A planar-type ionization chamber for tritium surface contamination measurements in fusion facility

摘要

Gamma irradiation from nuclides produced by neutron activation places significant influence on tritium surface contamination measurements after DT discharge in both Inertial Confinement Fusion (ICF) and Magnetic Confinement Fusion (MCF) facilities. A novel kind of gamma ray insensitive detector, Planar-type Ionization Chamber (PIC), has been developed and it can be used to measure tritium surface contamination directly with air as working gas. Theoretical calculations on both energy deposition and electric field were used in the design and several kinds of experiments were carried out to check the performance of the PIC detector. Results indicate that the PIC detector can be operated at gamma dose as high as 35.5 mu Gy/h. With the sensitive area 100 cm(2), the lower detection limit of the detector is around 16.1 Bq/cm(2), and the detection efficiency is 11.5 %.