Vacuum effects on the radiation chemical yields in PADC films exposed to gamma rays and heavy ions

In order to understand the vacuum effects on the sensitivity of PADC detectors from the viewpoint of molecule structural modification along nuclear tracks, a series of FT-IR spectrometric studies has been made for PADC films exposed to He and C ions at energies below 6 MeV/n, as well as to gamma rays from an intense Co-60 source, under the both conditions of in air and in vacuum. The radiation chemical yields for the losses of ether and carbonate ester bonds are hardly affected by the environmental conditions in the cases of He and C ion irradiations. For gamma ray, the yields are about half in vacuum compared to those in air. The formation of OH groups is fairly suppressed in vacuum in all cases. Recombination of free radicals resulted in modified polymeric network formation would be enhanced in heavy ion irradiations rather than in that of gamma irradiations.

► Characteristics of tracks in PADC formed after vacuum irradiations are examined.
► G values are not sensitive for irradiation environment for He and C ions.
► G value for gamma ray in vacuum is about half of that in air.
► Generated OH groups should be the damage which enhance track etch rate.