共查询到17条相似文献，搜索用时 31 毫秒
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利用MCNP程序对450kV X光机建立模型,计算各参考辐射质下的原级谱、平均光子能量。对ISO4037-1中已有范围的管电压与附加过滤片厚度关系曲线进行二次拟合,确定模拟厚度范围。利用MCNP计算各附加过滤组合下的平均光子能量值,并与外推法得出的平均光子能量值进行对比,将相对偏差最小时的附加过滤作为最终确定值。从部分能量点的模拟与测量结果的对比可看出,模拟得出的平均光子能量在2%以内与PTB及中国计量院测量结果保持一致,附加过滤最大相对偏差为18%。 相似文献
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2008年6月,美国用德尔他-2火箭成功发射“γ射线大面积空间望远镜”(GLAST)。GLAST高为2.8m,直径为2.5m,发射质量为4277kg,运行在高550km、倾角为28.5°、周期为95min的圆轨道上。它是新一代γ射线天文探测卫星,其性能比在1991-1999年运行的“康普顿”γ射线观测台(CGRO)有很大 相似文献
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针对武器装备专用电气参数检测设备现场计量保障对校准环境和便携型计量标准的严苛技术要求,研制了一种便携式智能化校准装置。该装置实现了现场校准微环境自动控制,以及板卡级高精度电学计量标准源与标准表设计内容,编制了校准设备显示图像识别软件,配合程控式开关触发装置,可实现装备电气检测设备智能化现场校准,具有较好的推广应用前景。 相似文献
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γ射线望远镜简介γ射线在光谱的X射线之外．波长小于0．01纳米，最短波长没有极限，已探测到的最短波长为10亿亿分之一纳米。 相似文献
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M.E.
zel H.A. Mayer-Ha elwander 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》1984,3(10-12)
Poor angular resolution of present day gamma ray telescopes (1° at 100 MEV) together with the complicated gamma ray sky structures at compareable angular extents and poor statistics available necessitate the selection of those gammas which will increase the observable signal from a suspected source. A method for such a selection using the pre-known time signature of the source as its signal, has been developed (Özel and Mayer-Haβelwander, 1983). In an iterative procedure based on the improvement of source signal, generalized zones around the source are defined, from which gamma rays should be accepted to construct the optimum light curve of the source. These zones depend on the energy of the probed gamma rays, on the spatial structure and intensity of the background around the source, on the (estimated and/or tentative) intetnsity of the source and finally on the observing instrument's angular and energy response functions. The method, when applied to simulated and observed COS-B data demonstrated its feasibility and merits over the previonsly used circular event-acceptance cones method which was the basis of searches for gamma ray emission from radio pulsars (see for example Kniffen et al., 1974; Ögelman, et al. 1976; Kanbach, et al., 1977; and references therein). Present method does not introduce “trials” which usually reduce the significance of the results obtained, fully accounts the available knowledge on the topography of gamma ray sky, makes use of all the information about the sky, source and the instrument and therefore is the proper way of handling gamma ray data in pulsar-type searches.Presently, method is applied in the analyses of COS-B data in the context of searches for gamma ray emitting X-ray and radio pulsars. Results will be published elsewhere. 相似文献
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在近地空间(LEO)和深空探测中,航天员遭受的辐射风险主要来自于银河宇宙线(GCR)照射.银河宇宙线的辐射剂量是航天员辐射风险评价的基础.国际放射防护委员会(ICRP)于2013年提出了新的航天员空间辐射剂量估算方法,以更准确给出空间重离子辐射的剂量.基于此方法,开发了宇宙线粒子在物质中输运的蒙特卡罗程序,并在程序中实现用中国成年男性人体数字模型来仿真航天员.采用该程序计算了粒子(Z=1~92)各向同性照射航天员时器官的通量-器官剂量转换因数,并估算出航天员在近地轨道空间受银河宇宙线辐射的剂量. 相似文献
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J. Bernabeu I. Casanova 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2008
The radiation environment on the surface of the Moon presents a new source of particles resulting from the interaction of incoming solar protons and galactic cosmic rays with the lunar regolith. Here we present a study of the fluence profile of primary and secondary particles on the top 1 m layer of lunar regolith for the spectrum of one of the hardest spectrum solar event, that of February 1956. Different regolith compositions and their influence in proton and neutron production and backscattering is considered, as well as the nature of the backscattered radiation. Simple geometry Monte Carlo simulations have been used also for calculating regolith shielding properties, and it is shown that a layer of at least 50 cm regolith is needed for significantly reducing the dose levels received by astronauts in a hypothetical lunar habitat. 相似文献
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K.T. Lee T.L. Wilson 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2009
We report on the results of a continuing study of the photon luminescence of the Moon induced by Galactic Cosmic Rays (GCRs) and space radiation from the Sun, using the Monte Carlo program FLUKA. Understanding the space radiation environment is critical to future exploration of the Moon, and this includes photons. The model of the lunar surface is taken to be the chemical composition of soils found at various landing sites during the Apollo and Luna programs, averaged over all such sites to define a generic regolith for the present analysis. This surface model then becomes the target that is bombarded by Galactic Cosmic Rays (GCRs) and Solar Energetic Particles (SEPs) or Solar Particle Events (SPEs) above 1 keV in FLUKA to determine the photon fluence albedo produced by the Moon’s surface when there is no sunlight and Earthshine. The result is to be distinguished from the gamma-ray spectrum produced by the radioactive decay of radiogenic constituents lying in the surface and interior of the Moon. From the photon fluence we derive the spectrum which can be utilized to examine existing lunar spectral data and to aid future orbiting instrumentation in the measurement of various components of the space-radiation-induced photon luminescence present on the Moon. 相似文献
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A.L. Mishev 《Advances in Space Research (includes Cospar's Information Bulletin, Space Research Today)》2014
The radiation environment in the troposphere of the Earth is governed by cosmic rays of galactic and solar origin. During major solar energetic particles events the radiation environment changes dramatically. As a results the risk of biological effects due to exposure to ionizing radiation of aircrew increases. Here we present a numerical model for computation of absorbed dose in air due to cosmic rays of galactic and solar origin. It is applied for computation of radiation environment at flight altitude in the equatorial region during several major ground level enhancements, namely GLE65 on 28 October 2003, GLE69 on 20 January 2005 and GLE70 on 13 December 2006. The model is based on a full Monte Carlo simulation of cosmic ray induced atmospheric cascade. The cascade simulation is carried out with CORSIKA 6.990 code with corresponding hadron generators FLUKA 2011 and QGSJET II. The contribution of different cascade components, namely electromagnetic, hadron and muon is explicitly obtained. The spectra of arriving solar energetic particles are calculated from ground level measurements with neutron monitors and satellite data from GOES. The obtained results are discussed. 相似文献
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采用Monte Carlo方法,通过模拟研究了不同强度雷暴电场对LHAASO探测面宇宙线次级电子能量的影响.在电场作用下,电子的能量分布发生了变化.在低能段总电子数目增加明显,而在高能段电场的影响不明显.当电场强度为1700V·cm-1（大于逃逸电场）时,能量<120MeV的电子被加速,能量<60MeV的总电子数目呈指数增长（增幅高达约2252%）,雷暴电场对次级粒子的加速机制与相对论电子逃逸雪崩机制（RREA）相符.当电场强度为1000V·cm-1（小于逃逸电场）时,能量<70MeV的电子被加速,其数目明显增加,但是增幅（约86%）远小于逃逸电场时的幅度.对电场强度小于逃逸电场时的雷暴电场加速宇宙线次级粒子的物理机制进行了讨论.研究结果可为理解LHAASO实验数据特点以及研究雷暴期间宇宙线强度的变化等提供参考. 相似文献
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针对大密度变化非连续介质气体流场的仿真难题,实现了分区可变时间步长方法,为了保证宏观物理量通量在界面上连续,针对穿过两个时间步长不相等的区之间的界面的分子执行剩余时间缩放处理。提出了一种高效的分区界面和壁面处理算法,将每个界面设定为只属于一个区,将跨过多个区的壁面分解成分别只属于一个区的多个壁面,并规定仿真分子只能与本区的界面和壁面相互作用。对喷管流场的模拟表明,此方法可以大大提高计算效率。 相似文献