Дисертації з теми "SoLi∂ detector"

Cette thèse présente la recherche d'oscillations d'antineutrinos actifs vers des antineutrinos stériles avec le détecteur SoLi∂. Ce détecteur promeut un concept innovant basé sur un sandwich de plastiques scintillant formé de polyvinyle-toluène composite et de scintillateurs 6LiF:ZnS(Ag). Trois contributions principales à cette recherche sont rapportées dans ce document. La première concerne une nouvelle méthode de reconstruction basée sur l'algorithme ML-EM. Elle vise à transformer la réponse brute du détecteur en une liste de positions (avec des énergies dédiées) où l'interaction physique réelle dans le détecteur a eu lieu. La seconde concerne l'étalonnage en énergie du détecteur. Elle comprend à la fois l'étalonnage relatif au moyen de muons cosmiques horizontaux et l'exploration de plusieurs options pour la détermination de l'échelle d'énergie absolue. Enfin, la thèse présente une nouvelle méthode de sélection des candidats antineutrinos basée sur l'analyse de la partie électromagnétique du signal de désintégration bêta inverse et leur classement en fonction de la géométrie des événements dans le détecteur (topologies). L'analyse a été développée en aveugle et la méthode a été validée avec une petite fraction de l'échantillon de données
This thesis presents the search for active-to-sterile antineutrino oscillations with the SoLi∂ detector, which has an innovative concept based on a sandwich of composite polyvinyl-toluene and 6LiF:ZnS(Ag) scintillators. Three main contributions to this search are reported. The first one describes the new reconstruction method based on the ML-EM algorithm. It is aimed at transformation of the raw detector response to the list of positions (with dedicated energies) where actual physics interaction in the detector took place. The second one describes the energy calibration of the detector. It includes both relative calibration with the cosmic horizontal muons and exploration of several options for the absolute energy scale derivation. Finally, the thesis presents a novel method for selecting antineutrino candidates based on the analysis of the electromagnetic part of the inverse beta decay signal and categorising them according to the geometry of the events in the detector (topologies). The analysis was developed blindly and the method was validated with a small fraction of the data sample

Orientadores: Jacobus Willibrordus Swart, Pierre Kaufmann
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: O telescópio solar submilimétrico operando nas freqüências de 212 e 405 GHz detectou uma nova componente espectral das emissões de explosões solares, com máximo em algum ponto da faixa Terahertz, simultaneamente com a conhecida componente espectral em microondas, trazendo sérios desafios para interpretação. O diagnostico deste tipo de emissão transiente em freqüências THz traz desafios tecnológicos que são objetivo deste estudo. Este projeto consiste em um estudo das características de filtros e sensores não refrigerados para aplicação em projeto aeroespacial na faixa Terahertz do espectro eletromagnético. Foram estudados e caracterizados detectores bolométrico, piroeletrico, e optoacustico, precedidos por filtros passa-baixa que suprimem a radiação na faixa do visível e infravermelho próximo do espectro eletromagnético, filtros passa-banda centrados na freqüência THz desejada, e modulador mecânico. O detector a célula de Golay mostrou ser o mais sensível. Foi selecionado para o protótipo de fotômetro THz que serviu para definir parâmetros de projeto para o modelo de vôo, para observação solar fora da atmosfera terrestre, em balões estratosféricos, satélites, ou estações no solo com atmosfera excepcionalmente transparente. O sistema foi concebido para observar todo o disco solar e detectar pequenas variações relativas de temperatura causadas por explosões em regiões especifica do Sol. Obteve-se mínima detectabilidade de variações relativas de temperatura da ordem de 1 K com resolução temporal de subsegundo
Abstract: The solar submillimeter-wave telescope, operating at 212 and 405 GHz frequencies detected a new flare spectral component emission, peaking in the THz range, simultaneously with the well known microwaves component, bringing challenging constrains for interpretation. The diagnostics of this kind of transient emission at THz frequencies also bring technical challenges, which are the subject of this study. The project consists in a study of the characteristics of filters and uncooled detectors for aerospace project application at THz range of the electromagnetic spectrum. Three types of uncooled sensors were tested: bolometric, pyroelectric, and optoacoustic, proceeded by low-pass filters to suppress the visible and infrared radiation, band-pass filter centered at THz frequency, and a chopper. The Golay cell sensor was considered the most sensible detector of all, and was selected for the photometer prototype THz system to observe the Sun outside the terrestrial atmosphere on stratospheric balloons or satellites, or at exceptionally transparent ground stations. The system was designed to observe the whole solar disk detecting small relative changes in input temperature caused by flares at localized positions of the Sun. The minimum relative temperature variation detected was about 1 K with subsecond time resolution
Mestrado
Eletrônica, Microeletrônica e Optoeletrônica
Mestre em Engenharia Elétrica

The current and possible uses of semiconductor solid state detectors in nuclear physics are briefly discussed. The theory of solid state detectors is discussed with emphasis on the silicon PIN diode detector. A fabrication process for silicon surface barrier position sensitive solid state detectors has been developed at UBC based on the work of J.B.A. England. A fabrication process recipe is included. A prototype surface barrier detector system has been built and tested at UBC and TRIUMF using this process. The device has 1 mm position resolution in one direction, an active area of 40 mm in diameter and a mass thickness of 55 mg/cm². The measured efficiency for 50 MeV pions is 70% and expected rate capability is in excess if 1 MHz per strip. The detector efficiency is limited by a marginal signal-to-noise ratio.
Science, Faculty of
Physics and Astronomy, Department of
Graduate

Orientador: Elnatan Chagas Ferreira
Texto em inglês
Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação
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Resumo: A constante preocupação em aumentar a produtividade das plantações de uma forma sustentável e otimizando o uso dos insumos agrícolas (água, fertilizantes, pesticidas e produtos para correção do PH) levou ao desenvolvimento da agricultura de precisão, que permite determinar a quantidade correta de insumos para cada região do solo (tipicamente um hectare), evitando o desperdício. Sensores de umidade de solo de baixo custo e fácil aplicação no campo são fundamentais para permitir um controle preciso da atividade de irrigação, sendo que os sensores que melhor atendem estes requisitos são os chamados sensores de dissipação de calor ou sensores de transferência de calor. Estes sensores, entretanto, apresentam um problema de baixa sensibilidade na faixa de umidade mais importante para as plantas (umidade de solo 'teta'v variando entre 5% e 35%), pois, para cobrir esta variação de 30% em 'teta'v com resolução de 1%, é necessário medir variações de temperatura de aproximadamente 0,026 ºC nos sensores de pulso de calor a duas pontas e 0,05 ºC para os sensores de pulso de calor de ponta simples. Neste trabalho foi desenvolvido um novo sensor de umidade de solo do tipo pulso de calor de ponta simples, baseado em um único elemento: um transistor bipolar de junção npn, que é usado tanto como aquecedor e como sensor de temperatura de alta precisão. Resultados experimentais, obtidos em medidas realizadas através de uma técnica de interrogação especialmente desenvolvida para este novo sensor mostram que neste trabalho foi possível obter uma sensibilidade cerca de uma ordem de grandeza maior do que nos sensores de pulso de calor com uma ponta e cerca de 20 vezes maior do que nos sensores de pulso de calor de duas pontas. Outra vantagem da técnica desenvolvida é que o aumento da sensibilidade não é obtido às custas do aumento da corrente drenada da bateria para aquecer o sensor. No sensor desenvolvido é utilizada uma corrente de apenas 6 mA para gerar o aquecimento (com energia dissipada de 1,5 J), enquanto que que os sensores de pulso de calor com ponta simples requerem cerca de 50 mA (com 2,4 J de energia dissipada) para operar. Os sensores de pulso de calor de ponta dupla também são fabricados com resistores que requerem cerca de 50 mA para o aquecimento (0.8 J de energia dissipada) para operar corretamente
Abstract: The concern regarding sustainable development and crop inputs optimization (such as water, fertilizers, pesticides and soil PH correction products) has led to the development of the precision agriculture concept, that allows to determine the exact amount of each input required on each ground section (typically one hectare), avoiding waste of inputs. Low-cost and easily handled soil moisture sensors are very important for allowing a precise irrigation control. The class of sensors which fulfill those requirements are the heat transfer sensors, where there are basically two types of devices: dual (or multi) probe heat pulse sensors and single probe heat pulse sensors. However, these sensors have a low sensitivity in the most important range of soil humidity 'teta'v for plants (usually from 5% ? 'teta'v ? 35%). To cover this 30% soil humidity range with 1% resolution it is necessary to measure temperature with a resolution of 0,026 ºC in the dual/multi probe heat pulse sensors and 0,05 ºC in the single probe heat pulse sensor. In this work it was developed a new type of single probe heat pulse sensor, comprised of a single element: an npn junction bipolar transistor, that plays the role of both the heating element and a high accuracy temperature sensor. Experimental results, obtained through an interrogation technique especially developed for this sensor, show sensitivity about one order of magnitude greater than the typical sensitivity of the single probe heat pulse sensors and 20 times greater than dual probe heat pulse sensors. Another great advantage of the developed interrogation technique is that the increase in sensibility is not obtained through a higher current being drained from the batteries that power the sensor. The developed sensor operates at a much lower current level than the other sensors, draining only 6 mA from the battery (with an energy of 150 mW). The single probe heat pulse sensor requires 50 mA and 1.5 J of energy to operate, whilst the dual probe heat pulse sensors are manufactured with resistors which also drain 50 mA from the battery with 0.8 J of dissipated energy
Mestrado
Eletrônica, Microeletrônica e Optoeletrônica
Mestre em Engenharia Elétrica

In this work novel solid-state neutron detectors based on Gallium Nitride (GaN) have been produced and characterized. GaN is a radiation hard semiconductor which is commonly used in commercial optoelectronic devices. The important design consideration for producing GaN-based neutron detectors have been examined, and device simulations performed. Scintillators and p-i-n diode-type neutron detectors have been grown by metalorganic chemical vapor deposition (MOCVD) and characterized. GaN was found to be intrinsically neutron sensitive through the Nitrogen-14 (n, p) reaction. Neutron conversion layers which produce secondary ionizing radiation were also produced and evaluated. GaN scintillator response was found to scale highly linearly with nuclear reactor power, indicating that GaN-based detectors are suitable for use in the nuclear power industry. This work is the first demonstration of using GaN for neutron detection. This is a novel application for a mature semiconductor material. The results presented here provide a proof-of-concept for solid-state GaN-based neutron detectors which offer many potential advantages over the current state-of-the-art, including lower cost, lower power operation, and mechanical robustness. At present Helium-3 proportional counters are the preferred technology for neutron detection, however this isotope is extremely rare, and there is a global shortage. Meanwhile demand for neutron detectors from the nuclear power, particle physics, and homeland security sectors requires development of novel neutron detectors which are which are functional, cost-effective, and deployable.

The purpose of this research is to determine the feasibility of creating an affordable and durable neutron detector for usage in the field surveys, site inspections, and transportation hub monitoring. Currently, organic scintillating detectors are an established method of detecting neutrons but are either costly, fragile solids like stilbene, or flammable liquids like benzene. In this work, several scintillation mixtures were tested with a PuBe source, which emits both neutrons and gamma rays. The pulse shape discrimination method was utilized to separate the signal pulses created from the mixed radiation field of the PuBe source. Two candidate mixtures were selected for solidification with elastomers for their verified neutron detection capabilities. The solid detectors measured high energy neutrons and gamma rays from the PuBe source. The solidified detectors have a Figure of Merit for separating neutrons of 0.859 ±0.419 and cost $0.13 per gram, while commercially available stilbene separates neutrons from gammas with a Figure of Merit of 4.70 and costs $64.36 per gram. This research shows that it is feasible to create affordable solid organic scintillators sensitive to high energy neutrons.

A exposição da população em geral à radiação ionizante surge principalmente a partir de fontes naturais. A principal contribuição é decorrente da inalação do radônio (Rn-222), um gás que ocorre naturalmente (UNSCEAR, 2000). A concentração de Rn-222 num ambiente é controlada por fatores como a permeabilidade do solo e teor de água, a variabilidade meteorológica, características de construção da fundação e da pressão diferencial positivo habitual entre o solo e o ambiente interno. Estudos indicam que a concentração de radônio, apresenta uma variação significativa no subsolo, térreo e andares superiores das edificações. O objetivo deste estudo é determinar os níveis de radônio, nos subsolos, térreos e andares acima do nível do solo, em uma universidade na cidade de São Paulo e um edifício residencial na cidade de Peruíbe. As medidas de Rn-222 foram realizadas através do método passivo com detectores de traços nucleares de estado sólido (CR-39). Os ambientes estudados apresentam concentrações de Rn-222 bastante inferiores aos valores recomendados pela Comissão Internacional de Proteção Radiológica, publicados no documento de 2009, de 300 Bq/m3 para residências e 1000 Bq/m3 para locais de trabalho. No edifício residencial na cidade de Peruíbe, analisaram-se ainda, as concentrações de Ra-266, Th-232 e K-40 em materiais de construção utilizados na construção do edifício, por meio de espectrometria gama. A dose efetiva total para o morador devido à exposição externa foi de 0,8 mSv a-1, inferior ao limite de dose anual para público em geral de 1 mSv a-1.
Exposure of the general population to ionizing radiation comes mainly from natural sources. The main contribution is due to inhalation of radon (Rn-222), a gas that occurs naturally (UNSCEAR, 2000). The Rn-222 concentration in the environment is controlled by factors such as soil permeability and water content, the weather variability, materials used in the foundation and the usual positive pressure differential between the soil and the internal environment. Studies indicate that the concentration of radon shows a wide variation in the basement, ground floor and upper floors of buildings. The objective of this study is to determine radon levels in basements, ground floor and floors above ground level, at a university in the city of São Paulo and in one residential building in the city of Peruíbe. Rn-222 measurements were performed using the method with nuclear track of solid state detectors (CR-39). The studied environments present Rn-222 concentration well below the values recommended by the International Commission on Radiological Protection, published in the 2009 document, of 300 Bq/m3 for homes and 1000 Bq/m3 for the workplace. In the residential building, the concentration of Ra-266, Th-232 and K-40 in the materials used in the building construction was also analyzed, by gamma spectrometry. The effective total dose for the resident due to external exposure was 0.8 mSv y-1, lower than the annual dose limit for the general public of 1 mSv y-1.

Mass spectrometry has long been used as a scientific tool in a wide variety of applications. A portable mass spectrometer would make many of these applications faster and more efficient. One of the key components of a mass spectrometer is its ion detection system; to make a mass spectrometer portable, this system must be small and involve as few components as possible. Single ion detection has been achieved through several methods, nearly all of which are well-known and understood. These methods, however, often require bulky vacuum and/or cooling systems in order to achieve high sensitivity. An ion detection system that can achieve high sensitivity under atmospheric pressure and normal temperature conditions would make portable mass spectrometry much more feasible. This thesis introduces a new method of detecting ions which does not require a vacuum or cold temperatures to operate: the solid-state ion detector, or SSID. Although ion detection using solid-state devices has been investigated previously, this work introduces metal-oxide-semiconductor field-effect transistors (MOSFETs) in a cascode configuration which acts as the primary detector when combined with a Faraday cup and mechanical switch. This detector is followed by a second amplifying stage which features RC-filters to help reduce noise and improve the detector's overall sensitivity. The detector is placed on a printed circuit board that was designed to fit a pre-determined system. Additional power circuitry for the mechanical switch was also designed and added to the detector circuitry. The SSID will be most sensitive when the input capacitance is made as small as possible. With this in mind, MOSFETs with a very low (< 1pF) gate capacitance were fabricated at BYU for use in the SSID. The performance of these MOSFETs was compared to a commercially available device in the same configuration. When tested, both MOSFETs had a sensitivity of hundreds of electrons when integrated in the complete SSID circuit. The commercial MOSFET demonstrated an estimated sensitivity of 150 electrons. The SSID shows much promise, and suggestions are made for further improving it to achieve even higher sensitivity levels. If made more sensitive, the next step would be to create an array of SSID detectors to be used in a portable mass spectrometer.

Thesis (M.S.)--Michigan State University. Dept. of Biosystems and Agricultural Engineering, 2008.
Title from PDF t.p. (viewed on Aug. 10, 2009) Includes bibliographical references (p. 90-92). Also issued in print.

Cette thèse présente de nouveaux développements en détection de particules chargées et traitement tout-numérique d'impulsions pour application à l'analyse avec des faisceaux d'ions rapides (IBA). Un ensemble de 16 détecteurs gravés sur une puce de Si est mis en œuvre, ce qui fournit un angle solide de détection environ 100 fois plus grande que celle des détecteurs utilisés auparavant pour l'IBA. Seize chaines d'acquisition sont également mises en œuvre avec une approche 'tout-numérique' pour le traitement des signaux issus des détecteurs. Dans son ensemble, le système ainsi développé a une résolution en énergie équivalent à celle des détecteurs standards. La considérable quantité d'information ainsi générée est traitée de manière cohérente en ajustant des spectres en énergie simulé aux spectres mesurés grâce à un algorithme de recuit simulé, avec le NDF DataFurnace. Les grandes angles solides disponibles sont exploitées pour des études par rétrodiffusion de Rutherford (RBS) et canalisation d'ions de l'isolant topologique Bi2Se3 enrichi en fer en vue d'études de l'effet thermoélectrique, de spintronique ou encore la computation quantique, ainsi que pour des études par RBS et analyse par réactions nucléaires (NRA) de matériaux pour la photovoltaïque organique, basés sur tetraphenyldibenzoperiflanthene (DBP) comme photo-absorbant avec oxydes de métaux de transition pour injection de charge
This thesis presents new developments in charged particle detection and digital pulse processing for application in analysis with fast ion beams - Ion Beam Analysis (IBA). In particular a charged particle detector array, consisting of 16 independent charged particle detectors on a single silicon chip is implemented giving an overall solid angle of detection around two orders of magnitude greater than the standard charged particle detectors used in IBA. Sixteen parallel data acquisition channels are implemented using a fully digital approach for nuclear pulse processing. The overall system has an energy resolution equivalent to that of standard detectors. The large amount of data generated is handled in a self-consistent way by spectrum fitting with a simulated annealing algorithm via the NDF DataFurnace. The large solid angles thus achieved are exploited in Rutherford Backscattering Spectrometry (RBS) and ion channelling studies of the topological insulator Bi2Se3 enriched in Fe, in view of studies of the thermo-electric effect, spintronics and quantum computing, and in RBS and Nuclear Reaction Analysis (NRA) studies of organic photovoltaic materials based on tetraphenyldibenzoperiflanthene (DBP) as the photo-absorber and transition metal oxide charge injectors

This work investigates advanced single-electron transistor (SET) devices for detection of charge motion in solid-state systems. In particular, novel, nanoscale twin-SET and double-island SET (DISET) detectors are introduced as sensitive charge detectors. Some advantages over conventional SET detectors in terms of noise performance, sensitivity and versatility are pointed out. With the prospect of present, transistor-based microelectronics facing serious limitations due to quantum effects and heat dissipation, alternative computing paradigms ??? such as quantum computers, quantum-dot cellular automata and single-electronics ??? have emerged, promising an extension of highlevel integration and computing power beyond the above limitations. The most promising proposals are based on solid-state systems, and readout of a computational result often requires ultra-sensitive charge detectors capable of sensing the motion of single charges on fast timescales. SETs have been shown to combine all these qualities. However, random fluctuations of the background charge in solid-state systems can affect SETs and cause errors during readout. A twin-SET detector is presented that consists of two independent SETs, which were used to detect controlled single electron transfers on a small, floating metal double-dot. By cross-correlating the two SET signals, rejection of random charge noise is successfully demonstrated, thus decreasing the error probability during readout. Detection of single-electron transfer in a double-dot is also demonstrated using a double-island SET. In addition, conductance suppression in this novel DISET detector allows the detection of electrostatically degenerate charge con- figurations of a double-dot, which cannot be achieved with single-island SETs. We consider the noise performance of the DISET, and an intuitive definition of the DISET charge sensitivity suggests that under certain conditions, DISETs can have a better charge sensitivity than conventional SETs, which would be attractive for quantum limited measurements. Finally we present the first study of a DISET operated at radio-frequencies (rf-DISET), compatible with charge detection on ms timescales. This capability is a prerequisite when reading out the charge state of quantum mechanical systems. A very good charge sensitivity (5.6 x 10i6 e/pHz) and noise temperature (2.1 K) of the rf-DISET setup are reported.

Future spectroscopic observational programmes at Mount John University Observatory require the ability to acquire spectra with significantly higher spectrophotometric accuracy and geometrical stability than can currently be achieved. Therefore a solid-state linear-diode-array image detector system has been designed and developed for use with the MJUO échelle spectrograph. A review of those electromechanical design techniques of significance to astronomical instrumentation is presented. Their application is exemplified with a complete electromechanical design for the detector, which is found to allow each electronic sub-system implemented within that design to achieve its theoretical level of performance. The requirements for the video processing electronics of a solid-state image detector are explicitly developed, and are used to design the electronics for this detector. Subtle sources of electronic instability which can appear as noise or base-line shifts are identified and controlled in this design. In particular, differential non-linearity is identified in an existing preamplifier design, and so an alternative design is implemented. The readout noise of the entire detector system is measured to be 200 e-/h pairs for a noiseless signal source of zero impedance to ground. This increases to 350 e-/h pairs when the impedance of this source is equal to that of the diode array, due to an additional noise contribution of 290 e-/h pairs. The net readout noise with the RL936F/30 diode array is 450 e-/h pairs, which is the quadratic sum of the detector system noise with the two 210 e-/h pair samples of diode capacitance thermodynamic noise. Thus the diode array is not found to contribute any noise in excess of its theoretical thermodynamic noise. A temperature controller is developed for use with sensors which are cooled in cryogenic dewars. A short term control precision of 1.6 mK r.m.s. is achieved which is entirely due to the theoretical noise of the temperature sensor. The long term precision over all operating conditions is ±20 mK, which is dependent on the design of the dewar. The hardware and software which provide interactive instrument control and data reduction are described. In particular, they provide for flexible control of the detector sub-systems during data acquisition and testing, and enable a high level of data reduction to be undertaken while the detector is integrating. An observational programme has been carried out with this detector sys tern on the southern RS CVn sys tern HR4492. Radial velocity measurements with a precision of ±0.5 km s-¹ have enabled a new ephemeris for the binary motion to be determined, namely HJD = 2446317.5 ± 21.82E. It is used to interpret Hα line profile variations in terms of probable mass transfer within the system.

X-ray fluorescence from thin foils inserted into the NPS linac have been used to measure the the integrated electron beam current only. The measured x-ray flux and the known inner shell ionization cross sections are used to obtain measurements of dark currents of the order of ten to the minus fourteenth amperes. The same arrangement allows continuous, in-situ energy calibration of our Si(Li) detector in the electromagnetic noise environment of the linac. This technique was originally developed to perform absolute production efficiency measurements of parametric x-ray generation in the 5-60 KeV range

This dissertation research has focused on the design of two spectroscopic instruments that operate outside of the UV/visible region for the analysis of volatile organic hydrocarbons and hard-to-separate hydrocarbon mixtures. The first design was solid state near infrared spectrometer. The fast acquisition rate of the NIR spectrometer allowed the monitoring of the bromination of 1-hexene. The concentrations of 1-hexene and 1,2-dibromohexane were determined for the reaction using classical least squares. The root mean squared errors of prediction for 1-hexene and 1,2-dibromohexane concentrations were 0.01 and 0.003 M, respectively. This research project also focused on the investigation of the effects of instrumental parameters on partial least squares models by comparing the results obtained from four different spectrometers. The results indicate that instrumental parameters, such as resolution and wavelength coverage, have a larger effect on experimental results than the analysis method (NIR or Raman). The second instrument design investigated here was a vacuum ultraviolet ICP-AES which monitored the 130 to 200 nm wavelength range. Fifteen nonmetals were used to determine the quantitative characteristics of the design. All elements demonstrated detection limits in the ppb range. The most sensitive emission line in this work was the aluminum 167.079 nm line which had a detection limit of 200 ppt. A VUV atomic emission line database was developed to provide an analytical reference for future investigations. The database included the emission lines from 76 elements over the 130 to 195 nm wavelength region. Over 2200 lines were observed and reported. Over 1000 of the lines were previously unreported in the two major existing references for the VUV. This work is the first VUV reference to provide truly comparable intensities for a large number of elements. A GC-VUV-ICP-AES was developed to investigate the potential of VUV-ICP atomic emission spectroscopy to provide both quantitative and qualitative information for mixtures. Chlorine and carbon chromatograms were obtained simultaneously for volatile organic hydrocarbon (VOC) mixtures. The work showed that GC-VUV-ICP-AES has the potential of generating empirical formulas for compounds by simultaneously quantitating each element in the compound and determining their ratios.

The natural ²
³
⁸U, ²
³
²
Th and ⁴°
K radioactive content of vineyard soil was measured with an in-situ gamma-ray detector. The activity concentration measured with the in-situ detector are normalized using the laboratory-determined activity concentrations of several samples from the vineyard site. To determine the activity concentration of a particular soil sample, the gamma-ray photopeak detection efficiencies are required. In this work, the detection efficiencies were derived for each soil sample using gamma-ray photopeaks associated with the radionuclide of ²
³
⁸U, ²
³
²
Th present in the sample, and the ⁴°
K, 1460.8 keV gamma-ray peak, from KCl salt.

Electrochemical biosensors have long been used for measuring pH changes in complex biological samples. This research work involves investigating iridium sensors as a potential tool for detecting viral RNA by means of pH sensing during transcription mediated amplification (TMA). The iridium oxide film was formed on gold wire by electrochemical deposition. When complementary DNA/RNA bases are hybridized, they release a pyrophosphate molecule which is eventually hydrolyzed, contributing to the pH change during the TMA reaction which in turn is measured in voltage (mV) by the iridium sensor. Firstly a standard method for bacteriophage MS2 RNA amplification method was established. A Real Time PCR assay for MS2 RNA using TaqMan probe chemistry was used to quantify the MS2 RNA and used as a gold standard for later project. We then used transcription mediated amplification (TMA) technique using reverse transcriptase and RNA polymerase enzymes for producing MS2 RNA amplicons and resulting protons generated during amplification were measured with iridium sensors. The iridium oxide sensor showed linear pH potential response and showed a near ideal Nernstian behaviour in the pH range 2 – 12 with a slope of -60mV/pH. Since TMA is an isothermal amplification technique the iridium sensors produced reproducible and reliable measurements. To increase the cation selective permeability and inhibit possible interferences the iridium oxide sensor was coated with 5% Nafion. The sensor showed the same linearity in voltage response against RNA concentrations in protein enriched samples (20 mg/ml albumin) compare to RNA in water. The iridium oxide sensor was a rapid method of viral RNA detection as the detection time for MS2 RNA was 10 minutes. The lower limit of detection of the iridium sensor was 5ng of MS2 RNA which was comparable to the established real time PCR sensitivity. To further enhance the sensor’s the sensitivity the iridium oxide sensor was prepared on a 3 mm × 3 mm glass slide which increased the slope for 5 ng of MS2 RNA from 3.25mV/min to 4.07mV/min resulting in an improved limit of detection.

An image processing technique was applied to detect roddon soil features from UK-DMC2 base data. Roddon soil features represent former watercourses in English Fenland, now raised banks with altered soil composition. They can be clearly seen on remotely sensed imagery as bright features in contrast to the darker surrounding peat land. Based on difference in brightness of roddons and surrounding peat soil the Soil Brightness Index (SBI) was applied to detect the roddons. To identify the edges of these features where there is a large spectral contrast a non-directional filter was applied together with an image enhancing technique to better differentiate the roddons form other non-soil features. Understanding the location of roddons will allow adaptive farming practices that account for differences in soil properties, and help optimizing yields.

Desde el descubrimiento de los rayos X en 1895 y su primera aplicación médica un año después, se han desarrollado diferentes técnicas de imagen médica. La tomografía por emisión es una rama de las imágenes médicas que permite a los médicos realizar un seguimiento de los procesos fisiológicos en el paciente. Un compuesto radiactivo llamado radiotrazador se inyecta en el cuerpo del paciente. La molécula radiotrazador se elige para cumplir una tarea específica en el organismo que permite el seguimiento de un proceso fisiológico concreto. Los dos principales de técnicas de tomografía por emisión son PET y SPECT. En PET (Tomografía por Emisión de Positrones) el radiotrazador inyectado es un emisor de positrones. El positrón emitido se aniquila con un electrón produciendo un par de fotones gamma emitidos “back -to-back”. El escáner PET (por lo general de forma cilíndrica) detecta estos pares de fotones y reconstruye una imagen de la concentración del radiotrazador en el organismo. En SPECT (Tomografía Computarizada por Emisión Simple de Fotones) un solo fotón gammas es emitido en cada desintegración radiactiva del compuesto. El sistema de SPECT consiste en (al menos) una cámara gamma. Una cámara gamma está compuesta por un colimador mecánico y un fotodetector capaz de registrar la posición de la interacción. El colimador mecánico esta compuesto por un material denso con aperturas que sólo permite el paso de los fotones procedentes de una dirección particular. Los fotones colimados son detectados por el detector obteniendo una proyección del radiotrazador en el volumen del cuerpo del paciente. A partir de estas proyecciones se obtiene una imagen tomografía de la concentración del radiotrazador- SPECT es la técnica de tomografía de emisión más ampliamente utilizado debido a la gran variedad de radiotrazadores disponibles, y el bajo coste en comparación con PET. Sin embargo, SPECT tiene limitaciones intrínsecas debido a la colimación mecánica: baja eficiencia ya que sólo una fracción de los fotones gamma puede pasar a través del colimador, una relación proporcional inversa entre la eficiencia y la resolución de la imagen ( A mayor tamaño de las aperturas del colimador mayor será la eficiencia pero la resolución de la imagen empeorara) , y la cámara debe girar aumentando el tiempo de exposición . El concepto de cámara Compton fue concebido con el fin de superar estas limitaciones. Una cámara de Compton consta de dos detectores, llamados “scatterer” y “absorber”, trabajando en coincidencia. En un evento de coincidencia el fotón gamma (emitido por el radiotrazador) alcanza el “scatterer” y cambia de dirección como consecuencia de una interacción Compton. La gamma dispersada alcanza el “absorber" donde es absorbida en una interacción fotoeléctrica. Con la posición de ambas interacciones y las correspondientes energías, se puede reconstruir la superficie de un cono que contiene el punto desde donde el fotón gamma fue emitido. Con los conos reconstruidos a partir de varias coincidencias, es posible reconstruir una imagen de la actividad en el cuerpo del paciente. La cámara Compton tiene el potencial de superar todas las limitaciones intrínsecas de los SPECT ya que: cada gamma tiene una probabilidad de ser dispersado y producir una coincidencia, la resolución de la imagen no está vinculada a la eficiencia, y es posible obtener imágenes tridimensionales sin mover la cámara. Sin embargo, la complejidad de la reconstrucción de la imagen y los límites en la tecnología de detectores, han impedido que el concepto de cámara Compton se convertirse en un sistema de imagen médica viable. El proyecto VIP (“Voxel Imaging PET”) propone un diseño de detector de estado sólido (CdTe) con tecnología pixel para superar las limitaciones de los detectores basados en cristales de centelleo utilizados en PET. VIP cuenta con un diseño modular en el que el elemento básico es el modulo de detección. El módulo contiene los detectores de estado sólido que están segmentados en “voxels” de tamaño milimétrico. Gracias a un chip de lectura desarrollado en el proyecto, cada uno de los “voxels” del detector constituye un canal independiente para la medición de la energía, posición, y el tiempo de llegada de los fotones gamma detectados. Los módulos son apilados con el fin de formar los sectores de PET. Poner varios de estos sectores juntos, permite construir un anillo PET. Aunque el módulo VIP ha sido diseñado para el PET, la flexibilidad del diseño del módulo permite explorar otras posibles aplicaciones, como PEM (Mamografía por Emisión de positrones) y la cámara de Compton. En esta tesis se evaluará una cámara de Compton basado en el concepto detector VIP. Los detectores “scatterer” y “absorber” están compuestos de módulos de detección especial diseñados. Los módulos son apilados para crear los detectores. En el “scatterer” se utiliza Silicio como material activo a fin de maximizar la probabilidad de interacción Compton de los fotones. En el “absorber”, CdTe se utiliza como material activo con el fin de detener los fotones gamma que salen del “scatterer”. La excelente resolución en la energía de los detectores de estado sólido combinado con el tamaño milimétrico de los “voxels”, permiten obtener una alta precisión en la reconstrucción de los conos Compton que no se puede lograr con cristales de centelleo. En esta tesis vamos a utilizar simulaciones de Monte Carlo para evaluar y optimizar el diseño de la cámara Compton. Se utilizarán dos algoritmos de reconstrucción de imagen diferentes. La simulación nos permitirá obtener los parámetros geométricos óptimos, así como el rendimiento esperado de la cámara de Compton en términos de eficiencia en la detección y de resolución de la imagen. Se ha evaluado también un prototipo con menor campo de visión.
Since the discovery of the X-rays in 1895 and their first medical application one year later, many different medical imaging techniques have been developed. Emission tomography is a branch of medical imaging that allows the doctors to track physiological processes in the patient. A radioactive compound called radiotracer is injected in the body of the patient. The radiotracer molecule is chosen to fulfill an specific task in the organism allowing to track a concrete physiological process. The two main emission tomography techniques are PET and SPECT. In PET (Positron Emission Tomography) the injected radiotracer is a positron emitter. The emitted positron annihilates with an electron producing a pair of back-to-back gamma photons. The PET scanner (usually having a cylindrical shape) detects these photons pairs and reconstructs an image of the radiotracer concentration. In SPECT (Single Photon Emission Computerized Tomography) a single gamma photon is emitted in each radioactive decay of the radiotracer compound. The SPECT system consists of (at least) one gamma camera. A gamma camera is composed by a mechanical collimator and a position sensitive photodetector. The mechanical collimator consists of a thick material with holes that only allow the passing of photons coming from a particular direction. The collimated photons are detected by the photodetector obtaining a projection of the radiotracer in the volume of the patient body. A three dimensional image of the radiotracer concentration in the patient body is obtained from the projections obtained in several directions. SPECT is the most widely used emission tomography technique because of the large variety of available radiotracers, and the relative low cost when compared with PET. However, SPECT has intrinsic limitations due to the mechanical collimation: low efficiency as only a fraction of the gamma photons can pass through the collimator, an inverse proportional relationship between the efficiency and the image resolution (the bigger the collimator holes the higher the efficiency but the lower the image resolution), and the camera must be rotated increasing exposure time. The concept of Compton camera has been proposed in order to overcome those limitations. A Compton camera consists of two detectors, called scatterer and absorber, working in coincidence. In a coincidence event the gamma photon (emitted by the radiotracer) reaches the scatterer and undergoes a Compton interaction, scattering into a certain angle. The scattered gamma reaches the absorber where it undergoes a photoelectric interaction and is absorbed. Using the positions of both interactions and the corresponding deposited energies, one can reconstruct a cone surface which contains the emission point of the gamma photon. With the cones reconstructed from several coincidences, an image of the activity in the patient body can be obtained. The Compton camera has the potential to overcome all the intrinsic limitations of SPECT as: each gamma has a probability to be scattered and produce a coincidence event, the image resolution is not tied to the efficiency, and it is possible to obtain three dimensional images without moving the camera. However, the complexity of the image reconstruction and the limits in the detector technology has prevented the Compton camera concept to become a viable medical imaging system. The VIP (Voxel Imaging PET) project proposes a novel detector design based on pixelated solid state (CdTe) technology to overcome the limitations of scintillator detectors used in PET. VIP features a modular design in which the basic element is the detector module unit. The module contains the solid state detectors which are segmented in millimeter size voxels. Thanks to a dedicated read-out chip developed within the project, each one of the voxels is an independent channel for the measurement of energy, position, and time of arrival of the detected gamma photons. The module detectors are stacked in order to form PET sectors. Putting several of these sectors together leads to a seamless PET ring. Although the VIP module has been designed for PET, the flexibility of the module design allows to explore other possible applications like PEM (Positron Emission Mammography) and Compton camera. In this thesis we will evaluate a Compton camera based on the VIP detector concept. The scattering and the absorber detectors will be made from the stacking of specially designed module units. Silicon will be used as detector material in the scatterer in order to maximize the Compton interaction probability for the incoming gamma photons. In the absorber, CdTe will be used as detector material in order to stop the gamma photons emerging from the scatterer. The excellent energy resolution of the solid state detectors combined with the millimeter size of the detector voxels, result in a high accuracy in the reconstruction of the Compton cones that cannot be achieved with scintillator crystals. In this thesis we will use Monte Carlo simulations in order to evaluate and model the proposed Compton camera. Two different image reconstruction algorithms will be used. The simulation will allow us to obtain the optimal geometrical parameters as well as the expected performance of the Compton camera in terms of detection efficiency and image resolution. A smaller FOV (Field-Of-View) prototype will be also evaluated.

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.

Current detection of pathogenic organisms in water relies on the use of indicators (turbidity, Escherichia coli, total coliforms, fecal coliforms etc.) or time consuming assays that can only be done in a specialized laboratory. In this research a simple assay was developed for rapid and sensitive recovery and identification of waterborne pathogens from environmental samples. The assay developed involves capturing target pathogens onto an activated capture surface, exposing the capture surface to antibody conjugated micro-retroreflectors, and then inserting the capture surface into an inexpensive, simple reader to detect the retroreflection signal to confirm the presence of target pathogens. Antibody (capture molecule: IgG and IgM) fragments specific to Cryptosporidium, as a model waterborne pathogen, were produced and immobilized site specifically and randomly onto gold-coated surfaces as well as corner cube micro-retroreflectors (ccμRR). A shear test performed to determine the critical shear stress that antigen-antibody bonds are able to endure showed that the organism-antibody bond could resist up to a shear stress of 126 dyne/cm2 and beyond this critical value immobilized Cryptosporidium oocysts were lost from the system. Capture tests were designed to determine the optimum operating conditions of the parallel flow sampling device using IgG-Fab', IgG-Fab, and IgM-Fab' activated surfaces. Capture efficiencies did not differ significantly within the range of flow rate used (14 – 42 mL/min), but improvement was noticed when the cell depth was decreased from 250 μm to 125 μm. Site specifically oriented IgG-Fab' activated surfaces resulted in significantly better capture efficiencies than surface with randomly immobilized IgG-Fab fragments. The capture efficiency of IgG-Fab' activated surfaces was significantly different than that of IgM-Fab' immobilized surfaces. There was no significant difference in capture efficiency using the surfaces activated with dilutions (1:8, 1:4, 1:2, and 1:1.5) of antibody fragments originally made of 500μg of IgG1 antibody. The use of BSA as a blocking agent improved the reproducibility of the capture efficiency. CcμRR were suspended in solution and activated with IgG-Fab' to use as a recognition molecule. The current set up of the detector system is capable of detecting the presence and absence of a large number of ccμRR attached on the solid surface.

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2016.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 187-192).
Rural Indian farmers lack an available, affordable, usable, and actionable means to diagnose soil health, which is a prerequisite for judicious application of fertilizer. Although government labs and mobile kits are available, these fail to meet the aforementioned qualities; as a result fewer than 5% of rural Indian farmers have ever performed a soil test. This thesis details the design and characterization of a point-of- use soil testing device, comprising a set of disposable ion-selective electrode (ISE) strips and a handheld electrochemical reader, which together transduce soil analyte concentrations into a numeric input for a mobile-phone based fertilizer recommendation engine. As a proof-of-concept, potassium (K+) selective electrodes are studied, because K+ is essential to plant growth and reproduction. The strips employ a simple two electrode system, wherein carbon nanotube and silver chloride inks are the electrode contacts, plasticizer-free butyl acrylate ion selective membranes are located on the working electrodes, and sodium-chloride doped polyvinyl butyral membranes provide stable reference potentials. The electrodes were fabricated by a combined screen printing and drop casting process, and the protocol, extraction solution, and reference potential stability were tuned to maximize ISE performance and repeatability. Using a mathematical model and supporting experiments, we verified that hydrogen selectivity determines the detection limit, and furthermore, that scientists can tune the ionophore-ionic site ratio to minimize this effect. Using the final electrode fabrication process, a set of 20 full ISE devices in the presence of 0.02M SrCl2 extraction solution were shown to have sub-uM detection limits and near-Nernstian average sensitivity (61 mV/decade). When compared to ICP data for a set of 30 soil samples using the final reader, the sensors demonstrated a 0.898 correlation factor. Workshops in India were conducted to determine user needs and corresponding product attributes, as well as a "usability index" for the system assessed across farmer demographics. The favorable system performance proves that solid-state ISEs are a promising technology for soil diagnostics in resource-constrained environments.
by Ron Rosenberg.
S.M.

Energy calibration of CdTe detectors is usually done using known reference sources disregarding the exact amount of charge that is collected in the pixels. However, to compare detector and detector model the quantity of charge collected is needed. We characterize the charge collection in a CdTe detector comparing test pulses, measured data and an improved TCAD simulation model [1]. The 1 mm thick detector is bump-bonded to a TIMEPIX chip and operating in Time-over-Threshold (ToT) mode. The resistivity in the simulation was adjusted to match the detector properties setting a deep intrinsic donor level [2]. This way it is possible to adjust properties like trap concentration, electron/hole lifetime and mobility in the simulation characterizing the detector close to measured data cite [3].

The diploma thesis is focused on the determination of tetracyclines, sulfonamides and fluoroquinolones from soil. Antibiotics such as tetracycline, chlortetracycline, oxytetracycline. ciprofloxacin, trimethoprim, sulfamethaxazole and sulfadiazin were selected due to frequent use in veterinary medicine. Due to the fact that the soil is a complex matrix and contains many components that can interfere with the detection signal of analytes, it was necessary to use the MAX column in the SPE method, which removes fulvic aned humic acid from analytes and the HLB column Final analysis of the analytes was performed by liquid chromatography with mass detesction (LC-MS). The method was also used for real soil samples, which were delivered from ÚKZUS.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Physics, 2004.
Includes bibliographical references (p. 69-71).
A high-power, low noise photo-detector, in conjunction with a current shunt actuator has been used in an AC-coupled servo to stabilize the intensity of a 10 Watt continuous-wave Nd:YAG laser. A relative intensity noise of 1 x 10⁻⁸ [square root] Hz at 10 Hz has been achieved.
by Jameson Graef Rollins.
S.M.

Doctor of Philosophy
Department of Chemistry
Stefan H. Bossmann
Cancer is a group of diseases that are characterized by uncontrolled growth and spread of cells. In order to treat cancer successfully, it is important to diagnose cancers in their early stages, because survival often depends on the stage of cancer detection. For that purpose, highly sensitive and selective methods must be developed, taking advantage of suitable biomarkers. The expression levels of proteases differ from one cancer type to the other, because different cancers arise from different cell types. According to the literature, there are significant differences between the protease expression levels of cancer patients and healthy people, because solid tumors rely on proteases for survival, angiogenesis and metastasis. Development of fluorescence-based nanobiosensors for the early detection of pancreatic cancer and non-small-cell lung cancer is discussed in this thesis. The nanobiosensors are capable of detecting protease/arginase activities in serum samples over a broad range. The functionality of the nanobiosensor is based on Förster resonance energy transfer and surface energy transfer mechanisms. The nanobiosensors for protease detection feature dopamine-coated Fe/Fe₃O₄ nanoparticles, consensus (cleavage) peptide sequences, meso-tetra(4-carboxyphenyl)porphine (TCPP), and cyanine 5.5. The consensus peptide sequences were synthesized by solid-supported peptide synthesis. In this thesis, improved consensus sequences were used, which permit faster synthesis and higher signal intensities. TCPP, which is the fluorophore of the nanoplatform, was connected to the N-terminal end of the oligopeptides while it was still on the resin. After the addition of TCPP, the TCPP-oligopeptide was cleaved off the resin and linked to the primary amine groups of Fe/Fe₃O₄-bound via a stable amide bond. In the presence of a particular protease, the consensus sequences attached to the nanoparticle can be cleaved and release TCPP to the aqueous medium. Upon releasing the dye, the emission intensity increases significantly and can be detected by fluorescence spectroscopy or, similarly, by using a fluorescence plate reader. In sensing of arginase, posttranslational modification of the peptide sequence will occur, transforming arginine to ornithine. This changes the conformational dynamics of the oligopeptide tether, leading to the increase of the TCPP signal. This is a highly selective technology, which has a very low limit of detection (LOD) of 1 x 10⁻¹⁶ molL⁻¹ for proteases and arginase. The potential of this nanobiosensor technology to detect early pancreatic and lung cancer was demonstrated by using serum samples, which were collected from patients who have been diagnosed with pancreatic cancer and non-small cell lung cancer at the South Eastern Nebraska Cancer Center (lung cancer) and the University of Kansas Cancer Center (pancreatic cancer). As controls, serum samples collected from healthy volunteers were analyzed. In pancreatic cancer detection, the protease/arginase signature for the detection of pancreatic adenocarcinomas in serum was identified. It comprises arginase, MMPs -1, - 3, and -9, cathepsins -B and -E, urokinase plasminogen activator, and neutrophil elastase. For lung cancer detection, the specificity and sensitivity of the nanobiosensors permit the accurate measurements of the activities of nine signature proteases in serum samples. Cathepsin -L and MMPs-1, -3, and -7 permit detecting non-small-cell lung-cancer at stage 1.

This project assesses two aspects of DNA detection of Phytophthora species from soil samples. Firstly, a nested PCR protocol was established with both primary and nested PCR specific for P. cinnamomi detection. PCR amplification of P. cinnamomi DNA isolated from soil was optimised with the addition of bovine serum albumin and formamide. This was found to improve both the specificity and sensitivity of PCR amplification of DNA in the presence of inhibitors co-extracted along with the target DNA from soil samples. The application of diagnostic nested PCR with the addition of BSA and formamide was verified by comparison with routine culture based detection methods. In all cases, nested PCR detection incorporating BSA and formamide was found to be considerably more sensitive than the culture based detection methods. The second component of this thesis investigates the simultaneous detection of multiple species of Phytophthora using microarray analysis. Microarray based detection has been previously limited by variable and inconsistent hybridisation intensities across the diversity of probes used in each array. In this study a novel concept for the differentiation of detection targets using duplex melting kinetics is introduced. A microarray assay was developed on a PamChip „¥ microarray enabling the differentiation of target Phytophthora species using the melting kinetics of probe-target duplexes. In the majority of cases the hybridization kinetics of target and non-target duplexes differed significantly. Analysis of the melting kinetics of duplexes formed by probes with target and non-target DNA was found to be an effective method for determining specific hybridization and was independent of fluctuations in hybridization signal intensity. This form of analysis was more robust than the traditional approach based on hybridisation intensity, and allowed the detection of individual Phytophthora species and mixtures there of.

The use of flow injection analysis with fluorescence detection was evaluated using the host-guest phenomenon between the cyclodexnins and DL-Iysine and Lserine. Auorescence enhancement, kinetic and equilibrium studies were recorded and the effect of pH and time on fluorescence were also observed. Rhodamine isothiocyanate was conjugated to insulin. Insulin and dye were mixed in different ratios, and the dye : insulin ratio was detennined for each conjugate. These conjugates were checked for immunoreactivity. Insulin-biotin and antibody-iminobiotin conjugates were also prepared. Insulin : biotin ratio was also determined. An insulin-biotin avidin-Texas Red complex was also prepared. Each was checked for immunoreactivity. Protein G-agarose, protein A-controlled pore glass(CPG), streptavidin-agarose, and avidin D-agarose-biotin-antibody solid phase immunoreactors were used in flow injection immunoassay of insulin. In these immunoassays, antibody, insulin and labelled insulin were incubated in vitro and then injected onto the immunoreactor. A binding buffer carried the sample through the immunoreactor and a fluorescent detector. An acidic buffer then eluted the components of the sample bound to the immunoreactor, which were then measured. An assay range for insulin was developed in each solid phase assay.

Methods currently available for the detection and enumeration of genetically modified micro-organisms in the environment include culturing methods, direct microscopic detection and nucleic hybridization techniques. The aim of this project was to develop luminescence as a molecular based-marker system in Pseudomonas fluorescens. The lux genes, originally isolated from Vibrio fischeri, were introduced into Ps. fluorescens on plasmid vectors and on the chromosome. The efficiency of these two strategies for the detection of Ps. fluorescens in soil was assessed. Luminometry was used to estimate biomass concentration during growth. The sensitivity of luminescence detection was greater for the plasmid marked Ps. fluorescens in both liquid culture and soil, however, cellular light output was less closely linked to biomass concentration. Enumeration of cells by luminometry was only possible for growing cells as light output is correlated with microbial activity. The lux chromosomal marker was stable in liquid culture for at least 200 generations and in soil for up to 135 days. The plasmid borne lux genes had a half-life of 20 generations in liquid culture. After inoculation in sterile soil, plasmid loss was only observed during cellular growth. The frequency of transfer of the lux genes from Ps. fluorescens, by conjugation and transformation, was assessed in liquid culture. Mobilisation of these genes by three self transmissible plasmids was negligible due to the instability of these vectors in this host. Transformation of Ps. stutzeri with lux genes, by cell contact, was at frequencies below levels of detection. Luminescence provided a valuable marker for tracking pseudomonads in soil. Detection of marked strains by luminometry provided a sensitive, rapid and non-extractive technique for enumeration of growing cells and measurement of microbial activity. As the chromosomally encoded lux genes were stable, regardless of growth conditions, and emitted sufficient levels of light to enable visual enumeration of colonies by eye, this was considered the best system for long term risk assessment studies.

This project assesses two aspects of DNA detection of Phytophthora species from soil samples. Firstly, a nested PCR protocol was established with both primary and nested PCR specific for P. cinnamomi detection. PCR amplification of P. cinnamomi DNA isolated from soil was optimised with the addition of bovine serum albumin and formamide. This was found to improve both the specificity and sensitivity of PCR amplification of DNA in the presence of inhibitors co-extracted along with the target DNA from soil samples. The application of diagnostic nested PCR with the addition of BSA and formamide was verified by comparison with routine culture based detection methods. In all cases, nested PCR detection incorporating BSA and formamide was found to be considerably more sensitive than the culture based detection methods. The second component of this thesis investigates the simultaneous detection of multiple species of Phytophthora using microarray analysis. Microarray based detection has been previously limited by variable and inconsistent hybridisation intensities across the diversity of probes used in each array. In this study a novel concept for the differentiation of detection targets using duplex melting kinetics is introduced. A microarray assay was developed on a PamChip microarray enabling the differentiation of target Phytophthora species using the melting kinetics of probe-target duplexes. In the majority of cases the hybridization kinetics of target and non-target duplexes differed significantly. Analysis of the melting kinetics of duplexes formed by probes with target and non-target DNA was found to be an effective method for determining specific hybridization and was independent of fluctuations in hybridization signal intensity. This form of analysis was more robust than the traditional approach based on hybridisation intensity, and allowed the detection of individual Phytophthora species and mixtures there of.

This project assesses two aspects of DNA detection of Phytophthora species from soil samples. Firstly, a nested PCR protocol was established with both primary and nested PCR specific for P. cinnamomi detection. PCR amplification of P. cinnamomi DNA isolated from soil was optimised with the addition of bovine serum albumin and formamide. This was found to improve both the specificity and sensitivity of PCR amplification of DNA in the presence of inhibitors co-extracted along with the target DNA from soil samples. The application of diagnostic nested PCR with the addition of BSA and formamide was verified by comparison with routine culture based detection methods. In all cases, nested PCR detection incorporating BSA and formamide was found to be considerably more sensitive than the culture based detection methods. The second component of this thesis investigates the simultaneous detection of multiple species of Phytophthora using microarray analysis. Microarray based detection has been previously limited by variable and inconsistent hybridisation intensities across the diversity of probes used in each array. In this study a novel concept for the differentiation of detection targets using duplex melting kinetics is introduced. A microarray assay was developed on a PamChip microarray enabling the differentiation of target Phytophthora species using the melting kinetics of probe-target duplexes. In the majority of cases the hybridization kinetics of target and non-target duplexes differed significantly. Analysis of the melting kinetics of duplexes formed by probes with target and non-target DNA was found to be an effective method for determining specific hybridization and was independent of fluctuations in hybridization signal intensity. This form of analysis was more robust than the traditional approach based on hybridisation intensity, and allowed the detection of individual Phytophthora species and mixtures there of.

The work here presented concerns the characterization and the performance study of very thin Low-Gain Avalanche Detector (LGAD) prototypes; the goal is to evaluate if such a sensor is suitable for the Time-Of-Flight (TOF) system of the ALICE 3 experiment, a next generation heavy-ion experiment (LHC Run 5). A total of 18 sensors with a thickness of 25 μm and 35 μm were characterized; both single channel and matrices, with different inter-pad design and doping profile were compared to two 50 μm-prototypes. Preliminary tests with a laser setup allowed to evaluate the light-sensitive areas in terms of efficiency, uniformity of the response and edge effects. Finally, timing performances were analyzed. Promising results were found for the 25 μm-thick sensors, which showed a time resolution better than 16 ps for a gain 20 and reaching nearly 13 ps for a gain 30.

Les neutrinos sont les particules fondamentales de matière les plus abondantes dans l’univers. Ils ont été détectés pour la première fois en 1956. Depuis lors, plusieurs expériences ont tenté de percer leurs mystères. Ils n’interagissent que par interaction faible, ils sont donc difficiles à détecter. On sait aujourd’hui qu’ils ont une masse très faible, et qu’ils peuvent osciller entre trois saveurs leptoniques. Cependant, de nombreuses questions perdurent sur leur masse, leur nature ou encore l’existence de neutrinos stériles. Cette thèse appréhende ces deux dernières questions à l’aide de deux expériences différentes : SuperNEMO et SoLid. Le but de l’expérience SuperNEMO est de rechercher la nature du neutrino, c’est-à-dire s’il est sa propre anti-particule (particule de Majorana) ou non (particule de Dirac). Pour cela, on cherche à détecter des doubles désintégrations bêta sans émission de neutrinos car ce processus n’est possible que si les neutrinos sont des particules de Majorana. Des feuilles sources de l’émetteur double bêta ⁸²Se seront installées au centre du démonstrateur SuperNEMO qui est actuellement en construction au Laboratoire Souterrain de Modane. Ce détecteur est composé d’une chambre à fils pour détecter les traces des deux électrons émis lors des désintégrations et d’un calorimètre pour mesurer leurs énergies. La mesure de la double désintégration bêta sans émission de neutrinos est très compliquée car si ce processus existe, il est extrêmement rare. Par conséquent, un travail important est fait pour réduire le bruit de fond des rayons cosmiques ou de la radioactivité naturelle. Dans cette thèse, des simulations des différents bruits de fonds ont été faites pour comprendre leur impact sur la mesure de l’énergie des électrons issus de la double désintégration bêta du ⁸²Se. Il est montré que la radioactivité du verre des photomultiplicateurs ne sera pas négligeable mais qu’elle pourra être mesurée précisément dans certains canaux d'analyse. Des feuilles de cuivre ont aussi été simulées à la place des sources de ⁸²Se pour montrer qu’elles peuvent aider à contrôler le bruit de fond efficacement. Suite à ces travaux, il a été décidé d’installer des feuilles de cuivre parmi les sources de ⁸²Se. La deuxième expérience sur laquelle porte cette thèse est l’expérience SoLid qui cherche à prouver l’existence de neutrinos stériles. Plusieurs anomalies expérimentales pourraient être expliquées par des oscillations d'antineutrinos de réacteurs vers des neutrinos stériles. Le détecteur SoLid cherche à mettre en évidence un signal d'oscillation auprès du réacteur BR2 en Belgique en mesurant le flux d’antineutrinos en fonction de leur énergie et de la distance parcourue, grâce à une grande segmentation. La détection des antineutrinos de réacteur se fait par désintégration bêta inverse. L’interaction d’un antineutrino se traduit donc par l’émission en coïncidence d’un positron et d’un neutron. Les positrons sont détectés dans des cubes de plastique scintillant en PVT et les neutrons sont détectés par des feuilles de ⁶LiF:ZnS posées sur chacun des cubes. Un premier prototype, SM1, a montré l’intérêt de cette technologie notamment pour discriminer les bruits de fonds. Une partie des travaux de cette thèse a consisté à développer et exploiter un banc de test afin d'optimiser la collection de lumière du détecteur pour améliorer la résolution en énergie de SoLid. En testant différents matériaux et différentes configurations du détecteur, les mesures sur le banc de test ont montré qu’une résolution en énergie de 14 % pouvait être atteinte pour le détecteur SoLid (contre 20 % pour le prototype SM1). Les améliorations proposées ont été prises en compte dans la construction du détecteur SoLid qui s’est achevée en 2017. Une analyse des premières données du détecteur est également présentée pour montrer la sensibilité de SoLid à la détection des antineutrinos de réacteur
Neutrinos are the most abundant fundamental particles of matter in the Universe. They were detected for the first time in 1956. Since then, several experiments have tried to unveil their mysteries. They only interact weakly so they are difficult to detect. It is known that their masses are very low and that they can oscillate between three leptonic flavours. However, several questions remain about their masses, their nature or the existence of sterile neutrinos. This thesis addresses the last two questions with two different experiments: SuperNEMO and SoLid. The goal of the SuperNEMO experiment is to understand the nature of neutrinos, whether it is its own antiparticle (Majorana particle) or not (Dirac particle). This is investigated by searching for neutrinoless double beta decay as this process is possible only if neutrinos are Majorana particles. Source foils of the double beta emitter ⁸²Se are installed at the center of the SuperNEMO demonstrator which is being assembled at the Modane Underground Laboratory. This detector is composed of a wire chamber to detect the tracks of the two electrons emitted in the decays and a calorimeter to measure their energies. Neutrinoless double beta decay measurement is very difficult because if this process exists, it is extremely rare. An important work has thus to be done to decrease backgrounds from cosmic rays or natural radioactivity. In this thesis, different backgrounds have been simulated to understand their impact on the measurement of the energy of the two electrons from ⁸²Se double beta decay. It is shown that radioactivity from photomultipliers glasses will not be negligible but it will be possible to measure it precisely in dedicated channels. Copper foils have also been simulated in the source strips to demonstrate that they can help to control efficiently the backgrounds. Following this work, it has been decided to install copper foils in addition to ⁸²Se foils. The second experiment investigated in this thesis is the SoLid experiment which is looking for the existence of sterile neutrinos. Several experimental anomalies could be explained by oscillations of reactor antineutrinos toward sterile neutrinos. The SoLid detector is looking for an oscillation signal at the Belgian BR2 reactor by measuring the antineutrino flux as a function of their energy and their traveling distance thanks to a fine segmentation. The reactor antineutrinos are detected via inverse beta decay. The antineutrino interaction signal is thus the emission in coincidence of a positron and a neutron. Positrons are detected by plastic scintillator cubes in PVT and neutrons are detected by ⁶LiF:ZnS sheets placed on 2 faces of each cube. A first prototype, SM1, has demonstrated the advantages of this technology, particularly to discriminate backgrounds. A part of the work of this thesis consisted in developing and exploiting a test bench to optimize the light collection of the detector in order to improve the energy resolution of the SoLid detector. By testing different materials and configurations, the test bench measurement demonstrated that an energy resolution of 14 % can be achieved for SoLid phase I, while it was 20 % for the SM1 prototype. The improvements proposed have been taken into account for the SoLid detector construction that was achieved in 2017. An analysis of the first detector data is also presented to show SoLid sensitivity to reactor antineutrino detection

In case of a release of radioactive nuclides into the environment it is necessary to  have reliable methods to estimate the potential effect on people and the ecosystem. In this context the total activity deposited, the elemental composition and the depth distribution are of importance. An efficient in situ method to estimate the average contamination over larger areas using high purity germanium (HPGe) detectors has been developed. The method combines simulation of photon transport with measured detector properties. The total activity of 137Cs determined from gamma-ray spectra recorded in situ are compared to results from soil sampling. Another in situ method has been developed to determine the depth distribution of a radionuclide contamination, using an array of small detectors inserted into the ground, as an alternative to the standard procedure of soil sampling. The possibility to use cadmium telluride (CdTe) detectors as well as lanthanum bromide (LaBr3) detectors has been investigated. As a demonstration of the developed method the small-scale variation of the activity distributions in an area covering 350 m2 have been measured and is compared to results obtained by other methods.
At the time of the doctoral defense, the following paper was unpublished and had a status as follows: Paper 4: Submitted.