CubeSat X射线天文台NinjaSat上基于Xe的LCP-GEM探测器的气体选择
Gas selection for Xe-based LCP-GEM detectors onboard the CubeSat X-ray observatory NinjaSat
AI总结：
本文为NinjaSat卫星的Xe基GEM探测器筛选出Xe/Ar/DME混合气体，在1.2 atm下实现了2-50 keV探测能带，并在590 V电压下获得460的有效增益。
摘要：
我们为CubeSat X射线天文台NinjaSat上的基于Xe的气体电子倍增器（GEM）探测器——气体倍增计数器（GMCs）提出了一种气体选择方案。为了实现2-50 keV的能量通带，我们决定使用在1.2 atm压力下对高能X射线敏感的基于Xe的混合气体。此外，单个GEM需要超过300的有效增益，以便2 keV的X射线信号能够充分大于电噪声。起初，我们在1.0 atm下测量了9种基于Xe的混合气体（Xe、Ar、CO2、CH4和二甲基醚；DME的组合）中GEM的有效增益。Xe/Ar/DME混合气体获得了最高增益，而Xe/Ar/CO2、Xe/Ar/CH4和Xe+淬灭剂混合气体获得的增益相对较低。基于这些结果，我们选择了1.2 atm下的Xe/Ar/DME（75%/24%/1%）混合气体作为GMC的密封气体。然后，我们在所选混合气体中研究了有效增益对漂移区和感应区电场的依赖关系，范围分别为100-650 V cm$^{-1}$和500-5000 V cm$^{-1}$。有效增益对漂移电场的依赖性较弱，而与感应电场几乎呈线性正比关系：在5000 V cm$^{-1}$时比在1000 V cm$^{-1}$时高2.4倍。在最佳的感应和漂移电场下，飞行模型GMC在施加590 V的GEM电压时实现了460的有效增益。
英文摘要：
We present a gas selection for Xe-based gas electron multiplier (GEM) detectors, Gas Multiplier Counters (GMCs) onboard the CubeSat X-ray observatory NinjaSat. To achieve an energy bandpass of 2-50 keV, we decided to use a Xe-based gas mixture at a pressure of 1.2 atm that is sensitive to high-energy X-rays. In addition, an effective gain of over 300 is required for a single GEM so that the 2 keV X-ray signal can be sufficiently larger than the electrical noise. At first, we measured the effective gains of GEM in nine Xe-based gas mixtures (combinations of Xe, Ar, CO2, CH4, and dimethyl ether; DME) at 1.0 atm. The highest gains were obtained with Xe/Ar/DME mixtures, while relatively lower gains were obtained with Xe/Ar/CO2, Xe/Ar/CH4, and Xe+quencher mixtures. Based on these results, we selected the Xe/Ar/DME (75%/24%/1%) mixture at 1.2 atm as the sealed gas for GMC. Then we investigated the dependence of an effective gain on the electric fields in the drift and induction gaps ranging from 100-650 V cm$^{-1}$ and 500-5000 V cm$^{-1}$, respectively, in the selected gas mixture. The effective gain weakly depended on the drift field while it was almost linearly proportional to the induction field: 2.4 times higher at 5000 V cm$^{-1}$ than at 1000 V cm$^{-1}$. With the optimal induction and drift fields, the flight model GMC achieves an effective gain of 460 with an applied GEM voltage of 590 V.
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