Leak detection technology

Hiroki, Seiji ; Abe, Tetsuya ; Tanzawa, Sadamitsu

In recent large tokamak machines, the vacuum leak detection technology is highly important due to mainly a safety reason. However, such machines are huge, complicated, and inaccessible, so the conventional He leak detection method is not applicable in many cases. In this chapter, the essential technologies developed in JAEA are exhibited. The high-resolution quadrupole mass spectrometer (HR-QMS) has been developed, where 10 of the He/D peak ratio could be obtained. An improved method with fully circulating the water has been demonstrated, where krypton (Kr) was dissolved in water. For 10 Pa-m/s of two water leaks, the positional accuracy of 12.6% was obtained. Another valuable method has been developed, namely, a unidirectional in-vacuum movable total pressure gauge could detect the minimum 10 Pa-m/s level of air leaks. A special in-vacuum movable QMS head could detect the argon (Ar) leak of 1.910 Pa-m/s.