We performed two types of radiation testing on high-speed LSI chips to test their suitability for use in wideband observations by the Japanese next space VLBI mission, VSOP-2. In the total ionization dose experiment we monitored autocorrelation spectra which were taken with irradiated LSI chips and the source current at intervals up to 1,000 hours from the ionization dose, but we could not see any change of these features for the chips irradiated with dose rates expected in the VSOP-2 mission. In the single event effect experiment, we monitored the cross correlation phase and power spectra between the data from radiated and non-radiated devices, and the source current during the irradiation of heavy-ions. We observed a few tens of single event upsets as discrete delay jumps for each LSI. We estimated the occurrence rate of single events in space as between once a few days to once a month. No single event latch-up was seen in any of the LSIs. These results show that the tested LSIs have sufficient tolerance to the environment for space VLBI observations.
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