摘要:

We have derived accelerated particle and ambient gas abundances using solar flare gamma‐ray spectroscopy. We find that the derived accelerated particle composition is different from the composition observed in large proton flares; rather, it resemble that observed in3He‐rich flares. Our analysis also suggests that the ambient composition differs from the composition of both the photosphere and the corona.

ISSN:0094-243X    

DOI:10.1063/1.40918

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Solar gamma‐ray lines are produced through collisions of pairs of positive ions whose center of mass energies are above the relevant thresholds for excitation of gamma‐ray emitting states. Because of the low density of the solar plasma, prompt gamma rays are emitted by recoiling ions before significant energy loss has occurred. Thus, the lines are expected to be Doppler broadened to widths of the order of a hundred keV. Gamma‐ray lines resulting from proton and alpha‐particle (4He ion) beams on carbon and oxygen targets in the laboratory exhibit complex profiles which change rapidly with the gamma‐ray observation angle. Our earlier work has been limited to modeling laboratory and solar flare gamma‐ray profiles produced by proton excitation, but laboratory profiles of the carbon 4.44‐MeV line and oxygen 6.13‐MeV line from alpha excitation have now been successfully modeled. Solar flare gamma‐ray line profiles of the carbon and oxygen lines from heavy ions in the ambient solar medium interacting with representative high‐energy proton and alpha particle populations will be presented.

ISSN:0094-243X    

DOI:10.1063/1.40919

出版商:AIP    

年代:1991

数据来源: AIP

ISSN:0094-243X    

DOI:10.1063/1.40920

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We study the possibility of detecting halo cold dark matter through the annihilation process &khgr;&khgr;→&ggr;&ggr;. This process produces monoenergetic &ggr;‐rays, and many be a clear signature of particle dark matter. If there is a closure density of photino ‐so far a favoured candidate ‐we show that it will be very difficult to observe this annihilation line from a satellite or space station borne experiment. On the contrary, triplet neutrinos which have recently been suggested as a plausible solution of the dark matter conundrum, whilst elusive at accelerators, should produce a clear &ggr;‐ray line signal, well above background.

ISSN:0094-243X    

DOI:10.1063/1.40921

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A new era, of second generation experiments, using detectors made from enriched material is starting at present in double beta research. This allows to strongly improve the present limits on the neutrino mass. We review the present status, in particular of the HEIDELBERG‐MOSCOW experiment, by which for the first time evidence has been given that the technology of enriched HP Ge detector production can be mastered nowadays. We further explore possible future application of this technology in astrophysics, in particular dark matter search and high‐resolution c‐ray spectroscopy in future ESA and NASA satellite missions. Use of enriched73Ge detectors for the former would allow to extend the present LEP limits for spin‐interacting WIMPs considerably and use of enriched70Ge detectors in the satellite experiments would allow to drastically reduce the b‐backgrounds in these missions.

ISSN:0094-243X    

DOI:10.1063/1.40923

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We consider a medium of non‐negligible optical depth in which high energy line photons are Compton scattered. For the calculation of the angle and energy dependent specific intensities we first cast the correlations between the angles and energies of the incoming and the outgoing photons (as determined by the Compton conditions) into the form of a redistribution function, which is weighted by the Klein‐Nishina cross‐section in order to account for the energy dependence. We then discretized the angle × energy space so that the radiative transfer equation transforms from an intergro‐differential equation into a system of ordinary differential equations subject to boundary conditions on both sides. This system is subsequently solved in a numerically stable way without any further approximation by means of the discrete‐ordinate‐matrix‐exponential (‘‘Dome’’) method so that all emergent intensities and the energy converted into heat are obtained.Since the redistribution function is very complex and involves singular hyperplanes, our algorithm requires a relatively large memory space whereas the CPU times are rather modest, e.g. for 16 angles and 25 energies in both the input and the output channel, 30 Mby of memory and 30 sec of CPU time are needed on an IBM 3090 VF independent of the actual optical depth.First results for a plane‐parallel medium, which consists of cold electrons and which is irradiated from one side by &ggr; line photons, are presented and the accuracies of the derived radiation fields are discussed.

ISSN:0094-243X    

DOI:10.1063/1.40924

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The International Gamma‐Ray Astrophysics Laboratory (INTERGAL) is a candidate for the next ESA medium‐size scientific mission to be launched in 2000. INTEGRAL addresses the fine spectroscopy and accurate positioning of celestial, gamma‐ray sources in the energy range 15 keV to MeV. A joint ESA‐NASA assessment study has been completed recently. The slope of this study covered the mission’s scientific prospects; the overall payload concept; payload accommodation and system analysis and an investigation of possible mission scenarios within the framework of an international collaboration.

ISSN:0094-243X    

DOI:10.1063/1.40925

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

For the gamma‐ray satellite INTEGRAL, A 3‐D position‐sensitive imaging detector has been proposed. The instrument is based on a two layer CsI(Tl) device coupled with a coded aperture mask placed at ∼4 m from the detector. This particular configuration of discrete detection elements, together with the 3‐D position sensitivity will ensure good imaging capabilities throughout a large energy range from 40–50 keV up to ∼20–30 MeV. The imager will also have spectroscopy capability in the nuclear line region. In this work we present the first Monte‐Carlo simulation results regarding the reconstruction of the shadowgram of the mask pattern. A simulated image of a 511 keV Galactic Centre point source is presented for both the low and the high state.

ISSN:0094-243X    

DOI:10.1063/1.40926

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The low energy gamma‐ray telescope SIGMA, aboard the GRANAT observatory, is now entering in his second year of life. It has provided during the last year, high angular resolution images of the sky in the energy domain 35 keV‐1.3 MeV. The data accumulated in different background conditions on series of astrophysical sites allow us to present the results on in‐flight performances of this instrument.

ISSN:0094-243X    

DOI:10.1063/1.40927

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The gamma‐ray line sensitivity of the BATSE detectors depends primarily upon the characteristics of the detectors’ response and the nature of the backgrounds observed by the instruments. Using the example of the detectability of prompt annihilation radiation from nearby novae, the detector response characteristics and data analysis tools relevant to gamma‐ray line and continuum sensitivity determination will be presented. Sensitivities to gamma‐ray lines at various energies will be presented.

ISSN:0094-243X    

DOI:10.1063/1.40891

出版商:AIP    

年代:1991

数据来源: AIP