空间硬X射线编码孔成像望远镜样机的研制及初步实验结果

介绍了研制的一台空间硬X射线编码孔成像望远镜样机, 使用的位置灵敏探测器为CdZnTe半导体阵列探测器, 面积50mm×50mm, 位置分辨1.6mm. 码板材料为钨铁镍合金, 厚度0.7mm, 码元素尺寸3.2mm×3.2mm. 介绍了码板的编码技术、光学设计和图像重建方法. 实验室测定了样机的性能, 探测器对59.54keV(²⁴¹Am)的能量分辨率为11.6%. 成像实验对单个伽玛射线源的定位 精度为0.12°, 双源角分辨好于0.42°.     

HXMT主探测器磁屏蔽设计与实验结果

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%.     

写在前面的话

正我国第一颗X射线天文望远镜——硬X射线调制望远镜(HXMT)——预计于2016年年底发射升空。HXMT的成功研制表明我国在空间X射线天文探测器设计、制造以及配套的性能测试(标定)以及地面科学应用系统等方面取得了全面突破,跻身国际上少数能够自主研制一颗X射线天文卫星的全部科学仪器的国家。为介绍X射线天文科学研究和HXMT的基本情     

高功率微波介质击穿中X射线和紫外线的初步诊断

 研制了一套宽光谱探测系统,该系统包括紫外成像探测器和X射线成像探测器两个工作单元。利用该系统对高功率微波（HPM）源运行及聚四氟乙烯介质窗受微波场作用而发生击穿时实验环境中的紫外线和X射线进行了初步诊断。结果表明：HPM源运行参数为重复频率100 Hz,运行时间5 s,介质窗未发生击穿时,微波源二极管区产生的X射线剂量为9.28×10²～1.64×10³ Gy,介质窗发生击穿时,环境中X射线剂量为5.38×10²～1.09×10³ Gy;随着微波脉冲重复频率和运行时间的增加,产生的X射线剂量明显增加。此外,利用该系统证实了实验环境中紫外线的存在。     

一台高计数率GEM X射线成像装置原型

研制一种新型的三层级联倍增GEM气体探测器,其有效增益达到10⁵,用于高亮度X射线成像.设计和制作了的精密的微条读出和信号引出方法,采用高速SCSI接口的机箱控制器及计算机控制系统,用于该探测器的射线定位测量,在此基础上建立了一台GEM-X射线成像装置原型.实验结果显示：在X射线强度为10⁵Hz/mm,其增益稳定性<1%,位置分辨<100μm,并获得了清晰的两维图像.     

硬X射线调制望远镜卫星及其科学目标

正硬X射线调制望远镜(The Hard X-ray Modulation Telescope,简称:HXMT)是我国自主研制的第一颗X射线天文卫星,承载有高能X射线望远镜(20~250ke V,5000 cm2)、中能X射线望远镜(5~30ke V,952 cm2)、低能X射线望远镜(1~15ke V,384 cm2)以及空间环境监测器。HXMT具有扫描观测和定点观测两种工作模式,扫描观测可以进行宽波段大天区X射线巡天成像,定点观测可以研究黑洞、中子星等高能天体的多波段X射线快速光变,HXMT还可以监视天空的高能爆发现象。通过HXMT     

空间硬X射线调制望远镜

用宇宙作为物理实验室,探索在地球上无法企及的条件下,例如极早期宇宙或黑洞视界附近强引力场中的物理规律,已成为新世纪物理学和天文学共同的前沿课题;空间天文观测是其中一个最重要的研究途径.自主研制和发放空间硬X射线调制望远镜(HXMT),实现中国空间天文卫星零的突破,是中国<"十一·五"空间科学发展规划>的目标之一.HXMT将实现宽波段X射线(1-250 keV)巡天,其中在硬X射线波段具有世界最高灵敏度和空间分辨率,发现大批被尘埃遮挡的超大质量黑洞和未知类型天体,探测宇宙硬X射线背景辐射;HXMT还将通过对黑洞和其他高能天体宽波段X射线时变和能谱的观测,研究致密天体极端物理条件下的动力学和辐射过程.基于成像技术创新提出HXMT项目迄今已有15年,能不能抓住技术创新所提供的科学机遇仍然是一个严重的挑战.     

GEM气体探测器的增益特性

研制一种双层结构的GEM气体探测器用于X射线成像和带电粒子径迹测量.使用铜靶X射线管产生的高能量X射线对其气体放大倍数,电荷传输效率,增益稳定性进行测试.实验结果显示:在入射X射线通量为10⁵Hz/mm²时,双层GEM探测器的有效增益达到10⁴以上,并且具有长时间稳定性.     

高温超导3mm波成像技术研究

为了探讨高温超导探测器的应用前景 ,研制了 1 2元线列高温超导探测器和成像原理样机。1 2元高温超导探测器的黑体平均 D*≥ 1 .8× 1 0 9cm Hz1/ 2 W- 1,平均 R≥ 1 .9× 1 0 4 VW- 1和 3mm辐射响应平均 D* ≥ 7.5× 1 0 8cm Hz1/ 2 W- 1,平均 R≥ 1 .6× 1 0 4 VW- 1。采用能量探测器代替外差混频器件研制的成像系统对 3mm辐射成像获得成功 ,预示高温超导探测器 (Bolometer)在 3mm波可得到广泛应用。     

三级GEM气体探测器性能的实验研究

GEM探测器是一种新型微型气体探测器(Micro-Pattern Gas Detector), 在粒子物理实验及低能X射线成像系统中有着较大的应用前景. 文章研制了一种适用于低能X射线成像和带电粒子径迹测量的三级GEM气体探测器. 使用放射源⁵⁵Fe对其气体放大特性、电荷传输效率及能量分辨本领等性能进行了实验研究, 重点研究了传输区电场对气体有效增益和能量分辨本领的影响. 实验结果表明, 三级GEM探测器的暗电流和噪声较小, 有效增益能够达到10⁵以上并稳定地工作, 对5.9keV的X射线能量分辨率可达24%, 传输区电场强度大于3000V/(cm.atm)时, 能量分辨率基本稳定在30%左右.     

Observation constraints of the hard X-ray modulation telescope HXMT

The hard X-ray modulation telescope HXMT is a low orbit X-ray space telescope whose main science goals are to accomplish a hard X-ray all sky survey and to study timing and spectral characteristics of X-ray sources. HXMT has three kinds of science instruments: the high energy X-ray detector (HE), the medium energy X-ray detector (ME) and the low energy X-ray detector (LE). The observation schedule of HXMT is a key to achieving the science goal of HXMT, and the analysis of the observation constraints is one of the first tasks in making the observation schedule. This paper analyzes how the observation constraints influence the sky visibility and the visible time distribution of X-ray sources and discusses the schedule strategy with regard to the observation constraints.     

Simulation of the in-flight calibration of the collimator alignment and PSF for HXMT

The Hard X-ray Modulation Telescope (HXMT) is an X-ray astronomical satellite in 1–250 keV, consisting of three collimated instruments. We present the in-flight calibration approach of the collimator alignment and Point Spread Function (PSF) for HXMT, using both the direct fitting method and the imaging method. According to observational simulations of the Crab Nebula, we find that these two methods produce almost the same calibration accuracy of the alignment, and with a one-day scanning observation, the alignment can be calibrated to better than 0.45′ and 0.1′ along the wide and narrow directions of the Field of View (FOV) for a detector module, which corresponds to a localization accuracy of better than 0.1′ and meets the scientific requirement.     

Calibrating the HXMT collimators using diffuse illumination

We propose a new method to calibrate the HXMT collimators by measuring the optical point spread function (PSF) of the hard X-ray modulation telescope (HXMT). The light transmission of the collimator at different viewing angles with a camera and a diffuse backlight placed behind the collimator is measured. This method is much easier to accomplish than measuring the PSF with a parallel optical beam. The experimental results are very consistent with the simulations. The PSF of the collimator of the high energy X-ray telescope on HXMT is found to be in good agreement with the design, with accuracy better than 1 arcmin.     

Application of a multiscale maximum entropy image restoration algorithm to HXMT observations

This paper introduces a multiscale maximum entropy(MSME) algorithm for image restoration of the Hard X-ray Modulation Telescope(HXMT),which is a collimated scan X-ray satellite mainly devoted to a sensitive all-sky survey and pointed observations in the 1-250 keV range.The novelty of the MSME method is to use wavelet decomposition and multiresolution support to control noise amplification at different scales.Our work is focused on the application and modification of this method to restore diffuse sources detected by HXMT scanning observations.An improved method,the ensemble multiscale maximum entropy(EMSME) algorithm,is proposed to alleviate the problem of mode mixing exiting in MSME.Simulations have been performed on the detection of the diffuse source Cen A by HXMT in all-sky survey mode.The results show that the MSME method is adapted to the deconvolution task of HXMT for diffuse source detection and the improved method could suppress noise and improve the correlation and signal-to-noise ratio,thus proving itself a better algorithm for image restoration.Through one all-sky survey,HXMT could reach a capacity of detecting a diffuse source with maximum differential flux of 0.5 mCrab.     

HXMT准直器方案的优化设计

空间硬X射线调制望远镜(HXMT)的性能与探测器的总灵敏面积紧密相关. 利用蒙特卡罗工具对仪器的本底和点扩展函数进行计算分析, 提出了一种优化的准直器构造方案, 能减少探测单元总质量80多千克, 相当于至少5套新探测单元质量. 在同样的卫星载荷质量限制下, 新方案可以增加探测单元, 达到增大总探测灵敏面积, 提升HXMT灵敏度和角分辨率等性能的目的.     

A study of the pointed observation methods and sensitivity of HXMT

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.     

Lucy-Richardson迭代解谱在X射线荧光分析的应用

硬X射线调制望远镜是我国第一颗X射线天文卫星,其载荷低能X射线望远镜采用了SCD型探测器CCD236,主要对能量在0.7～13.0 keV的软X射线光子进行观测。卫星发射前,需要对探测器进行详细的性能标定,其中包括能量响应矩阵的标定。能量响应矩阵是能谱分析的关键。CCD236探测器输出能谱并不是观测光源的真实发射谱,而是发射谱与探测器能量响应矩阵的卷积结果。一般可以通过直接反卷积的方法还原光源的真实能谱。解谱过程可以看作是一维成像问题,利用能量响应矩阵与输出能谱进行反卷积解谱。常用的反卷积算法为Lucy-Richardson迭代算法,其利用条件几率的贝氏定理反复进行运算,进而对输出能谱进行反解,得到观测光源的真实发射能谱。通过能量响应矩阵对CCD236探测器的55Fe测量能谱进行解谱。经过解谱,能谱的能量分辨从144.3 eV提升到了65.6 eV@5.9 keV,连续谱成分被明显地抑制,提高了能谱的峰背比。反解能谱由两个半峰全宽很小的（<70.0 eV）高斯峰组成,两成分的强度比为8.4,能够很好地表征真实发射谱的结构。利用这种方法可对材料X射线荧光谱进行解谱,还原材料的荧光谱,提高能谱的能量分辨。反解结果中主要元素各类荧光线通过解谱彼此独立,能谱峰背比很高,可以很好地用于X射线荧光分析中,提高荧光谱的质量。     

Compressed ghost imaging based on differential speckle patterns

We propose a compressed ghost imaging scheme based on differential speckle patterns,named CGI-DSP.In the scheme,a series of bucket detector signals are acquired when a series of random speckle patterns are employed to illuminate an unknown object.Then the differential speckle patterns(differential bucket detector signals) are obtained by taking the difference between present random speckle patterns(present bucket detector signals) and previous random speckle patterns(previous bucket detector signals).Finally,the image of object can be obtained directly by performing the compressed sensing algorithm on the differential speckle patterns and differential bucket detector signals.The experimental and simulated results reveal that CGI-DSP can improve the imaging quality and reduce the number of measurements comparing with the traditional compressed ghost imaging schemes because our scheme can remove the environmental illuminations efficiently.     

Observation of B(s)(0) → J/ψf(2)'(1525) in J/ψK+ K- final states

The decay B(s)(0) → J/ψK+ K- is investigated using 0.16 fb(-1) of data collected with the LHCb detector using 7 TeV pp collisions. Although the J/ψ? channel is well known, final states at higher K+ K- masses have not previously been studied. In the K+ K- mass spectrum we observe a significant signal in the f(2)'(1525) region as well as a nonresonant component. After subtracting the nonresonant component, we find B(B(s)(0) → J/ψf(2)'(1525))/B(B(s)(0) → J/ψ?) = (26.4 ± 2.7 ± 2.4)%.     

Search for rare and forbidden eta(') decays

We have searched for rare and forbidden decays of the eta(') meson in hadronic events at the CLEO II detector. The search is conducted on 4.80 fb(-1) of e(+)e(-) collisions at 10.6 GeV center-of-mass energy at the Cornell Electron Storage Ring. We find no signals, and set 90% confidence level upper limits of their branching fractions: B(eta(')-->e(+)e(-)eta)<2.4x10(-3), B(eta(')-->e(+)e(-)pi(0))<1. 4x10(-3), B(eta(')-->e(+)e(-)gamma)<0.9x10(-3), and B(eta(')-->e&mgr;)<4.7x10(-4). We also fit the matrix element of the eta(')-->pi(+)pi(-)eta Dalitz plot with the parametrization |M|(2) = A|1+alphay|(2), where y is a linear function of the kinetic energy of the eta, and find Re (alpha) = -0.021+/-0.025.