Blowfish is a highly segmented neutron detector array consisting of 88 cells filled with BC-505 liquid scintillator. <p>The cells make up a spherical shape that covers approximately one quarter of the total solid angle of 4 pi steradians.<p> A high-priority measurement for Blowfish is the low energy contribution to the Gerasimov-Drell-Hearn (GDH) sum rule on the deuteron, which uses circularly polarized gamma rays. <p>The experimental data that needs to be collected are the absolute cross-sections when the gamma ray helicity and target polarization are parallel and anti-parallel. To extract absolute cross-sections from the data, it will be necessary to have characterized the efficiency of the detector.<p>Another measurement that would benefit from the efficiency calibration is the photodistegration of deuterium, which has already been performed. This measurement used linearly-polarized gamma rays at energies of 2.6, 3.5, 4.0 and 6.0 MeV. The relative cross-sections from this measurement provide much useful information, but to extract the absolute cross-sections the Blowfish efficiency calibration is needed. This thesis presents this efficiency calibration. <p> The efficiency calibration was done using a 252Cf source in a parallel plate ionization chamber over the energy range of 0 to 6 MeV. <p>To determine the absolute scale of the extracted efficiency curves, an efficiency analysis and simulation of a previously characterized BC-519 liquid scintillator cell needed to be performed along with a simulation of the Blowfish detector array. <p>The measured efficiencies were consistent with those predicted by the simulation over the desired energy range.

Blowfish is a highly segmented neutron detector array consisting of 88 cells filled with BC-505 liquid scintillator. <p>The cells make up a spherical shape that covers approximately one quarter of the total solid angle of 4 pi steradians.<p> A high-priority measurement for Blowfish is the low energy contribution to the Gerasimov-Drell-Hearn (GDH) sum rule on the deuteron, which uses circularly polarized gamma rays. <p>The experimental data that needs to be collected are the absolute cross-sections when the gamma ray helicity and target polarization are parallel and anti-parallel. To extract absolute cross-sections from the data, it will be necessary to have characterized the efficiency of the detector.<p>Another measurement that would benefit from the efficiency calibration is the photodistegration of deuterium, which has already been performed. This measurement used linearly-polarized gamma rays at energies of 2.6, 3.5, 4.0 and 6.0 MeV. The relative cross-sections from this measurement provide much useful information, but to extract the absolute cross-sections the Blowfish efficiency calibration is needed. This thesis presents this efficiency calibration. <p> The efficiency calibration was done using a 252Cf source in a parallel plate ionization chamber over the energy range of 0 to 6 MeV. <p>To determine the absolute scale of the extracted efficiency curves, an efficiency analysis and simulation of a previously characterized BC-519 liquid scintillator cell needed to be performed along with a simulation of the Blowfish detector array. <p>The measured efficiencies were consistent with those predicted by the simulation over the desired energy range.

Neutron diagnostics will play a fundamental role in future fusion plasma machines,where the harsh environment will make the use of many other type of diagnos-tics practically impossible. Complex techniques to measure the neutron spectrumemitted from tokamk plasmas have been developed over the years, producing stateof the art neutron spectrometers. However, recently compact neutron spectrom-eters have been gaining the interest of the research community. They are muchsimpler to operate and maintain, have lower cost and they can be employed in thechannels of a neutron camera, providing profile measurements. The drawbacks arethat they have a worse resolution and a response to neutrons that is not optimalfor spectroscopy.The goal of the work presented in this thesis is to estimate to which extenta compact detector such as a NE213 liquid scintillator can be used to performneutron emission spectroscopy analysis.The detector used for this study was installed in the back of the MPRu spec-trometer at JET in 2012. The characterization of the response of the detector wasdone using a combination of MCNPX simulations and real measurements. Thedata analysis was performed using the forward fitting approach: a model of theneutron spectrum is produced, then folded with the response of the detector andfinally compared with the data. Two types of plasma scenarios were analyzed, onewith NBI heating only, and another with NBI and third harmonic radio-frequencyheating. In both cases the TOFOR spectrometer was used as a reference to esti-mate the parameters in the model of the neutron spectrum.The results are promising and suggest that neutron spectroscopy can be per-formed with NE213 scintillators although the quality of the results, as given byperformance indicators such as uncertainties, is much lower than the performanceof high resolution spectrometers.

The SNO+ experiment will be the SNO detector filled with a neodymium-loaded liquid scintillator instead of heavy water. SNO+ will be used to detect neutrinos of much lower energy. Also, SNO+ will conduct a search for neutrinoless double beta decay with Nd-150. The Nd-loaded scintillator in SNO+ will be made from linear alkylbenzene (LAB). Both the LAB solvent and the Nd loading are new developments. The optical properties of this scintillator and information about radioactive backgrounds should be studied. A calibration source known as the scintillator bucket was deployed in the water-filled SNO detector in order to study some optical properties of Nd-loaded scintillator, raw LAB scintillator and distilled LAB scintillator. Using a neutron source attached to the bucket to produce events with known energy, with a model of the scintillator bucket simulated by an analysis tool called RAT, the light yield of the scintillator could be determined by comparing data measurements with simulations. This allowed the light yield, one of the main optical properties of the scintillator, to be measured and that value to be corrected in the Monte Carlo. The bucket was deployed both at the centre of the detector and at the bottom. After subtracting backgrounds from radon introduced in the scintillator during preparation and filling, constraints on the amount of Po-210 were obtained. Estimates on the K-40 content of the Nd-loaded scintillator were obtained by analyzing the radon-subtracted background spectra. By comparing the background spectra with the bucket deployed at the bottom of the acrylic vessel with spectra from the bucket at the centre, it was possible to estimate the K-40 content of the acrylic vessel. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2010-09-22 11:55:44.351

The starting SNO+ experiment, successor to the Sudbury Neutrino Observatory, is a neutrino detector using LAB based liquid scintillator as active medium. Situated in the SNOLab deep underground laboratory in Sudbury, Canada, the rock overburden amounts to about 6 km.w.e., providing an effective shielding against cosmic rays. The residual muon rate is 63 μ/day going through the detector volume. About 780 t of an LAB mixture inside an acrylic sphere with a 6 m radius will be observed by ≈ 9300 photomultipliers, surrounded by a ≈ 7000 t water shielding. SNO+ will be searching for low energy solar-, geo-, reactor- and supernova neutrinos, but the main goal is the observation of the neutrinoless double beta decay in Te-130. Under operating conditions, the scintillator will be cooled to about 12° C. This work investigated the effect of temperature changes on the light output of LAB based liquid scintillator in a range from -5° C to 30° C with α-particles and electrons in a small scale setup. Assuming a linear behaviour, a combined negative temperature coefficient of (−0.29 ± 0.01) %/° C is found. Considering hints for a particle type dependency, electrons show (−0.17 ± 0.02) %/° C whereas the temperature dependency seems stronger for α-particles (−0.35 ± 0.03) %/° C. A pulse shape analysis shows increased strength of a slow decay component at lower temperatures, pointing to reduced non-radiative triplet state de-excitations at lower temperatures. Furthermore, this work found upper bounds for the in-situ muon-induced isotope production via scaling calculations and simulations with Geant4 based software. For the most concerning isotope C-11, an upper limit of about 1.3 × 10^3 decays/kt/yr is found and a reduction technique, developed by the Borexino collaboration, can be effectively applied for SNO+. Also a muon reconstruction algorithm is implemented, performing reasonably well, but not good enough to improve the background reduction scheme. / Das zukünftige SNO+ experiment, Nachfolger des Sudbury Neutrino Observatory, ist ein Neutrino-Detektor mit LAB basierten Flüssigszintillator als aktivem Medium. Im SNOLab Untertagelabor (Sudbury, Kanada) gelegen, ist es durch die Felsüberdeckung von 6 km.w.e. hervorragend gegen kosmische Strahlung abgeschirmt. Die Rate der übrigen Myonen die das Detektorvolumen durchdringen beträgt ca. 63 μ/Tag. In einer Acrylkugel, mit einem Radius von 6 m, wird eine LAB Mischung von ≈ 9300 Photomultipliern beobachtet und von einer Wasserabschirmung von ≈ 7 kt umgeben. SNO+ wird nach niederenergetischen solaren-, Geo-, Reaktor- und Supernova Neutrinos suchen, aber das Hauptziel ist die Beobachtung von neutrinolosen doppelten Betazerfällen in Te-130. Unter den Betriebsbedingungen wird der Flüssigszintillator eine Temperatur von ca. 12° C annehmen. Diese Arbeit hat den Einfluss von Temperaturveränderungen in einem Bereich von -5° C to 30° C auf die erzeugte Lichtmenge untersucht. Dazu wurden α-Teilchen und Elektronen in einem kleineren Versuchaufbau beobachtet. Unter der Annahme eines linearen Verhaltens, wurde ein globaler negativer Temperaturkoeffizient von (−0.29 ± 0.01) %/° C gefunden. Unter Berücksichtigung von Hinweisen auf eine Teilchenartabhängigkeit, findet sich für Elektronen ein Koeffizient von (−0.17 ± 0.02) %/° C, wohingegen α-Teilchen eine stärkere Abhängikeit von (−0.35 ± 0.03) %/° C aufweisen. Eine Pulsformanalyse zeigt eine bei tieferen Temperaturen stärker ausgeprägte langsame Zerfallskomponente, was darauf hinweist dass die nicht-radiativen Abregungen der Triplet-Zustände bei niedrigeren Temperaturen reduziert sind. Weiterhin wurden in dieser Arbeit obere Ausschlußgrenzen für in-situ Myon-induzierte Isotopenproduktion gefunden, wozu Skalierungsrechnungen und Simulation mit auf Geant4 basierender Software benutzt wurden. Für das wichtigste Isotop C-11 wurde eine obere Grenze von 1.3 × 10^3 Ereignisse/kt/Jahr gefunden und eine Technik zur Reduzierung des Untergrundes, entwickelt von der Borexino Kollaboration, kann effektiv für SNO+ angewendet werden. Darüber hinaus wurde eine Myon Spurrekonstruktion implementiert, die sinnvolle Ergebnisse liefert, aber nicht gut genug ist um die Untergrund Reduzierung zu unterstützen.

Les progrès réalisés dans la maîtrise de la physique et de la détection des neutrinos ouvrent aujourd'hui la porte à la physique appliquée des antineutrinos. Dans cette optique, cette particule a en effet la particularité fondamentale de porter l'information de son lieu d'émission sans perturbation. Comme les neutrinos sont liés aux processus faibles tels que la désintégration nucléaire beta les applications se trouvent dans la surveillance des matières radioactives et des réacteurs nucléaires. Dans ce contexte, le projet Nucifer vise à construire et opérer un détecteur miniature d'antineutrinos de réacteur nucléaire, à installer au maximum à quelques dizaines de mètres d'un réacteur de puissance pour suivre sa puissance thermique et évaluer la quantité de plutonium produite. De plus, une réanalyse récente des mesures précédentes réalisées à proximité de réacteurs ces 40 dernières années montrent un écart significatif entre les taux de détection neutrinos attendus et mesurés. Parmi les hypothèses variées qui permettent d'expliquer cette anomalie se trouve une nouvelle oscillation entre neutrinos, impliquant nécessairement l'existence d'un quatrième neutrino, stérile. Pour mettre en évidence les antineutrinos et mesurer leur énergie, la détection beta inverse dans environ 850 kg de liquide scintillant dopé au gadolinium est utilisée. Toute la difficulté expérimentale provient des bruits de fond, qui peuvent être très importants lorsque le détecteur est installé ) proximité du réacteur ou de la surface. Le détecteur est maintenant intégré sur le réacteur nucléaire de recherche Osiris du CEA, situé à Saclay, et a commencé la prise de données en avril 2012. Malheureusement, une faible longueur d'atténuation du liquide et un niveau de bruit de fond gamma inattendu nous empêchent de distinguer les neutrinos. Nous attendons maintenant le remplacement du liquide et la construction d'un nouveau mur de plomb pour continuer l'étude du suivi du réacteur et pour tester l'hypothèse de neutrino stérile. / The major advances done in the understanding of neutrinos properties and in detector technology have opened the door to a new discipline: the Applied Antineutrino Physics. Indeed, this particle has the great advantage to carry information from its emission place without perturbation. Because neutrinos are inextricably linked to nuclear processes, new applications are in nuclear safeguards. In this context, the Nucifer project aims to test a small electron-antineutrino detector to be installed a few 10 meters from a reactor core for monitoring its thermal power and for testing the sensitivity to the plutonium content. Moreover, recent re-analysis of previous short-distance reactor-neutrino experiments shows a significant discrepancy between measured and expected neutrino count rates. Among the various hypotheses a new phenomenon as the existence of a fourth sterile neutrino can explain this anomaly. To be able to count neutrinos and get the corresponding energy spectrum, the detection is based on the inverse beta decay in about 850 kg of doped liquid scintillator. The experimental challenge is to operate such a small detector in a high background place, due to the closeness with the surface and the reactor radiations. The detector is now finished and data taking has begun at the Osiris research reactor in Saclay since april 2012. Sadly, unexpected low liquid attenuation length and high gamma background level prevented us to highlight neutrinos. We are now waiting for a liquid change and a new lead wall to study reactor monitoring and to test the sterile neutrino hypothesis.

It has been shown that neutrons emitted from the same 252Cf fission event are preferentially detected within small angles of each other and at angles around 180 degrees. The distribution of this angular anisotropy is dependent upon the nuclide emitting the neutrons. Coincident neutrons can be detected from a shielded source, so a study of the angular anisotropy between coincident neutrons is useful for this context. This could allow for the dynamic determination of the ratio of the rate of (alpha,n) neutron production to the spontaneous fission neutron production (designated alpha) used in neutron coincidence counting for safeguards. This could also be used to identify neutron emitting isotopes in a homeland security application. An angular frequency distribution for coincident neutrons was produced via experiments using an array of cylindrical liquid scintillators and a 252Cf source. It was found, in accordance with previous experiments, that the angular frequency distribution peaks at small angles and at angles around 180 degrees. A Monte Carlo, physics-based simulation program was created to simulate the distribution of angles between neutrons from the same fission event from 252Cf and 240Pu sources. The resulting distributions were clearly distinguishable from each other. The code was benchmarked to measured results from a 252Cf source at Lawrence Livermore National Laboratory. Knowledge of the unique angular distributions of coincident neutrons from various fissioning sources is useful for identification and verification purposes. Another practical application of angular anisotropy information for coincident neutrons from a given source is determining the ratio of the (alpha,n) to spontaneous fission rates for a source undergoing neutron coincidence counting. The utility of this was verified by using measurements made by faculty and students of the University of Michigan Nuclear Engineering Department for a MOX fuel pin at the Joint Research Center in Ispra, Italy. Good agreement between the predicted and declared values for alpha was found.

SNO+, the successor of the Sudbury Neutrino Observatory, is an upcoming low energy neutrino experiment, located in the 2 km deep laboratory SNOLAB, Canada. The spheric acrylic vessel in the detector center will contain 780 t of LAB. The main goal of SNO+ is the search for the neutrinoless double beta decay of 130Te, using a novel scintillator in which natural Te is bound with an initial loading of 0.3% via water and a surfactant. Within this thesis, the first measurement of the Alpha-particle and proton quenching parameters of loaded and unloaded LAB is described. These parameters are crucial for an efficient background suppression, necessary to reach a sensitivity above the current limit in 76Ge of T1/2(0v) > 2.1 x 10^(25) y (90% C.L.). For 0.3% Te-loading, the quenching parameter obtained is kB = (0.0070 +/- 0.0004) cm/MeV for Alpha-particles and kB = (0.0090 +/- 0.0003) cm/MeV for protons. Additionally, the spectral sensitivity of SNO+ to supernova electron anti-neutrinos and muon and tau (anti-)neutrinos is determined for the first time, using inverse beta decay and v-p elastic scattering with the measured quenching parameters. The obtained sensitivity to the mean energy of electron anti-neutrinos is E = 15.47^(+1.54)_(-2.43) MeV and of muon and tau (anti-)neutrinos is E = 17.81^(+3.49)_(-3.09) MeV. / SNO+, der Nachfolger des Sudbury Neutrino Observatorys, ist ein bevorstehendes Niederenergie-Neutrino-Experiment im 2 km tiefen Untergrundlabor SNOLAB in Kanada. Die Acryl-Kugel im Zentrum des Detektors wird mit 780 t LAB gefüllt werden. Das Hauptziel von SNO+ ist die Suche nach dem neutrinolosen Doppelbetazerfall von 130Te mit einem neuartigen Szintillator, in dem natürliches Te mit einer Anfangskonzentration von 0.3% über Wasser und ein Tensid gebunden wird. In dieser Arbeit wird erstmals die Messung der Alpha-Teilchen und Proton Quenching Parameter in diesem und in normalem LAB beschrieben. Die Parameter sind unverzichtbar für eine effiziente Untergrund Unterdrückung, die notwendig ist um auf das bestehende Limit in 76Ge von T1/2(0v) > 2.1 x 10^(25) y (90% C.L.) sensitiv zu sein. Der ermittelte Quenching Parameter bei 0.3% Te beträgt kB = (0.0070 +/- 0.0004) cm/MeV für Alpha-Teilchen und kB = (0.0090 +/- 0.0003) cm/MeV für Protonen. Zusätzlich wird erstmals die spektrale Sensitivität von SNO+ auf Supernova Elektron Anti-Neutrinos und Muon and Tau (Anti-)Neutrinos bestimmt über den inversen Betazerfall und die elastische v-p Streuung zusammen mit den gemessenen Quenching Parametern. Die ermittelte Sensitivität auf die mittlere Energie der Elektron Anti-Neutrinos ist E = 15.47^(+1.54)_(-2.43) MeV und der Muon und Tau (Anti-)Neutrinos ist E = 17.81^(+3.49)_(-3.09) MeV.

This report describes investigations of the NE213-detector and the possibility to utilize pulse shape analysis to separate neutrons and gammas in a mixed emission field. Neutron fluxes are often contaminated with gammas, to which the detectors are sensitive. Sorting out the unwanted gamma pulses from the interesting neutrons is therefore crucial in many situations, for instance in fusion reactor diagnostics, such as for neutron cameras. This can be done based on pulse shapes, which differ for gammas and neutrons interacting in the NE213-detector. By analyzing the pulse shapes from a digital transient recorder, neutrons can be distinguished from gammas. An experiment with a Cf-252 neutron source was set up and provided data. The separation algorithm was based on charge comparison and gave good results. Furthermore the results of the pulse shape analysis were verified by TOF-measurements. The lowest permissible energy for a reasonable separation was found to be around 0.5 MeV. Some conclusions on the limitations of the equipment were also made.

A real time low energy spectral measurement of the neutrinos coming from the Sun will give us a greater understanding of energy production in the Sun, and the mechanisms of neutrino mixing. We will, for the first time, measure the solar neutrino spectrum for all solar neutrinos <2MeV in particular pp, Be and CNO neutrinos, be able to compare the solar photon derived energy luminosity (Lï §) to the solar neutrino derived energy luminosity (Lï ®) independent of any solar model, explore dark energy with respect to mass varying neutrinos, and explore CNO abundances in the Sun. These measurements require new technology in Indium loaded scintillators and large scale detector designs, namely increased spatial resolution through a novel scintillation lattice. I will present the advances we are making to these fields at Virginia Tech as well as neutrino science and the physics of the LENS detector. / Ph. D.