Ultra wide band (UWB) is an extremely promising wireless technology for researchers and industrials. One of the most interesting is its high data rate and fading robustness due to selective frequency fading. However, beside such advantages, UWB system performance is highly affected by existing narrowband interference (NBI), undesired UWB signals and tone/multi-tone noises. For this reason, research about NBI cancellation is still a challenge to improve the system performance vs. receiver complexity, power consumption, linearity, etc. In this work, the two major receiver sections, i.e., analog (radiofrequency or RF) and digital (digital signal processing or DSP), were considered and new techniques proposed to reduce circuit complexity and power consumption, while improving signal parameters. In the RF section, different multiband UWB low-noise amplifier key design parameters were investigated like circuit configuration, input matching and desired/undesired frequency band filtering, highlighting the most suitable filtering package for efficient UWB NBI cancellation. In the DSP section, due to pulse transmitter signals, different issues like modulation type and level, pulse variety, shape and color noise/tone noise assumptions, were addressed for efficient NBI cancelation. A comparison was performed in terms of bit-error rate, signal-to-interference ratio, signal-to-noise ratio, and channel capacity to highlight the most suitable parameters for efficient DSP design. The optimum number of filters that allows the filter bandwidth to be reduced by following the required low sampling rate and thus improving the system bit error rate was also investigated.

Le noyau est généralement décrit comme un ensemble de protons et de neutrons liés dans un potentiel de champ moyen. Cependant afin d'obtenir une meilleure description, il convient de tenir compte des interactions locales dont principalement l'appariement. Les appariements neutron-neutron et proton-proton sont assez bien étudiés alors que ce n'est pas le cas de l'appariement neutron-proton. Celui-ci peut être soit isovectoriel similaire à l'appariement nn/pp, soit isoscalaire et donc dans ce cas vraiment méconnu. La surliaison des noyaux N=Z pourrait être une manifestation de l'appariement np.Nous avons effectué l'étude de l'appariement np par réactions de transfert de paires np. Dans ce cas il est attendu que la section efficace de transfert de paires np soit augmentée en présence d'un appariement np important. L'appariement np devrait être important dans les noyaux N=Z avec des orbitales de J élevé. Or, des faisceaux de ces noyaux ne sont accessibles que depuis le développement des installations de faisceaux radioactifs.Nous avons effectué notre expérience au GANIL (Caen) avec un montage permettant une détection des produits issus de la réaction de transfert (p, ³ He). Cette réaction met en jeu à la fois des paires np isovectorielles et isoscalaires. Nous avons utilisé des faisceaux de ⁵⁶ Ni et de ⁵²Fe permettant d'observer l'évolution de l'appariement np avec l'occupation de la couche 0f7/2.Tout d'abord, nous avons analysé les données issues de la réaction ⁵⁶Ni(p,d)⁵⁵Ni et extrait des résultats que nous avons comparé à ceux existants. Cette démarche a permis de valider la procédure d'analyse des données.Après analyse des données issues de la réaction ⁵⁶Ni(p,3He)⁵⁴Co, nous avons extrait les populations des états du ⁵⁴Co qui donnent des informations sur l'intensité relative des deux types d'appariement np pour le noyau ⁵⁶Ni et montrent que l'appariement np isovectoriel est dominant dans ce noyau.De plus, dans le cadre d'un développement d'un futur détecteur de particules chargées, un travail de R&D sur la discrimination des particules légères par la forme des signaux a été réalisé et est présenté. / A nucleus is described as a set of independent neutrons and protons linked by a mean-field potential. However, in order to have a better description one needs to take in account some residual interactions such as pairing. Neutron-neutron and proton-proton pairings are well-studied but neutron-proton pairing is not well-known. np pairing can be isovector pairing such as nn and pp pairing or isoscalar which is yet unknown. Overbinding of N=Z nuclei could be a manifestation of np pairing.We have studied np pairing through transfer reactions. In this case, the cross-section of np pair transfer is expected to be enhanced in the presence of important np pairing. np pairing is expected to be important in N=Z nuclei with high J orbitals. Since the development of radioactive beam facilities, such beams are only available.The experiment was performed at GANIL with an efficient set-up so as to detect products from the (p,³He) transfer reaction. This reaction is affected by isovector and isoscalar np pairing. We used ⁵⁶Ni and ⁵²Fe beams so as to see the effect of the occupancy of 0f7/2 shell on the np pairing.First, we analysed the data from the ⁵⁶Ni(p,d)⁵⁵Ni reaction and we compared the results with the literature to validate analysis procedure.After analysing data from the ⁵⁶Ni(p,3He)⁵⁴Co reaction and extracting the population of the various states of ⁵⁴Co, we obtained information about the relative intensity between isoscalar and isovector np pairing in ⁵⁶Ni showing the predominance of isovector np pairing in this nucleus .Moreover, in the framework of developing a new charged particle detector, R&D on the discrimination of light nuclei using pulse shape analysis was performed and is presented.

Eine mit Polyethylen abgeschirmte Americium-Beryllium-Quelle wurde bzgl. ihres schnellen und thermischen Neutronenfeldes sowie Photonenfeldes durch Messungen und Simulationen quantifiziert. Dafür wurden Strahlungsfeldgrößen wie spektrale Teilchenflussdichten, Teilchenflussdichten, UmgebungsÄquivalentdosisleistungen und Richtungs-Äquivalentdosisleistungen für die jeweiligen Felder in unterschiedlichen Abständen der Strahlungsquelle bestimmt. Die ermittelten Ergebnisse werden verwendet, um einen neuen Bestrahlungsstand als Referenzfeld für Neutronen und Photonen zu errichten.:Einleitung 1. Theoretische Grundlagen 1.1. Strahlungsfeldgrößen 1.1.1. Radiometrische Größen 1.1.2. Interaktionskoeffizienten 1.1.3. Dosimetrische Größen 1.1.4. Fluenz-zu-Dosis-Konversionskoeffizienten 1.2. Photonen 1.2.1. Wechselwirkung mit Materie 1.2.2. Nachweis durch Szintillationsdetektoren 1.3. Neutronen 1.3.1. Klassifizierung 1.3.2. Wechselwirkung mit Materie 1.3.3. Nachweis schneller Neutronen durch organische Szintillationsdetektoren 1.3.4. Nachweis thermischer Neutronen durch ³He-Zählrohre 1.4. Americium-Beryllium-Quellen 1.4.1. Neutronenerzeugung 1.4.2. Abschirmung 1.5. Detektoren 1.5.1. Szintillationsdetektoren 1.5.2. ³He-Zählrohre 1.6. Digitale Pulsverarbeitung 1.6.1. Pulsformdiskriminierung mit organischen Szintillationsdetektoren 1.7. Monte-Carlo-Strahlungstransportsimulationen 2. Geräte und Materialien 3. Methoden 3.1. Quantifizierung des schnellen Neutronenfeldes 3.1.1. PFD-unterstützte Flugzeitmethode 3.1.2. Einfache Entfaltungstechnik 3.2. Quantifizierung des thermischen Neutronenfeldes 3.3. Quantifizierung des Photonenfeldes 4. Messungen 4.1. Messung 1 4.2. Messung 2 4.3. Messung 3 4.4. Messung 4 4.5. Messung 5 4.6. Messung 6 4.7. Messung 7 4.8. Messung 8 4.9. Messung 9 4.10. Messung 10 5. Simulationen mit FLUKA 5.1. Nachmodellierung der Versuchsaufbauten 5.2. Nachbildung der Strahlungsfelder 5.2.1. Bestimmung der Korrekturfaktoren 5.3. Simulierte Größen 6. Ergebnisse 6.1. Quantifizierung des schnellen Neutronenfeldes 6.1.1. Strahlungsfeldgrößen mittels des Stilbendetektors 6.1.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.1.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.2. Quantifizierung des thermischen Neutronenfeldes 6.2.1. Strahlungsfeldgrößen mittels des ³He-Zählrohrs 6.2.2. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.3. Quantifizierung des Photonenfeldes 6.3.1. Strahlungsfeldgrößen mittels des CeBr₃-Detektors 6.3.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.3.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 7. Diskussion 7.1. Quantifizierung des schnellen Neutronenfeldes 7.1.1. Spektrale Teilchenflussdichten 7.1.2. Umgebungs-Äquivalentdosisleistungen 7.2. Quantifizierung des thermischen Neutronenfeldes 7.2.1. Teilchenflussdichten 7.3. Quantifizierung des Photonenfeldes 7.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV 7.3.2. Umgebungs-Äquivalentdosisleistungen 7.3.3. Richtungs-Äquivalentdosisleistungen 8. Zusammenfassung A. Bestimmte Strahlungsfeldgrößen A.1. Schnelles Neutronenfeld A.1.1. Spektrale Teilchenflussdichten A.1.2. Umgebungs-Äquivalentdosisleistungen A.2. Thermisches Neutronenfeld A.2.1. Teilchenflussdichten A.3. Photonenfeld A.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV A.3.2. Umgebungs-Äquivalentdosisleistungen A.3.3. Richtungs-Äquivalentdosisleistungen B. Zwischenergebnisse B.1. Quantifizierung des schnellen Neutronenfeldes B.1.1. Pulsladungshistogramme des Stilbendetektors für n₁-Neutronen B.1.2. Anzahlen der Rückstoßprotonen B.2. Quantifizierung des Photonenfeldes B.2.1. Simulierte und gemessene Größen zur Bestimmung der Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV / An americium-beryllium source shielded with polyethylene was quantified in regards to its fast and thermal neutron field, as well as its photon field via measurements and simulations. Therefore, radiation field quantities like spectral fluence rates, fluence rates, ambient dose rate equivalents and directional dose rate equivalents of the respective fields were determined in different distances from the radiation source. The produced results will be used for establishing a new irradiation workbench as reference field for neutrons and photons.:Einleitung 1. Theoretische Grundlagen 1.1. Strahlungsfeldgrößen 1.1.1. Radiometrische Größen 1.1.2. Interaktionskoeffizienten 1.1.3. Dosimetrische Größen 1.1.4. Fluenz-zu-Dosis-Konversionskoeffizienten 1.2. Photonen 1.2.1. Wechselwirkung mit Materie 1.2.2. Nachweis durch Szintillationsdetektoren 1.3. Neutronen 1.3.1. Klassifizierung 1.3.2. Wechselwirkung mit Materie 1.3.3. Nachweis schneller Neutronen durch organische Szintillationsdetektoren 1.3.4. Nachweis thermischer Neutronen durch ³He-Zählrohre 1.4. Americium-Beryllium-Quellen 1.4.1. Neutronenerzeugung 1.4.2. Abschirmung 1.5. Detektoren 1.5.1. Szintillationsdetektoren 1.5.2. ³He-Zählrohre 1.6. Digitale Pulsverarbeitung 1.6.1. Pulsformdiskriminierung mit organischen Szintillationsdetektoren 1.7. Monte-Carlo-Strahlungstransportsimulationen 2. Geräte und Materialien 3. Methoden 3.1. Quantifizierung des schnellen Neutronenfeldes 3.1.1. PFD-unterstützte Flugzeitmethode 3.1.2. Einfache Entfaltungstechnik 3.2. Quantifizierung des thermischen Neutronenfeldes 3.3. Quantifizierung des Photonenfeldes 4. Messungen 4.1. Messung 1 4.2. Messung 2 4.3. Messung 3 4.4. Messung 4 4.5. Messung 5 4.6. Messung 6 4.7. Messung 7 4.8. Messung 8 4.9. Messung 9 4.10. Messung 10 5. Simulationen mit FLUKA 5.1. Nachmodellierung der Versuchsaufbauten 5.2. Nachbildung der Strahlungsfelder 5.2.1. Bestimmung der Korrekturfaktoren 5.3. Simulierte Größen 6. Ergebnisse 6.1. Quantifizierung des schnellen Neutronenfeldes 6.1.1. Strahlungsfeldgrößen mittels des Stilbendetektors 6.1.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.1.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.2. Quantifizierung des thermischen Neutronenfeldes 6.2.1. Strahlungsfeldgrößen mittels des ³He-Zählrohrs 6.2.2. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 6.3. Quantifizierung des Photonenfeldes 6.3.1. Strahlungsfeldgrößen mittels des CeBr₃-Detektors 6.3.2. Strahlungsfeldgrößen mittels der Plausibilitätsmessungen 6.3.3. Strahlungsfeldgrößen mittels der FLUKA-Simulationen 7. Diskussion 7.1. Quantifizierung des schnellen Neutronenfeldes 7.1.1. Spektrale Teilchenflussdichten 7.1.2. Umgebungs-Äquivalentdosisleistungen 7.2. Quantifizierung des thermischen Neutronenfeldes 7.2.1. Teilchenflussdichten 7.3. Quantifizierung des Photonenfeldes 7.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV 7.3.2. Umgebungs-Äquivalentdosisleistungen 7.3.3. Richtungs-Äquivalentdosisleistungen 8. Zusammenfassung A. Bestimmte Strahlungsfeldgrößen A.1. Schnelles Neutronenfeld A.1.1. Spektrale Teilchenflussdichten A.1.2. Umgebungs-Äquivalentdosisleistungen A.2. Thermisches Neutronenfeld A.2.1. Teilchenflussdichten A.3. Photonenfeld A.3.1. Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV A.3.2. Umgebungs-Äquivalentdosisleistungen A.3.3. Richtungs-Äquivalentdosisleistungen B. Zwischenergebnisse B.1. Quantifizierung des schnellen Neutronenfeldes B.1.1. Pulsladungshistogramme des Stilbendetektors für n₁-Neutronen B.1.2. Anzahlen der Rückstoßprotonen B.2. Quantifizierung des Photonenfeldes B.2.1. Simulierte und gemessene Größen zur Bestimmung der Teilchenflussdichten der Photonen mit den Energien 511 keV, 2,2 MeV und 4,4 MeV

Die Grundlage vieler zukünftiger Flüssigszintillator-Neutrinoexperimente (SNO+, Daya Bay, LENA) ist das Lösungsmittel Lineare-Alkyl-Benzene (LAB, C6H5CnH2n+1, n = 10 - 13). Zusammen mit dem weit verbreiteten Szintillator 2,5-Diphenyloxazole (PPO) ist es ein farb- und geruchsloses Detektormaterial mit hohem Flammpunkt. Im Vergleich zu toluol- oder xylolbasierten Szintillatoren ist LAB+PPO preiswert und nicht gesundheitsschädlich. Die Eigenschaften von LAB machen es ebenfalls interessant für die Anwendung an nELBE, die Neutronenfugzeitanlage im Helmholtz-Zentrum Dresden - Rossendorf. Ein neuer Ansatz zur Bestimmung der Lichtausbeute im niederenergetischen Bereich (bis 2 MeV) wird vorgestellt. Kombiniert wurden Messungen mit (quasi) monoenergetischen Gammastrahlungs-Prüfstrahlern und einem in dieser Arbeit aufgebauten Compton-Spektrometer. Letzteres ermöglicht die Bestimmung der Lichtausbeute bis zu 5 keVee. Der Birks-Parameter wurde für eine Lösung von LAB + 3 g/l PPO sowie für den Flüssigszintillator NE-213 bestimmt. Die relative Lichtausbeute in Bezug auf letzteren konnte mit diesen Messmethoden ebenfalls ermittelt werden. Zur spektralen Analyse des Lumineszenzlichtes wurden Messungen an Fluoreszenz- und UV/VIS- Spektrometern durchgeführt. Die Pulsformdiskriminationsfähigkeit auf LAB basierenden Szintillatoren wurde während eines Flugzeitexperiments in einem gemischten n-gamma-Feld eines Cf(252)-Prüfstrahlers ermittelt. Dabei kamen unterschiedliche Algorithmen der semi-analogen und digitalen Pulsformdiskrimination zum Einsatz. / Linear alkyl benzene (LAB, C6H5CnH2n+1, n = 10 - 13) is the proposed solvent for the SNO+, the Daya Bay Neutrino and LENA experiment. In solution with the commonly used scintillator PPO it is a colourless, odourless and cheap liquid scintillator with a high fash point and low health hazard compared to toluene based ones. The properties of LAB make this scintillator interesting also for nELBE, the neutron time-of-fight facility at Helmholtz-Zentrum Dresden - Rossendorf. A new approach to measure the light yield in the low-energy range using a combination of quasi-monoenergetic photon sources and a Compton-spectrometer is described. The latter allows the measurement of the light yield down to 5 keVee (electron equivalent). The Birks- Parameter was determined for a homemade solution (LAB + 3 g/l PPO) and for NE-213. The light yield (relative to this standard scintillator) was confrmed by measurements using a fuorescence spectrometer. The ability of pulse-shape-discrimination in a mixed n-gamma- field of a Cf(252) source was tested using different digital and semi-analogue techniques.

Dans cette thèse, nous proposons une méthodologie de conception d’architectures de communication dédiées aux réseaux de capteurs basées sur la technique de radio impulsionnelle pour les transmissions ultralarge bande (ULB). La technique impulsionnelle proposée ici repose sur la modulation de forme d’impulsion. L’approche de conception architecturale présentée dans cette thèse se focalise plus particulièrement sur la forme des impulsions et leur génération, qui revêt un intérêt majeur puisqu’elle constitue le support de l’information échangée. L’étude sur le choix de la forme d’impulsion nous a conduit à proposer deux architectures différentes. Une première architecture repose sur les polynômes orthogonaux, et plus particulièrement sur les polynômes d’Hermite, pour la génération des impulsions, et sur une architecture de corrélation pour la détection et la reconnaissance des trains d’impulsions transmis. La deuxième architecture est basée sur la transformée en paquets d’ondelettes discrète et peut être exploitée selon deux modes d’utilisation différents, mono et multiutilisateurs. L’utilisation d’une architecture de synthèse à l’émission et d’analyse à la réception ouvre une nouvelle orientation pour les communications numériques, permettant à la transformée en ondelettes d’assurer à la fois la génération des impulsions à l’émission et leur reconnaissance à la réception. Un intérêt immédiat de la technique proposée permet notamment de faciliter l’accès multiutilisateurs au canal ultralarge bande, et d’autoriser des communications simultanées (Many-to-one, des nœuds vers le puits) ou du broadcast (One-to-many, du puits vers les nœuds) sans surcharger la couche MAC. L’architecture proposée s’inscrit donc à l’interface des couches PHY et MAC et permet de relâcher les contraintes de conception spécifiques à ces couches / In this thesis, we propose a design methodology for communication architectures dedicated to wireless sensor network based on impulse radio techniques for UWB communications. The impulse technique proposed in this work relies on pulse shape modulation. The architecture design approach proposed in this thesis focuses on pulses shape and their generation, which is of major interest as it constitutes the carrier of the information exchanged. The study on the choice of pulse shape led us to propose two different architectures. The first one is based on orthogonal polynomials, more especially on the Hermite polynomials, for impulse generation, and on a correlation architecture for detection and recognition of transmitted impulses. The second architecture is based on discrete wavelet packet transform and can be used according two different modes, mono and multi-users. The use of both synthesis and analysis architectures for emitter and receiver, respectively, offers a new way for digital communications and allows the wavelet transform to ensure the impulses generation on the transmitter and their recognition on the receiver. A major interest point of the proposed technique is to facilitate the multi-users access to the ultra-wideband channel and to allow simultaneous communications (many-to-one, from the sensors to the sink) or broadcast (one-to-many, from the coordinator to the nodes) but without overloading the MAC layer. Hence, the proposed architecture is part of the interface between both PHY and MAC layers, and allows to release their specific design constraints

Wireless communication companies require to use the frequency spectrum to operate. Both frequency licenses and infrastructure to reuse frequencies are costly resources subject to increasing demand. This work introduces a novel multiplexing method that saves spectrum called Spectral Shape Division Multiplexing (SSDM). Under certain configurations, SSDM displays higher flexibility and throughput than other spectrally efficient methods. SSDM defines the structure of a wireless multi-carrier by software. It is similar to Orthogonal Frequency Division Multiplexing (OFDM) in that both use overlapped sub-carriers to make efficient use of allocated spectrum. However, SSDM has several advantages. Where OFDM organizes sub-carriers orthogonally, SSDM allows arbitrary frequency steps enabling higher spectral efficiency. Similarly, while OFDM and other spectrally efficient methods use sinusoidal pulse forms, SSDM can use non-standard pulses providing a greater control of the carrier. In this thesis, a SSDM transceiver is implemented to reduce the spectrum utilization. SSDM presents an increase in spectral efficiency of 20% average with respect to OFDM. The cost of this gain is higher computational speed and signal to noise ratio. The mathematical models and possible architecture for an SSDM system with sinusoidal pulses is developed. The modem is compared with other spectrally efficient methods. Similarly, the trade-offs between spectral efficiency, bit-error rates, dimension of the carrier and sub-carrier spacing are subject of analysis.

<p>A Monte Carlo simulation of the Neutron Wall detector system has been performed using Geant4, in order to define optimum conditions for the detection and identification of multiple neutrons. Emphasis was put on studying the scattering of neutrons between different detectors, which is the main source of the apparent increase of the number of detected neutrons. The simulation has been compared with experimental data. The quality of neutron gated γ-ray spectra was improved for both two- and three-neutron evaporation channels. The influence of small amounts of γ rays mis-interpreted as neutrons was investigated. It was found that such γ rays dramatically reduce the quality of neutron gated γ-ray spectra.</p><p>The interaction properties of fast neutrons in a closed-end coaxial and a planar high-purity germanium detector (HPGe) were studied. Digitised waveforms of HPGe preamplifier signals were recorded for time-of-flight separated neutrons and γ rays, emitted by a ²⁵²Cf source. The experimental waveforms from the detectors were compared to simulated pulse shapes. In the analysis, special emphasis was given to the detection of elastically scattered neutrons, which may be an important effect to take into account in future spectrometers based on γ-ray tracking. No differences between neutron and γ-ray induced pulse shapes were found in this work.</p><p>A Monte Carlo simulation of the interactions of fast neutrons in the future 4π γ-ray spectrometer AGATA was also performed, in order to study the influence of neutrons on γ-ray tracking. It was shown that although there is a large probability of detecting neutrons in AGATA, the neutrons decrease the photo-peak efficiency of AGATA by only about 1% for each neutron emitted in coincidence with γ rays. The peak-to-background ratios in γ-ray spectra are, however, reduced to a much larger extent. The possibility of using AGATA as a neutron detector system was also investigated.</p>

A Monte Carlo simulation of the Neutron Wall detector system has been performed using Geant4, in order to define optimum conditions for the detection and identification of multiple neutrons. Emphasis was put on studying the scattering of neutrons between different detectors, which is the main source of the apparent increase of the number of detected neutrons. The simulation has been compared with experimental data. The quality of neutron gated γ-ray spectra was improved for both two- and three-neutron evaporation channels. The influence of small amounts of γ rays mis-interpreted as neutrons was investigated. It was found that such γ rays dramatically reduce the quality of neutron gated γ-ray spectra. The interaction properties of fast neutrons in a closed-end coaxial and a planar high-purity germanium detector (HPGe) were studied. Digitised waveforms of HPGe preamplifier signals were recorded for time-of-flight separated neutrons and γ rays, emitted by a 252Cf source. The experimental waveforms from the detectors were compared to simulated pulse shapes. In the analysis, special emphasis was given to the detection of elastically scattered neutrons, which may be an important effect to take into account in future spectrometers based on γ-ray tracking. No differences between neutron and γ-ray induced pulse shapes were found in this work. A Monte Carlo simulation of the interactions of fast neutrons in the future 4π γ-ray spectrometer AGATA was also performed, in order to study the influence of neutrons on γ-ray tracking. It was shown that although there is a large probability of detecting neutrons in AGATA, the neutrons decrease the photo-peak efficiency of AGATA by only about 1% for each neutron emitted in coincidence with γ rays. The peak-to-background ratios in γ-ray spectra are, however, reduced to a much larger extent. The possibility of using AGATA as a neutron detector system was also investigated.

Failed fuel refers to the breach in the fuel-clad of an irradiated fuel assembly in a nuclear reactor. Neutron detection or gamma detection is commonly used in Failed Fuel Detection and Locating (FFDL) system to monitor the activity of the coolant. Though these methods offer specific advantages under different conditions of the coolant, providing both types of detectors in FFDL system is impractical. This limitation is the motivation for the detector system developed in the present work. In the present work, effort has been made for realising a detector system for simultaneous measurement of neutron and gamma activity of the coolant, thus offering a two-parameter basis for failed fuel detection. NE213 liquid scintillator was chosen for this work as it has good detection capability for both neutrons and gammas. Additionally, the neutrons and gammas interacting with NE213 detector can be separated based on pulse shape discrimination. The work reported in this thesis includes fabrication details and different steps followed in assembling the NE213 detector. Details of experimental set-up developed for pulse height analysis and pulse shape analysis are covered. Results of experiments carried out to study the response of the NE213 detector to gamma and neutron sources using pulse height analyser are presented. The absolute gamma efficiency and relative gamma efficiency of NE213 detector are calculated. Neutron–gamma separation capability of NE213 detector based pulse shape analysis system is reported. Application of the developed detector system to analyse the coolant activity in FFDL system in a reactor is described. Response of the detector is compared with the existing FFDL system at different power levels of the reactor. Since failed fuel is a rare event, it was simulated using neutron and gamma sources. Pulse shape analysis spectra obtained under simulated failed fuel condition are presented.

L’apparition de la segmentation électrique des détecteurs au GeHP et de l’électronique numérique a ouvert la voie à des applications prometteuses, telles que le tracking γ, l’imagerie γ ou la mesure bas bruit de fond, pour lesquelles une connaissance fine de la réponse du détecteur est un atout. L’IPHC a développé une table de scan utilisant un faisceau collimaté, qui sonde la réponse d’un détecteur dans tout son volume en fonction de la localisation de l’interaction. Elle est conçue pour utiliser une technique innovante de scan 3D, le Pulse Shape Comparison Scan, qui a été d’abord simulée afin de démontrer son efficacité. Un détecteur AGATA a été scanné de manière approfondie. Des scan 2D classiques ont permis, entre autres, de mettre en évidence des effets locaux de modification de la collection des charges, liés à la segmentation. Pour la première fois, une base de données 3D, complète, de formes d’impulsions fonction de la position d’interaction a été établie. Elle permettra notamment d’améliorer les performances du spectromètre AGATA. / Recent developments of electrical segmentation of HPGe detectors, coupled with digital electronics have led to promising applications such as γ-ray tracking, γ-ray imaging or low-background measurements which will benefit from a fine knowledge of the detector response. The IPHC has developed a new scanning table which uses a collimated γ-ray beam to investigate the detector response as a function of the location of the γ-ray interaction. It is designed to use the Pulse Shape Comparison Scan technique, which has been simulated in order to prove its efficiency. An AGATA detector has been thoroughly scanned. 2D classical scans brought out, for example, local charge collection modification effects such as charge sharing, due to the segmentation. For the first time, a 3D, complete pulse-shape database has been established. It will especially allow to improve the overall AGATA array performances.