FABRICATION AND TESTING OF A DOUBLE-IONIZATION CHAMBER FOR ONLINE TRITIUM PRODUCTION-RATE MEASUREMENTS AND COMPARISON WITH THE STANDARD LIQUID-SCINTILLATION METHOD

At the LOTUS facility, an extremely efficient on-line line detector sy stem, based on the detection of the charged particles associated with the Li-6(n, alpha)t reaction, has been designed, fabricated, and teste d. The system offers an interesting possibility for directly measuring the tritium production rate (TPR) at any experimental site. The charg ed particles emitted in opposite directions can be detected by a doubl e parallel plate ionization chamber (DIC) configuration. The real even ts are identified by employing a coincidence circuit. The complete fab rication details, testing under different conditions, measurement of T PR, and its comparison with the liquid-scintillation method (LSM) are detailed. The DIC response to thermal neutrons agrees well with the th eoretical calculations. Also, the detector system is insensitive to a contact gamma dose rate of 1.3 rem/h. The direct TPR measurements and the salient feature of higher efficiency in comparison with the LSM ar e demonstrated. The TPR determined by both methods are in excellent ag reement.