Rapid Evaporation of Activated Material for Detector Testing*

The Short-Lived Isotope Counting System (SLICS) is being developed to measure radioactive fusion reaction products created in the Laboratory for Laser Energetics Omega facility with post-shot half-lives on the order of one second. SLICS was tested with a simulated ICF target designed to rapidly evaporate copper after deuteron activation in SUNY Geneseo's Pelletron accelerator. Copper was chosen due to its favorable half-life, cross-section, and abundance of Cu-66. Targets were made by electroplating a layer of copper onto tungsten ribbons. The copper was then evaporated from each target by rapidly heating it with a 100A current; SLICS then captured a portion of the copper evaporate and counted beta particles emitted from the Cu-66 to determine its activity. Several experimental trials were performed to investigate the optimal copper thickness for SLICS testing. It was found that a 25μm copper layer was thin enough to evaporate effectively and thick enough to stop the deuterons before they reached the tungsten. Thermal conduction between the tungsten and copper appeared to be the primary heating mode, but the role of radiative heating in later evaporation stages was also investigated.