Ionization, Secondary Emission, and Comptom Currents at Gamma Irradiated Interfaces

Energy and charge transport by secondary electrons across interfaces between gamma irradiated materials can be important for accurate predictions of radiation effects. In order to measure these charge transport effects air ionization and secondary electron emission currents were observed in a multiple cavity aluminum chamber adjacent to tungsten and beryllium under Co60 γ radiation. It is found that low-energy secondary emission measurements are within 3% of air ionization measurements made in the same chamber and that both measurements agree with previously reported ionization measurements of energy deposition profiles. Also, profiles obtained in relatively thin aluminum chambers (~ 20% of the maximum energy electron range), sandwiched between different combinations of beryllium and tungsten, can be accurately predicted from a linear superposition of single interface data. Finally, electric charge separation is observed at gamma irradiated boundaries even in the absence of applied electric fields. The sign and magnitude of the charge is found to depend upon the direction of the incident beam as well as the material combination. The change in electron current as a function of the distance from the interface can be obtained from the data presented.