Radiation Blistering and Deuterium Retention in Copper

Abstract

200 keV deuteron beams from a low energy accelerator have been used to study the retention of deuterium and radiation blistering of copper samples. These studies have been conducted over a range of target temperatures, deuteron current densities and deuteron fluences. By using the D(d,p)T reaction to depth profile the implanted deuterium it has been found that approximately 100% of the deuterium implanted at target temperatures of less than 140 K is retained within the target. Increasing the target temperature above 140K.has been found to produce a steady decrease in the amount of deuterium retained until at a temperature of 380 K only ~15% of the implanted deuterium remains within the target. Some samples implanted in the temperature range 140 to 320 K have shown an increased yield of protons from the D(d,p)T reaction due to the increased retention of deuterium in the near surface regions. The deuterium depth distributions have also been examined using a 2 MeV deuteron beam. This method has been found to provide useful information about the amount of deuterium retained around the low energy deuteron projected range despite a large separation, both in time and distance, between the accelerators used for the implantation and the profiling. The radiation blistering studies have involved measuring the onset of blistering using an in-situ method based on the scattering of laser light at a non-specular angle from the irradiated area. Additional information about the blister morphology has been obtained by SEM examination of these targets following irradiation. Discrete blisters are found to form rapidly at a well defined fluence. For a target temperature of 120 K, this critical fluence required for blistering has been found to depend strongly upon the incident current density and to be a minimum at a current density of (2+-1) A.m-2. Also at 120 K, a ring of blisters surrounding the main beam spot has been observed. Irradiations at higher target temperatures are found to produce two different blister morphologies. For target temperatures in the range 120 to 190 K and 300 to 380 K, semi-spherical blisters are found to form at fluences of approx. 2 x 10 22 d m-2 and 4 x 10 22 d.m-2 respectively. In the intermediate temperature region, irregularily shaped blisters are found to form at a fluence of~6 x 10 22d.m-2. The deuterium retained within the surface regions of the target has been related to the onset of blistering.