摘要:

The scientific instrument of the AGILE mission is innovative in many ways. It is an integrated instrument based on three detecting systems: (1) a Silicon Tracker, (2) a Mini-Calorimeter, and (3) an ultralight coded mask system with Si-detectors (Super-AGILE). For a relatively low mass (∼70 kg) and large ratio of expected performance over cost, AGILE is planned to provide (i) Optimal imaging in the energy bands 30 MeV–50 GeV (5–10 arcmin for intense sources) and 10–40 keV (1–3 arcmin). (ii) Optimal timing capabilities, with independent readout systems and minimal dead-times for the Silicon Tracker, Super-AGILE and Mini-Calorimeter. (iii) A very large field of view for the gamma-ray imaging detector (3 sr) and Super-AGILE (1 sr). ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303300

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The GLAST instrument concept is a gamma-ray pair conversion telescope that uses silicon microstrip detector technology to track the electron-positron pairs resulting from gamma-ray conversions in thin lead foils. A cesium iodide calorimeter following the tracker is used to measure the gamma-ray energy. Silicon strip technology is mature and robust, with an excellent heritage in space science and particle physics. It has many characteristics important for optimal performance of a pair conversion telescope, including high efficiency in thin detector planes, low noise, and excellent resolution and two-track separation. The large size of GLAST and high channel count in the tracker puts demands on the readout technology to operate at very low power, yet with sufficiently low noise occupancy to allow self triggering. A prototype system employing custom-designed ASIC’s has been built and tested that meets the design goal of approximately 200_W per channel power consumption with a noise occupancy of less than one hit per trigger per 10,000 channels. Detailed design of the full-scale tracker is well advanced, with non-flight prototypes built for all components, and a complete 50,000 channel engineering demonstration tower module is currently under construction and will be tested in particle beams in late 1999. The flight-instrument conceptual design is for a4×4array of tower modules with an aperture of 2.9 m2and an effective area of greater than 8000 cm2. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1307036

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Gamma rays with energy above 10 GeV interact with optical-UV photons resulting in pair production. Therefore, a large sample of high redshift sources of these gamma rays can be used to probe the extragalactic background starlight (EBL) by examining the redshift dependence of the attenuation of the flux above 10 GeV. GLAST, the next generation high-energy gamma-ray telescope, will for the first time have the unique capability to detect thousands of gamma-ray blazars up to redshifts of at leastz=4,with enough angular resolution to allow identification of a large fraction of their optical counterparts. By combining recent determinations of the gamma-ray blazar luminosity function, recent calculations of the high energy gamma-ray opacity due to EBL absorption, and the expected GLAST instrument performance to produce simulated samples of blazars that GLAST would detect, including their redshifts and fluxes, we demonstrate that these blazars have the potential to be a highly effective probe of the EBL. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303301

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Cadmium Zinc Telluride (CZT) is a semiconductor detector well suited for high energy X-ray astronomy. The High-Energy X-ray Imaging Spectrometer (HEXIS) program is developing this technology for use in a hard X-ray all-sky survey and as a focal plane imager for missions such as FAR_XITE and Constellation X. We have designed a novel electrode geometry that improves interaction localization and depth of interaction determination. The HEXIS program has flown two high altitude balloon payloads from Ft. Summer, NM to investigate background properties and shielding effects on a position sensitive CZT detector in the energy range of 20–350 keV. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303302

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

Position-sensitive CZT detectors for astrophysical research in the five-several hundred keV range are being developed at UCSD and WU. These can be used for large area detector arrays in coded mask imagers and small-area focal plane detectors for focusing X-ray telescopes. The detectors have crossed-strip readout and optimized strip widths and gaps to improve energy resolution. A model of charge drift in the detectors and charge induction on the electrodes has been developed to allow for a better understanding of these types of detectors and to improve their design. The model is described and its predictions are compared with laboratory measurements. In general, there is good agreement between the model and the measurements. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303303

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

We report on the simulation, construction, and performance of prototype CdZnTe imaging detectors with orthogonal coplanar anode strips. These detectors employ a novel electrode geometry with non-collecting anode strips in one dimension and collecting anode pixels, interconnected in rows, in the orthogonal direction. These detectors retain the spectroscopic and detection efficiency advantages of single carrier (electron) sensing devices as well as the principal advantage of conventional strip detectors with orthogonal anode and cathode strips, i.e. anN×Narray of imaging pixels are with only 2N electronic channels. Charge signals induced on the various electrodes of a prototype detector with8×8unit cells(1×1×5&hthinsp;mm3)are compared to the simulations. Results of position and energy resolution measurements are presented and discussed. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1307035

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

MARGIE (Minute-of-Arc Resolution Gamma-ray Imaging Experiment) is a large area(∼104&hthinsp;cm2),wide field-of-view (∼1 sr), hard X-ray/gamma-ray (∼20–600 keV) coded-mask imaging telescope capable of performing a sensitive survey of both steady and transient cosmic sources. MARGIE has been selected for a NASA mission-concept study for an Ultra Long Duration (100 day) Balloon flight. We describe our program to develop the instrument based on new detector technology of either cadmium zinc telluride (CZT) semiconductors or pixellated cesium iodide (CsI) scintillators viewed by fast-timing bi-directional charge-coupled devices (CCDs). The primary scientific objectives are to image faint Gamma-Ray Bursts (GRBs) in near-real-time at the low intensity (high-redshift) end of the logN-logS distribution, thereby extending the sensitivity of present observations, and to perform a wide field survey of the Galactic plane. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303304

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A deep all-sky imaging hard x-ray survey and wide-field monitor is needed to extend soft (ROSAT) and medium (ABRIXAS2) x-ray surveys into the 10–100 keV band at comparable sensitivity (∼0.05 mCrab). This would enable discovery and study of ≳3000 obscured AGN, which probably dominate the hard x-ray background; detailed study of spectra and variability of accreting black holes and a census of BHs in the Galaxy; Gamma-ray bursts and associated massive star formation (PopIII) at very high redshift and Soft Gamma-ray Repeaters throughout the Local Group; and a full galactic survey for obscured supernova remnants. The Energetic X-ray Imaging Survey Telescope (EXIST) is a proposed array of8×1&hthinsp;m2coded aperture telescopes fixed on the International Space Station (ISS) with160°×40°field of view which images the full sky each 90 min orbit. EXIST has been included in the most recent NASA Strategic Plan as a candidate mission for the next decade. An overview of the science goals and mission concept is presented. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303305

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

A high resolution Compton telescope has been identified by the Gamma Ray Astronomy Program Working Group (GRAPWG) as the highest priority major mission in gamma ray astrophysics following GLAST. This mission should provide 25–100 times improved sensitivity, relative to CGRO and INTEGRAL, for MeV gamma ray lines. It must have good performance for narrow and broad lines and for discrete and diffuse emissions. Several instrumental approaches are being pursued to achieve these goals. We discuss issues relating to this mission including alternative detector concepts, instrumental configurations, and background reduction techniques. We have pursued the development of position-sensitive solid-state detectors (Ge, Si) for a high spectral resolution Compton telescope mission. A ∼1 m2germanium Compton telescope of position-sensitive germanium detectors was the basis for one of the GRAPWG concepts. Preliminary Monte Carlo estimates for the sensitivities of this instrument are encouraging. However, there are technical challenges of cooling large volumes of Ge and providing the large number of spectroscopy channels. We also show that with only two Compton scatter interactions followed by a third interaction, the incident gamma ray energy and direction cone can be precisely determined in detectors with excellent energy and position resolution. Full energy deposition is not required. We present a promising concept for a high efficiency Compton instrument for which thick silicon strip detectors might be preferred. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303306

出版商:AIP    

年代:1900

数据来源: AIP

摘要:

The nuclear line region of the gamma ray spectrum remains one of the most challenging and elusive goals of high energy astrophysics. The scientific objectives are well defined, but require well over a factor of 10 increase in sensitivity compared to present day instruments to be achieved. The most promising approach to achieve this sensitivity and a broad range of scientific objectives is offered by an Advanced Compton Telescope (ACT) that would function in the 0.5 to 30 MeV energy range. The ACT builds on the successful COMPTEL instrument on NASA’s Gamma Ray Observatory by substituting modern detectors with over an order of magnitude better energy and spatial resolution. Germanium detectors are a natural choice, as they are available in large volumes, provide the best possible energy resolution, and are capable of fine spatial resolution. These improvements alone provide the required gain in sensitivity. Further optimization and the use of more sophisticated techniques promise even greater improvements. We discuss the current status of the germanium detector technology. New results from the characterization of a crossed strip detector using amorphous-germanium contacts and a demonstration of three-dimensional position resolution are presented. ©2000 American Institute of Physics.

ISSN:0094-243X    

DOI:10.1063/1.1303307

出版商:AIP    

年代:1900

数据来源: AIP