulse for a 0.8nC electron bunch charge and 150mJ laser pulse energy. In a 90-degree interaction configuration, 105 photons/pulse total photons were obtained (maximum). Transverse profiles of x-ray intensity and energy were measured by an x-ray CCD camera. These experiment profiles agreed with the analytical results. Imaging using this x-ray source was demonstrated as an application. X-ray images for some objects were taken with various lengths between the objects and the camera. As a result, the refraction contrast images were observed with 17keV x-rays.
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Wilke, R. N., J. Wallentin, M. Osterhoff, D. Pennicard, A. Zozulya, M. Sprung, and T. Salditt. "High-flux ptychographic imaging using the new 55 µm-pixel detector `Lambda' based on the Medipix3 readout chip." Acta Crystallographica Section A Foundations and Advances 70, no. 6 (September 12, 2014): 552–62. http://dx.doi.org/10.1107/s2053273314014545.
Abstract:
Suitable detection systems that are capable of recording high photon count rates with single-photon detection are instrumental for coherent X-ray imaging. The new single-photon-counting pixel detector `Lambda' has been tested in a ptychographic imaging experiment on solar-cell nanowires using Kirkpatrick–Baez-focused 13.8 keV X-rays. Taking advantage of the high count rate of the Lambda and dynamic range expansion by the semi-transparent central stop, a high-dynamic-range diffraction signal covering more than seven orders of magnitude has been recorded, which corresponds to a photon flux density of about 105 photons nm−2 s−1or a flux of ∼1010 photons s−1on the sample. By comparison with data taken without the semi-transparent central stop, an increase in resolution by a factor of 3–4 is determined: from about 125 nm to about 38 nm for the nanowire and from about 83 nm to about 21 nm for the illuminating wavefield.
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Tajudin, S. M., Y. Namito, T. Sanami, and H. Hirayama. "PHOTON FIELD OF ~100–200 KEV FOR ENVIRONMENTAL DOSEMETER CALIBRATION." Radiation Protection Dosimetry 188, no. 4 (January 16, 2020): 486–92. http://dx.doi.org/10.1093/rpd/ncz308.
Abstract:
Abstract As a reference photon field, several radionuclides have been used frequently, such as 241Am,137Cs and60 Co for calibration. These nuclides provide mono-energy photons for dosemeters covering few tens of keV–MeV. The main energy around 200 keV is important for both environmental and medical fields since the former should consider scattering photons and the later should measure photons from X-ray generator. In our previous work, a backscattered layout can provide a uniform photon field spectra and dose rate with an energy of 190 keV by using an affordable intensity 137 Cs gamma source. Several other quasi-monoenergetic photon fields in the range of 100–200 keV could be obtained by using several available gamma sources. Two calibrated environmental CsI(Tl) survey meters, Horiba PA-1000 and Mr. Gamma A2700, had been measured with the developed backscattered photon field to understand energy-dependent features in order to confirm dosemeter readings. Consequently, both scintillator instruments are sensitive for measurements of the relatively low dose rates at 190 keV.
27
AMENTE, CHERNET, and P. SINGH. "EFFECTS OF PHOTO-EXCITATION AND MAGNON SCATTERING ON FERROMAGNETIC TRANSITION TEMPERATURE OF THE DILUTED MAGNETIC SEMICONDUCTOR (Ga1 - x, Mnx)As." Modern Physics Letters B 25, no. 04 (February 10, 2011): 273–80. http://dx.doi.org/10.1142/s0217984911025699.
Abstract:
Effects of photo-excitation and spin-wave scattering on magnetization of the diluted magnetic semiconductor (DMS) ( Ga , Mn ) As are theoretically studied. Green function formalism is used to find expression for magnetization and ferromagnetic transition temperature TC starting with a model Hamiltonian consisting of magnons, photons and an interaction of magnons with photons. According to our calculation, there is TC in the absence of magnetic impurity, x = 0, indicating that there could be electronically unpaired influential carriers/holes induced by photon irradiation resulting in residual itinerant band magnetization which can be revealed by experiments. Unusual upturn in magnetization near 0 K temperature values for larger magnon–photon coupling constant is also indicated. Moreover, enhancement of magnetization is established with increase in impurity concentration and even further in the presence of photon–magnon coupling which however decreases due to spin-wave scattering. This leads to the conclusion that at lower temperatures photon irradiation and at higher temperatures spin-wave scattering could affect the system properties predominantly.
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Gnedin, Yu N., and M. Yu Piotrovich. "New results in searching for axions by astronomical methods." International Journal of Modern Physics A 31, no. 02n03 (January 20, 2016): 1641019. http://dx.doi.org/10.1142/s0217751x16410190.
Abstract:
We discuss the astronomical methods of searching for light Goldstone bosons (axions and arions). The basic idea is to use processes of coupling between axions and photons: a) the axion decay into two photons; b) the transformation process of photons into axions (arions) in the magnetic fields of stars and also of interstellar and intergalactic media; c) the inverse process of transformations of axions (arions) which are generated into cores of stars into X-ray photons. The decaying axions affect upon the diffuse extragalactic background radiation, the brightness of the night sky and especially on the intergalactic light of clusters of galaxies due to generation of the axion radiative decay emission line. The processes (b) and (c) are strongly dependent on polarization state of photon and may produce a noticeable amount of linear polarization.
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Rasulov, V. R., R. Ya Rasulov, I. Eshboltaev, and M. X. Kuchkarov. "TO THE THEORY OF THE TWO AND THREE PHOTONIC LINEAR CIRCULAR DICHROISMS IN CUBIC SYMMETRY SEMICONDUCTORS." SEMOCONDUCTOR PHYSICS AND MICROELECTRONICS 3, no. 3 (June 30, 2021): 51–55. http://dx.doi.org/10.37681/2181-1652-019-x-2021-3-9.
Abstract:
The linear - circular dichroism of two and three photon absorption of light in semiconductors of cubic symmetry of hole conductivity is theoretically investigated. The matrix elements of two and three - photon optical transitions occurring between the subbands of the semiconductor valence band are calculated. In this case, transitions associated with both non - simultaneous absorption of individual photons and simultaneous absorption of two photons are taken into account, and the spectral and temperature dependences of the coefficient of two and three - photon absorption of polarized radiation are determined
30
Kylafis, Nikolaos D., and Pablo Reig. "Correlation of time lag and photon index in GX 339-4." Astronomy & Astrophysics 614 (June 2018): L5. http://dx.doi.org/10.1051/0004-6361/201833339.
Abstract:
Context. Black hole transients, as a class, exhibit during their outbursts a correlation between the time lag of hard photons with respect to softer ones and the photon index of the hard X-ray power law. The correlation is not very tight and therefore it is necessary to examine it source by source. Aims. The objective of the present work is to investigate in detail the correlation between the time lag and the photon index in GX 339-4, which is the best studied black hole transient. Methods. We have obtained RXTE energy spectra and light curves and have computed the photon index and the time lag of the 9–15 keV photons with respect to the 2–6 keV photons. The observations cover the first stages of the hard state, the pure hard state, and the hard-intermediate state. Results. We have found a tight correlation between time lag and photon index Γ in the hard and hard-intermediate states. At low Γ, the correlation is positive; it becomes negative at high Γ By assuming that the hard X-ray power-law index Γ is produced by inverse Compton scattering of soft disk photons in the jet, we have reproduced the entire correlation by varying two parameters in the jet: the radius of the jet at its base R0 and the Thomson optical depth along the jet τ∥. We have found that as the luminosity of the source increases, R0 initially increases and then decreases. This behavior is expected in the context of the Cosmic Battery. Conclusions. Our jet model nicely explains the correlation with reasonable values of the parameters R0 and τ∥ These parameters also correlate between themselves. As a further test of our model, we predict the break frequency in the radio spectrum as a function of the photon index during the rising part of an outburst.
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Reig, Pablo, and Nikolaos D. Kylafis. "Inclination effects on the X-ray emission of Galactic black-hole binaries." Astronomy & Astrophysics 625 (May 2019): A90. http://dx.doi.org/10.1051/0004-6361/201935070.
Abstract:
Context. Galactic black-hole X-ray binaries (BHBs) emit a compact, optically thick, mildly relativistic radio jet when they are in hard and hard-intermediate states. In these states, BHBs exhibit a correlation between the time lag of hard with respect to softer photons and the photon index of the power law component that characterizes the X-ray spectral continuum above ∼10 keV. The correlation, however, shows large scatter. In recent years, several works have brought to light the importance of taking into account the inclination of the systems to understand the X-ray and radio phenomenology of BHBs. Aims. Our objective is to investigate the role that the inclination plays on the correlation between the time lag and photon index. Methods. We obtained RXTE energy spectra and light curves of a sample of BHBs with different inclination angles. We computed the photon index and the time lag between hard and soft photons and performed a correlation and linear regression analysis of the two variables. We also computed energy spectra and light curves of BHBs using the Monte Carlo technique that reproduces the process of Comptonization in the jet. We account for the inclination effects by recording the photons that escape from the jet at different angles. From the simulated light curves and spectra we obtained model-dependent photon index and time lags, which we compared with those obtained from the real data. Results. We find that the correlation between the time lag and photon index is tight in low-inclination systems and becomes weaker in high-inclination systems. The amplitude of the lags is also larger at low- and intermediate-inclination angles than at high inclination. We also find that the photon index and time lag, obtained from the simulated spectra and light curves, also follow different relationships for different inclination angle ranges. Our jet model reproduces the observations remarkably well. The same set of models that reproduces the correlation for the low-inclination systems, also accounts for the correlation for intermediate- and high-inclination systems fairly well. Conclusions. The large dispersion observed in the time lag – photon index correlation in BHBs can naturally be explained as an inclination effect. Comptonization in the jet explains the steeper dependence of the lags on the photon index in low- and intermediate-inclination systems than in high-inclination systems.
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Yacout, A. M., R. P. Gardner, and K. Verghese. "Monte Carlo Simulation of the X-Ray Fluorescence Spectra from Multielement Homogeneous and Heterogeneous Samples." Advances in X-ray Analysis 30 (1986): 121–32. http://dx.doi.org/10.1154/s0376030800021224.
Abstract:
AbstractA Monte Carlo model that predicts the entire photon, spectrum for energy-dispersive X-ray fluorescence (EDXRF) analyzers excited by radio-isotope sources from multielement homogeneous samples is developed and demonstrated. The components of the photon spectrum include: (1) the and Kα and Kβ characteristic primary, secondary and tertiary X rays from both the unscattered and scattered source photons, (2) the characteristic X rays excited by other characteristic X rays that have been scattered, and (3) the scattered source photons from single, double, and multiple scatters in the sample.The computer code NCSMCXF based on this model has been developed. It is capable of handling up to 20 elements per sample and provides a detailed account of the intensities of the X rays and backscattered source photons per unit source decay as well as a summary of the relative intensities from all elements present in the sample. Cubic splines are used within the code for photoelectric and total scattering cross sections and two-variable cubic splines for angular coherent and incoherent scattering distributions for efficiency in both computation time and storage. The code also provides the pulse-height spectrum of the sample by using the appropriate Si(Li) detector response function. The Monte Carlo predictions for benchmark experimental results on two alloy samples of known composition indicate that the model is very accurate. This approach is capable of replacing most of the experimental work presently required in EDXRF quantitative analysis.A previous Monte Carlo model that uses the simple assumption of spherical homogeneous particles to approximate sample heterogeneities has been modified to improve the computer execution time requirements for the heterogeneous sample case. A new technique for photon tracking in this medium is used and reduces the computation time requirement by half.
33
Hinger, V., A. al Haddad, R. Barten, A. Bergamaschi, M. Brückner, M. Carulla, S. Chiriotti-Alvarez, et al. "Advancing the JUNGFRAU detector toward low-energy X-ray applications." Journal of Instrumentation 17, no. 09 (September 1, 2022): C09027. http://dx.doi.org/10.1088/1748-0221/17/09/c09027.
Abstract:
Abstract The charge-integrating hybrid silicon pixel detector JUNGFRAU has found widespread use at free-electron laser and synchrotron facilities. The detector was designed for use with hard X-rays; yet, because of its low noise, high dynamic range, position resolution, and scalable size, JUNGFRAU is of high interest for soft X-ray applications. We discuss improvements of the readout chip and alterations of the entrance window at the back of the sensor that facilitate low-energy X-ray detection. The first use case of the improved system at a low-energy beamline demonstrates single photon sensitivity down to 800 eV. At lower energies, the readout noise of the hybrid detector hinders the resolution of single photons. We propose to couple the JUNGFRAU readout chip with charge-multiplying low-gain avalanche diode (LGAD) sensors to resolve X-ray photons with a minimum energy of 250 eV.
34
Yamamoto, Seiichi, Tomohiro Yamashita, Yusuke Kobashi, Takuya Yabe, Takashi Akagi, Mitsutaka Yamaguchi, Naoki Kawachi, et al. "Simultaneous imaging of prompt gamma photons and prompt X-rays during irradiation of proton beams to human torso phantom at clinical dose level." Journal of Instrumentation 18, no. 07 (July 1, 2023): P07046. http://dx.doi.org/10.1088/1748-0221/18/07/p07046.
Abstract:
Abstract Although both prompt gamma photon and prompt X-ray imaging are promising methods for observing a beam shape and estimating the range of the beam from outside a subject, the images using these two methods have not been compared under realistic conditions such as in a human torso phantom. To clarify the imaging capability of prompt gamma photon and prompt X-ray imaging, simultaneous imaging with these methods was conducted during irradiation by proton beams to a human torso phantom at clinical dose level. After a human torso phantom was set on the bed of a proton therapy system, proton pencil beams of three different energies at clinical dose level and a patient planning beam for prostate cancer were used to irradiate the phantom. Prompt gamma photons and prompt X-rays emitted from the phantom were simultaneously imaged by a developed gamma camera and an X-ray camera during irradiation with proton beams to the human torso phantom. For all of the tested beams, we could obtain the beam shapes of prompt gamma photons and prompt X-rays images. The ranges could be estimated within a difference of 11 mm and 14 mm from the calculated dose for prompt gamma photon and prompt X-ray images, respectively. For both types of images, time sequential images and time count rate curves could be derived. We could clarify the imaging capabilities of prompt gamma photons and prompt X-rays were different by the simultaneous imaging during proton irradiation to a human torso phantom. Although both methods had advantages and disadvantages, we confirmed that both methods are promising for beam imaging in a torso phantom and also for future clinical use in proton therapy.
35
Stoupin, Stanislav, Sergey Antipov, and Alexander M. Zaitsev. "High-dynamic-range transmission-mode detection of synchrotron radiation using X-ray excited optical luminescence in diamond." Journal of Synchrotron Radiation 27, no. 3 (March 13, 2020): 708–12. http://dx.doi.org/10.1107/s1600577520001174.
Abstract:
Enhancement of X-ray excited optical luminescence in a 100 µm-thick diamond plate by introduction of defect states via electron beam irradiation and subsequent high-temperature annealing is demonstrated. The resulting X-ray transmission-mode scintillator features a linear response to incident photon flux in the range 7.6 × 108 to 1.26 × 1012 photons s−1 mm−2 for hard X-rays (15.9 keV) using exposure times from 0.01 to 5 s. These characteristics enable a real-time transmission-mode imaging of X-ray photon flux density without disruption of X-ray instrument operation.
36
Jemian, P. R., and G. G. Long. "Silicon photodiode detector for small-angle X-ray scattering." Journal of Applied Crystallography 23, no. 5 (October 1, 1990): 430–32. http://dx.doi.org/10.1107/s0021889890005167.
Abstract:
A photodiode X-ray detector was built to measure small-angle X-ray scattering (SAXS) at a synchrotron-radiation source in conjunction with a double-crystal diffractometer SAXS camera at photon energies between 5 and 11 keV. The photodiode detector response in this energy range is linear at photon counting rates up to 1012 photons s−1 and thus it was not necessary to attenuate the monochromatic X-ray beam with calibrated foils. SAXS data taken with a scintillation counter and the photodiode detector are compared, demonstrating marked improvement in counting statistics, rate of data acquisition and signal-to-noise ratio.
37
Plavin, A. V., R. A. Burenin, Y. Y. Kovalev, A. A. Lutovinov, A. A. Starobinsky, S. V. Troitsky, and E. I. Zakharov. "Hard X-ray emission from blazars associated with high-energy neutrinos." Journal of Cosmology and Astroparticle Physics 2024, no. 05 (May 1, 2024): 133. http://dx.doi.org/10.1088/1475-7516/2024/05/133.
Abstract:
Abstract Bright blazars were found to be prominent neutrino sources, and a number of IceCube events were associated with them. Evaluating high-energy photon emission of such blazars is crucial for better understanding of the processes and regions where neutrinos are produced. Here, we focus on hard X-ray emission observed by the SRG/ART-XC telescope, by the Swift/BAT imager, and by the INTEGRAL/IBIS telescope. Their energy range ≳10 keV is well-suited for probing photons that potentially participate in neutrino production by interacting with ultrarelativistic protons. We find that neutrino-associated blazars tend to demonstrate remarkably strong X-ray emission compared to other VLBI blazars in the sky. Both neutrinos and hard X-rays are found to come from blazars at cosmological distances z ∼ 1, and are boosted by relativistic beaming that makes it possible to detect them on Earth. Our results suggest that neutrinos are produced within compact blazar jets, with target X-ray photons emitted from accelerated jet regions.
38
TAKIZAWA, Y., T. IKEDA, T. OKU, C. OTANI, K. KAWAI, H. SATO, H. M. SHIMIZU, H. MIKAMI, H. MIYASAKA, and H. WATANABE. "DEVELOPMENT OF SUPERCONDUCTING TUNNEL JUNCTIONS FOR EUV DETECTORS." Surface Review and Letters 09, no. 01 (February 2002): 561–65. http://dx.doi.org/10.1142/s0218625x02002646.
Abstract:
Superconducting tunnel junctions (STJs) are applicable to as photon detectors with an energy resolution and a high photon-counting rate. The absorption of a photon in the superconductor of the STJ generates a number of quasiparticles that is proportional to the photon energy. Especially for soft X-ray and extreme ultraviolet (EUV) applications, STJs have good performance because of their high absorption efficiency below 1 keV. We are developing an energy-dispersive photon detector for EUV radiation using STJs with Al trapping layers. We evaluated the performance of the detector for EUV photons by using the Synchrotron Facility at KEK-PF in Tsukuba, Japan. We achieved an energy resolution of FWHM=18 eV (including the external noise of 17.6 eV) for 55 eV EUV photons with a 100 × 100 μ m 2 STJ. We present details of the junction design and discuss our experiments and the results.
39
Osgood, R. M., Y. Ait-El-Aoud, K. Bullion, S. Dinneen, R. Kingsborough, M. Rothschild, and S. Kooi. "Fabry-Perot interference pattern scattered by a sub-monolayer array of nanoparticles." Materials Research Express 9, no. 1 (January 1, 2022): 016202. http://dx.doi.org/10.1088/2053-1591/ac487c.
Abstract:
Abstract Understanding scattering of visible and infrared photons from nanomaterials and nanostructured materials is increasingly important for imaging, thermal management, and detection, and has implications for other parts of the electromagnetic spectrum (e.g., x-ray scattering and radar). New, interesting reports of photon scattering as a diagnostic probe, from inelastic x-ray scattering and interference to ‘nano-FTIR’ microscopy using infrared photons, have been published and are under active investigation in laboratories around the world. Here, we report, for the first time to our best knowledge, the experimental discovery of a Fabry–Perot interference pattern that is scattered by the sub-monolayer array of plasmonic Ag nanoparticles, and confirm it analytically and with rigorous numerical FDTD simulations.
40
Marras, Alessandro, Jonathan Correa, Sabine Lange, Vahagn Vardanyan, Tim Gerhardt, Manuela Kuhn, Frantisek Krivan, et al. "Characterization of the Percival detector with soft X-rays." Journal of Synchrotron Radiation 28, no. 1 (January 1, 2021): 131–45. http://dx.doi.org/10.1107/s1600577520013958.
Abstract:
In this paper the back-side-illuminated Percival 2-Megapixel (P2M) detector is presented, along with its characterization by means of optical and X-ray photons. For the first time, the response of the system to soft X-rays (250 eV to 1 keV) is presented. The main performance parameters of the first detector are measured, assessing the capabilities in terms of noise, dynamic range and single-photon discrimination capability. Present limitations and coming improvements are discussed.
41
MARIOTTO, C. BRENNER, and V. P. GONÇALVES. "NONLINEAR GLUON EVOLUTION AND PHOTON PRODUCTION IN HADRONIC COLLISIONS." International Journal of Modern Physics E 16, no. 09 (October 2007): 2984–88. http://dx.doi.org/10.1142/s0218301307008872.
Abstract:
In this contribution we consider the influence of nonlinear gluon evolution in the production of prompt photons at the LHC pp collider. We consider the EHKQS parton distributions, which are based on the GLR-MQ evolution equations, and imply in an enhanced small-x gluon distribution at Q2 ≤ 10 GeV 2 relative to the LO DGLAP gluon distribution. We find an enhancement of low-pT photons for both single and double photon production. Consequences of this effect for the Quark-Gluon Plasma searches and for the QCD background to Higgs are also discussed.
42
Tanaka, Shotaro, Shuto Suzuki, Tomohiro Mishima, and Kazuhiro Kanda. "Performance of BL07A at NewSUBARU with installation of a new multi-layered-mirror monochromator." Journal of Synchrotron Radiation 28, no. 2 (February 11, 2021): 618–23. http://dx.doi.org/10.1107/s1600577520016781.
Abstract:
Soft X-rays excite the inner shells of materials more efficiently than any other form of light. The investigation of synchrotron radiation (SR) processes using inner-shell excitation requires the beamline to supply a single-color and high-photon-flux light in the soft X-ray region. A new integrated computing multi-layered-mirror (MLM) monochromator was installed at beamline 07A (BL07A) of NewSUBARU, which has a 3 m undulator as a light source for irradiation experiments with high-photon-flux monochromatic light. The MLM monochromator has a high reflectivity index in the soft X-ray region; it eliminates unnecessary harmonic light from the undulator and lowers the temperature of the irradiated sample surfaces. The monochromator can be operated in a high vacuum, and three different mirror pairs are available for different experimental energy ranges; they can be exchanged without exposing the monochromator to the atmosphere. Measurements of the photon current of a photodiode on the sample stage indicated that the photon flux of the monochromatic beam was more than 1014 photons s−1 cm−2 in the energy range 80–400 eV and 1013 photons s−1 cm−2 in the energy range 400–800 eV. Thus, BL07A is capable of performing SR-stimulated process experiments.
43
Fernandez, Jorge E., and Francesco Teodori. "Major and Minor Contributions to X-ray Characteristic Lines in the Framework of the Boltzmann Transport Equation." Quantum Beam Science 6, no. 2 (May 19, 2022): 20. http://dx.doi.org/10.3390/qubs6020020.
Abstract:
The emission of characteristic lines after X-ray excitation is usually explained as the consequence of two independent and consecutive physical processes: the photoelectric ionization produced by incoming photons and the successive spontaneous atomic relaxation. However, the photoelectric effect is not the only ionization mechanism driven by incoming photons. It has been recently shown that Compton ionization is another possible process that contributes not negligibly to the ionization of the L and M shells. In addition, the secondary electrons from these two interactions, photoelectric and Compton, are also able to ionize the atom by means of so-called impact ionization. Such a contribution has been recently described, showing that it can be relevant in cases of monochromatic excitation for certain lines and elements. A third mechanism of line modification is the so-called self-enhancement produced by absorption of the tail of Lorentzian distribution of the characteristic line, which mainly modifies the shape of the lines but also produces an intensity increase. The four effects contribute to the formation of the characteristic line and must be considered to obtain a precise picture in terms of the shell and the element. This work furnishes a review of these contributions and their formal theoretical descriptions. It gives a complete picture of the photon kernel, describing the emission of characteristic X-rays comprising the main photoelectric contribution and the three effects of lower extent. All four contributions to the characteristic X-ray line must be followed along successive photon interactions to describe multiple scattering using the Boltzmann transport equation for photons.
44
Galea, C. A., C. P. S. Swanson, S. A. Cohen, and S. J. Thomas. "Use of a Mylar filter to eliminate vacuum ultraviolet pulse pileup in low-energy x-ray measurements." Review of Scientific Instruments 93, no. 9 (September 1, 2022): 093531. http://dx.doi.org/10.1063/5.0101712.
Abstract:
We describe a method to reduce vacuum ultraviolet (VUV) pulse pileup (PPU) in x-ray pulse-height Silicon Drift Detector (SDD) signals. An Amptek FAST SDD, with C1 (Si3N4) window, measures bremsstrahlung emitted from PFRC-2 plasma to extract the electron temperature (T e) and density (n e). The C1 window has low transmissivity for photons with energy below 200 eV though will transmit some VUV and soft x-ray photons, which PFRC-2 plasmas abundantly emit. Multi-VUV-photon PPU contaminates the interpretation of x rays with energy [Formula: see text] 100 eV, particularly in a low-energy exponential tail. The predicted low transmissivity of ∼1 μm thick Mylar [polyethylene terephthalate (PET)] to photons of energy [Formula: see text] eV led to the selection of Mylar as the candidate filter to reduce VUV PPU. Experiments were conducted on an x-ray tube with a graphite target and on a quasi-Maxwellian tenuous plasma (n e ∼ 109 cm−3) with effective temperatures reaching 1500 eV. A Mylar filter thickness of 850 nm is consistent with the results. The Mylar-filter-equipped SDD was then used on the PFRC-2 plasma, showing a substantial reduction in the low-energy x-ray signal, supporting our hypothesis of the importance of VUV PPU. We describe the modeling and experiments performed to characterize the effect of the Mylar filter on SDD measurements.
45
Dubrovich, Viktor, and Timur Zalialiutdinov. "Some Features of the Direct and Inverse Double-Compton Effect as Applied to Astrophysics." Physics 3, no. 4 (November 29, 2021): 1167–74. http://dx.doi.org/10.3390/physics3040074.
Abstract:
In the present paper, the process of inverse double-Compton (IDC) scattering is considered in the context of astrophysical applications. It is assumed that the two hard X-ray photons emitted from an astrophysical source are scattered on a free electron and converted into a single soft photon of optical range. Using the QED S-matrix formalism for the derivation of a cross-section of direct double-Compton (DDC) scattering and assuming detailed balance conditions, an analytical expression for the cross-section of the IDC process is presented. It is shown that at fixed energies of incident photons, the inverse cross-section has no infrared divergences, and its behavior is completely defined by the spectral characteristics of the photon source itself, in particular by the finite interaction time of radiation with an electron. Thus, even for the direct process, the problem of resolving infrared divergence actually refers to a real physical source of radiation in which photons are never actually plane waves. As a result, the physical frequency profile of the scattered radiation for DDC as well as for IDC processes is a function of both the intensity and line shape of the incident photon field.
46
Dyubkov, V. S., S. M. Polozov, and V. I. Rashchikov. "MEPhI’s option of lab scale Compton source." Seriya 3: Fizika, Astronomiya, no. 1_2023 (June 2, 2023): 2310403–1. http://dx.doi.org/10.55959/msu0579-9392.78.2310403.
Abstract:
A development and construction of comparatively cheap and compact (several meters scale) X-ray sources is possible with the help of inverse Compton backscattering of laser photons on an electron bunch. Such sources can be used in the field of materials science (new materials, diagnostics of nanostructures at the atomic level), research of nano- and biosystems, medicine and pharmacology (new drugs R&D), physics and chemistry of fast-flowing processes (burning, explosion). It is suggested that compact storage synchrotron will operate with normal conducting S-band top-up linac. Linac will provides bunches with tunable energy in the range of 20– 60 MeV to generate the photon flux with tunable energy [1, 2]. The use of a storage ring provides the following advantages: comparatively high average intensity of the generated photon flux, high brightness, photon beam energy tuning in a wide range, high degree of monochromaticity and coherence of the generated photons. There are current results of the design of a compact storage ring for generating the photons in the energy range of 5-45 keV and investigations of the development of relativistic picosecond electron beam dynamics instabilities in the report.
47
Yamamoto, Seiichi, Hiroshi Watabe, Kohei Nakanishi, Takuya Yabe, Mitsutaka Yamaguchi, Naoki Kawachi, Kei Kamada, et al. "A triple-imaging-modality system for simultaneous measurements of prompt gamma photons, prompt x-rays, and induced positrons during proton beam irradiation." Physics in Medicine & Biology 69, no. 5 (February 22, 2024): 055012. http://dx.doi.org/10.1088/1361-6560/ad25c6.
Abstract:
Abstract Objective. Prompt gamma photon, prompt x-ray, and induced positron imaging are possible methods for observing a proton beam’s shape from outside the subject. However, since these three types of images have not been measured simultaneously nor compared using the same subject, their advantages and disadvantages remain unknown for imaging beam shapes in therapy. To clarify these points, we developed a triple-imaging-modality system to simultaneously measure prompt gamma photons, prompt x-rays, and induced positrons during proton beam irradiation to a phantom. Approach. The developed triple-imaging-modality system consists of a gamma camera, an x-ray camera, and a dual-head positron emission tomography (PET) system. During 80 MeV proton beam irradiation to a polymethyl methacrylate (PMMA) phantom, imaging of prompt gamma photons was conducted by the developed gamma camera from one side of the phantom. Imaging of prompt x-rays was conducted by the developed x-ray camera from the other side. Induced positrons were measured by the developed dual-head PET system set on the upper and lower sides of the phantom. Main results. With the proposed triple-imaging-modality system, we could simultaneously image the prompt gamma photons and prompt x-rays during proton beam irradiation. Induced positron distributions could be measured after the irradiation by the PET system and the gamma camera. Among these imaging modalities, image quality was the best for the induced positrons measured by PET. The estimated ranges were actually similar to those imaged with prompt gamma photons, prompt x-rays and induced positrons measured by PET. Significance. The developed triple-imaging-modality system made possible to simultaneously measure the three different beam images. The system will contribute to increasing the data available for imaging in therapy and will contribute to better estimating the shapes or ranges of proton beam.
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Büscher, Julia, Alessandro Mirone, Michał Stękiel, Dominik Spahr, Wolfgang Morgenroth, Eiken Haussühl, Victor Milman, et al. "Elastic stiffness coefficients of thiourea from thermal diffuse scattering." Journal of Applied Crystallography 54, no. 1 (February 1, 2021): 287–94. http://dx.doi.org/10.1107/s1600576720016039.
Abstract:
The complete elastic stiffness tensor of thiourea has been determined from thermal diffuse scattering (TDS) using high-energy photons (100 keV). Comparison with earlier data confirms a very good agreement of the tensor coefficients. In contrast with established methods to obtain elastic stiffness coefficients (e.g. Brillouin spectroscopy, inelastic X-ray or neutron scattering, ultrasound spectroscopy), their determination from TDS is faster, does not require large samples or intricate sample preparation, and is applicable to opaque crystals. Using high-energy photons extends the applicability of the TDS-based approach to organic compounds which would suffer from radiation damage at lower photon energies.
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Dong, Aijun, Chang Liu, Qijun Zhi, Ziyi You, Qibin Sun, and Bowen Du. "Spectral and Timing Properties of H 1743-322 in the “Faint” 2005 Normal Outburst." Universe 8, no. 5 (May 6, 2022): 273. http://dx.doi.org/10.3390/universe8050273.
Abstract:
H 1743-322 is a well-known black hole X-ray binary (BH XRBs) that has been observed in several outbursts over the past. In this work, we have performed the spectral and timing analysis of H 1743-322 during the “faint” 2005 outburst for the first time with the RXTE/PCA data. In this outburst, the spectral and timing parameters (e.g., Tin, Γ, Rin, rms and QPOs, etc.) presented an obvious change and a q-like pattern was found in the Hardness Intensity Diagram (HID), which often named as the hysteresis effect of BH XRBs. The radius of the innermost stable circular orbit was constrained as RISCO∼3.50 Rg, which predicts that H 1743-322 is a lower-spin black hole. We further explored the correlation between timing and spectral properties. The relation of photon index Γ and X-ray flux, F3–25keV, presented a transition between negative and positive correlation when the X-ray luminosity, L3–25keV, is above and below a critical X-ray luminosity, LX,crit≃2.55×10−3 LEdd, which can be well explained by the Shakura-Sunyaev disk–corona model (SSD-corona) and advection-dominated accretion flow (ADAF). We also found the tight linear, negative correlation between photon index Γ and the total fractional rms. Since the amount of soft photons from the accretion disk seems invariable, an increase of the number of soft photons will dilute the variability from the harder photons. Therefore, the softer the X-ray spectra will result in the smaller total fractional rms. The above results suggested that the 2005 outburst of H 1743-322 was a normal outburst and H 1743-322 represented similar properties with other black hole X-ray binaries.
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Klysubun, Wantana, Pinit Kidkhunthod, Pongjakr Tarawarakarn, Panidtha Sombunchoo, Chanapa Kongmark, Sukit Limpijumnong, Saroj Rujirawat, Rattikorn Yimnirun, Gamolwan Tumcharern, and Kajornsak Faungnawakij. "SUT-NANOTEC-SLRI beamline for X-ray absorption spectroscopy." Journal of Synchrotron Radiation 24, no. 3 (April 4, 2017): 707–16. http://dx.doi.org/10.1107/s1600577517004830.
Abstract:
The SUT-NANOTEC-SLRI beamline was constructed in 2012 as the flagship of the SUT-NANOTEC-SLRI Joint Research Facility for Synchrotron Utilization, co-established by Suranaree University of Technology (SUT), National Nanotechnology Center (NANOTEC) and Synchrotron Light Research Institute (SLRI). It is an intermediate-energy X-ray absorption spectroscopy (XAS) beamline at SLRI. The beamline delivers an unfocused monochromatic X-ray beam of tunable photon energy (1.25–10 keV). The maximum normal incident beam size is 13 mm (width) × 1 mm (height) with a photon flux of 3 × 108to 2 × 1010 photons s−1(100 mA)−1varying across photon energies. Details of the beamline and XAS instrumentation are described. To demonstrate the beamline performance,K-edge XANES spectra of MgO, Al2O3, S8, FeS, FeSO4, Cu, Cu2O and CuO, and EXAFS spectra of Cu and CuO are presented.