Mitigating the effects of particle background on the Athena Wide Field Imager
Mitigating the effects of particle background on the Athena Wide Field Imager
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DOI：
10.1117/1.jatis.8.1.018001
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发表时间：
2022-01
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通讯作者：
E. Miller;C. Grant;M. Bautz;S. Molendi;R. Kraft;P. Nulsen;E. Bulbul;S. Allen;D. Burrows;Tanja Eraerds;V. Fioretti;F. Gastaldello;D. Hall;M. Hubbard;J. Keelan;N. Meidinger;E. Perinati;A. Rau;D. Wilkins
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作者：
E. Miller;C. Grant;M. Bautz;S. Molendi;R. Kraft;P. Nulsen;E. Bulbul;S. Allen;D. Burrows;Tanja Eraerds;V. Fioretti;F. Gastaldello;D. Hall;M. Hubbard;J. Keelan;N. Meidinger;E. Perinati;A. Rau;D. Wilkins
抽象的。雅典娜号上飞行的广域成像仪（WFI）将开创研究炎热而充满活力的宇宙的下一个时代。雅典娜雄心勃勃的科学计划包括对微弱、弥散源的观测，这些源受到高能宇宙射线粒子产生的背景中统计和系统不确定性的限制。这些粒子产生易于识别的“宇宙射线轨迹”，以及粒子与仪器相互作用产生的二次光子或 X 射线产生的不易识别的信号。此类次级粒子产生与光学器件聚焦的 X 射线相同的信号，并且在不消除这些珍贵光子的情况下无法进行过滤。作为估计未拒绝背景水平并减轻其影响的更大努力的一部分，我们在这里展示了利用宇宙射线粒子轨迹和次级事件之间的空间相关性的背景降低技术的研究结果。我们使用 Geant4 模拟生成真实的粒子背景信号，将其分类到模拟的 WFI 帧中，并以与预期飞行和地面软件类似的方式处理这些帧，以生成仅包含粒子背景的真实 WFI 观测。正在研究的技术是自反符合（SAC），然后选择性地过滤粒子轨迹周围的探测器区域，将 WFI 变成自己的反符合探测器。我们证明，SAC 可有效改善微弱、扩散源观测的系统不确定性，但代价是由于信号减少而导致统计不确定性。如果将每一帧的足够像素脉冲高度信息遥测到地面，则可以根据科学目标有选择地应用该技术，从而提供灵活性而不影响其他科学的数据质量。这里提出的结果与任何未来的硅基像素化 X 射线成像探测器相关，并且可以允许 WFI 和类似仪器探测真正微弱的 X 射线表面亮度。
Abstract. The Wide Field Imager (WFI) flying on Athena will usher in the next era of studying the hot and energetic Universe. Among Athena’s ambitious science programs are observations of faint, diffuse sources limited by statistical and systematic uncertainty in the background produced by high-energy cosmic ray particles. These particles produce easily identified “cosmic-ray tracks” along with less easily identified signals produced by secondary photons or x-rays generated by particle interactions with the instrument. Such secondaries produce identical signals to the x-rays focused by the optics and cannot be filtered without also eliminating these precious photons. As part of a larger effort to estimate the level of unrejected background and mitigate its effects, we here present results from a study of background-reduction techniques that exploit the spatial correlation between cosmic-ray particle tracks and secondary events. We use Geant4 simulations to generate a realistic particle background signal, sort this into simulated WFI frames, and process those frames in a similar way to the expected flight and ground software to produce a realistic WFI observation containing only particle background. The technique under study, self-anti-coincidence (SAC), then selectively filters regions of the detector around particle tracks, turning the WFI into its own anti-coincidence detector. We show that SAC is effective at improving the systematic uncertainty for observations of faint, diffuse sources, but at the cost of statistical uncertainty due to a reduction in signal. If sufficient pixel pulse-height information is telemetered to the ground for each frame, then this technique can be applied selectively based on the science goals, providing flexibility without affecting the data quality for other science. The results presented here are relevant for any future silicon-based pixelated x-ray imaging detector and could allow the WFI and similar instruments to probe to truly faint x-ray surface brightness.