Speaker
Koichi Sasaki
Description
See the full Abstract at http://ocs.ciemat.es/EPS2018ABS/pdf/I1.303.pdf
Sensitive measurement of sheath electric field by Stark spectroscopy using
the Balmer-alpha line of atomic hydrogen
K. Sasaki and S. Nishiyama
Division of Quantum Science and Engineering, Hokkaido University, Sapporo, Japan
The measurement of sheath electric field has focused on using high Rydberg states for a
long time since they have sensitive Stark effects to weak electric fields. However, Rydberg
states are difficult to detect because of their small transition probabilities. In this work, we
shifted our approach from Rydberg states to lower-lying energy states. Lower-lying energy
states can be detected easily because of large transition probabilities. The less sensitive Stark
effects of lower-lying states are compensated by employing saturation spectroscopy which has
ultrafine, Doppler-free spectral resolution. We demonstrated the measurement of sheath electric
field in an inductively coupled hydrogen plasma by measuring the Stark spectra of the Balmer-
alpha line of atomic hydrogen. We realized a sensitive detection limit of 10 V/cm and a fine
spatial resolution of 0.2 mm by the developed method. Since the developed method utilizes
an economical, maintenance-free diode laser system, it may be useful in various experiments
which need the measurements of electric fields in plasmas.
References
[1] S. Nishiyama, H. Nakano, M. Goto, and K. Sasaki, J. Phys. D: Appl. Phys. 50, 234003 (2017).
[2] S. Nishiyama, K. Katayama, H. Nakano, M. Goto, and K. Sasaki, Appl. Phys. Express 10, 036101 (2017).
