Dissertations / Theses on the topic 'Physics detectors'

The current network of three terrestrial interferometric gravitational wave detectors have observed ten binary black holes and one binary neutron star to date in the frequency band from 10 Hz to 5 kHz. Future detectors will increase the sensitivity by up to a factor of 10 and will push the sensitivity band down to lower frequencies. However, observing sources lower than a few Hz requires going into space where the interferometer arms can be longer and where there is no seismic noise. A new 100 km space detector, TianGO, sensitive to the frequency band from 10 mHz to 100 Hz is described. Through its excellent ability to localize sources in the sky, TianGO can use binary black holes as standard candles to help resolve the current tension between measurements of the Hubble constant. Furthermore, all of the current and future detectors, on both the ground and in space, are limited by quantum shot noise at high frequencies, and some will be limited by quantum radiation pressure at low frequencies as well. Much effort is made to use squeezed states of light to reduce this quantum noise, however classical noise and losses severely limit this reduction. One would ideally design a gravitational wave transducer that, using its own ability to generate ponderomotive squeezing due to the radiation pressure mediated interaction between the optical modes of the light and the mechanical modes of the mirrors, approaches the fundamental limits to quantum measurement. First steps in this direction are described and it is shown that it is feasible that a large scale 40 m interferometer can observe this ponderomotive squeezing in the near future. Finally, a method of removing the effects of the vacuum fluctuations responsible for the quantum noise in gravitational wave detectors and its application to testing for the presence of deviations from general relativity is described.

The papers submitted in this volume present contributions and reviews on the physics of the scintillation process together with contributions to the development of scintillation detection techniques and the use of these techniques in nuclear physics research and in the applications of nuclear methods to other fields.

This thesis is mainly about the search for exotic heavy particles -Intermediate Mass Magnetic Monopoles, Nuclearites and Q-balls with the SLIM experiment at the Chacaltaya High Altitude Laboratory (5230 m, Bolivia), establishing upper limits (90% CL) in the absence of candidates, which are among the best if not the only one for all three kind of particles. A preliminary study of the background induced by cosmic neutron in CR39 at the SLIM site, using Monte Carlo simulations. The measurement of the elemental abundance of the primary cosmic ray with the CAKE experiment on board of a stratospherical balloon; the charge distribution obtained spans in the range 5≤Z≤31. Both experiments were based on the use of plastic Nuclear Track Detectors, which records the passage of ionizing particles; by using some chemical reagents such passage can be make visible at optical microscopes.

This thesis is mainly about the search for exotic heavy particles -Intermediate Mass Magnetic Monopoles, Nuclearites and Q-balls with the SLIM experiment at the Chacaltaya High Altitude Laboratory (5230 m, Bolivia), establishing upper limits (90% CL) in the absence of candidates, which are among the best if not the only one for all three kind of particles. A preliminary study of the background induced by cosmic neutron in CR39 at the SLIM site, using Monte Carlo simulations. The measurement of the elemental abundance of the primary cosmic ray with the CAKE experiment on board of a stratospherical balloon; the charge distribution obtained spans in the range 5≤Z≤31. Both experiments were based on the use of plastic Nuclear Track Detectors, which records the passage of ionizing particles; by using some chemical reagents such passage can be make visible at optical microscopes.

Lab measurements and Monte Carlo simulations have been carried out for the evaluation of the Straw-type detectors used in the NA62 experiment at CERN. In addition, analyses of experiment data was used in corrections to improve the reconstruction of particle tracks, ultimately leading to improved resolution of the detector system as a whole. 97.7 percent of the Straws were aligned to within 30 microns, quantified as the deviation from zero of the mean of the inherent residual distribution of each Straw. A drift time dependence on where along the Straw the particle ionized have been corrected for; before the correction the dependence was as big as 6 ns. A radius-drift time relation based on the leading edge timing distribution has been deduced and implemented. Upon implementation artifacts from the piecewise fits used became evident. An alternative approach using residuals has been put forward.

La presente dissertazione descrive il design, la caratterizzazione e il funzionamento di sistemi elettronici per esperimenti di Fisica delle particelle (LHCb) e Fisica del neutrino (CUORE e CUPID). A partire dal 2019, l'esperimento LHCb presso l'acceleratore LHC sarà aggiornato per lavorare a luminosità più elevata e molti dei suoi rivelatori dovranno essere riprogettati. Il rivelatore RICH, in particolare, dovrà adottare un sistema optoelettronico totalmente nuovo. Lo sviluppo di questo sistema ha già raggiunto una fase avanzata e diversi test eseguiti su fascio hanno permesso di verificare le prestazioni dell'intero sistema. Per migliorare la stabilità, il filtraggio e la regolazione delle tensioni di alimentazione del circuito di front-end, è stato sviluppato un regolatore lineare a basso dropout e resistente alla radiazione, denominato ALDO. Sono qui presentate le strategie di progetto, la misurazione delle prestazioni e i risultati delle campagne di irraggiamento di questo dispositivo. Nel campo della fisica del neutrino, grandi array di macrobolometri, come quelli adottati dall'esperimento CUORE e dal suo futuro aggiornamento CUPID, offrono delle caratteristiche uniche per lo studio del doppio decadimento beta senza neutrini. Il loro funzionamento richiede particolari strategie progettuali nel sistema elettronico di lettura, che è qui descritto nella sua interezza. Sono anche presentate nel dettaglio le misure di qualifica e ottimizzazione dei parametri di funzionamento di tutto il sistema, oltre che l'integrazione all'interno dell'area sperimentale. Infine sono presentati gli aggiornamenti di alcuni sottosistemi elettronici in vista della fase finale di CUPID.
The present dissertation describes design, qualification and operation of several electronic instrumentations for High Energy Particle Physics experiments (LHCb) and Neutrino Physics experiments (CUORE and CUPID). Starting from 2019, the LHCb experiment at the LHC accelerator will be upgraded to operate at higher luminosity and several of its detectors will be redesigned. The RICH detector will require a completely new optoelectronic readout system. The development of such system has already reached an advanced phase, and several tests at particle beam facilities allowed to qualify the performance of the entire system. In order to achieve a higher stability and a better power supply regulation for the front-end chip, a rad-hard low dropout linear regulator, named ALDO, has been developed. Design strategies, performance tests and results from the irradiation campaign are presented. In the Neutrino Physics field, large-scale bolometric detectors, like those adopted by CUORE and its future upgrade CUPID, offer unique opportunities for the study of neutrinoless double beta decay. Their operation requires particular strategies in the readout instrumentation, which is described here in its entirety. The qualification and optimization of the working parameters as well as the integration of the system in the experimental area are also thoroughly discussed, together with the latest upgrades of two electronic subsystems for the future CUPID experiment.

L’Organització Europea per a la Investigació Nuclear (CERN) està implementant actualment una important actualització del Gran Col·lisionador d’Hadrons (LHC) de 27 quilòmetres, amb l’objectiu d’expandir l’abast de la física, augmentant la lluminositat i desencadenant la consegüent multiplicació d’interaccions per feix de partícules. Les noves condicions operatives de l’LHC d’alta lluminositat (HL-LHC) tindran un impacte directe en els sensors de traçat de silici dels detectors principals, els experiments ATLAS i CMS, causant un gran augment de l’ocupació dels sensors i danys per radiació. Aquesta tesi doctoral investiga el disseny i l’optimització d’una nova generació de detectors de micropistes de silici capaços de suportar les severes condicions operatives esperades per a l’actualització HL-LHC. En primer lloc, l’estudi aborda el desenvolupament dels detectors de micropistes de silici des del punt de vista del disseny. Es presenten elements bàsics del dispositiu i es discuteix el seu disseny en base a consideracions de rendiment. Es presenta una nova eina de generació de disseny automàtic (ALGT) basada en Python, amb l’objectiu d’abordar la necessitat de prototips de detectors de micropistes de grans dimensions en les etapes d’I+D de l’actualització del traçador intern (ITk) d’ATLAS. El ALGT s’utilitza per dissenyar un prototip de sensor de micropistes de grans dimensions, diversos sensors en miniatura i díodes. Aquests dispositius es generen i s’organitzen en un disseny d’oblea complet de 6 polzades, per a la participació d’Infineon Technologies AG en l’enquesta de mercat per a la fabricació de sensors de micropistes per al ITk d’ATLAS. A més, es presenten dissenys d’una àmplia gamma d’estructures de test microelectròniques amb diferents aplicacions. Es proposa un conjunt d’estructures de test per al desenvolupament de tecnologies de micropistes, juntament amb un xip de test capaç de cobrir tots els tests planificats per al control de qualitat (QA) durant la producció dels sensors de micropistes d’ATLAS. D’altra banda, per millorar la connexió de lectura, també es proposen diversos dissenys d’adaptadors de “”pitch”” integrats (EPA) per minimitzar els possibles inconvenients associats amb la introducció d’una segona capa de metall en l’estructura del sensor. Es realitza una caracterització extensa en el marc de l’enquesta de mercat dels sensors de micropistes per l’ATLAS ITk. Els dispositius fabricats per les empreses candidates, Infineon Technologies AG i Hamamatsu Photonics K.K., s’avaluen abans i després d’irradiacions amb protons, neutrons i gammes, fins a les influències esperades a la fi de la vida útil de l’HL-LHC. Les estructures de test i els xips de test per QA dissenyats també es caracteritzen, amb l’objectiu de validar el seu disseny, ampliar l’avaluació de la tecnologia de micropistes i proporcionar valors de referència per als tests de producció d’ATLAS. Es presenten estudis i desenvolupaments addicionals amb aplicació en experiments de física d’altes energies (HEP) en general. Temes candents, com la sensibilitat a la humitat dels sensors de grans dimensions o l’efectivitat del “”punch-through protection”” en un escenari de pèrdua de feix, s’investiguen àmpliament. També es mostra un estudi complet de les noves estructures d’EPA proposades i els resultats dels primers sensors de micropistes fabricats en oblees de 6 polzades al Centro Nacional de Microelectrónica (IMB-CNM). Els dissenys i les caracteritzacions presentades contribueixen a definir el disseny final dels sensors de micropistes d’ATLAS per a l’actualització HL-LHC, i les investigacions addicionals revelen conclusions d’interès general que poden establir les bases per a futurs desenvolupaments.
La Organización Europea para la Investigación Nuclear (CERN) está implementando actualmente una importante actualización del Gran Colisionador de Hadrones (LHC) de 27 kilómetros, con el objetivo de expandir el alcance de la física, aumentando la luminosidad y desencadenando la consiguiente multiplicación de interacciones por haz de partículas. Las nuevas condiciones operativas del LHC de alta luminosidad (HL-LHC) tendrán un impacto directo en los sensores de trazado de silicio de los detectores principales, los experimentos ATLAS y CMS, causando un gran aumento de la ocupación del detector y daños por radiación. Esta tesis doctoral investiga el diseño y la optimización de una nueva generación de detectores de micropistas de silicio capaces de soportar las severas condiciones operativas esperadas para la actualización HL-LHC. En primer lugar, el estudio aborda el desarrollo de los detectores de micropistas de silicio desde el punto de vista del diseño. Se presentan elementos básicos del dispositivo y se discute su diseño en base a consideraciones de rendimiento. Se presenta una nueva herramienta de generación de diseño automático (ALGT) basada en Python, con el objetivo de abordar la necesidad de prototipos de detectores de micropistas de gran tamaño en las etapas de I + D de la actualización del trazador interno (ITk) de ATLAS. El ALGT se utiliza para diseñar un prototipo de sensor de micropistas de gran tamaño, varios sensores en miniatura y diodos. Estos dispositivos se generan y se organizan en un diseño de oblea completo de 6 pulgadas, para la participación de Infineon Technologies AG en la encuesta de mercado para la fabricación de sensores de micropistas para el ITk de ATLAS. Además, se presentan diseños de una amplia gama de estructuras de test microelectrónicas con diferentes aplicaciones. Se propone un conjunto de estructuras de test para el desarrollo de tecnologías de micropistas, junto con un chip de test capaz de cubrir todos los tests planificados para el Quality Assurance (QA) durante la producción de los sensores de micropistas de ATLAS. Por otro lado, para mejorar la conexión de lectura, también se proponen varios diseños de adaptadores de “pitch” integrados (EPA) para minimizar los posibles inconvenientes asociados con la introducción de una segunda capa de metal en la estructura del sensor. Se realiza una caracterización extensa en el marco de la encuesta de mercado de los sensores de micropistas para ATLAS ITk. Los dispositivos fabricados por las empresas candidatas, Infineon Technologies AG y Hamamatsu Photonics K.K., se evalúan antes y después de irradiaciones con protones, neutrones y gammas, hasta las fluencias esperadas al final de la vida útil del HL-LHC. Las estructuras de test y los chips de test para QA diseñados también se caracterizan, con el objetivo de validar su diseño, ampliar la evaluación de la tecnología de micropistas y proporcionar valores de referencia para los tests de producción de ATLAS. Se presentan estudios y desarrollos adicionales con aplicación en experimentos de física de altas energías (HEP) en general. Temas candentes, como la sensibilidad a la humedad de los sensores de gran tamaño o la efectividad del “punch-through protection” en un escenario de pérdida de haz, se investigan ampliamente. También se muestra un estudio completo de las nuevas estructuras de EPA propuestas y los resultados de los primeros sensores de micropistas fabricados en obleas de 6 pulgadas en el Centro Nacional de Microelectrónica (IMB-CNM). Los diseños y las caracterizaciones presentadas contribuyen a definir el diseño final de los sensores de micropistas de ATLAS para la actualización HL-LHC, y las investigaciones adicionales revelan conclusiones de interés general que pueden sentar las bases para futuros desarrollos.
The European Organization for Nuclear Research (CERN) is currently implementing a major upgrade of the 27-kilometre Large Hadron Collider (LHC), with the aim to expand the physics reach, increasing the luminosity and triggering the consequent multiplication of interactions per bunch crossing. The new High-Luminosity LHC (HL-LHC) operational conditions will have a direct impact in the silicon tracking sensors of the main detectors, the ATLAS and CMS experiments, causing a large increase of detector occupancy and radiation damage. This PhD thesis investigates the design and optimization of a new generation of silicon strip detectors able to withstand the severe operational conditions expected for the HL-LHC upgrade. Firstly, the study tackles the development of the silicon strip detectors from a layout design point of view. Basic device elements are presented and its design is discussed based on performance considerations. A new python-based Automatic Layout Generation Tool (ALGT) is presented, with the aim to address the need for large area prototypes of strip detectors at the R&D stages of the ATLAS Inner-Tracker (ITk) upgrade. The ALGT is used to design a large area strip sensor prototype, several miniature sensors and diodes. These devices are generated, and arranged in a full 6-inch wafer layout design, for the participation of Infineon Technologies AG in the ATLAS ITk strip sensor Market Survey. In addition, layout designs of a wide range of microelectronic test structures with different applications are presented. A set of test structures for the development of strip technologies is proposed, along with a test chip able to cover all the routine tests planned for the Quality Assurance (QA) works during the ATLAS strip sensor production. On the other hand, in order to improve the readout connection, several designs of Embedded Pitch Adaptors (EPA) are also proposed to minimize the possible drawbacks associated to the introduction of a second metal layer on the sensor structure. An extensive characterization is performed in the frame of the ATLAS ITk strip sensor Market Survey. Devices fabricated by the candidate foundries, Infineon Technologies AG and Hamamatsu Photonics K.K., are evaluated before and after proton, neutron and gamma irradiations, up to fluences expected at the end of the HL-LHC lifetime. Test structures and QA test chips designed are also characterized, with the objective to validate its design, expand the technology evaluation and provide reference values for the ATLAS production tests. Additional studies and developments are presented with application in High Energy Physics (HEP) experiments in general. Hot topics, such as the humidity sensitivity of large area sensors or the effectiveness of the punch-through protection in a beam-loss scenario, are extensively investigated. A complete study of the new EPA structures proposed, and results of the first strip sensors fabricated in 6-inch wafers at Centro Nacional de Microelectrónica (IMB-CNM), are also shown. The layout designs and characterizations presented, contribute to define the final design of the ATLAS strip sensors for the HL-LHC upgrade, and the additional investigations reveal conclusions of general interest that can lay the foundation for future developments.

Two detectors for charged particle identification have been built and tested. First, a test setup for a diffusion box threshold detector, using a 5 cm thick aerogel radiator has been designed and tested at the KEK PS facility in Japan. Using white Millipore paper as a diffuse reflector inside a diffusion box, the Ĉerenkov light gets scattered randomly until it hits one of the photomultipliers. On average up to 20 photoelectrons detected for pions at 1.2 GeV/c have been observed. Second, collection of Ĉerenkov light with an acrylic wavelength shifting plate was investigated. The test setup consisted of a plate, 30 cm long, 10 cm wide, and 1 cm thick placed behind a 5 cm deep stack of aerogel tiles. On the long ends the wavelength shifter was read out by two 5-inch photomultipliers. The response of the system to pions and protons at 1.2 GeV/c momentum was measured at the KEK PS facility in Japan. On average 6 photoelectrons radiated in the aerogel could be detected.

Presented in this thesis is a summary of the development of gallium arsenide position sensitive detectors. These are aimed at various applications with the original motivation being experimental particle physics. An account is given of basic semiconductor physics relevant to particle detectors. A review of electronics applicable to reading out charged signals from semiconductor detectors is included. Applications of gallium arsenide X-ray detectors are described together with results from a Monte-Carlo simulation of the spectrum obtained from an X-ray source. The design, fabrication and laboratory testing of detectors is presented for pixel and microstrip detectors and other test structures. Test beam results are also presneted for pixel and microstrip detectors. An introduction to ATLAS detector simulation is also given, with examples of detector descriptions for the GaAs Forward Semiconductor Tracker. Results from a generator level study of b-jets from the process Hbb and predictions of influences in the Forward Tracker are also given.

Semiconductor-based gamma-ray-imaging detectors are under development for use in high-resolution nuclear medicine imaging applications. These detectors, based on cadmium zinc telluride, hold great promise for delivering improved spatial resolution and detection efficiency over current methods. This dissertation presents work done on three fronts, all directed toward enhancing the practicality of these imaging devices. Electronic readout systems were built to produce gamma-ray images from the raw signals generated by the imagers. Mathematical models were developed to describe the detection process in detail. Finally, a method was developed for recovering the energy spectrum of the original source by using maximum-likelihood estimation techniques. Two electronics systems were built to read out signals from the imaging detectors. The first system takes signals from a 48 x 48-pixel array at 500 k samples per second. Pulse-height histograms are formed for each pixel in the detector, all in real time. A second system was built to read out four 64 x 64 arrays at 4 million pixels per second. This system is based on digital signal processors and flexible software, making it easily adaptable to new imaging tasks. A mathematical model of the detection process was developed as a tool for evaluating possible detector designs. One part of the model describes how the mobile charge carriers, which are released when a gamma ray is absorbed in a photoelectric interaction, induce signals in a readout circuit. Induced signals follow a "near-field effect," wherein only carriers moving close to a pixel electrode produce significant signal. Detector pixels having lateral dimensions that are small compared to the detector thickness will develop a signal primarily due to a single carrier type. This effect is confirmed experimentally in time-resolved measurements and with pulse-height spectra. The second part of the model is a simulation of scattering processes that take place when a gamma ray is absorbed within the detector volume. A separate simulation predicts the spreading of charge carriers due to diffusion and electrostatic forces. The models are used in a technique to improve the energy resolution of the detectors by estimation of the source spectrum using the Expectation-Maximization algorithm.

An electron-positron linear collider is an option for future large particle accelerator projects. Such a collider would focus on precision tests of the Higgs boson properties. This thesis describes three studies related to the optimisation of highly granular calorimeters and one study on the sensitivity of Higgs couplings at CLIC. Photon reconstruction algorithms were developed for highly granular calorimeters of a future linear collider detector. A sophisticated pattern recognition algorithm was implemented, which uses the topological properties of electromagnetic showers to identify photon candidates and separate them from nearby particles. It performs clustering of the energy deposits in the detector, followed by topological characterisation of the clusters, with the results being considered by a multivariate likelihood analysis. This algorithm leads to a significant improvement in the reconstruction of both single photons and multiple photons in high energy jets compared to previous reconstruction software. The reconstruction and classification of tau lepton decay products was studied. Utilising highly granular calorimeters, the high resolution of energy and invariant mass of the tau decay products enabled a high classification rate. A hypothesis test was performed for expected decay final states. A multivariate analysis was trained to classify decay final states with a machine learning method. The performance of tau decay classification is used for the electromagnetic calorimeter optimisation at the ILC or CLIC. A proof-of-principle analysis using the correlation between the polarisations of the tau pair from a boson decay as a signature to differentiate the Higgs boson from the Z boson is presented. Sensitivity of Higgs couplings at CLIC was studied using the double Higgs production process. Algorithms were developed for signal event selection. The event selection relies on the jet reconstruction and the flavour tagging. A multivariate analysis is performed to select signal events. An attempt at extracting Higgs trilinear self-coupling and quartic coupling was conducted.

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 219-229).
Quantum vacuum fluctuations impose strict limits on precision displacement measurements, those of interferometric gravitational-wave detectors among them. Introducing squeezed states into an interferometer's readout port can improve the sensitivity of the instrument, leading to richer astrophysical observations. In recent years, this technique has been used to improve the sensitivity of the GEO600 [1011 and the Initial LIGO detector at Hanford, WA [102]. Squeezed states could be employed in advanced gravitational-wave detectors, such as Advanced LIGO, to further push the limits of the observable gravitational wave universe. To maximize the benefit from squeezing, environmentally induced disturbances such as back scattering and angular jitter need to be mitigated. Also, optomechanical interactions dictate that the quadrature of the squeezed vacuum state must rotate by 900 at around 50 Hz in order to achieve a broadband sensitivity improvement for Advanced LIGO. In this thesis we describe a series of experiments that lead to a ultra-high vacuum (UHV) compatible, low phase noise, and frequency-dependent squeezed vacuum source required for Advanced LIGO and future gravitational-wave detectors. In order to develop the required technology, two proof-of-principal experiments were conducted. In the first experiment, we built a UHV compatible squeezed vacuum source and homodyne readout and operated them in UHV conditions. We also commissioned a control scheme that achieved a record low 1.30-7 mrad of phase noise. This is a nearly tenfold improvement over previously reported measurements with audio-band squeezed vacuum sources. In the second experiment we used a 2-m-long, high-finesse optical resonator to produce frequency-dependent squeezed quadrature rotation around 1.2kHz. This demonstration of audio-band frequency-dependent squeezing uses technology and methods that are scalable to the required rotation frequency for Advance LIGO, firmly establishing the viability of this technique for application in current and future gravitational-wave detectors. We conclude with a discussion of the implications of these results for squeezing enhancement in Advanced LIGO and beyond.
by Eric Oelker.
Ph. D.

The work in this thesis is focused on characterisation and evaluation of two classes of science grade imaging radiation detectors. The first class is Monolithic Active Pixel Sensors (MAPS). The advances in CMOS fabrication technologies over the last four decades allowed MAPS to compete with Charge-Coupled Devices (CCD) in many applications. The technology also provides relatively inexpensive ways to tailor design to suit specific application needs. It is important to understand performance capabilities of new sensor designs through characterisation and optimisation of readout parameters. In this work three MAPSs were characterised. The first one - HEPAPS4 - designed for charged particle detection, with the potential technology application in the vertex detector for the International Linear Collider. The noise of the sensor was measured to be 35±5 e, which agrees well with simulated data. The dark current was found to be 175 pA/cm2. The SNR performance for minimum ionising particles detection was demonstrated to be 40. The sensor was also evaluated for indirect detection of thermal and fast neutrons using lithium and polyethylene converters. The technology performed well in such an application with an estimated fast neutron detection efficiency of ~0.01%. The second sensor characterised – Vanilla MAPS – was designed to evaluate new techniques for fast readout, small noise and reduced image lag. The system was capable to readout 150 full frames (520x520 pixels) per second; the sensor showed 14±4 e noise and decreased image lag. The dark current was found to be ~50 pA/cm2. The back-thinned version of the sensor demonstrated dramatic improvement in quantum efficiency from 0% to 20% at 220 nm. The third device is parametric sensor eLeNA. It features 14 test structure designed to evaluated noise reduction architectures. The most promising structures showed temporal noise values as low as 6 e and 20 e fixed pattern noise. Medipix as an example of the second class of imaging detectors - hybrid pixel detectors - was evaluated in two applications. It was used as the core element of the ATLAS radiation background monitoring system. The sensors were covered with neutron converters, which extended the number of radiation types that can be detected. X-ray calibration was performed, showing excellent tolerance of all 18 devices characterised. Detection efficiencies were estimated to be ~1% for thermal and ~0.1% for fast neutrons. The second application of Medipix was mass spectrometry. The detector was place in the focal plane of a prototype mass spectrometer. 2D representation of data allowed focusing correction of the ion beam. The system was capable to detect ions in the range of 5-25 keV. The detector characterisation with broad range of ions (from Cu to Pb) showed very good abundance agreement with table data.

Recent advances in particle accelerators have increased the demands being placed on detectors. Novel detector designs are being implemented in many different areas including, for example, high luminosity experiments at the LHC or at next generation synchrotrons. The purpose of this thesis was to characterise some of these novel detectors. The first of the new detector types is called a 3D detector. This design was first proposed by Parker, Kenney and Segal (1997). In this design, doped electrodes are created that extend through the silicon substrate. When compared to a traditional photodiode with electrodes on the opposing surfaces, the 3D design can combine a reasonable detector thickness with a small electrode spacing resulting in fast charge collection and limited charge sharing. The small electrode spacing leads to the detectors having lower depletion voltages. This, combined with the fast collection time, makes 3D detectors a candidate for radiation hard applications. These applications include the upgrades to the Large Hadron Collider (LHC) leading to the High Luminosity Large Hadron Collider (HL-LHC). The limited charge sharing of the devices can also improve their performance when being employed as imaging sensors. This will provide benefits in X-ray diffraction experiments. The first experiment to evaluate the 3D detector design analysed for this thesis involved utilising a telescope consisting of 6 calibrated detector planes and a beam of pions from the Super Proton Synchrotron (SPS) at CERN. Once the tracks through the telescope were reconstructed, these gave predicted hits on the 3D detector that could be compared to the recorded energy depositions. By making this comparison, a measure of the detector’s efficiency in various regions of the pixels was made. The overall efficieny of the pixel was measured at 93.0±0.5%. The detector was also rotated with respect to the incident beam, increasing the efficiency to 99.8±0.5% for an angle of 10◦, and the detector bias was altered to measure the effect of over-depletion. Measurements of the charge sharing and resolution properties of the device were also reported. Another detector design that was investigated was a slim edge detector. Instead of the typical guard ring structures that a normal device would employ, this detector reduced the size of these structures to enable easier tiling of the detectors. This was done by scanning the reduced edge and the standard edge of the detector with an X-ray beam with a width FWHM of 7 μm and 15 keV. The noise level of the strip closest to the cleaved edge was twice as large as that of the adjacent strip with no degradation of the charge collection capacity. The next experiment to evaluate a short, double sided 3D strip detector was a Transient Current Technique (TCT) experiment. The TCT technique allows the electric field in the 3D devices to be probed in a way not possible before. The TCT technique uses the current waveform produced by the detector in response to a near delta function point laser pulse (illumination). The waveforms are recorded as a function of illumination position over the surface of the device under test as a function of detector bias. This data gives information on the portion of the induced signal from electron or hole motion. From the rise times of the signals the velocity profile of the carriers in the devices and therefore electric fields can be determined. The collected charge was calculated from the integral of the waveforms. The detectors were tested prior to irradiation, after irradiating to a dose of 5 x 10^15 1MeV equivalent neutrons/cm^2, and after periods of annealing at elevated temperatures. Annealing was achieved in situ by warming to 60 ◦C for 20 to 600 minutes corresponding to room temperature annealing of between 8 and 200 days. Before irradiation, full lateral depletion between the columns occurs at low bias voltages, at approximately 3 V. A uniform carrier velocity between the columns is not achieved until the bias is equal to 40 V. Both the drift of electrons and holes provide equal contributions to the measured signals. After irradiation there is clear charge multiplication enhancement along the line between columns with a very non-uniform velocity profile in the unit cell of the device. In addition, charge trapping greatly suppresses the contribution of the holes on the signal produced. The final novel detector type was an Active Pixel Sensor (APS). Recent developments in CMOS fabrication processes have allowed new sensors to be developed and tailor-made for specific applications. These challenge traditional Charge Coupled Devices (CCD) in some areas. The characterisation of the APS device took place in an X-ray diffraction experiment at the Diamond Light Source where it was evaluated alongside a CCD. The camera gain and stability had been determined prior to the experiment taking place. During the experiment, the dark current, noise, signal to noise and image lag performance was evaluated and compared between the APS and the CCD. The signal to noise of the APS and the CCD was comparable (150 and 200 respectively) when the same integration time was used.

To further increase the sensitivity of the aLIGO detectors, upgrading the monolithic fused silica suspension is considered for an upgrade option: a higher stress in the fibre and a longer final stage. One of the challenges for this upgrade will be producing thinner and longer fibres that can hold the test mass safely. Since laser power fluctuations during the fibre fabrication process can produce potentially weak fibres, we present a laser intensity stabilisation technology for fused silica fibre fabrication that was investigated to allow further improvements on fibre production consistency which could be applied to aLIGO upgrades. Fibres fabricated with this new technique showed 30% decreased standard deviation of breaking stress, which indicates that the application of intensity stabilisation technology can improve the statistical strength of fused silica fibres. Combined with a longer polishing duration, the average breaking stress also improved by 9%. As higher stress in the fibre and the longer final stage can improve the detector's sensitivity, these enhanced technologies will enable us to fabricate thin and robust fibres that can achieve future suspension upgrade requirements.

Gamma-ray detectors based on high-density semiconductors, such as cadmium zinc telluride, are being developed for applications in nuclear medicine, astronomy and the monitoring of nuclear weapons material. In contrast to the more commonly used scintillators, which convert gamma-ray energy into light, semiconductors directly convert the energy of a gamma ray into electrical current. This direct conversion often leads to the perception that gamma-ray detection in semiconductors is not an estimation problem. This dissertation presents the contrasting view that gamma-ray detection in semiconductors is fundamentally an estimation problem, and it is only through the appropriate analysis of gamma-ray signals that optimal energy resolution and spatial resolution can be achieved. To estimate interaction parameters, such as the energy of the gamma ray and its interaction position, it is first necessary to have an accurate model of the detector system. In this work, the system consists of slabs of CdZnTe with arrays of pixel electrodes mounted on integrated readout circuits. A theoretical model of detector behavior is presented, including a new model for charge spreading in the detector. Methods for experimentally determining detector behavior are developed based on mapping detectors with narrow beams of gamma rays. Estimating the interaction positions and energies proceeds from a statistical model of the production of pixel signals, derived from our physical model. Energies and interaction positions are estimated by maximizing the likelihood function. The likelihood is the probability that a gamma ray with a given position and energy will produce an observed set of pixel signals. This maximum-likelihood estimation improves the energy resolution over simpler methods and can give the interaction position in three dimensions. A likelihood function can be calculated for an entire set of gamma rays, in which case an image can be estimated from the raw data without ever estimating individual interaction positions and energies. The Expectation-Maximization algorithm is used to reconstruct images and energy spectra by maximizing the ensemble likelihood function. In this work, the list-mode form of the algorithm is used, meaning that the raw data consist of lists of pixel signals for each gamma ray. Both spatial and energy resolution improve when this algorithm is applied to the raw pixel signals.

This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Thesis: Ph. D., Massachusetts Institute of Technology, Department of Physics, February, 2020
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 157-172).
With the conclusion of the first two observing runs of the Advanced LIGO detectors, which saw the first direct detection of gravitational waves, we are firmly in the era of gravitational-wave astronomy. To reach the highest sensitivities, current interferometric gravitational-wave detectors are designed for hundreds of kilowatts of circulating optical power. At these high circulating powers, the sensitivity of the detectors to gravitational waves will be limited by the quantum properties of the light: shot noise at frequencies above ~ 100 Hz, and quantum radiation pressure noise at lower frequencies. To reach the high powers necessary for achieving the quantum noise limits imposed by the light, it is essential to solve the control problems and understand the additional noise introduced by high power operation. Additionally, development of high-power laser sources that reach the stringent noise and reliability requirements is crucial. This work comprises three experiments aimed at reaching the radiation-pressure-dominated regime of interferometric gravitational-wave detectors. The first part presents results from a high-power, meter-long Fabry-Prot Michelson interferometer to probe classical and quantum radiation pressure effects using a gram-scale mechanical oscillator. The second part is an exploration of the effects of electric fields and charging of test masses on the sensitivity of the LIGO detectors, which may limit the ability to observe radiation-pressure effects. Finally, we describe the development and characterization of a high-power, narrow-linewidth ytterbium-doped fiber amplifier for use in future gravitational-wave detectors.
by Aaron Buikema.
Ph. D.
Ph.D. Massachusetts Institute of Technology, Department of Physics

During my PhD I have been involved in two experiments, LHCb (at CERN) and CUORE (at LNGS). The former is devoted to search of physics beyond the Standard Model. I collaborated to characterize MaPMTs and develop the read-out electronic system. Such equipment will be used for the upgrade of the RICH detector, responsible for the particle identification. CUORE is an experiment searching the neutrinoless double beta decay in tellurium 130. I collaborated to develop and mount the electronic apparatus. The studies on the linear power supply, the slow control communication system and the ultra-precise and ultra-stable pulser board for the bolometer response stabilization, will be described.
During my PhD I have been involved in two experiments, LHCb (at CERN) and CUORE (at LNGS). The former is devoted to search of physics beyond the Standard Model. I collaborated to characterize MaPMTs and develop the read-out electronic system. Such equipment will be used for the upgrade of the RICH detector, responsible for the particle identification. CUORE is an experiment searching the neutrinoless double beta decay in tellurium 130. I collaborated to develop and mount the electronic apparatus. The studies on the linear power supply, the slow control communication system and the ultra-precise and ultra-stable pulser board for the bolometer response stabilization, will be described.

The use of Liquid Argon Time-Projection Chambers in neutrino physics is looking increasingly certain as the field moves to larger, finer-grained detectors capable of delivering the physics reach required for the next generation of experiments studying neutrino oscillations and CP violation in the lepton sector. This thesis explores reconstruction procedures for use in a Liquid Argon Time-Projection Chamber (LAr TPC). Fully automated reconstruction of neutrino events in these environments has not been successfully demonstrated previously, although several collaborations across the world are working towards this goal. A number of algorithms and techniques are discussed, and their applicability to the field of reconstruction in fine-grained detector environments is assessed. The techniques presented here are fully automated and characterised to the maximum extent possible, and may be combined to produce a software reconstruction chain that is free from human intervention. In addition to these algorithms, a framework for running chained reconstruction tasks is presented and demonstrated to work in conjunction with the algorithms developed. Muon identification is also presented, using cuts justified from the truth information available from simulations. The algorithms and cuts together are used to analyse simulated neutrino events throughout the thesis, focusing on charged current muon neutrino interactions at energies of 0:77 GeV and 4:5 GeV, and considering interactions producing u + p (referred to as CCQE) or u + p + n+ (referred to as CC1n) final states.

Gravitational waves in f(R) gravity excite monopole and m = 0±2 quadrupole resonance modes of a spherical detector. This document reviews the basic ideas of general relativity and gravitational waves, and then applies those concepts to an f( R) gravitational wave. The acoustic response of a GW incident with a spherical detector is reviewed in detail, and the absorption cross section for an f(R) GW impinging on the spherical detector is calculated. Minimum detectable scalar wave amplitudes are explored for the Mario Schenberg detector. The mass of the scalar mode affects its detectability.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2003.
Includes bibliographical references (p. 239-243).
As the first generation of laser interferometric gravitational wave detectors near operation, research and development has begun on increasing the instrument's sensitivity while utilizing existing infrastructure. In the Laser Interferometer Gravitational Wave Observatory (LIGO), significant improvements are being planned for installation in 2007 to increase the sensitivity to test mass displacement, hence sensitivity to gravitational wave strain, by improved suspensions and test mass substrates, active seismic isolation, and higher input laser power. Even with the highest quality optics available today, however, finite absorption of laser power within transmissive optics, coupled with the tremendous amount of optical power circulating in various parts of the interferometer, result in critical wavefront deformations which will cripple the performance of the instrument. Discussed is a method of active wavefront correction via direct thermal actuation on optical elements of the interferometer; or, "thermally adaptive optics". A simple nichrome heating element suspended off the face of an affected optic will, through radiative heating, remove the gross axisymmetric part of the original thermal distortion. A scanning heating laser- will then be used to remove any remaining non-axisymmetric wavefront distortion, generated by inhomogeneities in the substrate's absorption, thermal conductivity, etc. This work includes a quantitative analysis of both techniques of thermal compensation, as well as the results of a proof-of-principle experiment which verified the technical feasibility of each technique.
by Ryan Christopher Lawrence.
Ph.D.

The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) is a ground based gamma-ray telescope located in Albuquerque, NM. This thesis describes the development of an instrument, at McGill University, to study the angular response of the STACEE photon detectors to specific lighting conditions. The STACEE photon detectors consist of a photomultiplier tube (PMT) which is optically coupled to a Dielectric Totally Internally Reflecting Concentrator (DTIRC). A deeper understanding and parameterization of each constituent of the STACEE detector is integral to optimizing of the performance of the detector itself.

Silicon tracking detectors are frequently used in particle collider experiments, as they can provide excellent spatial precision with little material in order to cause minimal track disruption. Due to a progressive increase in collider luminosities, a common trend in these experiments is the need for higher levels of radiation damage resistance. One proposed class of designs for pixel trackers in high luminosity colliders is the Silicon 3D trench detector. The same design can be scaled up for photon science applications.

The work discussed in this dissertation was performed as part of a collaboration between BNL, NYU, CNM and SUNY Stony Brook. The central aim of the work presented here was to evaluate the manufactured 3D trench detector prototypes and study their behavior in detail by performing a series of experimental measurements and TCAD simulations.

An experiment to measure the detector response to an Americium radioactive source was designed and used to study the noise level and charge collection efficiency of detector prototypes. An experimental system which measured the detector response to an infrared laser with computer controlled precision positioning was developed. This system was used to obtain laser pulse response maps of detectors, which in turn were utilized to investigate the dependence of charge collection efficiency of detectors on position, collection time and bias voltage. The same mapping technique was also used to study the change in irradiated detector response.

Detector response was simulated using the Silvaco TCAD Suite. These simulations were used to study depletion in large photon detectors and charge collection in response to laser hits. Approximate simulations of radiation damage were also performed to investigate the behavior of irradiated detectors. Leakage current and capacitance simulations before and after irradiation were also performed and compared to the experimental measurements. While significant variations in detector response between different prototypes were observed during the experiments, simulation results are still capable of explaining the general properties of the detectors. The combination of the simulation and the experimental results provides an understanding of the signal generation process in these detectors.

One observed problem is the large bias currents due to manufacturing surface defects. A double-sided version of the trench detector is proposed to mitigate this problem. Electric fields, depletion region shape and formation, bias voltage and transient current response of these detectors are simulated and compared with those of the standard trench detectors. Computer simulations show that the double-sided detectors also have some performance advantages over the original designs including larger more uniform spatial charge collection efficiency and higher radiation damage resistance. These simulation results and the general insensitivity of the proposed detectors to surface defects make the double-sided detectors worthy of further study.

The semiconductor ZnO has a band gap of 3.3 eV and has potential in applications as transparent and conducting layers for electronic devices. In the present work, experiments have been carried out to deposit thin films of ZnO on glass and silicon substrates by RF magnetron sputtering. The deposition experiments were performed at substrate temperatures in a range from room value to 400°C. Resistivity measurements were performed on the films. The resistivity increased as the substrate temperature was increased from room value to 400°C. The films on the silicon substrates were then processed into ZnO(n)-Si(p) heterojunctions whereas the ones on glass substrates were processed into metal-ZnO-metal MSM devices. Dark current-voltage and capacitance-voltage characteristics of the fabricated devices have been studied in order to determine the effects of substrate temperature during the deposition. In addition, post deposition heat treatment experiments were performed and the effects were examined by the electrical measurements. For the samples deposited at room temperature, the resistivity was observed to decrease drastically after a heat treatment at 150°C for 30 minutes.
Illuminated characteristics of both the heterojunctions and MSM devices were also studied in a wavelength range from 300 to 700 nm. It was observed that UV responsivity for the ZnO-Si heterojunctions shows an increase from 210 to 300°C and a large decrease at 400°C. Under illumination, the current at given voltage increases for all samples and this has been confirmed to be mainly due to the bandgap absorption. From the post deposition heat treatment experiments carried out at low temperatures, the dark current was observed to increase with heat treatment time. However, the photocurrent was also observed to increase with the heat treatment time.

Computational imaging with single-pixel detectors utilises spatial correlation of light to obtain images. A series of structured illumination is generated using a spatial light modulator to encode the spatial information of an object. The encoded object images are recorded as total intensities with no spatial information by a single-pixel detector. These intensities are then sent to correlate with their corresponding illumination structures to derive an image. This correlation imaging method was first recognised as a quantum imaging technique called ghost imaging (GI) in 1995. Quantum GI uses the spatial correlation of entangled photon pairs to form images and was later demonstrated also by using classical correlated light beams. In 2008, an adaptive classical GI system called computational GI which employed a spatial light modulator and a single-pixel detector was proposed. Since its proposal, this computational imaging technique received intensive interest for this potential application. The aim of the work in this thesis was to improve this new imaging technique into a more applicable stage. Our contribution mainly includes three aspects. First an advanced reconstruction algorithm called normalised ghost imaging was developed to improve the correlation efficiency. By normalising the object intensity with a reference beam, the reconstruction single-to-noise ratio can be increased, especially for a more transmissive object. In the second work, a computational imaging scheme adapted from computational GI was designed by using a digital light projector for structured illumination. Compared to a conventional computational GI system, the adaptive system improved the reconstruction efficiency significantly. And for the first time, correlation imaging using structured illumination and single-pixel detection was able to image a 3 dimensional reflective object with reasonable details. By using several single-pixel detectors, the system was able to retrieve the 3 dimensional profile of the object. In the last work, effort was devoted to increase the reconstruction speed of the single-pixel imaging technique, and a fast computational imaging system was built up to generate real-time single-pixel videos.

3D detectors are a novel variety of photodiode radiation detector, invented by Parker, Kenney and Segal (1997). Instead of having n- and p-type contacts on the front and back surfaces of a silicon substrate, like a standard photodiode, they have columns of doped material passing through the thickness of the silicon. This structure means that the detector can combine a reasonable substrate thickness with a very small electrode spacing, resulting in a low depletion voltage, fast charge collection and low charge sharing. These detectors have a couple of promising applications. Their fast charge collection and low depletion voltage should make them very radiation-tolerant. So, they could be used for future particle physics experiments at the Super Large Hadron Collider (SLHC), where high levels of radiation damage are expected. Also, their low charge sharing means they could potentially improve X-ray diffraction measurements at synchrotrons such as Diamond Light Source. This would allow these experiments, for example, to determine the structures of biological molecules more accurately. However, before 3D devices can be used in practical experiments, their design and fabrication must be optimised to ensure that reliable, high-performance detectors can be produced on a reasonably large scale. The aim of this thesis is to evaluate and understand the behaviour of a variety of 3D detectors using a combination of lab tests and computer simulations. Using these results, future fabrication runs can then be re-designed to improve their performance. Firstly, the "Synopsys TCAD" simulation package was used to determine the optimum design for 3D detectors at the SLHC. It was found that the device behaviour depends strongly on the electrode spacing, and the choice of spacing requires a trade-off between different effects. Using a smaller spacing reduces the detector's operating voltage, and improves the charge collection efficiency by reducing carrier trapping. However, reducing the spacing also increases the capacitance, resulting in greater noise, and also increases the insensitive volume occupied by the columns. At SLHC radiation damage levels, the optimal electrode spacing was found to be 40-55 micrometres. CNM (Centro Nacional de Microelectronica) in Barcelona have produced a set of "double sided" 3D detectors. The n- and p-type columns in these devices are etched from opposite sides of the substrate and do not pass through the full substrate thickness. Computer simulations show that these detectors should give similar performance to full-3D detectors. The main difference is that these devices have slower charge collection around their front and back surfaces. Basic electrical characterisation of the detectors showed that they have low depletion voltages. However, the guard ring current varied a great deal between detectors, though this was fixed by using better guard structures. Charge collection tests on these detectors using beta particles gave mixed results. A heavily-irradiated detector gave a relatively high collection signal, similar to the simulated value, which demonstrated the structure's radiation hardness. However, an unirradiated detector gave an unexpectedly low collection signal. This was perhaps due to poor coupling between this detector and the readout chip. Three of these "double-sided" 3D detectors were bonded to Medipix2 pixel readout chips. These chips are specifically designed for X-ray detection, and can count individual photon hits. The detectors worked successfully, and initial lab tests demonstrated that they depleted extremely rapidly. The detectors were then tested in an X-ray beam at Diamond Light Source. These tests showed that the detectors have lower charge sharing than a standard planar photodiode. For example, 24% of the hits on a double-sided 3D detector at 22V were shared, compared to 40% on a planar detector at 100V. A set of devices with a simplified "single-type-column" structure, fabricated by FBK-IRST in Trento, were also tested. Simulations showed that although this structure will have a low depletion voltage and fast electron collection, the hole collection will be slow. This will result in poorer behaviour than full- and double-sided 3D detectors. This was confirmed by lab tests, which showed that when the detector was coupled to fast readout electronics, the charge collection efficiency was reduced due to ballistic deficit.

Measurements of modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) for metal/film portal detectors are reported for the Cobalt-60 and 10 MV spectra. The detectors consist of a double-emulsion portal film secured between plates of aluminum, copper, brass or lead with thicknesses from 0 to 4.81 mm. The study of MTF, NPS, and DQE shows that both photons and secondary electrons produced within the front-plate and backscattered electrons from the back-plate affect metal/film portal imaging. Study of DQE indicates that the best portal detectors are those without back-plates, and with high density front-plates with thicknesses less than the maximum electron range.
This MTF data was modeled with the logit analysis. It is shown that the parameters resulting from the logit analysis depend on the mass thickness and the atomic number of the metal plates.
Metal/amorphous selenium (a-Se) electrostatic-based detectors have been developed for portal imaging. The detectors consist of a-Se photoconductive layers of varied thicknesses deposited on plates of varying thicknesses of aluminum, copper, and stainless steel. The metal-plates of the detectors face the incident 6 MV and Co-60 photon spectra during imaging. The sensitivity of the a-Se detectors to dose, electric field across the a-Se layer, plate type, and a-Se thickness is studied. A model showing a cubic relationship between the a-Se latent surface voltage and dose is derived and experimentally verified. A contrast-detail phantom is used to study the image quality and contrast-resolution characteristics of the metal/a-Se detectors. The metal/a-Se detectors produce better quality contrast-detailed images at a considerably lower dose than that offered by the other commercial available portal systems, mainly due to the low inherent noise of the novel detectors.
A semi-automatic technique for the direct set-up alignment of radiosurgical circular fields from an isocentric linac to treatment room laser cross-hairs is described. Because film or a-Se is each sensitive to laser and ionizing radiation, they are used to acquire images of the positioning lasers superimposed directly onto the radiosurgical circular fields. An algorithm extracts the coordinates of the center of the collimator image and of the intersection of the laser cross-hair image and subsequently determines the deviation, to within a precision of ∼0.04 mm. The technique is also used to perform quality assurance on a Clinac-18 linac and shows a (0.53 +/- 0.05) mm wobble from the nominal isocenter of the linac.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2006.
Includes bibliographical references (p. 83-85).
Despite their intrinsic advantages due to co-location, the two LIGO (Laser Interferometer Gravitational Wave Observatory) Hanford interferometers have not been used in the search for the stochastic gravitational wave background due to their coupling to a shared environment, which may be comparable to or exceed any gravitational signal. In this thesis, using data from LIGO's fourth science run, we demonstrate a technique to relate the H1-H2 coherence to coupling with physical environmental channels. We show that the correspondence is tight enough to correctly identify regions of high and low coupling and the nature of the coupling in the data set. A simple thresholding provides frequency vetoes, which we can use to derive a significantly cleaner coherence spectrum. Next, using this frequency veto technique and data from the first epoch of LIGO's fifth, currently running science run, we design, implement, and perform a search for astrophysical populations of gravitational wave emitters, which emit predominantly in the kilohertz region of the spectrum, a region totally inaccessible to detectors separated by thousands of kilometers. As well as providing us with a proof-of-concept, the results provide an advanced look at the physical results to come from H1-H2 by the end of S5.
by Nickolas Fotopoulos.
S.M.

In 1905, Einstein postulated that the speed of light is not only finite, but that its speed in vacuum is a universal limit that no process can exceed. The Theory of General Relativity later extended this concept to include gravitational interactions, and Eddington's timely measurements of stellar positions during a solar eclipse in 1919 confirmed that gravity's effect on spacetime is both real and entirely physical -- not merely a mathematical curiosity. With the death of Newton's notions of universal time and instantaneous gravity came the idea of gravitational waves as distortions in space-time that propagate the gravitational interaction at the speed of light. These gravitational waves are emitted from any object undergoing a non-axi-symmetric acceleration of mass, but -- due to the exceptionally weak coupling between gravitational waves and matter -- are expected to induce displacements of the order of 10^-18 m in kilometre-scale detectors: the extraordinary diminutiveness of this effect has thus far precluded any direct detection of the phenomenon. Numerous gravitational wave detectors have been built since the 1960s, in the form of both interferometric detectors and resonant mass devices. Interferometric detectors currently represent the most promising form of detector, due to their relatively wide-band response to gravitational wave signals and promising levels of sensitivity. In recent years a worldwide network of these interferometric detectors (LIGO, GEO600, Virgo and TAMA300) have begun to approach (or indeed reach) their design sensitivities. Although these detectors have started to provide upper limit results for gravitational wave emission that are of astrophysical significance, there have as yet been no direct detections. As such, work is underway to upgrade and improve these detectors. However, increasing the signal sensitivity necessarily leads to an increase in their sensitivity to their limiting noise sources. Two critical noise limits that must be characterised, understood, and hopefully reduced for the benefit of future detectors, are thermal noise (from mirror substrates, reflective coatings and suspension systems) and photon noise -- associated with the intrinsic shot noise of light and the noise due to light's radiation pressure. Two interferometric experiments designed to help inform on these phenomena were constructed at the University of Glasgow's Institute for Gravitational Research. The first experiment compared the relative displacement noise spectra of two specially constructed optical cavities, to extract the thermal noise spectrum of a single test mirror. In future experiments, this optic could be changed and the thermal noise spectrum for any suitable combination of mirror substrate and reflective coating evaluated. The second experiment involved the investigation of suitable control schemes for a three-mirror coupled optical cavity. As the resonant light power in interferometers increases in future devices (in order to decrease the photon shot noise) the need to de-couple the control schemes that govern the respective cavities so that they can be controlled independently, becomes more important. As a three-mirror cavity effectively represents a simple coupled system, it provides a suitable test-bed for characterising suitable control schemes for more advanced interferometers. Together, these experiments may provide information useful to the design of future gravitational wave interferometers.

Les Détecteurs a Inductance Cinétique (KID) ont récemment attiré l'attention de la communauté des détecteurs fonctionnants à très basse température (~100 mK). Haute sensibilité, une fabrication simple, une lecture à faible constante de temps et un multiplexage fréquentielle intrinsèque, ouvrent de nouvelles possibilités pour les expériences necessitant des matrices de détecteurs ultra-sensibles avec un grand nombre de pixels. En astronomie millimétrique, l'instrument New IRAM KID Array (NIKA) est aujourd'hui la meilleure démonstration des performances optiques des ces détecteurs. Cette dernière est composée de plusieurs centaines des KIDs répartis sur deux bandes spectrales. NIKA est installé de manière permanente au telescope (30 mètres) IRAM à Pico Veleta (Grenade, Espagne). Pendant les campagnes d'observation NIKA, nous avons démontré des performances comparables aux bolomètres et l'instrument est aujourd'hui ouvert à la communauté des astronomes. Ces résultats favorables ont déclenché le développement d'une géneration plus ambitieuse : NIKA2. Cette dernière fonctionnera avec pas moins de quelques ~5000 pixels. De plus, il existe une volonté d'étendre la technologie de KID pour les futures missions spatiales d'observation. Dans ce cadre, il est important d'étudier l'interaction des rayons cosmiques avec les matrices de KIDs. Nous avons réalisé une étude avancée permettant aujourd'hui d'entrevoire la physique derrière les intéractions à haute énergie dans les substrats et leur propagation sous forme de phonons jusque dans les pixels. Le travail effectué dans cette thèse est centré principalement sur le développement des instruments (les matrices des detecteurs et le software de lecture et acquisition des donnes) dédiés aux KIDs pour ces mesures
Kinetic Inductance Detectors (KID) have recently drawn the attention of the low-temperature detectors community. High sensitivity, low fabrication complexity, small time constant and most notably the intrinsic capability of frequency multiplexed readout open new possibilities for experiments which need large format arrays of ultra sensitive light detectors. In millimeter Astronomy, the New IRAM KID Array (NIKA) instrument is today the most beautiful demonstration of this statement. It is a two bands hundreds-pixels KID based camera permanently installed at the focal plane of the IRAM 30-m telescope of Pico Veleta (Granada, Spain). Thanks to the NIKA observational campaign, we have de nitively demonstrated performances comparable to the state-of-art of bolometers and the instrument is today opened to the astronomers community. This encourages further array scaling and opens the path to next generation kilo-pixels ground-based cameras, like NIKA-2. Moreover, the will to extend KID technology to space mission needs the interaction with cosmic rays to be investigated. The understanding of the physics behind substrate-higher energy particles interactions led us to implement a fully independent system for the phonon-mediated particle detection with KID arrays. The work carried out through this PhD thesis concerned the development of optimized Lumped Element Kinetic Inductance Detectors (LEKID) and the implementation of dedicated readout techniques for the aforementioned activities

The Sudbury Neutrino Observatory (SNO), a heavy water Cherenkov experiment, was designed to detect solar Boron-8 neutrinos via their elastic scattering interactions on electrons, or charged current and neutral current (NC) interactions on deuterium. In the third phase of SNO, an array of Helium-3 proportional counters was deployed to detect neutrons produced in NC interactions. A simulation of the current pulses and energy spectra of the main kinds of ionization events inside these Neutral Current Detectors (NCDs) was developed. To achieve this, electron drift times in NCDs were evaluated with a Monte Carlo method, and constrained by using wire alpha activity inside the counters. The pulse calculation algorithm applies to any ionization event, and takes into account processes such as straggling, electron diffusion, and propagation through the NCD hardware. A space charge model was developed to fully explain the energy spectra of neutron and alpha events. Comparisons with data allowed the various classes of alpha backgrounds to be identified, and gave evidence for the spatial non-uniformity of Uranium-238 and Thorium-232 chain nuclei in the counter walls. The simulation was applied to determine the fractional contents of the main types of alpha backgrounds in each NCD string. The number of neutron capture events in the array was extracted via a statistical separation, using Monte Carlo generated alpha background pulse shape parameter distributions and minimal energy information. The inferred total Boron-8 solar neutrino flux is: φ_NC< = 5.74 ± 0.77 (stat) ± 0.39 (sys) x 10⁶ cm^-2s^-1 in agreement with Standard Solar predictions and previous SNO results.

Thesis (M.S. in Applied Physics)--Naval Postgraduate School, December 2009.
Thesis Advisor(s): Karunasiri, Gamani. Second Reader: Smith, Craig. "December 2009." Description based on title screen as viewed on January 28, 2010. Author(s) subject terms: Zinc Selenide, photodetectors, ultraviolet, Schottky, responsivity, current-voltage, depletion region, bandgap, melanoma, dark current, forward biased, reverse biased. Includes bibliographical references (p. 39-40). Also available in print.

Gravitational waves are a result of Einstein's theory of general relativity which postulates that these waves, created by asymmetrically accelerating masses, propagate through the Universe as ripples in the curvature of space-time at the speed of light. Gravitational waves have yet to be directly detected, however, there is sufficient indirect evidence of their existence through observations of inspiraling pulsars and white dwarfs. There is a worldwide network of interferometric detectors that are currently being, or have already been, upgraded to an advanced detector status. In order to get these detectors to a sensitivity high enough to stand a chance of detecting gravitational waves, researchers around the world have been developing innovative and novel technologies, and investigating high quality, low mechanical loss materials, to reduce the limiting noise sources of these instruments. One noise source that may become more conspicuous as gravitational wave detectors become more sensitive is noise due to the movement of electrical charges on the detector optics. Charge can be transferred to the detector optics through various processes such as; dust abrasion on the surface of the optics as the vacuum chamber is being pumped out, contact with nearby structures such as earthquake stops, cleaning of the optics and cosmic rays. In some instances the charge density transferred can be as high as 10^(-7) C/m^2 which would cause the sensitivity of advanced detectors to be significantly reduced at frequencies less than 100Hz. The work contained within this thesis investigates different methods of mitigating the effects of charging noise through the use of glow and corona discharges. It is shown that both of these methods successfully reduce surface charge on silica with an advanced LIGO style optical coating and that these methods do not cause damage to the optical coating within the sensitivity of the equipment. Investigations were carried out to see if the charge deposited on the detector optics during cleaning could be reduced by mixing carbon nano-tubes into the polymer based cleaning solution used to clean the advanced LIGO optics. It is shown that mixing carbon nano-tubes into the polymer cleaning solution does not reduce the amount of charge deposited on the optics. This thesis also presents experimental verification of the frequency dependence of charging noise. Using a torsion balance it was possible to measure charging noise directly and confirm that it does follow the Weiss theory of charging noise.

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Physics, 2007.
Includes bibliographical references (p. 213-225).
A detailed theoretical and experimental study of techniques necessary for quantum-enhanced laser- interferometric gravitational wave (GW) detectors was carried out. The basic theory of GWs and laser-interferometric GW detectors, quantum noise in GW detectors, the theory of squeezed states including generation, degradation, detection, and control of squeezed states using sub-threshold optical parametric oscillators (OPOs) and homodyne detectors, experimental characterization of these techniques (using periodically poled KTiOPO4 in an OPO at 1064 nm for the first time), key requirements for quantum-enhanced GW detectors, and the propagation of a squeezed state in a complex interferometer and its interaction with the interferometer field were studied. Finally, the experimental demonstration of quantum-enhancement in a prototype GW detector was performed. By injecting a squeezed vacuum field of 9.3 dB (inferred) or 7.4 ± 0.1 dB (measured) at frequencies above 3 kHz and a cutoff frequency for squeezing at 700 Hz into the antisymmetric port of the prototype GW detector in a signal-recycled Michelson interferometer configuration, the shot noise floor of the detector was reduced broadband from 7.0 x 10-7 m/viH- to 5.0 x 10-17 m/V/H while the strength of a simulated GW signal was retained, resulting in a 40% increase in signal-to-noise ratio or detector sensitivity, which is equivalent to a factor of 1.43 = 2.7 increase in GW detection rate for isotropically distributed GW sources that are confined to the frequency band in which squeezing was effective. This is the first implementation of quantum-enhancement in a prototype GW detector with suspended optics and readout and control schemes similar to those used in LIGO and Advanced LIGO. It is, therefore, a critical step toward implementation of quantum-enhancement in long baseline GW detectors.
by Keisuke Goda.
Ph.D.

Thesis: S.B., Massachusetts Institute of Technology, Department of Physics, 2020
In title on title page, "[Beta]" is the Greek letter. Cataloged from the official PDF of thesis.
Includes bibliographical references (pages 47-49).
In this thesis, we consider the [Beta]+/EC decay of 124Xe and take the first steps towards characterizing a hypothetical experiment to detect it, making use of techniques traditionally employed in neutrinoless double beta decay experiments. We use a simulated large-volume scintillation detector modeled on the Super-Kamiokande experiment, fully implementing this detector in RAT/Geant4. This allows us to extract authentic spectra for the experimental signature of the [Beta]+/EC decay in 124Xe, paving the way for future sensitivity studies. We also consider the relevance of next-generation techniques for background discrimination, specifically particle identification based on counting Cherenkov photons. We find that discrimination between [Beta] and [Beta] particles is readily possible in experiments run at the 1.25 MeV energy scale and also see evidence for the possibility of distinguishing between [Beta]+ and [Beta]- particles via their Cherenkov signatures
by Eleanor Graham.
S.B.
S.B. Massachusetts Institute of Technology, Department of Physics

Previous studies of modulation transfer function (MTF), noise power spectrum (NPS), and detective quantum efficiency (DQE) of metal-plate/film portal detectors have been performed on limited combinations of front and back metal-plates. We report on these parameters for an extensive set of forty-nine front-back metal-plate combinations. The portal detector consists of a double emulsion RP (Kodak localization therapy) film placed between metal-plates: Al, Cu, brass and Pb of thicknesses varying from 0.30 to 4.80 mm. Radiation sources included a Theratron Co-60 unit, and a Varian Clinac-18 linear accelerator delivering a polyenergetic 10 MV X-ray spectrum. In terms of the absolute efficiency of the detectors, the best DQE is obtained with the detector consisting of a 1.75 mm Cu front plate and a 1.62 mm Al back plate for the Clinac-18, and with the detector consisting of a 0.95 mm Cu front plate and a 0.80 mm Cu or a 1.62 mm Al back plate for the Co-60 gamma ray source.

This thesis is primarily concerned with the design of the type of metal detectors found on industrial production lines such as in the food industry. In paI1icuiar it concentrates on the analysis and design of their search coils. The analysis is restricted to continuous wave detectors, i.e. those which use a constantly alternating magnetic field. The alternative type, which employs a pulsed magnetic field, is mentioned for comparison purposes only. A broad introduction into the physics and technology of present day metal detectors is first presented. This includes some of the real life problems encountered in high sensitivity systems and discusses their various merits in overcoming these difficulties. This is followed by a mathematical analysis of some common coil aITangements hased around the simplified model of a metal sphere. Formulas are delived which predict the received signal strengths and a computer program is introduced which solves this mathematical model. From these, solutions are found for the optimum frequency. coil spacing and number of coil turns. Experimental results are then presented which confirm the theory insofar as the general relations between frequency, sphere size and signal strength. FUl1her experiment<.; also suggest ways in which present coil designs might be improved hy reducing the area around the detector that must be kept clear of metal. Finally, two new coil designs are suggested which are based on both the mathematical and experimental work. Useful extensions to the mathematical model are also suggested which would enable a closer approximation to a real detector set-up.