Characteristics of saturation spectroscopy at the Balmer-α line of atomic hydrogen in a linear magnetized plasma source

Abstract

We adopted saturation spectroscopy for observing a Doppler-free spectrum of the Balmer-α line of atomic hydrogen in a linear magnetized plasma source. The spectrum was composed of a broadband offset and many peaks which were assigned as fine-structure components of the Balmer-α line with Zeeman splitting. We examined the amplitudes of the offset and line components as functions of the pump laser power and the discharge gas pressure. The saturation parameter or the amplitude of the saturation spectrum was discussed by referring to the theory of saturation spectroscopy. In addition, the physical origin of the broadband offset component was speculated on the basis of the pressure dependence of the saturation spectrum.

Doppler shift measurement of Balmer-alpha line spectrum emission from a plasma in a negative hydrogen ion source

“…The Balmer-line spectrum has the fine structure composed of 3D-2P, and 3P-2S transitions [6]. Several peaks are identified by absorption spectroscopy in the frequency interval of about 10 GHz [7]. This causes spectrum broadening of more than 14 pm width, while the instrumentation width of the measurement system should add 12.5 pm to the line spectrum broadening.…”

“…A surface collision simulation program ACAT (Atomic Collision in Amorphous Target) was run to see the energy spread for the H 0 particles produced by surface collision processes. There are several uncertainties in calculating velocity distribution of hydrogen ions/neutrals leaving the surface using the ACAT code [7], but the previous model was employed this time without any modification.…”

Stark spectroscopy at Balmer-αline of atomic hydrogen for measuring sheath electric field in a hydrogen plasma

“…For example, the linewidth of a pulsed tunable laser is ∼ 0.2 cm −1 (6 GHz) and the Doppler broadening width of the Balmer-α line of atomic hydrogen is approximately 10 GHz (15 pm) at a temperature of 1000 K. Our idea is to use a spectroscopic method having Doppler-free spectral resolution [27,28]. We employed saturation spectroscopy at the Balmer-α line of atomic hydrogen [29,30]. Since it is possible to construct the system of saturation spectroscopy by using a tunable single-mode diode laser, we can realize an easy-to-use system having an ultrafine resolution with a low experimental cost.…”

Analysis of neutral hydrogenic emission spectra in a tokamak

“…Passive and active spectroscopic diagnostics utilizing the hydrogenic isotopes are important and common in the nuclear fusion research mainly because they are the composite particles of the plasmas where the nuclear fusion reactions take place [1][2][3]. Passive spectroscopy on the plasma particles takes advantage of strong and dominant thermal emission from the Balmer-α transitions (656.281 nm for hydrogen, H α , and 656.101 nm for deuterium, D α ) [4,5]. Although most of such emission phenomena occur near the boundary of the plasma, the signals are line-integrated and the information from the passive spectroscopy represents the global properties.…”