Study on the temporal evolution characteristics of Cu and Mo in a low-pressure environment using the FO-LIBS

Fiber-Optic Laser-Induced Breakdown Spectroscopy (FO-LIBS) technology offers excellent remote diagnostic capabilities and flexibility in complex environments, making it highly promising for monitoring the elemental distribution in wall materials of future fusion devices. This study focused on the low-pressure conditions, where a FO-LIBS experimental system was developed to systematically analyze the temporal evolution of Cu and Mo plasma spectra under pressures ranging from 0.2 to 20 Pa. The results demonstrated that the intensities of key spectral lines, such as Cu I and Mo I, show linear growth with increasing laser energy within the specified pressure range. Additionally, the intensities of these characteristic spectral lines decrease significantly as pressure rises, becoming much weaker than at atmospheric pressure. The presence of an argon atmosphere further reduces these spectral line intensities. Time-resolved measurements indicate that plasma lifetimes are approximately 400 ns under 0.2 Pa, which happens earlier than under atmospheric pressure. Calculated electron densities, estimated using the Stark broadening method, correspond with the trends in spectral line intensity variations. This research provides optimized FO-LIBS parameter selection for in situ elemental diagnostics under low-pressure environments in fusion devices.