A crosstalk and non-uniformity correction method for the space-borne Compton polarimeter POLAR

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• 作者：Hualin Xiao ; ^a ; ^b ; ^{hualin.xiao@psi.ch" class="auth_mail" title="E-mail the corresponding author} ; Wojtek Hajdas^a ; Bobing Wu^b ; Nicolas Produit^c ; Tianwei Bao^b ; Tadeusz Batsch^e ; Franck Cadoux^d ; Junying Chai^b ; Yongwei Dong^b ; Minnan Kong^b ; Siwei Kong^b ; Dominik K. Rybka^e ; Catherine Leluc^d ; Lu Li^b ; Jiangtao Liu^b ; Xin Liu^b ; Radoslaw Marcinkowski^a ; Mercedes Paniccia^d ; Martin Pohl^d ; Divic Rapin^d ; Haoli Shi^b ; Liming Song^b ; Jianchao Sun^b ; Jacek Szabelski^e ; Ruijie Wang^b ; Xing Wen^b ; Hanhui Xu^b ; Laiyu Zhang^b ; Li Zhang^b ; Shuangnan Zhang^b ; Xiaofeng Zhang^b ; Yongjie Zhang^b ; Ania Zwolinska^e
• 关键词：Multi-anode photomultiplier ; Non-uniformity ; Crosstalk ; Gamma-ray burst ; Polarization
• 刊名：Astroparticle Physics
• 出版年：2016
• 出版时间：October 2016
• 年：2016
• 卷：83
• 期：Complete
• 页码：6-12
• 全文大小：923 K

文摘

In spite of extensive observations and numerous theoretical studies in the past decades several key questions related with Gamma-Ray Bursts (GRB) emission mechanisms are still to be answered. Precise detection of the GRB polarization carried out by dedicated instruments can provide new data and be an ultimate tool to unveil their real nature. A novel space-borne Compton polarimeter POLAR onboard the Chinese space station TG2 is designed to measure linear polarization of gamma-rays arriving from GRB prompt emissions. POLAR uses plastics scintillator bars (PS) as gamma-ray detectors and multi-anode photomultipliers (MAPMTs) for readout of the scintillation light. Inherent properties of such detection systems are crosstalk and non-uniformity. The crosstalk smears recorded energy over multiple channels making both non-uniformity corrections and energy calibration more difficult. Rigorous extraction of polarization observables requires to take such effects properly into account. We studied influence of the crosstalk on energy depositions during laboratory measurements with X-ray beams. A relation between genuine and recorded energy was deduced using an introduced model of data analysis. It postulates that both the crosstalk and non-uniformities can be described with a single matrix obtained in calibrations with mono-energetic X- and gamma-rays. Necessary corrections are introduced using matrix based equations allowing for proper evaluation of the measured GRB spectra. Validity of the method was established during dedicated experimental tests. The same approach can be also applied in space utilizing POLAR internal calibration sources. The introduced model is general and with some adjustments well suitable for data analysis from other MAPMT-based instruments.