A tritium detector for the Tokamak Fusion Test Reactor

We have developed a device for on-line dynamic detection of tritium transferred during regeneration of neutral beam injector cryopanels at the Tokamak Fusion Test Reactor (TFTR) at Princeton Plasma Physics Laboratory (PPPL). The detector has been calibrated with various tritium-containing gas mixtures, dynamically tested in flowing gas streams and installed in TFTR´s neutral beam forevacuum line. The device measures tritium partial pressure in the regeneration line by beta scintillation detection and total gas pressure by capacitance manometry. The tritium partial pressure detection range is 10^-5 to 2 Torr-T₂, covered with three multiplier voltage gain settings. Careful operation, to avoid exposure to high tritium partial pressures, can lower the detection limit to 2×10^-6 Torr of tritium. The relative error on tritium pressure measurement in a flowing mixture (1% T₂ in D₂) was less than 3%