Laser Absorption Spectroscopy for Diagnostics of a Neutral Helium Beam

Abstract

The density resolution of a measurement system using laser absorption spectroscopy is evaluated in order to diagnose a fraction of metastable helium atoms (2 ³S₁) in a neutral helium beam. Experiments performed in a hollow cathode device show that the density resolution of the present system is about 5 × 10¹³ m^-3 for a 1 m absorption length. Optimization of absorption scheme and improvements of signal detection are suggested, which shows that laser absorption spectroscopy is a promising diagnostic method for a neutral helium beam.