FABRICATION, MEASUREMENTS, AND MODELING OF SEMICONDUCTOR RADIATION DETECTORS FOR IMAGING AND DETECTOR RESPONSE FUNCTIONS

In the first part of this dissertation, we cover the development of a diamond semiconductor alpha-tagging sensor for associated particle imaging to solve challenges with currently employed scintillators. The alpha-tagging sensor is a double-sided strip detector made from polycrystalline CVD diamond. The performance goals of the alpha-tagging sensor are 700-picosecond timing resolution and 0.5 mm spatial resolution. A literature review summarizes the methodology, goals, and challenges in associated particle imaging. The history and current state of alpha-tagging sensors, followed by the properties of diamond semiconductors are discussed to close the literature review. The materials and methods used to calibrate the detector readout, fabricate the sensor, perform simulations, take measurements, and conduct data analysis are discussed. The results of our simulations and measurements are described with challenges and interpretations. The first part of the dissertation is concluded with potential solutions to challenges with our diamond alpha-tagging sensor design, recommendations of work to help further verify or refute diamonds viability for alpha tagging in associated particle imaging. In the second part of this dissertation, we cover the development of a high-purity germanium detector response function for the Los Alamos National Laboratory Detector Response Function Toolkit. The goal is to accurately model the pulse-height spectra measured by semiconductor radiation detectors. The literature review provides information on high-purity germanium radiation detectors and semiconductor charge transport kinematics. The components of the electronic readout and their effect on radiation measurements are discussed. The literature review ends with a discussion on different methods for building detector response functions. In the methods section, we explain our methodology for building detector response functions. This includes models of radiation transport, electrostatics, charge transport, and electronic readout components. Within the methods section, there are results from individual components to demonstrate their functionality. The results section is reserved for demonstrating the use of the detector response function as a whole. We provide the modeled pulse-height spectra for different radiation sources and user input parameters. These are compared to experimentally measured datasets. The second part of the dissertation concludes with a discussion of the benefits, drawbacks, and future improvements that could be made

Mejoras en la detección de rayos gamma con cristales centelladores de última generación y aplicaciones

Tesis inédita de la Universidad Complutense de Madrid, Facultad de Ciencias Físicas, Departamento de Física Atómica, Molecular y Nuclear, leída el 05/07/2013Depto. de Estructura de la Materia, Física Térmica y ElectrónicaFac. de Ciencias FísicasTRUEunpu

List-mode data acquisition based on digital electronics - State-of-the-art report

This report deals with digital radiation detection systems employing list-mode data collection, which improves data analysis capabilities. Future data acquisition systems shall also ultimately enable the movement of detection data from first responders electronically to analysis centres rather than the costly and time consuming process of moving experts and/or samples. This new technology is especially useful in crisis events, when time and resources are sparse and increased analysis capacity is required. In order to utilise the opportunities opened by these new technologies, the systems have to be interoperable, so that the data from each type of detector can easily be analysed by different analysis centres. Successful interoperability of the systems requires that European and/or international standards are devised for the digitised data format. The basis of such a format is a list of registered events detailing an estimate of the energy of the detected radiation, along with an accurate time-stamp for recorded events (and optionally other parameters describing each event).JRC.G.5-Security technology assessmen

Search for the double beta decay of Zr-96 with NEMO-3 and calorimeter development for the SuperNEMO experiment

Using 9.4 g of Zr-96 and 1221 days of data from the NEMO-3 detector corresponding to 0.031 kgy, the obtained 2vbb decay half-life measurement is [2.35 \pm 0.14(stat) \pm 0.16(syst)] \times 10_{19}yr. Different characteristics of the final state electrons have been studied, such as the energy sum, individual electron energy, and angular distribution. The 2v nuclear matrix element is extracted using the measured 2vbb half-life and is 0.049 \pm 0.002. The 0vbb decay half-life is excluded at the 90% CL to > 9.2 \times 10_^{21}yr corresponding to a limit on the effective Majorana neutrino mass of < 7.2 – 19.4 eV. Limits on other mechanisms of 0vbb have also been set. Due for commissioning in 2012, SuperNEMO is the next generation detector which improves upon the proven technology and success of NEMO-3 to achieve a half-life sensitivity of ~10_{26} yr (90% CL) for Se-82 which corresponds to a neutrino mass of 50-100 meV. An energy resolution of 7% FWHM at 1 MeV has been obtained for the calorimeter baseline design of SuperNEMO which is currently in the R&D phase. This result not only meets the requirement stipulated by the R&D proposal, but is unprecedented for this type of calorimeter design

Two new installations for non-destructive sample analysis: PIXE and PGAA

A new Proton Induced X-Ray Emission (PIXE) set-up has been designed and built at the Tandem Accelerator of the University of Cologne. The PIXE installation is used for the determination of elemental composition of thin samples or sample surfaces. The set-up was calibrated and tested with various types of samples. The experiments have been automated and the standard analogue based acquisition system has been replaced by a digital one based on the XIA DGF-4C modules. A small Peltier-cooled XFlash detector has been generally in use and brings many advantages when compared with common Si(Li) detectors. A scanning device can be used for macro-scanning of the surface of PIXE samples and the 2D elemental distribution can be determined. The absolute analysis of the sample composition with a commercial program GUPIX is described. Representative analysis of various samples is presented and compared to literature values or to the results of the PGAA method. The PIXE installation is now ready for routine use. A new Prompt Gamma-Ray Activation Analysis (PGAA) facility is now being designed for the research reactor FRM-II in Garching by Munich. The PGAA instrument at FRM-II will use a beam of cold neutrons for the determination of the elemental and isotopic composition of a sample bulk. A number of Monte Carlo simulations were performed to obtain the most convenient beam guide geometry for the cold neutrons; first to keep the neutron flux as high as possible and also to find out, how to focus the neutrons to a small spot of 1x1 mm^2. The divergence of the neutron beam was also part of the study. The challenging task is to make the PGAA facility flexible for four different instrumental set-ups: standard PGAA, Position-Sensitive PGAA, Cold Neutron Tomography and an Ge Array for nuclear structure experiments. The expected parameters of the PGAA facility at FRM-II are then compared to the former one at Paul Scherrer Institute (PSI) in Switzerland. In close cooperation with the PGAA group at the Budapest Neutron Centre (BNC) in Budapest, interesting geological samples were measured and analyzed. Small amounts of samples (100 - 300 mg) were analyzed to demonstrate the reliability of the PGAA analysis even for such cases. The results of the analysis for geological standards and meteorites, both either as stones or as homogeneous powders are presented and discussed. PIXE and PGAA analysis for the same samples were performed, the results were compared and conclusions about when PIXE and PGAA are competitive and when complementary are given. In case of PGAA, comparison with Instrumental Neutron Activation Analysis (INAA) is also discussed

Fission Yield Measurements from Deuterium-Tritium Fusion Produced Neutrons Using Cyclic Neutron Activation Analysis and Coincidence Counting.

The work described in this dissertation used cyclic neutron activation analysis (CNAA) coupled with gamma-gamma coincidence counting with high-purity germanium detectors to measure the independent and cumulative fission yields of short-lived fission products from thorium-232, uranium-235, and uranium-238. Fission yields of short-lived fission products are needed to enhance the precision and expediency of pre- and post-detonation nuclear forensics. The measurements presented in this work illustrate the large differences in the delayed gamma-ray response following a nuclear detonation. The work performed in this dissertation applied non-destructive CNAA using deuterium-tritium fusion produced neutrons to induce fission. Irradiated targets were shuttled from the irradiation position at the face of the neutron generator to a radiation detection system in less than 0.3 seconds using a pneumatic transfer system. Delayed gamma-rays emitted by fission progeny with half-lives on the order of seconds to several minutes were acquired using three high-purity germanium detectors operating in coincidence. Gamma emissions from this timescale exhibit the largest differences in intensity between individual actinides because of order-of-magnitude variations in independent fission yields for fission products at the wings and valley of the fission product distribution curve. Fission product decay data from the listed targets were evaluated to measure the fission yields of arsenic-84, selenium-86, bromine-88, krypton-90 and -92, rubidium-94, strontium-94, -95, and -96, yttrium-96m, zirconium-99, barium-143, and lanthanum-146. Time-dependent gamma-ray spectra were used to measure the fission yields of the listed radioisotopes along with: bromine-86 and -87, krypton-89, yttrium-97m and -99, tellurium-136, iodine-136 metastable and ground states, xenon-138, -139, and -140, cesium-140 and -142, and barium and lanthanum-144. All of the measured fission yields have yet to be experimentally determined, with exception to the noble gases. In the near term, these fission yields will improve the accuracy of the fission yields of fission products with half-lives on the order of hours to days produced by deuterium-tritium fusion neutron induced fission. Better precision in the fission yields of longer lived fission products improves the accuracy of the nuclear forensics process. In the future, these fission yields could aid nuclear forensics analyses from a global array of high-resolution gamma spectrometers.PhDNuclear Engineering and Radiological SciencesUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/133371/1/bpnuke_1.pd

Indirect Studies of Astrophysical Radiative Capture Reactions

The first study in this work focuses on the 23Mg(p,g)24Al reaction. Although several resonances may contribute to the overall rate at novae temperatures, the resonance at ~475 keV is thought to be dominant. The strength of this resonance has been directly measured using a radioactive 23Mg beam impinging on a windowless H2 gas target using the DRAGON facility at TRIUMF; however, recent high-precision 24Al mass measurements have called this result into question. An indirect measurement of the proton width using the 23Na(d,p)24Na reaction in inverse kinematics has been performed to study the mirror state of the ~475 keV resonance in 24Na. A measurement of the spectroscopic factor of the 2512 keV state in 24Na is also presented. These results are discussed with a focus on previous theory calculations and experimental results. The second study attempts to probe the photon strength function in 58Fe. The photon strength function can provide insight into the properties of nuclei that are difficult to directly measure. In particular, Hauser-Feshbach reaction models typically use this statistical quantity to describe electromagnetic coupling. By constraining this theoretical input, a more accurate understanding of a given nucleus can be attained. This quantity may also be useful in making inferences about other neutron capture reactions. An analysis of multi-step gamma cascades from individual resonances from the 57Fe(n,g)58Fe reaction is presented. Comparisons of this experimental data to gamma-cascades simulated by DICEBOX is shown, and constraints on the photons strength function are proposed