物理学报2017，Vol.66Issue(11)：63-70,8.DOI:10.7498/aps.66.112901
硬X射线调制望远镜低能探测器量子效率标定
Quantum efficiency calibration for low energy detector onboard hard X-ray modulation telescope satellite
摘要
Abstract
Low energy X-ray telescope,working over 0.7-15 keV energy band,is one of the main payloads in the hard X-ray modulation telescope satellite.The primary scientific objectives are to survey large sky area to investigate galactic X-ray transient sources as well as the cosmic X-ray background,and to observe X-ray binaries or black holes for studying the dynamics and emission mechanism in strong gravitational or magnetic field.The detector of low energy X-ray telescope is CCD236,a new generation of swept charge device,which has good time and energy resolution.Quantum efficiency (QE) of the detector has a crucial influence on X-ray spectrum fitting and absolute luminosity calculation.To provide valuable scientific data,QE should be calibrated in detail.In this paper,QE calibration is accomplished with respect to a silicon drift detector (SDD),using an Fe-55 radioactive source,at energy points Mn-Kα (5.899 keV) and Mn-Kβ (6.497 keV).The energies of Mn-Kα and Mn-Kβ are near that of iron-K,which is an important line in X-ray observation.Additionally,Mn-Kα and Mn-Kβ X-ray will partially pass through the depletion region of CCD236,and these energy points can be used to measure the depletion thickness.This experiment is set up in a vacuum cooling chamber.The X-ray source perpendicularly illuminates SDD and CCD236 through a small hole,whose area is far less than those of two detectors;therefore,QE measurements are irrelevant to neither the distance nor the azimuth angle between the X-ray source and the detector.For CCD236,split events should be corrected.Energy spectra of SDD and CCD236 are fitted with two Gaussian distributions,respectively,to obtain peak positions and standard variations of Mn-Kα and Mn-Kβ.With known structure of SDD,the QE of CCD236 can be calculated.QE values at Mn-Kα and Mn-Kβ are 71％ and 62％,respectively.QE and temperature are uncorrelated with each other in a temperature range from-95 ℃ to-30 ℃.According to the specific structure of CCD236 and the measured QE,without considering the effect of channel stop,the best-fit thickness of depletion region is obtained to be 38 [μm.When CCD236 is applied with different driving or substrate voltages,no obvious variation of QE is observed.It indicates that the thickness values of depletion region with high and low level voltages are equal.Furthermore,it shows that working CCD236 is deep depleted,and the thickness of depletion region will not change because it reaches its maximum,the edge of epitaxial layer and substrate layer.关键词
电荷耦合器件/量子效率/耗尽层Key words
charge-coupled device/quantum efficiency/depletion region引用本文复制引用
朱玥,李炜,韩大炜,霍嘉,胡渭,李茂顺,张艺,祝宇轩,刘苗,赵晓帆,陈勇,张子良,杨彦佶,薛荣峰,崔苇苇,陆波,王娟,陈田祥,王于仨..硬X射线调制望远镜低能探测器量子效率标定[J].物理学报,2017,66(11):63-70,8.基金项目
Project supported by the Young Scientists Fund of the National Natural Science Foundation of China (Grant No.11403024)and the Main Direction Program of Knowledge Innovation of Chinese Academy of Sciences (Grant No.KZCX2-EW-J01).国家自然科学基金青年科学基金(批准号:11403024)和中国科学院知识创新工程重要方向性项目(批准号:KZCX2-EW-J01)资助的课题. （Grant No.11403024）
