共查询到20条相似文献，搜索用时 46 毫秒
1.
《New Astronomy Reviews》2002,46(8-10):597-604
The ESA-Mission INTEGRAL (International Gamma-Ray Astrophysics Laboratory) is the next step in low-energy gamma-ray astronomy (up to 10 MeV) and will be launched in 2002. The spectrometer SPI—one of its two main instruments—is dedicated to high-resolution line spectroscopy (ΔE=2.5 keV FWHM at 1.3 MeV). SPI will concentrate on the study of lines from radioactive isotopes. A wealth of new information is expected from interstellar line emission with narrow line profiles, but exciting results are also expected from line profile measurements of individual line emitting objects such as supernovae, supernova remnants, and novae. 相似文献
2.
D. J. Forrest E. L. Chupp J. M. Ryan M. L. Cherry I. U. Gleske C. Reppin K. Pinkau E. Rieger G. Kanbach R. L. Kinzer G. Share W. N. Johnson J. D. Kurfess 《Solar physics》1980,65(1):15-23
The Solar Maximum Mission Gamma Ray Experiment (SMM GRE) utilizes an actively shielded, multicrystal scintillation spectrometer to measure the flux of solar gamma rays. The instrument provides a 476-channel pulse height spectrum (with energy resolution of 7% at 662 keV) every 16.38 s over the energy range 0.3–9 MeV. Higher time resolution (2 s) is available in three windows between 3.5 and 6.5 MeV to study prompt gamma ray line emission at 4.4 and 6.1 MeV. Gamma ray spectral analysis can be extended to 15 MeV on command. Photons in the energy band from 300–350 keV are recorded with a time resolution of 64 ms. A high energy configuration also gives the spectrum of photons in the energy range from 10–100 MeV and the flux of neutrons 20 MeV. Both have a time resolution of 2 s. Auxiliary X-ray detectors will provide spectra with 1-sec time resolution over the energy range of 10–140 keV. The instrument is designed to measure the intensity, energy, and Doppler shift of narrow gamma ray lines as well as the intensity of extremely broadened lines and the photon continuum. The main objective is to use this time and spectral information from both nuclear gamma ray lines and the photon continuum in a direct study of the dynamics of the solar flare/particle acceleration phenomena. 相似文献
3.
The primary scientific objectives of the Hard X-Ray Burst Spectrometer (HXRBS) to be flown on the Solar Maximum Mission are as follows: (1) To determine the nature of the mechanisms which accelerate electrons to 20–100 keV in the first stage of a solar flare and to > 1 MeV in the second stage of many flares; and (2) to characterize the spatial and temporal relation between electron acceleration, storage and energy loss throughout a solar flare.Measurements of the spectrum of solar X-rays will be made in the energy range from 20 to 260 keV using an actively-shielded CsI(Na) scintillator with a thickness of 0.635 cm and a sensitive area of 71 cm2. Continuous measurements with a time resolution of 0.128 s will be made of the 15-channel energy-loss spectrum of events in this scintillator in anticoincidence with events in the CsI(Na) shield. Counting-rate data with a time resolution as short as 1 ms will also be available from a limited period each orbit using a 32K-word circulating memory triggered by a high event rate.In the first year after launch, it is expected that approximately 1000 flares will be observed above the instrument sensitivity threshold, which corresponds to a 20–200 keV X-ray flux of 2 × 10–1 photons (cm2 s)–1 lasting for at least one second. 相似文献
4.
《New Astronomy Reviews》2002,46(8-10):625-629
High resolution γ-ray spectroscopy at energies around 1 MeV, as with SPI on board INTEGRAL, is a powerful tool for astronomy with radioactivities. We do not expect the SPI signal-to-background ratio for any of the anticipated γ-ray sources to exceed a few percent; hence detailed modelling of the instrumental background will be crucial. We exploit the similarities between TGRS on board WIND and SPI with respect to orbit and radiation environment, as well as detector design and material composition, to anticipate the most important instrumental background lines and their production channels in SPI at the energies of selected γ-ray lines of astrophysical relevance. 相似文献
5.
T. Villela J. Braga F. D'Amico U. B. Jayanthi J. A. Neri 《Astrophysics and Space Science》1994,214(1-2):161-170
We describe an imaging telescope for observations of celestial sources in the energy range between 30 keV and 1.8 MeV onboard stratospheric balloons. The detector is a 41 cm diameter, 5 cm thick NaI(Tl) crystal coupled to 19 photomultipliers in an Anger camera configuration. It is surrounded by a plastic scintillator 15 cm thick on the sides, 0.2 cm thick at the top and 20 cm thick at the bottom. The imaging device is based upon a 19 × 19 element square MURA (Modified Uniformly Redundant Array) coded mask mounted in an one-piece mask-antimask configuration. The detector's spatial resolution is about 10 mm at 100 keV. This is the first experiment to use such a mask pattern and configuration for astrophysical purposes. The expected 3 sensitivity for an on-axis source observed for 104 s at a residual atmosphere of 3.5 g cm–2 is 1.44 × 10–5 photons cm–2 s–1 keV–1 at 100 keV and 1.00 × 10–6 photons cm–2 s–1 keV–1 at 1 MeV. The angular resolution is approximately 14 arcminutes over a 13°field of view. The instrument is mounted in an automatic platform with a capability for pointing and stabilization in both azimuth and elevation axis with 2 arcmin accuracy.Presented at the 2nd UN/ESA Workshop, held in Bogotá, Colombia, 9-13 November, 1992. 相似文献
6.
硬X射线能带 (2 0KeV～ 1MeV)是我们了解天体物理中高能辐射过程的一个好窗口。成像硬X射线望远镜可以提供更好的分辨率和灵敏度来研究硬X射线天体物理学。本文介绍了成像硬X射线望远镜在美国和欧洲的发展 ,这包括 :1 )EXITE2 ,由美国哈佛———史密松林天体物理中心设计和运行的一个光电开关成像硬X射线望远镜 ;2 )EXIST ,一个成像硬X射线全天巡天望远镜 ,将于 2 0 1 0年由ULDB (EXIST -LINE)或国际空间站 (EXIST -ISS)承载 ;3)HERO ,由NASA/MSFC建造的一个新的硬X射线光学仪器。 相似文献
7.
8.
Chen Zhang Shuang-Nan Zhang 《中国天文和天体物理学报》2009,9(3)
High angular resolution X-ray imaging is always useful in astrophysics and solar physics. In principle, it can be performed by using coded-mask imaging with a very long mask-detector distance. Previously, the diffraction-interference effect was thought to degrade coded-mask imaging performance dramatically at the low energy end with its very long mask-detector distance. The diffraction-interference effect is described with numerical calculations, and the difffraction-interference cross correlation reconstruction method (DICC) is developed in order to overcome the imaging performance degradation. Based on the DICC, a super-high angular resolution principle (SHARP) for coded-mask X-ray imaging is proposed. The feasibility of coded mask imaging beyond the diffraction limit of a single pinhole is demonstrated with simulations. With the specification that the mask element size is 50 × 50 μm2 and the mask-detector distance is 50 m, the achieved angular resolution is 0.32arcsec above about 10keV and 0.36arcsec at 1.24keV (λ = 1 nm), where diffraction cannot be neglected. The on-axis source location accuracy is better than 0.02 arcsec. Potential applications for solar observations and wide-field X-ray monitors are also briefly discussed. 相似文献
9.
10.
E. Bissaldi A. von Kienlin G. Lichti H. Steinle P. N. Bhat M. S. Briggs G. J. Fishman A. S. Hoover R. M. Kippen M. Krumrey M. Gerlach V. Connaughton R. Diehl J. Greiner A. J. van der Horst C. Kouveliotou S. McBreen C. A. Meegan W. S. Paciesas R. D. Preece C. A. Wilson-Hodge 《Experimental Astronomy》2009,24(1-3):47-88
One of the scientific objectives of NASA’s Fermi Gamma-ray Space Telescope is the study of Gamma-Ray Bursts (GRBs). The Fermi Gamma-Ray Burst Monitor (GBM) was designed to detect and localize bursts for the Fermi mission. By means of an array of 12 NaI(Tl) (8 keV to 1 MeV) and two BGO (0.2 to 40 MeV) scintillation detectors, GBM extends the energy range (20 MeV to > 300 GeV) of Fermi’s main instrument, the Large Area Telescope, into the traditional range of current GRB databases. The physical detector response of the GBM instrument to GRBs is determined with the help of Monte Carlo simulations, which are supported and verified by on-ground individual detector calibration measurements. We present the principal instrument properties, which have been determined as a function of energy and angle, including the channel-energy relation, the energy resolution, the effective area and the spatial homogeneity. 相似文献
11.
Alexey Boyarsky Denys Malyshev † rey Neronov Oleg Ruchayskiy 《Monthly notices of the Royal Astronomical Society》2008,387(4):1345-1360
Using the high-resolution spectrometer SPI on board the International Gamma-Ray Astrophysics Laboratory ( INTEGRAL ), we search for a spectral line produced by a dark matter (DM) particle with a mass in the range 40 keV < M DM < 14 MeV , decaying in the DM halo of the Milky Way. To distinguish the DM decay line from numerous instrumental lines found in the SPI background spectrum, we study the dependence of the intensity of the line signal on the offset of the SPI pointing from the direction toward the Galactic Centre. After a critical analysis of the uncertainties of the DM density profile in the inner Galaxy, we find that the intensity of the DM decay line should decrease by at least a factor of 3 when the offset from the Galactic Centre increases from 0° to 180°. We find that such a pronounced variation of the line flux across the sky is not observed for any line, detected with a significance higher than 3σ in the SPI background spectrum. Possible DM decay origin is not ruled out only for the unidentified spectral lines, having low (∼3σ) significance or coinciding in position with the instrumental ones. In the energy interval from 20 keV to 7 MeV, we derive restrictions on the DM decay line flux, implied by the (non-)detection of the DM decay line. For a particular DM candidate, the sterile neutrino of mass M DM , we derive a bound on the mixing angle. 相似文献
12.
Recent work by Dyer and Morfill has shown that satellite measurements of the diffuse cosmic X-ray spectrum made with crystal scintillators may include errors due to radioactive spallation products formed in the detector by inner belt and cosmic ray protons.
An estimate is made of the magnitude of this source of background for the various experimental situations and it is shown that apparent features at 40 keV and 1 MeV are likely to be due to radioactive decays in the instruments. A review is made of experiments covering the range 1 keV-100 MeV in order to ascertain whether a single exponent spectrum is capable of fitting the experimental results. The astrophysical implications of such a spectrum are briefly considered.
Suggestions are made for the location and correction for background of future experiments.
相似文献13.
《Solar physics》2002,210(1-2):3-32
RHESSI is the sixth in the NASA line of Small Explorer (SMEX) missions and the first managed in the Principal Investigator
mode, where the PI is responsible for all aspects of the mission except the launch vehicle. RHESSI is designed to investigate
particle acceleration and energy release in solar flares, through imaging and spectroscopy of hard X-ray/gamma-ray continua
emitted by energetic electrons, and of gamma-ray lines produced by energetic ions. The single instrument consists of an imager,
made up of nine bi-grid rotating modulation collimators (RMCs), in front of a spectrometer with nine cryogenically-cooled
germanium detectors (GeDs), one behind each RMC. It provides the first high-resolution hard X-ray imaging spectroscopy, the
first high-resolution gamma-ray line spectroscopy, and the first imaging above 100 keV including the first imaging of gamma-ray
lines. The spatial resolution is as fine as ∼ 2.3 arc sec with a full-Sun (≳ 1°) field of view, and the spectral resolution
is ∼ 1–10 keV FWHM over the energy range from soft X-rays (3 keV) to gamma-rays (17 MeV). An automated shutter system allows
a wide dynamic range (>107) of flare intensities to be handled without instrument saturation. Data for every photon is stored in a solid-state memory
and telemetered to the ground, thus allowing for versatile data analysis keyed to specific science objectives. The spin-stabilized
(∼ 15 rpm) spacecraft is Sun-pointing to within ∼ 0.2° and operates autonomously. RHESSI was launched on 5 February 2002,
into a nearly circular, 38° inclination, 600-km altitude orbit and began observations a week later. The mission is operated
from Berkeley using a dedicated 11-m antenna for telemetry reception and command uplinks. All data and analysis software are
made freely and immediately available to the scientific community.
Supplementary material to this paper is available in electronic form at http://dx.doi.org/10.1023/A:1022428818870 相似文献
14.
F. E. Christensen K. D. Joensen P. Gorenstein W. C. Priedhorsky N. J. Westergaard H. W. Schnopper 《Experimental Astronomy》1995,6(4):33-46
It is shown that compact designs of multifocus, conical approximations to highly nested Wolter I telescopes, as well as single reflection concentrators, employing realistic graded period W/Si or Ni/C multilayer coatings, allow one to obtain more than 1000 cm2 of on-axis effective area at 40 keV and up to 200 cm2 at 100 keV. The degree of concentration is defined by a focusing factor i.e., the effective area divided by the half power focal area. For the cases studied, this is 400 at 40 keV and 200 at 100 keV for a 2 arcmin imaging resolution. This result is quite insensitive to the specifics of the telescope configuration provided that mirrors can be coated to an inner radius of 3 cm. Specifically we find that a change of focal length from 5 to 12 m affects the effective area by less than 10%. In addition the result is insensitive to the thickness of the individual mirror shell provided that it is smaller than roughly 1 mm. The design can be realized with foils as thin (0.4 mm) as used for ASCA and SODART or with closed, slightly thicker (1.0 mm) mirror shells as used for JET-X and XMM. The effect of an increase of the inner radius is quantified on the effective area for multilayered mirrors up to 9 cm. The calculated Field of View (full width at half maximum), ranges from 9 arcmin at 1 keV to 5 arcmin at 60 keV. Finally, the continuum sensitivity of the design assuming a signal to noise ratio of 5 and a 10% energy bandwidth has been calculated. For a balloon flight observation of 104 sec. with a telescope having 2 arcmin imaging resolution the point source sensitivity is 3 · 10–6 photons/cm2/s/keV up to 70 keV for a W/Si coated telescope and up to 100 keV for a Ni/C coated telescope. For a satellite observation time of 105 sec and an imaging resolution of 1 arcmin the sensitivity is 10–7 photons/cm2/s/keV which demonstrates the great potential of this hard X-ray imaging telescope in the energy range up to 100 keV. 相似文献
15.
Yu. D. Kotov V. N. Yurov E. E. Lupar K. F. Vlasik A. I. Arkhangelsky A. S. Glyanenko I. V. Rubtsov V. V. Kadilin V. G. Tyshkevich 《Solar System Research》2011,45(2):97-122
The NATALYA-2M high-energy radiation spectrometer is an element of the complex of scientific equipment of the CORONAS-PHOTON
satellite. The instrument intended for registering gamma radiation of solar flares in the broad energy range of 0.2–1600 MeV
as well as neutrons of solar origin with energies of 20–300 MeV represents itself as a scintillation spectrometer based on
CsI(Tl) crystals with a total area of 32 × 38 cm2 and the thickness of 18 cm. The spectra and time profiles of the gamma quanta count rates are measured in four subranges:
R (0.2–2 MeV), L (1–18 MeV), M (7–250 MeV), and H (50–1600 MeV). Depending on the gamma radiation energy, the effective area
of the instrument varies within the range from 750 to 900 cm2, and the energy resolution at the Cs-137 line (662 keV) is 10%, it being about 30% at energies higher than 50 MeV. A system
of stabilization based on the signal from the generator of reference light pulses is used to provide stability and automated
adjustment of the parameters of spectrometric modules. The measuring channels of the instrument are calibrated during the
flight using a source of “tagged” gamma quanta on the Co-60 radioactive isotope. Polystyrene scintillation counters are used
to provide protection from the background of charged particles. The “CORONAS-PHOTON” spacecraft (SC) was launched from the
Plesetsk spaceport on January 30, 2009, to a low circular near-Earth orbit (the altitude is 550 km, the inclination is 82.5°).
On February 27, the first scientific data were obtained from the NATALYA-2M instrument. The results of the flight calibration
of the instrument detectors in different energy channels demonstrated good agreement with the ground measurements. The paper
describes the instrument and observational potentials of the NATALYA-2M spectrometer, gives the results of the adjustment
and calibration, and exemplifies the registration of gamma-ray bursts (GRBs)on the orbit. 相似文献
16.
17.
Based on the results from three balloon flights, made at Hyderabad(7.6°N geomagnetic latitude) using omnidirectional gamma ray spectrometers, the different aspects of the low energy atmospheric gamma rays at equatorial latitudes in the energy interval 100 keV to 1 MeV are investigated and detailed discussion is presented. The energy loss spectrum in this energy range is found to consist of a continuum superimposed on which is a photopeak due to 0.51 MeV line arising from electron positron annihilation. The continuous background spectrum is similar to that observed at mid and high latitudes. The intensity of 0.51 MeV line is estimated to be 0.079 ± 0.01 photons cm−2 sec−1 at 6 g cm−2 over Hyderabad and the altitude dependence of its intensity is established for this low latitude station. The latitude effect of the intensity of this line at 6 g cm−2 is derived for the first time by comparing the results of the present measurements with those available for mid and high latitudes. The contribution of the cosmic gamma rays to the observed count rates at 6 g cm−2 is shown to be negligible in the case of the omnidirectional spectrometers of the type used in the present observations even for low latitude stations. 相似文献
18.
We have evaluated several solid state detectors which offer excellent energy resolution at room temperature for soft X-rays. For soft X-rays (< 1 keV to 20 keV), silicon P-intrinsic-N (PIN) and avalanche-mode photodiodes (APD's) have been studied. Using commercially available charge sensitive pre-amplifiers, these photodiodes provide 1 keV resolution without cooling. Their detection efficiencies are limited to about 20 keV and 15 keV, respectively. To overcome this constraint, we have studied thick (1.5 mm) PIN detectors made by Micron Semiconductor Ltd., U.K., as well as compound semiconducting materials with high Z constituents such as CZT and PbI2. PbI2 allows high detection efficiencies of photons up to 100 keV with detectors 100–300 microns thick. These new detectors offer the capability to study the low-energy spectral evolution of Gamma ray bursts (GRBs). A matrix of these detectors could be used as an image plane detector with moderate spatial resolution for imaging. 相似文献
19.
D. E. Roa R. K. Smither X. Zhang K. Nie Y. Y. Shieh N. S. Ramsinghani N. Milne J. V. Kuo J. L. Redpath M. S. A. L. Al-Ghazi P. Caligiuri 《Experimental Astronomy》2005,20(1-3):229-239
The objective of this project is to develop and construct an innovative imaging system for nuclear medicine and molecular imaging that uses photon diffraction and is capable of generating 1–2 mm spatial resolution images in two or three dimensions. The proposed imaging system would be capable of detecting radiopharmaceuticals that emit 100–200 keV gamma rays which are typically used in diagnostic nuclear medicine and in molecular imaging. The system is expected to be optimized for the 140.6 keV gamma ray from a Tc-99m source, which is frequently used in nuclear medicine. This new system will focus the incoming gamma rays in a manner analogous to a magnifying glass focusing sunlight into a small focal point on a detector's sensitive area. Focusing gamma rays through photon diffraction has already been demonstrated with the construction of a diffraction lens telescope for astrophysics and a scaled-down lens for medical imaging, both developed at Argonne National Laboratory (ANL). In addition, spatial resolutions of 3 mm have been achieved with a prototype medical lens. The proposed imaging system would be comprised of an array of photon diffraction lenses tuned to diffract a specific gamma ray energy (within 100–200 keV) emitted by a common source. The properties of photon diffraction make it possible to diffract only one specific gamma ray energy at a time, which significantly reduces scattering background. The system should be sufficiently sensitive to the detection of small concentrations of radioactivity that can reveal potential tumor sites at their initial stages of development. Moreover, the system's sensitivity would eliminate the need for re-injecting a patient with more radiopharmaceutical if this patient underwent a prior nuclear imaging scan. Detection of a tumor site at its inception could allow for an earlier initiation of treatment and wider treatment options, which can potentially improve the chances for cure. 相似文献
20.
S. R. Kane 《Solar physics》1982,113(1-2):145-164
The propagation, cofinement and total energy of energetic (>25 keV) electrons in solar flares are examined through a brief review of the following hard X-ray measurements: (1) spatially resolved observations obtained by imaging instruments; (2) stereoscopic observations of partially occulted sources providing radial (vertical) spatial resolution; and (3) directivity of the emission measured through stereoscopic observations and the center-to-limb variation of the occurrence frequency of hard X-ray flares. The characteristics of the energetic electrons are found to be quite distinct in impulsive and gradual hard X-ray flares. In impulsive flares the non-thermal electron spectrum seems to extend down to 2 keV indicating that the total energy of non-thermal electrons is much larger than that assumed in the past. 相似文献