Investigation of charge sharing among electrode strips for a CdZnTe detector

We have investigated charge sharing among the anode strips of a CdZnTe (CZT) detector using a 30 micrometer collimated gamma-ray beam. We compared the laboratory measurements with the predictions from our modeling of the charge transport within the detector. The results indicate that charge sharing is a function of the interaction depth and the energy of the incoming photon. Also, depending on depth, a fraction of the electrons might drift to the inter-anode region causing incomplete charge collection. Here, we show that photoelectron range and diffusion of the charge cloud are the principal causes of charge sharing and obtain limits on the size of the electron cloud as a function of position in the detector.Comment: 16 pages 10 figures. Accepted for publication in Nuclear Instruments and Methods -

Evaluation of 2009 Oregon crash data reported to the Motor Carrier Management Information System Crash File

This report is part of a series evaluating the data reported to the Motor Carrier Management Information System (MCMIS) Crash File undertaken by the Center for National Truck and Bus Statistics at the University of Michigan Transportation Research Institute. Earlier studies have shown that reporting to the MCMIS Crash File was generally incomplete. This report examines reporting by the State of Oregon. Because key variables used in the evaluation process are not recorded in the computerized state data files, it was not possible to calculate an overall reporting rate for Oregon. It appears that Oregon reported 28 of 30 qualifying vehicles in fatal crashes, and the 1,120 total vehicles actually reported is reasonably close to the number predicted by a model that estimates the number of vehicles reportable to the MCMIS Crash file. However, it was not possible to evaluate the extent of underreporting or overreporting. An evaluation of timeliness in reporting shows that Oregon tended to upload records to the MCMIS Crash file well after the 90-day grace period ended. Only about 5 percent of records submitted were uploaded within the grace period. Missing data rates are low for most variables, though specific problems were noted with the hazmat variables. Corresponding data elements in the MCMIS and Oregon crash files were reasonably consistent except as noted with the straight truck and truck tractor configurationsFederal Motor Carrier Safety Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/89597/1/102789.pd

Evaluation of 2009 Virginia crash data reported to the Motor Carrier Management Information System Crash File

This report is part of a series evaluating the data reported to the Motor Carrier Management Information System (MCMIS) Crash File undertaken by the Center for National Truck and Bus Statistics at the University of Michigan Transportation Research Institute. Earlier studies have shown that reporting to the MCMIS Crash File was generally incomplete. This report examines the factors that are associated with reporting rates for the State of Virginia. MCMIS Crash File records were matched to the Virginia Crash file to determine the nature and extent of underreporting. Overall, it appears that Virginia is reporting 75.2 percent of crash involvements that should be reported to the MCMIS Crash file. Because police officers are instructed to code tractors with trailers as single unit trucks with three axles, reporting rates by truck configuration were not calculated, but the reporting rate for all trucks is 76.1 percent, and the reporting rate for buses is 67.4 percent. The reporting rate for fatal crashes is 84.1 percent, 77.3 percent for injured/transported crashes, and 73.0 percent for towed/disabled crashes. The Virginia Police Crash Report form has a Commercial Motor Vehicle Section and it appears that the data recorded in this section plays a major role in determining what information gets uploaded to the MCMIS Crash file. Missing data rates are low for most variables. Corresponding data elements in the MCMIS and Virginia Crash files were reasonably consistent for several variables examined.Federal Motor Carrier Safety Administrationhttp://deepblue.lib.umich.edu/bitstream/2027.42/89600/1/102792.pd

Spectrum of the gamma-ray diffuse component observed from HEAO-1

The spectrum of the diffuse X and gamma ray background was measured between 15 keV and 4 MeV with the scintillation detectors aboard the HEAO 1 satellite. The apertures of the detectors were modulated on time scales of hours and the difference in counting rates measured the diffuse component flux. The observed spectrum is presented and compared with other measurements. At least two components are indicated, one below -100 keV and the other above. Possible origins are discussed

Spectra and positions of galactic gamma-ray sources

The UCSD/MIT Hard X-Ray and Low Energy Gamma-Ray Experiment aboard HEAO-1 scanned the galactic center region during three epochs in 1977 and 1978 from 13 to 180 keV. The results are presented from the scanning epoch of 1978 September. Twenty-two known 2 to 10 keV source positions were necessary for an acceptable fit to the data. The spectra of the 16 strongest, least confused sources are all consistent with power laws with photon spectral indices ranging from 2.1 to 7.2. Acceptable fits to thermal bremsstrahlung models are also possible for most sources. No one source in this survey can be extrapolated to higher energy to match the intensity of the gamma-ray continuum as measured by HEAO-1 large field of view detectors, which implies that the continuum is a composite of contributions from a number of sources

Study of aircraft in intraurban transportation systems, volume 1

An analysis of an effective short range, high density computer transportation system for intraurban systems is presented. The seven county Detroit, Michigan, metropolitan area, was chosen as the scenario for the analysis. The study consisted of an analysis and forecast of the Detroit market through 1985, a parametric analysis of appropriate short haul aircraft concepts and associated ground systems, and a preliminary overall economic analysis of a simplified total system designed to evaluate the candidate vehicles and select the most promising VTOL and STOL aircraft. Data are also included on the impact of advanced technology on the system, the sensitivity of mission performance to changes in aircraft characteristics and system operations, and identification of key problem areas that may be improved by additional research. The approach, logic, and computer models used are adaptable to other intraurban or interurban areas

Spectral Hardness Decay with Respect to Fluence in BATSE Gamma-Ray Bursts

We have analyzed the evolution of the spectral hardness parameter Epk as a function of fluence in gamma-ray bursts. We fit 41 pulses within 26 bursts with the trend reported by Liang & Kargatis (1996) which found that Epk decays exponentially with respect to photon fluence. We also fit these pulses with a slight modification of this trend, where Epk decays linearly with energy fluence. In both cases, we found the set of 41 pulses to be consistent with the trend. For the latter trend, which we believe to be more physical, the distribution of the decay constant is roughly log-normal, with a mean of 1.75 +/- 0.07 and a FWHM of 1.0 +/- 0.1. Regarding an earlier reported invariance in the decay constant among different pulses in a single burst, we found probabilities of 0.49 to 0.84 (depending on the test used) that such invariance would occur by coincidence, most likely due to the narrow distribution of decay constant values among pulses.Comment: 17 pages, 7 figure pages, 2 table pages, submitted to The Astrophysical Journa

Evolution of the Low-Energy Photon Spectra in Gamma-Ray Bursts

We report evidence that the asymptotic low-energy power law slope alpha (below the spectral break) of BATSE gamma-ray burst photon spectra evolves with time rather than remaining constant. We find a high degree of positive correlation exists between the time-resolved spectral break energy E_pk and alpha. In samples of 18 "hard-to-soft" and 12 "tracking" pulses, evolution of alpha was found to correlate with that of the spectral break energy E_pk at the 99.7% and 98% confidence levels respectively. We also find that in the flux rise phase of "hard-to-soft" pulses, the mean value of alpha is often positive and in some bursts the maximum value of alpha is consistent with a value > +1. BATSE burst 3B 910927, for example, has a alpha_max equal to 1.6 +/- 0.3. These findings challenge GRB spectral models in which alpha must be negative of remain constant.Comment: 12 pages (including 6 figures), accepted to Ap