Avalanche photodiodes (APDs) are well-suited for single-photon detection on quantum communication satellites as they are a mature technology with high detection efficiency without requiring cryogenic cooling. They are, however, prone to significantly increased thermal noise caused by in-orbit radiation damage. Previous work demonstrated that a one-time application of thermal annealing reduces radiation-damage-induced APD thermal noise. Here we examine the effect of cyclical proton irradiation and thermal annealing. We use an accelerated testing environment which emulates a realistic two-year operating profile of a satellite in low-Earth-orbit. We show that repeated thermal annealing is effective at maintaining thermal noise of silicon APDs within a range suitable for quantum key distribution throughout the nominal mission life, and beyond. We examine two strategies—annealing at a fixed period of time, and annealing only when the thermal noise exceeds a pre-defined limit. We find both strategies exhibit similar thermal noise at end-of-life, with a slight overall advantage to annealing conditionally. We also observe that afterpulsing probability of the detector increases with cumulative proton irradiation. This knowledge helps guide design and tasking decisions for future space-borne quantum communication applications.

中文翻译：

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雪崩光电二极管的反复辐射损伤和热退火

雪崩光电二极管（APD）非常适合用于量子通信卫星上的单光子检测，因为它们是一种成熟的技术，具有很高的检测效率，并且不需要低温冷却。但是，由于轨道内辐射损坏，它们容易显着增加热噪声。先前的工作表明，一次性进行热退火可以减少辐射损伤引起的APD热噪声。在这里，我们检查了循环质子辐照和热退火的影响。我们使用一个加速的测试环境，该环境模拟了低地球轨道上卫星的实际两年运行情况。我们表明，反复进行热退火可以有效地将硅APD的热噪声保持在适合整个正常任务寿命以及以后的量子密钥分配的范围内。我们研究了两种策略-在固定的时间段内进行退火，以及仅在热噪声超过预定限制时才进行退火。我们发现这两种策略在寿命终止时都表现出相似的热噪声，与有条件地进行退火相比，总体优势略微。我们还观察到探测器的后脉冲概率随累积质子辐照而增加。这些知识有助于指导未来的星载量子通信应用的设计和任务分配决策。