Turning Instrument Background Into Science Data for Structural Features of Radiation Belts

Approaches regarding how to turn the instrument background counts into scientifically valuable data are presented in this Technical Report on Methods. The background counts due to penetrating energetic particles of radiation belts detected on Cluster CIS HIA and CODIF instruments and the Double Star HIA instrument are used in these approaches. In HIA spectrograms, the background counts are seen simultaneously in all energy channels marking the entry and exit of the radiation belts by the spacecraft, therefore, the locations of the boundaries of the outer and inner belts can be determined. In the case when HIA measurements are not readily available, a new method is proposed in which supplementary data streams within the CODIF telemetry is exploited. It employs separate counts that register "start," "stop," and "non-valid" signals increasing in the presence of penetrating particles even when no corresponding increase are shown in the energy-time spectrograms. The locations of the radiation belt boundaries are defined by following the changes in counts gradients with time and visual inspection of all the available measurements. The July-August 2007 and September-October 2012 time periods are analyzed for method demonstration on a presence of a third radiation belt, or storage ring.

Prototypic Lightweight Alloy Design for Stellar-Radiation Environments

The existing literature data shows that conventional aluminium alloys may not be suitable for use in stellar-radiation environments as their hardening phases are prone to dissolve upon exposure to energetic irradiation, resulting in alloy softening which may reduce the lifetime of such materials impairing future human-based space missions. The innovative methodology of crossover alloying is herein used to synthesize an aluminium alloy with a radiation resistant hardening phase. This alloy-a crossover of 5xxx and 7xxx series Al-alloys-is subjected to extreme heavy ion irradiations in situ within a TEM up to a dose of 1 dpa and major experimental observations are made: the Mg32(Zn,Al)49 hardening precipitates (denoted as T-phase) for this alloy system surprisingly survive the extreme irradiation conditions, no cavities are found to nucleate and displacement damage is observed to develop in the form of black-spots. This discovery indicates that a high phase fraction of hardening precipitates is a crucial parameter for achieving superior radiation tolerance. Based on such observations, this current work sets new guidelines for the design of metallic alloys for space exploration.