Single-photon detectors in space must retain useful performance characteristics despite being bombarded with sub-atomic particles. Mitigating the effects of this space radiation is vital to enabling new space applications which require high-fidelity single-photon detection. To this end, we conducted proton radiation tests of various models of avalanche photodiodes (APDs) and one model of photomultiplier tube potentially suitable for satellite-based quantum communications. The samples were irradiated with 106 MeV protons at doses approximately equivalent to lifetimes of 0.6 , 6, 12 and 24 months in a low-Earth polar orbit. Although most detection properties were preserved, including efficiency, timing jitter and afterpulsing probability, all APD samples demonstrated significant increases in dark count rate (DCR) due to radiation-induced damage, many orders of magnitude higher than the 200 counts per second (cps) required for ground-to-satellite quantum communications. We then successfully demonstrated the mitigation of this DCR degradation through the use of deep cooling, to as low as $-86^{\circ}\mbox{C}$ . This achieved DCR below the required 200 cps over the 24 months orbit duration. DCR was further reduced by thermal annealing at temperatures of +50 to $+100^{\circ}\mbox{C}$ .

中文翻译：

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减轻空间应用单光子探测器的辐射损伤。

尽管受到亚原子粒子的轰击，太空中的单光子探测器仍必须保持有用的性能特征。减轻这种空间辐射的影响对于实现需要高保真单光子探测的新空间应用至关重要。为此，我们对各种模型的雪崩光电二极管（APD）和一种可能适用于卫星量子通信的光电倍增管模型进行了质子辐射测试。样品被 106 MeV 质子照射，剂量大约相当于近地极轨道上 0.6、6、12 和 24 个月的寿命。尽管保留了大多数检测特性，包括效率、定时抖动和后脉冲概率，但所有 APD 样本均表现出由于辐射引起的损伤，暗计数率 (DCR) 显着增加，比每秒 200 次计数 (cps) 高出许多数量级地面到卫星量子通信所需的。然后，我们成功地证明了通过使用深度冷却可以将这种 DCR 退化缓解到低至 $-86^{\circ}\mbox{C}$ 。这使得 DCR 在 24 个月的轨道持续时间内低于所需的 200 cps。通过在 +50 至 $+100^{\circ}\mbox{C}$ 温度下进行热退火，DCR 进一步降低。