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Full-Text Articles in Physical Sciences and Mathematics
Performance Of Cdznte Strip Detectors As Sub-Millimeter Resolution Imaging Gamma Radiation Spectrometers, M Mayer, V Boykin, M L. Cherry, J F. Courville, F P. Doty, A Drake, T G. Guzik, L A. Hamel, K Larson, John R. Macri, Mark L. Mcconnell, James M. Ryan, O Tousignant
Performance Of Cdznte Strip Detectors As Sub-Millimeter Resolution Imaging Gamma Radiation Spectrometers, M Mayer, V Boykin, M L. Cherry, J F. Courville, F P. Doty, A Drake, T G. Guzik, L A. Hamel, K Larson, John R. Macri, Mark L. Mcconnell, James M. Ryan, O Tousignant
Space Science Center
We report & gamma;-ray detection performance measurements and computer simulations of a sub-millimeter pitch CdZnTe strip detector. The detector is a prototype for & gamma;-ray astronomy measurements in the range of 20-200 keV. The prototype is a 1.5 mm thick, 64×64 orthogonal stripeCdZnTe detector of 0.375 mm pitch in both dimensions, with approximately one square inch of sensitive area. Using discrete laboratory electronics to process signals from an 8×8 stripe region of the prototype we measured good spectroscopic uniformity and sub-pitch (~0.2 mm) spatial resolution in both x and y dimensions. We present below measurements of the spatial uniformity, relative …
Balloon-Borne Coded Aperture Telescope For Arc-Minute Angular Resolution At Hard X-Ray Energies, Mark L. Mcconnell, V Boykin, R M. Kippen, K Larson, John R. Macri, M Mayer, James M. Ryan, P P. Altice, M L. Cherry, S B. Ellison, B Price, T G. Guzik, R Lockwood, M B. Barakat, K Johnston, N Zotov, M Elaasar
Balloon-Borne Coded Aperture Telescope For Arc-Minute Angular Resolution At Hard X-Ray Energies, Mark L. Mcconnell, V Boykin, R M. Kippen, K Larson, John R. Macri, M Mayer, James M. Ryan, P P. Altice, M L. Cherry, S B. Ellison, B Price, T G. Guzik, R Lockwood, M B. Barakat, K Johnston, N Zotov, M Elaasar
Space Science Center
We are working on the development of a new balloon-borne telescope, MARGIE (minute-of-arc resolution gamma ray imaging experiment). It will be a coded aperture telescope designed to image hard x-rays (in various configurations) over the 20 - 600 keV range with an angular resolution approaching one arc minute. MARGIE will use one (or both) of two different detection plane technologies, each of which is capable of providing event locations with sub-mm accuracies. One such technology involves the use of cadmium zinc telluride (CZT) strip detectors. We have successfully completed a series of laboratory measurements using a prototype CZT detector with …
Charge-Coupled Devices With Fast Timing For Astrophysics And Space Physics Research, M L. Cherry, P P. Altice, S B. Ellison, T G. Guzik, John R. Macri, Mark L. Mcconnell, G Y. Mclean, James M. Ryan, Paul P. Suni
Charge-Coupled Devices With Fast Timing For Astrophysics And Space Physics Research, M L. Cherry, P P. Altice, S B. Ellison, T G. Guzik, John R. Macri, Mark L. Mcconnell, G Y. Mclean, James M. Ryan, Paul P. Suni
Space Science Center
A charge coupled device is under development with fast timing capability (15 millisecond full frame readout, 30 microsecond resolution for measuring the time of individual pixel hits). The fast timing CCD will be used in conjunction with a CsI microfiber array or segmented scintillator matrix detector to detect x rays and gamma rays with submillimeter position resolution. The initial application will be in conjunction with a coded aperture hard x ray/gamma ray astronomy instrument. We describe the concept and the readout architecture of the device.
Comptel Measurements Of Mev Gamma-Ray Burst Spectra, R M. Kippen, James M. Ryan, A Connors, Mark L. Mcconnell, C Winkler, L O. Hanlon, V Schonfelder, J Greiner, M Varendorff, W Collmar, W Hermsen, L Kuiper
Comptel Measurements Of Mev Gamma-Ray Burst Spectra, R M. Kippen, James M. Ryan, A Connors, Mark L. Mcconnell, C Winkler, L O. Hanlon, V Schonfelder, J Greiner, M Varendorff, W Collmar, W Hermsen, L Kuiper
Space Science Center
We present results from the on-going spectral analysis of gamma-ray bursts measured by the COMPTEL instrument in its main Compton “Telescope” observing mode (0.75–30 MeV). Thus far, 18 bursts have been analyzed from three years (April 1991–April 1994) of observations. The time-averaged spectra of these events above 1 MeV are all consistent with a simple power law model with spectral index in the range 1.5–3.5. Exponential, thermal bremsstrahlung and thermal synchrotron models are statistically inconsistent with the burst sample, although they can adequately describe some of the individual burst spectra. We find good agreement between burst spectra measured simultaneously by …
Hard X‐Ray Polarimetry Of Solar Flares With Batse, Mark L. Mcconnell, D J. Forrest, W T. Vestrand, M Finger
Hard X‐Ray Polarimetry Of Solar Flares With Batse, Mark L. Mcconnell, D J. Forrest, W T. Vestrand, M Finger
Space Science Center
We describe a technique for measuring the polarization of hard X‐rays from solar flares based on the angular distribution of that portion of the flux which is scattered off the top of the Earth’s atmosphere. The scattering cross section depends not only on the scatter angle itself, but on the orientation of the scatter angle with respect to the incident polarization vector. Consequently, the distribution of the observed albedo flux will depend on the direction and the polarization properties (i.e., the level of polarization and polarization angle) of the source. Since the albedo component can represent a relatively large fraction …
The Angular Distribution Of Comptel Gamma-Ray Bursts, R M. Kippen, James M. Ryan, A Connors, Mark L. Mcconnell, H Hartmann, C Winkler, L O. Hanlon, V Schonfelder, J Greiner, M Varendorff, W Collmar, W Hermsen, L Kuiper
The Angular Distribution Of Comptel Gamma-Ray Bursts, R M. Kippen, James M. Ryan, A Connors, Mark L. Mcconnell, H Hartmann, C Winkler, L O. Hanlon, V Schonfelder, J Greiner, M Varendorff, W Collmar, W Hermsen, L Kuiper
Space Science Center
The superior burst location capability of the COMPTEL instrument aboard the Compton Gamma-Ray Observatory allows us to study the small-scale angular distribution of burst sources with good sensitivity even though the number of burst detections is small. We accumulate four years (April 1991–April 1995) of observations to form a catalog of 27 burst locations whose mean 1σ uncertainty is ∼1°. We find that the COMPTEL bursts are consistent with an isotropic distribution of sources, yet the spatial coincidence of two of the bursts within COMPTEL’s angular resolution indicates the possibility of repetition. This possibility is studied using the two-point angular …
Using Batse To Measure Gamma-Ray Burst Polarization, Mark L. Mcconnell, D J. Forrest, W T. Vestrand, M H. Finger
Using Batse To Measure Gamma-Ray Burst Polarization, Mark L. Mcconnell, D J. Forrest, W T. Vestrand, M H. Finger
Space Science Center
We describe a technique for measuring the polarization of hard x-rays from γ-ray bursts based on the angular distribution of that portion of the flux which is scattered off the top of the Earth’s atmosphere. The scattering cross section depends not only on the scatter angle itself, but on the orientation of the scatter angle with respect to the incident polarization vector. Consequently, the distribution of the observed albedo flux will depend on the direction and the polarization properties (i.e., the level of polarization and polarization angle) of the source. Although the BATSE design (with its large field-of-view for each …
Looking For The Source Of ∼Hour-Long Soft X-Ray Emission Following Grb 780506, A Connors, Mark L. Mcconnell
Looking For The Source Of ∼Hour-Long Soft X-Ray Emission Following Grb 780506, A Connors, Mark L. Mcconnell
Space Science Center
GRB 780506, a gamma-ray burst discovered in HEAO 1 A-4 data, was unusual in three respects. First, it was well-measured (by HEAO 1 A-2) in 2–60 keV X-rays. Second, two minutes after it ended, HEAO 1 A-2 detected a faint resurgence of 2–10 keV flux, lasting roughly an hour. From recently calculated position constraints, it appears the source of the extended flux is consistent with the source of the burst, and probably not from a serendipitous transient along the Galactic plane. Third, it now appears GRB 780506 belongs to a newly discovered softer subclass of gamma-rays bursts. This subclass is …
Extended Γ‐Ray Emission In Solar Flares, G Rank, K Bennett, H Bloemen, H Debrunner, J Lockwood, Mark L. Mcconnell, James M. Ryan, V Schonfelder, R Suleiman
Extended Γ‐Ray Emission In Solar Flares, G Rank, K Bennett, H Bloemen, H Debrunner, J Lockwood, Mark L. Mcconnell, James M. Ryan, V Schonfelder, R Suleiman
Space Science Center
During the solar flare events on 11 and 15 June 1991, COMPTEL measured extended emission in the neutron capture line for about 5 hours after the impulsive phase. The time profiles can be described by a double exponential decay with decay constants on the order of 10 min for the fast and 200 min for the slow component. Within the statistical uncertainty both flares show the same long‐term behaviour. The spectrum during the extended phase is significantly harder than during the impulsive phase and pions are not produced in significant numbers before the beginning of the extended emission. Our results …
Comptel Solar Flare Measurements, James M. Ryan, Mark L. Mcconnell
Comptel Solar Flare Measurements, James M. Ryan, Mark L. Mcconnell
Space Science Center
We review some of the highlights of the COMPTEL measurements of solar flares. These include images of the Sun in γ rays and neutrons. One of the important features of the COMPTEL instrument is its capability to measure weak fluxes of γ rays and neutrons in the extended phase of flares. These data complement the spectra taken with the COMPTEL burst spectrometer and the telescope during the impulsive phase of flares. We focus our attention on some of these general capabilities of the instrument and the latest results of two long‐duration γ‐ray flares, i.e., 11 and 15 June 1991