Kazuyuki Hirose

The memory reliability of magnetic tunnel junctions has been examined from the aspect of their potential use in disaster-resilient computing. This computing technology requires memories that can keep stored information intact even in power-cut emergency situations. Such a requirement has been quantified as a score of acceptable flip probability, which is the failure in time (FIT) rate of 1 for a single-interface perpendicular magnetic tunnel junction (p-MTJ) with a disk diameter of 20 nm. For comparison with this acceptable probability, p-MTJ memory reliability has been evaluated. The risk of particle radiation bombardments, i.e., alpha particles and neutrons-the well-known soft error sources on the ground-has been evaluated from the aspects of both frequency of bombardments and the hazardous effects of bombardments. This study highlights that high-energy terrestrial neutrons may lead to soft errors in p-MTJs, but the flip probability, or the risk, is expected to be lower than 1 x 10(-6) FIT/p-MTJ, which is much smaller than the target probability. It has also been found that the use of p-MTJs can reduce the risk by three orders of magnitude compared with that of the conventional SRAMs. Few risks have been suggested for other radiation particles, such as alpha particles and thermal neutrons. (C) 2017 The Japan Society of Applied Physics

This paper presents analysis results for the onorbit performance of a solar array paddle of the X-ray astronomy satellite Suzaku. The current generated by the solar array was decreasing significantly for approximate one year after mid-2011. We estimated the degradation of the output by simulating the on-orbit environment according to the JPL prediction method. The analysis results indicate that the on-orbit degradation of the solar array paddle is greater than the predicted performance degradation in a space environment. We determined that the difference between the on-orbit data and the analysis results could be attributed to either an increase in cell temperature or radiation degradation due to solar flares.