Gas leak detection by diode laser absorption spectrometry

Abstract Diode laser atomic absorption measurements of argon traces in low-pressure discharges were carried out to detect and measure gas leaks in a test chamber. Helium flows as a carrier gas through the test chamber and the discharge. In the case of a leak, air and thus also its natural content of argon is mixed to the helium gas-flow through the chamber. The argon content of the mixed gas flow through the discharge is determined by wavelength modulation diode laser atomic absorption spectrometry. The resulting absorption signal is a measure for the existing leak-rate. For barometric pressure of ambient air lowest detectable leak rates are typically 10 −6 mbar l s −1 . By application of pure Ar with pressures above 1 bar detectable leak rates can in practice be lower than 10 −8 mbar l s −1 .