X-ray silicon-on-insulator (SOI) pixel sensors, “XRPIX,” are being developed for the next-generation x-ray astronomical satellite, “FORCE.” The XRPIX is fabricated with the SOI technology, which makes it possible to integrate a high-resistivity Si sensor and a low-resistivity Si complementary metal oxide semiconductor (CMOS) circuit. The CMOS circuit in each pixel is equipped with a trigger function, allowing us to read out outputs only from the pixels with x-ray signals at the timing of x-ray detection. This function thus realizes high throughput and high time resolution, which enables to employ anti-coincidence technique for background rejection. A new series of XRPIX named XRPIX6E developed with a pinned depleted diode (PDD) structure improves spectral performance by suppressing the interference between the sensor and circuit layers. When semiconductor x-ray sensors are used in space, their spectral performance is generally degraded owing to the radiation damage caused by high-energy protons. Therefore, before using an XRPIX in space, it is necessary to evaluate the extent of degradation of its spectral performance by radiation damage. Thus, we performed a proton irradiation experiment for XRPIX6E for the first time at Heavy Ion Medical Accelerator in Chiba in the National Institute of Radiological Sciences. We irradiated XRPIX6E with high-energy protons with a total dose of up to 40 krad, equivalent to 400 years of irradiation in orbit. The 40-krad irradiation degraded the energy resolution of XRPIX6E by 25 ± 3 % , yielding an energy resolution of 260.1 ± 5.6 eV at the full-width half maximum for 5.9 keV X-rays. However, the value satisfies the requirement for FORCE, 300 eV at 6 keV, even after the irradiation. It was also found that the PDD XRPIX has enhanced radiation hardness compared to previous XRPIX devices. In addition, we investigated the degradation of the energy resolution; it was shown that the degradation would be due to increasing energy-independent components, e.g., readout noise.

中文翻译：

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具有钉扎耗尽二极管结构的 X 射线 SOI 像素传感器的质子辐射硬度

X 射线绝缘体上硅 (SOI) 像素传感器“XRPIX”正在为下一代 X 射线天文卫星“FORCE”开发。XRPIX 采用 SOI 技术制造，可以集成高电阻率 Si 传感器和低电阻率 Si 互补金属氧化物半导体 (CMOS) 电路。每个像素中的 CMOS 电路都配备了触发功能，使我们能够在 X 射线检测的时机仅从具有 X 射线信号的像素中读出输出。因此，该功能实现了高吞吐量和高时间分辨率，从而能够采用反重合技术进行背景抑制。一个名为 XRPIX6E 的新系列 XRPIX 采用钉扎耗尽二极管 (PDD) 结构开发，通过抑制传感器和电路层之间的干扰来提高光谱性能。当半导体X射线传感器在太空中使用时，由于高能质子引起的辐射损伤，其光谱性能通常会下降。因此，在太空中使用 XRPIX 之前，有必要评估其光谱性能因辐射损伤而退化的程度。因此，我们首次在国立放射科学研究所千叶的重离子医学加速器上对 XRPIX6E 进行了质子辐照实验。我们用高能质子照射 XRPIX6E，总剂量高达 40 krad，相当于在轨照射 400 年。40 krad 辐射使 XRPIX6E 的能量分辨率降低了 25 ± 3 %，在 5.9 keV X 射线的半高全宽处产生了 260.1 ± 5.6 eV 的能量分辨率。但是，该值满足 FORCE 的要求，6 keV 时为 300 eV，即使在辐照后也是如此。还发现与以前的 XRPIX 设备相比，PDD XRPIX 具有增强的辐射硬度。此外，我们研究了能量分辨率的下降；结果表明，性能下降的原因是与能量无关的分量增加，例如读出噪声。