中国散裂中子源在大气中子单粒子效应研究中的应用评估

由于缺少可用的散裂中子源,多年来我国在大气中子单粒子效应方面主要依靠模拟仿真和单能中子试验的方式开展研究.随着中国散裂中子源(CSNS)通过国家验收,基于CSNS开展大气中子单粒子效应研究成为可能.本文利用CSNS反角白光中子源开展多款静态随机存取存储器器件的中子单粒子效应试验,并与早期开展的高原大气试验结果进行对比,对CSNS在大气中子单粒子效应研究中的应用进行评估.结果表明,相同器件在CSNS反角白光中子源测得的单粒子翻转截面小于大气试验的结果,且不同器件的翻转截面与特征尺寸没有明显的单调关系.分析得到前者由于CSNS反角白光中子谱偏软;后者由于特征尺寸降低导致的临界电荷变小和灵敏体积变小对截面的贡献是竞争关系.针对截面偏小的问题,根据能谱差异分析了中子能量阈值对器件翻转截面的影响,发现能量阈值取12MeV进行计算时,器件在CSNS反角白光中子源和高原大气中子环境中能够得到较一致的截面.研究结果表明CSNS反角白光中子源能够用于加速大气中子单粒子效应试验.考虑到CSNS的运行功率正在逐步提高,且多条规划中的白光中子束线与大气中子能谱更为接近,预期未来CSNS将能更好地应用于大气中子单粒子效应研究.

Application and evaluation of Chinese spallation neutron source in single-event effects testing

Due to the lack of available spallation neutron source, the atmospheric neutron single event effect (SEE) in China were studied mainly by means of simulation and single energy neutron test. Since the Chinese spallation neutron source (CSNS) passed the national acceptance, it has become possible to carry out the research on atmospheric neutron SEE by using the CSNS. In this paper, the neutron SEE experiments of 3 kinds of SRAMs with different feature sizes are carried out for the first time by using the CSNS back-n. The application of CSNS back-n in the study of atmospheric neutron SEE is evaluated by comparing with the results of the earlier plateau experiment. The results show that the cross section of the single event upset is smaller than that of the plateau test, and the cross sections of different devices have no obvious monotonic relationship with feature size. The reason for the former result is that the energy spectrum of CSNS back-n is slightly softer than that of the atmospheric neutron. The reason for the second result is that small feature size means small critical charge and small sensitive volume, and these two factors compete with each other when they make the contribution to the cross section. According to the difference in energy spectrum and cross section among the SRAM devices, a correction factor is proposed to correct the test results based on CSNS back-n. For the difference in energy spectrum, different energy thresholds will produce different ratios between the cross sections by using CSNS back-n and atmospheric neutron. The neutrons of CSNS back-n are mainly concentrated around 1 MeV, which is close to the energy threshold of general SRAM devices. Thus, inaccurate energy threshold estimation will introduce a large error into the cross section of SEU. Thus, the relation between the correction factor and the energy threshold is analyzed. If 12 MeV is selected as the energy threshold to calculate the cross section, more consistent results could be obtained for our DUT in CSNS back-n and atmospheric neutron environment. In a word, the results show that the CSNS back-n can be used to speed up the atmospheric neutron SEE test, but the result should be corrected to evaluate the threat from atmospheric neutron. Fortunately, with the continuous increase of CSNS operating power, the neutron flux and the accelerated factor of CSNS will increase synchronously. Besides, other 3 white light neutron beams are planned in the CSNS project, the planned energy spectra are closer to those of atmospheric neutron. It is expected that the CSNS will be better applied to the study of atmospheric neutron SEE.