LAUSR

Abstract Helium (He) inductively coupled plasma (ICP) was generated by a right-helical-type RF antenna. At a fixed He pressure of 20 mTorr, the optical emission spectrum from the He plasma was measured with RF power. The E-H mode transition and the characteristic hysteresis of the mode transition were confirmed by a change in the spectral line intensity of the 3 3 D − 2 3 P transition at 587.6 nm. By laser absorption spectroscopy using a laser light with a wavelength of 1083 nm resonant to the 2 3 S → 2 3 P absorption transition, the line-integrated He 2 3 S metastable density was measured and found to show consistent behavior with the spectral line intensity of the 3 3 D − 2 3 P transition during the E-H mode transition. The line-integrated He 2 3 S metastable atom density exhibited distinctly different longitudinal distributions in the E and H modes.