Molecular Zeeman spectroscopy for H2 Fulcher-α band spectra as a local measurement of rovibrational structures

Abstract

A diagnostic technique for the local measurement of emissions from the molecular hydrogen has been developed. In the presence of an external magnetic field, the emission position can be deduced from the Zeeman patterns in the spectral line shape, and with the aid of the coronal model the rovibronic emission intensity provides the local rovibrational temperatures. In order to evaluate the Zeeman effect on the hydrogen molecule, a quantum-mechanical calculation is performed. The experimentally observed Fulcher-α rovibronic band spectra under a magnetic field strength of about 7T are well represented by the calculation. The temporal evolution of the emission position as well as the rovibrational temperatures are measured in the 8.2GHz lower hybrid current drive discharges of the TRIAM-1M tokamak [H. Zushi et al., Nucl. Fusion 45, S142 (2005)]. The measured emission is found to originate from the region where the plasma comes in contact with the limiter, and the observed increase in the rotational temperature suggests a rise in the limiter surface temperature.

Development of multiwavelength-range fine-resolution spectrometer for hydrogen emissions and its application to large helical device periphery plasmas

“…[3][4][5][6][7] From the observation of the line shape of the hydrogen Balmer-␣ emission from large helical device 3 ͑LHD͒ and Torus of Research Institute for Applied Mechanics ͑TRIAM-1M͒, 4 the emission locations of the atomic hydrogen in the peripheral region were determined from the Zeeman effect, together with the flow velocity and the temperature estimated from the Doppler effect. Regarding the molecular hydrogen, the Fulcher-␣ band spectra were measured for TRIAM-1M, and then the emission locations and the rotational and vibrational temperatures of hydrogen molecules were determined 5 with a similar analysis to that of the hydrogen Balmer-␣ spectra. 3,4 A simultaneous measurement of the line shapes of these spectra may provide the information about the neutral hydrogen transport as well as the dissociative dynamics of the molecules in the peripheral region.…”

Development of Multi-Wavelength-Range High-Resolution Spectrometer for Hydrogen Atomic and Molecular Emission Lines

“…Those of the Balmer-β and -γ line shapes were also detected. They were relatively small since the Zeeman split of the spectrum is proportional to the square of its wavelength [8], while the Doppler broadening is proportional to the wavelength. We analyzed the observed atomic spectra with a fitting calculation described in Ref.…”

“…From atomic emission line ratios, the electron density, temperature, and dissociation ratios have been estimated [3][4][5] from the comparison with a collisional-radiative model of hydrogen developed by Sawada et al [6,7]. From molecular line ratios, the rotational and vibrational temperatures, which are related to the background gas temperature, have been determined [8,9]. On the other hand, spatially resolved emission intensities and velocities of hydrogen atoms and molecules have been determined with a technique based on the Zeeman patterns appeared in the emission line shapes by several groups [8,10,11].…”

“…From molecular line ratios, the rotational and vibrational temperatures, which are related to the background gas temperature, have been determined [8,9]. On the other hand, spatially resolved emission intensities and velocities of hydrogen atoms and molecules have been determined with a technique based on the Zeeman patterns appeared in the emission line shapes by several groups [8,10,11].…”

Fulcher-α Band Spectra in Mixed Hydrogen Isotope Plasmas

“…In the mixed condition, overlaps of the spectra can cause an error in the temperature estimation. This can be severer under strong magnetic fields because of the Zeeman split in the spectral line shapes [6]. Moreover, the difference in the ro-vibrational temperatures with respect to the molecular species is expected.…”