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arXiv 2602.02134astro-ph.IM
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JWST NIRSpec在L2轨道上的宇宙射线经验

JWST NIRSpec's Cosmic Ray Experience at L2

NASA Goddard Space Flight Center(美国国家航空航天局戈达德太空飞行中心);Observational Cosmology Laboratory(观测宇宙学实验室);Center for Research and Exploration in Space Science and Technology(空间科学与技术研究探索中心)

Bernard J. Rauscher, D. J. Fixsen

AI总结:

JWST NIRSpec在L2轨道上经历宇宙射线撞击,撞击率随时间变化,研究其影响及未来任务的潜在挑战。

摘要:

我们对JWST NIRSpec的‘黑暗’曝光中的宇宙射线相互作用进行了表征。在太阳/地球-月球L2晕轨道上,JWST会遇到穿透NIRSpec辐射屏蔽层的高能离子。在运行的第一三年中,屏蔽后的宇宙射线撞击率从约4.3降至2.3 ions cm⁻² s⁻¹。一次典型的撞击会影响约7.1个像素,需要在校准期间进行缓解,并在λco = 5.4 μm的HgCdTe探测器材料中沉积约6 keV(相当于约5200个电荷)。相应的线性能量转移约为0.86 keV μm⁻¹。由于我们目前接近太阳最大值,银河宇宙射线通量预计会随着太阳活动下降而增加,导致NIRSpec的速率从2.3增加到4.3 ions cm⁻² s⁻¹,预计在2027年初达到,并可能在2030年代初达到约6 ions cm⁻² s⁻¹。我们研究了罕见的“雪球”撞击以及较少见的由二次 shower 事件引起的校准挑战。我们探讨了这些现象的可能起源,包括重离子、屏蔽产生的二次粒子或HgCdTe探测器材料中的非弹性散射。我们讨论了这些发现对未来任务,包括南希·格蕾丝·罗曼空间望远镜的影响。

英文摘要:

We characterize cosmic ray interactions in blanked-off \JWST NIRSpec ``dark'' exposures. In its Sun/Earth-Moon L2 halo orbit, \JWST encounters energetic ions that penetrate NIRSpec's radiation shielding. The shielded cosmic ray hit rate decreased from approximately $4.3$ to $2.3~\mathrm{ions~cm^{-2}}~s^{-1}$ during the first three years of operation. A typical hit affects about 7.1~pixels necessitating mitigation during calibration and deposits around $6~\mathrm{keV}$ in the $λ_\mathrm{co} = 5.4~μ$m HgCdTe detector material (equivalent to $\sim5200$ charges). The corresponding linear energy transfer is about $0.86~\mathrm{keV~μm^{-1}}$. As we are currently near solar maximum, galactic cosmic ray flux is expected to increase as solar activity declines, leading to an anticipated rise in the NIRSpec rate from $2.3$ to $4.3~\mathrm{ions~cm^{-2}}~s^{-1}$ by early 2027 and potentially reaching $\sim6~\mathrm{ions~cm^{-2}}~s^{-1}$ in the early 2030s. We investigate rare, large ``snowball'' hits and, less frequently, events with secondary showers that pose significant calibration challenges. We explore their possible origins as heavy ions, secondary particles from shielding, or inelastic scattering in the HgCdTe detector material. We discuss the implications of these findings for future missions including the Nancy Grace Roman Space Telescope.

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