Author:
Fushimi Kimika,Nishiyama Shusuke,Tomioka Satoshi,Sasaki Koichi
Abstract
Abstract
We applied saturated cavity ringdown spectroscopy (CRDS) to the measurement of the
Doppler-free absorption spectrum of the Balmer-α line of atomic hydrogen in an inductively
coupled hydrogen plasma. The spectrum was used for estimating the electric field in the sheath
region in the vicinity to a biased electrode. The absorption frequency (the absorption
coefficient multiplied by the speed of light) and the saturation parameter were estimated by
fitting the experimental ringdown curve with the theory reported by Giusfredi and coworkers
(Phys. Rev. Lett.
104 (2010) 110801). We detected the Lamb dip corresponding to the
2p
2
P
o
3/2 - 3d
2
D
5/2 transition in the absorption spectrum in the field-free
condition. We observed the change in the Lamb dip spectrum when we repeated the measurement in
the sheath, and we succeeded in estimating the sheath electric field of 220–230 V/cm at a distance
of 1.8 mm from the electrode which was biased at -100 V with respect to the ground potential. The
experimental results indicate the potential of saturated CRDS for the measurement of sheath
electric fields in plasmas.
Subject
Mathematical Physics,Instrumentation