Radioluminescence of individual deuterium–tritium‐filled glass microbubble laser targets

Visible radioluminescence was observed from single 200‐μm‐diam deuterium–tritium (D–T)‐filled glass microbubble laser targets. Most of the light is caused by tritium beta particles hitting the glass, and no beta particles escape outside the microbubble. At room temperature, white light is created with an efficiency of 0.2 to 0.3 photons/beta particle. This efficiency rises an order of magnitude at 35 K, probably because of freezing of radiation defects into the glass. It decreases when the D–T liquifies and drops even lower upon solidification. This is probably caused by pooling of the D–T at the bottom of the microbubble plus light absorption in small crystallites. Radioluminescence offers a means of certifying the D–T fill of individual microbubble laser targets made of transparent material.