Charge trapping, resulting in a decreased and spatially dependent electric field, has long been a concern for wide bandgap semiconductor detectors. While significant work has been performdto ...characterize this degradation at varying temperatures and radiation environments, this work concentrates upon examining the event-to-event response in a flash X-ray environment. The following workinvestigates if charge trapping is a problem for CZT detectors, with particular emphasis on flash X-ray radiation fields at cold temperatures. Results are compared to a non-flash radiation field, using an Am-241 alpha source and similar temperature transitions. Our ability to determine if a response change occurred was hampered by the repeatability of our flash X-ray systems; a small responsechange was observed with the Am-241 source. Due to contrast of these results, we are in the process of revisiting the Am-241 measurements in the presence of a high radiation environment. If the response change is more pronounced in the high radiation environment, asimilar test will be performed in the flash X-ray environment.
The MiniBooNE Collaboration observes unexplained electronlike events in the reconstructed neutrino energy range from 200 to 475 MeV. With 6.46x10;{20} protons on target, 544 electronlike events are ...observed in this energy range, compared to an expectation of 415.2+/-43.4 events, corresponding to an excess of 128.8+/-20.4+/-38.3 events. The shape of the excess in several kinematic variables is consistent with being due to either nu_{e} and nuover _{e} charged-current scattering or nu_{mu} neutral-current scattering with a photon in the final state. No significant excess of events is observed in the reconstructed neutrino energy range from 475 to 1250 MeV, where 408 events are observed compared to an expectation of 385.9+/-35.7 events.
The sidereal time dependence of MiniBooNE νe and ν¯e appearance data is analyzed to search for evidence of Lorentz and CPT violation. An unbinned Kolmogorov–Smirnov (K–S) test shows both the νe and ...ν¯e appearance data are compatible with the null sidereal variation hypothesis to more than 5%. Using an unbinned likelihood fit with a Lorentz-violating oscillation model derived from the Standard Model Extension (SME) to describe any excess events over background, we find that the νe appearance data prefer a sidereal time-independent solution, and the ν¯e appearance data slightly prefer a sidereal time-dependent solution. Limits of order 10−20 GeV are placed on combinations of SME coefficients. These limits give the best limits on certain SME coefficients for νμ→νe and ν¯μ→ν¯e oscillations. The fit values and limits of combinations of SME coefficients are provided.
The observation of neutrino oscillations is clear evidence for physics beyond the standard model. To make precise measurements of this phenomenon, neutrino oscillation experiments, including ...MiniBooNE, require an accurate description of neutrino charged current quasielastic (CCQE) cross sections to predict signal samples. Using a high-statistics sample of nu_(mu) CCQE events, MiniBooNE finds that a simple Fermi gas model, with appropriate adjustments, accurately characterizes the CCQE events observed in a carbon-based detector. The extracted parameters include an effective axial mass, M_(A)(eff)=1.23+/-0.20 GeV, that describes the four-momentum dependence of the axial-vector form factor of the nucleon, and a Pauli-suppression parameter, kappa=1.019+/-0.011. Such a modified Fermi gas model may also be used by future accelerator-based experiments measuring neutrino oscillations on nuclear targets.
The MiniBooNE detector Aguilar-Arevalo, A.A.; Anderson, C.E.; Bartoszek, L.M. ...
Nuclear instruments & methods in physics research. Section A, Accelerators, spectrometers, detectors and associated equipment,
02/2009, Letnik:
599, Številka:
1
Journal Article
Recenzirano
The MiniBooNE neutrino detector was designed and built to look for
ν
μ
→
ν
e
oscillations in the
(
sin
2
2
θ
,
Δ
m
2
)
parameter space region where the LSND experiment reported a signal. The ...MiniBooNE experiment used a beam energy and baseline that were an order of magnitude larger than those of LSND so that the backgrounds and systematic errors would be completely different. This paper provides a detailed description of the design, function, and performance of the MiniBooNE detector.
The MiniBooNE Collaboration reports a search for nu_{micro} and nuover_{micro} disappearance in the Deltam;{2} region of 0.5-40 eV;{2}. These measurements are important for constraining models with ...extra types of neutrinos, extra dimensions, and CPT violation. Fits to the shape of the nu_{micro} and nuover_{micro} energy spectra reveal no evidence for disappearance at the 90% confidence level (C.L.) in either mode. The test of nuover_{micro} disappearance probes a region below Deltam;{2} = 40 eV;{2} never explored before.
The excellent inherent energy resolution of CdZnTe and the evolution of techniques to fabricate this material into large, multi-pixel monolithic arrays, have encouraged the development of practical, ...multi-function, x-ray imaging systems. These systems are capable of simultaneously recording the x-ray image of an object while identifying the average atomic number of each of its internal components. The primary improvement of this new sensor technology is the ability to break down the detected radiation into energy bins after passing through the sample. The reduced fraction of scattered radiation recorded in a collimated, linear scanner image makes it possible to separate differing energy regions of the beam with a single bremsstrahlung source and a single, multiple discriminators. Such imaging systems have immediate applications in security and contraband detection, as well as a number of specialized uses in medical imaging. This review covers recent work carried out at SAIC in the development of these systems including the characterization of the detector devices, the requirements for the electronic readout system and a number of examples of images taken with prototype systems. Studies have been conducted with examples of both linear and area arrays using relatively simple processing electronics. Problems of incomplete charge collection and energy separation are discussed along with potential solutions to these issues. Imaging measurements made with these systems exhibit noise limits set by the available statistics and excellent point spread functions. Practical limitations in the useful pixel resolution approach 0.1 mm with stopping thickness of several millimeters. This suggests that high resolution scanners with x-ray tube potentials of several hundred kilovolts are feasible with this technology.
Tomographic Imaging with Cosmic Ray Muons MORRIS, C. L.; ALEXANDER, C. C.; BACON, J. D. ...
Science & global security,
10/15/2008, Letnik:
16, Številka:
1-2
Journal Article
Recenzirano
Over 120 million vehicles enter the United States each year. Many are capable of transporting hidden nuclear weapons or nuclear material. Currently deployed X-ray radiography systems are limited ...because they cannot be used on occupied vehicles and the energy and dose are too low to penetrate many cargos. We present a new technique that overcomes these limitations by obtaining tomographic images using the multiple scattering of cosmic radiation as it transits each vehicle. When coupled with passive radiation detection, muon interrogation could contribute to safe and robust border protection against nuclear devices or material in occupied vehicles and containers.
The sidereal time dependence of MiniBooNE ν e and ν ¯ e appearance data is analyzed to search for evidence of Lorentz and CPT violation. An unbinned Kolmogorov–Smirnov (K–S) test shows both the ν e ...and ν ¯ e appearance data are compatible with the null sidereal variation hypothesis to more than 5%. Using an unbinned likelihood fit with a Lorentz-violating oscillation model derived from the Standard Model Extension (SME) to describe any excess events over background, we find that the ν e appearance data prefer a sidereal time-independent solution, and the ν ¯ e appearance data slightly prefer a sidereal time-dependent solution. Limits of order 10 - 20 GeV are placed on combinations of SME coefficients. These limits give the best limits on certain SME coefficients for ν μ → ν e and ν ¯ μ → ν ¯ e oscillations. The fit values and limits of combinations of SME coefficients are provided.
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