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The Hard X-ray Modulation Telescope (HXMT) is an X-ray astronomy satellite consisting of three slat-collimated instruments, the High Energy X-ray Instrument (HE), the Medium Energy X-ray Instrument (ME), and the Low Energy X-ray Instrument (LE). HXMT will carry out an all sky survey and make pointed observations in the 1-250 keV energy band. In order to get the source and background fluxes simultaneously in the pointed observations, two methods, i.e., the combined field of view (FOV) method and the off-axis pointing method are proposed in this paper. Comprehensive analyses of the sensitivities of the three instruments by using these two methods are presented, respectively. It is found that the off-axis pointing method has a higher sensitivity for HE and ME but a lower sensitivity for LE. Since the axes of the three instruments are aligned along the same direction, the off-axis pointing method is recommended as the main method in the pointed observation for HXMT; the combined FOV method can be used when LE is the most relevant instrument in order to satisfy the scientific objective of the observation. 相似文献
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A thermal control system (TCS) based on the resistance heating method is designed for the High Energy Detector (HED) on the Hard X-ray Modulation Telescope (HXMT). The ground-based experiments of the active thermal control for the HED with the TCS are performed in the ambient temperature range from -15 to 20 ℃ by utilizing the pulse width to monitor the interior temperature of a NaI(Tl) crystal. Experimental results show that the NaI(Tl) crystal's interior temperature is from 17.4 to 21.7 ℃ when the temperature of the PMT shell is controlled within (20±3) ℃ with the TCS in the interesting temperature range, and the energy resolution of the HED is maintained at 16.2% @ 122 keV, only a little worse than that of 16.0% obtained at 20 ℃. The average power consumption of the TCS for the HED with a low-emissivity shell is about 4.3 W, which is consistent with the simulation. 相似文献
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HXMT主探测器磁屏蔽设计与实验结果 总被引:1,自引:0,他引:1
硬X射线调制望远镜(HXMT)致力于实现硬X射线的高灵敏度巡天观测, 描绘硬X射线天图, 并对特殊天体作高灵敏度连续观测, 得到其辐射的能谱和时间变化等. 为了减少空间磁场对观测的影响, 确保本底计数的稳定性和能谱测量的精度, 我们用坡莫合金制成的磁屏蔽罩对HXMT主探测器的光电倍增管(PMT)进行了磁屏蔽处理. 实测表明, 在地面地磁场环境下PMT的最大增益变化幅度为6%; 它与自动增益控制系统配合能使在轨PMT增益变化幅度小于1%, 探测器本底计数变化小于0.1%. 相似文献
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CHENG Ze-Hao WANG Huan-Yu CAO Xue-Lei ZHANG Fei ZHANG Cheng-Mo YANG Jia-Wei LIANG Xiao-Hua GAO Min PENG Wen-Xi 《中国物理C(英文版)》2010,34(2):198-203
A prototype of the ME readout electronics onboard the Hard X-ray Modulate Telescope (HXMT) satellite is developed. Application Specific Integrated Chip (ASIC) is used to construct the front end electronics due to a large number of detectors. Field Programmable Gate Array (FPGA) is connected to the ASIC as a state machine controller and data FIFO in the DAQ system. A USB board is designed to communicate between the DAQ system and the computer. The design goals and features, the operation of the system and the preliminary performance of the prototype are described. The testing results show that the design goals of the prototype system have been achieved. 相似文献
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The Low Energy X-ray Instrument (LE) of the Hard X-ray Modulation Telescope (HXMT) uses the Swept Charge Device (SCD) to detect the X-rays in 1-15 keV. The performance of SCD is vulnerable to temperature. We analyzed the thermal condition of LE at different satellite working attitudes with the Finite Element Method (FEM). It is shown that the angle between the sunlight and the normal line of the barrier should be less them 26°, to keep the SCD detectors working in the required temperature range, i.e. -40 ℃ to -80 ℃. We find that the performance of LE is very stable in this temperature range, with a typical energy resolution of 160 eV at 5.9 keV. 相似文献
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WANG Yu-Sa CHEN Yong XU Yu-Peng WANG Juan CUI Wei-Wei LI Wei HAN Da-Wei ZHANG Zi-Liang CHEN Tian-Xiang LI Cheng-Kui YANG Yan-Ji LIU Xiao-Yan HUO Jia ZHANG Jun-Min ZHENG Yi-Qian 《中国物理C(英文版)》2010,34(12)
The Low Energy X-ray Instrument (LE) of the Hard X-ray Modulation Telescope (HXMT) uses the Swept Charge Device (SCD) to detect the X-rays in 1-15 keV. The performance of SCD is vulnerable to temperature. We analyzed the thermal condition of LE at different satellite working attitudes with the Finite Element Method (FEM). It is shown that the angle between the sunlight and the normal line of the barrier should be less them 26°, to keep the SCD detectors working in the required temperature range, i.e. -40 ℃ to -80 ℃. We find that the performance of LE is very stable in this temperature range, with a typical energy resolution of 160 eV at 5.9 keV. 相似文献
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A prototype of the ME readout electronics onboard the Hard X-ray Modulate Telescope (HXMT) satellite is developed. Application Specific Integrated Chip (ASIC) is used to construct the front end electronics due to a large number of detectors. Field Programmable Gate Array (FPGA) is connected to the ASIC as a state machine controller and data FIFO in the DAQ system. A USB board is designed to communicate between the DAQ system and the computer. The design goals and features, the operation of the system and the preliminary performance of the prototype are described. The testing results show that the design goals of the prototype system have been achieved. 相似文献
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The determination of the sensitivity of the acoustical characteristics of vibrating systems with respect to the variation of the design parameters predicting these characteristics is a necessary and important step of the acoustic design and optimization process. Acoustic design sensitivity analysis includes the computation and evaluation of the sensitivity information required for this procedure. In this study, a boundary element code performing the sensitivity analysis of the acoustic pressure by using the matrix sensitivities with respect to different design variables has been developed. The effect of the precision of boundary element discretization on the acoustic pressure sensitivity is examined via this code. The formulation is applied to a multi-source system and the dimension sensitivity analysis of near field pressures of two-dilating-spherical source is performed. The last application is devoted to a real sound source: a washing machine sitting on the floor. Sensitivity of the field pressures to the machine’s dimensions (size), surface velocity and frequency is examined on the bases of the boundary element model of the machine and half-space condition. The impacts of these variables are compared; and a limiting speed for the machine responding both the acoustical and operational requirements is determined. 相似文献
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为了寻求高灵敏度的石墨烯基的SO_2气体传感器,本文采用基于密度泛函理论的第一性原理方法,研究纯净石墨烯(PG)、单空位缺陷(SVG)、SW缺陷(SWG)、Mn掺杂修饰的石墨烯(Mn-PG)及掺杂和缺陷共修饰的石墨烯(Mn-SVG和Mn-SWG)对SO_2分子的吸附特性.研究表明:PG和SWG对SO_2分子的吸附作用较弱,对SO_2分子不具有敏感性;SO_2分子在SVG表面的吸附能够有效调控其电子结构的变化,使其由金属性转变为半金属性,但其吸附能较低(0.636 eV);结合了Mn掺杂和SV缺陷的Mn-SVG基底尽管增大了与SO_2分子相互作用,但未能引起该体系电子结构和磁性的明显改变;相比之下,SO_2分子在Mn-PG和Mn-SWG基底上具有较强的吸附稳定性;同时,该分子吸附可诱发Mn-PG和Mn-SWG体系磁矩的急剧降低和电导率的显著变化,故可作为探测和清除环境中SO_2分子理想材料.该研究为设计新型石墨烯气体传感器提供理论参考. 相似文献
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探讨了随机平衡傅里叶振幅敏感性分析方法(RBD-FAST)和扩展傅里叶振幅敏感性分析方法(EFAST)在陆面过程模式参数敏感性研究中的应用. 试验中使用通用陆面过程模式(CoLM)和通榆退化草地2008年夏季观测资料, 针对陆气相互作用中重要的要素: 感热通量(SH)、潜热通量(LH)、地表温度(ST), 2 m气温(T2m)和2 m湿度(Q2m), 分析了11 个参数(土深、1–5层黏土比率、孔隙度、最大露水厚度、50%植物根深、地表空气粗糙度和冠层下土壤拖曳系数)的敏感性大小. 结果表明, RBD-FAST和EFAST对参数的一阶敏感性检验结果较为一致且与之前的研究结果类似, EFAST方法还可以得到考虑了参数间相互作用的整体敏感性. RBD-FAST的优势主要表现为在极大地减少了计算消耗机的同时, 一次取样即可计算所有参数的一阶敏感性, 而EFAST的优势则在于通盘考虑了参数之间的相互影响, 可以得到更为合理的整体敏感性序列. 针对不同需求, 选择使用这两种敏感性分析方法, 有助于提高陆面过程模式参数化方案的改进效率. 相似文献
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Sensitivity is one of the important performances for sensor. Theoretical results show that we can choose a long wavelength monitoring point, a high strain dependent birefringence coefficient polarization maintaining fiber (PMF) and a low birefringence PMF to improve the axial strain sensitivity of PMF loop mirror, and experimental results show that the axial strain sensitivity has respectively been improved by 8.06, 30.73, and 22.26% by these methods. The advantage of these methods is to improve the axial strain sensitivity without increasing system complexity. These results help to improve the temperature, displacement, torsion, curvature and liquid level sensitivities of PMF loop mirror. These results can also be applied in photonic crystal fiber loop mirror. 相似文献
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The dendrite growth process of transparent NaBi(WO4)2 with small prandtl and high melting point was studied by using the in-situ observation system. According to the dynamic images and detailed information, there are two kinds of restriction effect on the dendrite growth, the competition between arms and branches and the convection in the melt. The dendrite growth rate was time dependent, and the rate of arm growth reached the maximum 5.8 mm/s in the diffusive-advective region and rapidly decreased in the diffusive-convective region. The growth rate of branch had the same change trends as the arm's. Based on the EPMA-EDS data of solidification structure of quenched NaBi(WO4)2 melt, it was found that there were component differences from stoichiometric concentration in the melt near the interface during the growth process. 相似文献
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