A new design for a low-level proportional counter for tritium

A new design for a low-level tritium proportional counter is described. The design is based on the multiwire proportional counter (MPC) and drift-chamber (MWDC) concept used in high-energy physics. The MPC plane is subdivided into several detection strips, and logic (L) analysis of the projection length of an ionizing track on this plane replaces the anticoincidence counter. The performance of the counter in the rejection of background events was evaluated by simulation for several configurations. It is shown that the preferred configuration is cylindrical. For a fine enough subdivision the analysis by L only can perform better than the combination of energy (E) and rise-time (R) analyses. A residual background due to events very close to the walls of the counter can also be eliminated by logic. Thus, it is possible to count tritium in the new counter by logic only. The results of the simulation are confirmed by experimental data from the literature and from a prototype counter. (author)