Synchrotron radiation studies of spectral response features caused by Te inclusions in a large volume coplanar grid CdZnTe detector
We report preliminary results from a synchrotron radiation study of Te inclusions in a large volume single crystal CdZnTe (CZT) coplanar-grid detector. The experiment was carried out by probing individual inclusions with highly collimated monochromatic X- and γ-ray beams. It was found that for shallow X-ray interaction depths, the effect of an inclusion on measured energy loss spectra is to introduce a ∼10% shift in the peak centroid energy towards lower channel numbers. The total efficiency is however not affected, showing that the net result of inclusions is a reduction in the Charge Collection Efficiency (CCE). For deeper interaction depths, the energy-loss spectra shows the emergence of two distinct peaks, both downshifted in channel number. We note that the observed spectral behaviour shows strong similarities with that reported in semiconductors, which exhibit polarization effects, suggesting that the underlying mechanism is common.

title: Gamma-Ray Burst 980329 and Its X-Ray Afterglow
abstract: The gamma-ray burst (GRB) 980329 is the brightest gamma-ray burst detected so far with the Wide Field Cameras aboard BeppoSAX, in both gamma rays and X-rays. With respect to its fluence (2.6×10−5 ergs s−1 cm−2 in 50-300 keV), it would be in the top 4% of gamma-ray bursts in the 4B catalog (Meegan et al.). The time-averaged burst spectrum from 2 to 20 keV and from 70 to 650 keV can be well described by the empirical model of Band et al. The resulting photon index above the break energy is exceptionally hard at -1.32±0.03. An X-ray afterglow was detected with the narrow-field instruments aboard BeppoSAX 7 hr after the event within the error box as determined with the Wide Field Cameras. Its peak flux is (1.4±0.2)×10−12 ergs s−1 cm−2 (2-10 keV). The afterglow decayed according to a power-law function with an index of -1.35±0.03. GRB 980329 is characterized by being bright and hard and by lacking strong spectral evolution.

title: BeppoSAX observations of GRB970402
abstract: GRB970402 is the fourth gamma-ray burst detected by BeppoSAX simultaneously in the Gamma Ray Burst Monitor (GRBM) and one of the two Wide Field Cameras (WFCs). A rapid pointing of the BeppoSAX Narrow Field Instruments (NFIs) 8 hours after the GRB led to the identification of an unknown weak X-ray source: 1SAX J1450.1-6920. Its position was approximately at the center of the 3 arcmin error circle derived from the WFC image. Both the Medium Energy (MECS, 2-10 keV) and Low Energy (LECS, 0.1-10 keV) concentrators detected the source. A follow-up observation performed 1.5 days later and lasting 54 ks showed that the source had faded almost to, but not below the detectability threshold. The flux decrease between the two observations was a factor ~= 2.5. 1SAX J1450.1-6920 was the second X-ray afterglow associated with a GRB. Searches promptly started at other wavelengths (optical, IR, radio) did not reveal any transient event within the 3 arcmin error circle.

title: A BeppoSAX observation of the massive x-ray binary 4U1700-37
abstract: A 0.5-200 keV BeppoSAX spectrum of the non- pulsating high-mass X-ray binary 4U 1700-37 is presented. The spectrum is well characterized by the standard accret- ing pulsar model of an absorbed power-law with a photon in- dex of 1:07 0:02 0:03 , sharply modified by an exponential cutoff above 5:9 0:2 keV. The e-folding energy of the cutoff is 23:9 0:5 keV. A soft bremsstrahlung component with a tem- perature of0:20:1 keV is also required, together with a narrow iron line at 6.5 keV. Both continuum components are absorbed by a column of (5:1 0:2) 10 22 atom cm 2 . There is some evidence for the presence of a broad cyclotron absorption fea- ture at 37 keV, although we cannot exclude the possibility that this is due to an incorrect modeling of the continuum, or instrumental effects. The hypothesis that the compact object is a neutron star rather than a black hole seems most likely.

title: THE COMPLEX X-RAY SPECTRUM OF THE LOW-MASS X-RAY BINARY 4U 1626-67
abstract: We report on observations of the X-ray pulsar 4U 1626-67 by the LECS instrument on-board Bepposax. We confirm the recent ASCA discovery of excess emission near 1 keV (Angelini et al. 1995). The pulse period of 7.66794 +/- 0.00004 s indicates that the source continues to spin-down. The phase averaged spectrum is well fit by an absorbed power-law of photon index 0.61 +/- 0.02 and a blackbody of temperature 0.33 +/- 0.02 keV, together with an emission feature at 1.05 +/- 0.02 keV. This spectral shape is similar to that observed by ASCA during the spin-down phase, but significantly different from measurements during spin-up. This suggests that the change in spectrum observed by ASCA may be a stable feature during spin-down intervals. The source intensity is a factor ~2 lower than observed by ASCA three years earlier, confirming that 4U 1626-67 continues to become fainter with time.

title: SLAC Linac Preparations for FACET
abstract: The SLAC 3km linear electron accelerator has been cut at the two-thirds point to provide beams to two independent programs. The last third provides the electron beam for the Linac Coherent Light Source (LCLS), leaving the first two-thirds available for FACET, the new experimental facility for accelerator science and test beams. In this paper, we describe this separation and projects to prepare the linac for the FACET experimental program.

title: Simple technique for determining the mean lifetime of the cosmic ray μ meson
abstract: A single scintillation counter is used for determining the lifetime of cosmic ray μ mesons. The experimental arrangement has a greater detection rate and a higher detection efficiency than the conventional multidetector delayed coincidence technique.

title: The age distribution of galactic cosmic rays
abstract: The general solution for the distribution of ages for primary galactic cosmic rays is given for a class of steady-state, bounded models of cosmic-ray diffusion in the Galaxy. Both one-and threedimensional models are considered, with point sources and distributed sources. In all models, the age distribution, is approximately exponential for ages longer than the average age, although for shorter ages the distribution depends on the details of the model. The leaky-box model, with an exponential age distribution, is thus a good approximation to most diffusive models. It is shown that one-dimensional (‘disk’) models are consistent with both age and anisotropy data for galactic cosmic rays regardless of whether production takes place near the galactic center or throughout the disk.

title: Two-component model for cosmic-ray fluctuations at neutron monitor energies

title: Camtrac - A high energy gamma-ray telescope utilizing a coded aperture mask and drift chambers

title: A Simple Model for Galactic Cosmic Rays which is Consistent with Age and Anisotropy Data