Effect of argon additive in negative hydrogen ion sources

Abstract

Using the photodetachment technique we investigated the hydrogen negative ion density in the extraction region of a magnetically filtered multicusp ion source when argon is added to hydrogen. We found that the negative-ion density goes up at most by a factor of 1.5 when argon is added to low base hydrogen pressure (0.05 or 0.1 Pa), but goes down when argon is added to higher initial hydrogen pressure (0.5 or 1 Pa). Adding argon did not enhance the Werner and Lyman bands in the vacuum ultraviolet, which indicates that argon addition does not increase the production rate of vibrationally excited H2 molecules. The increase of the negative-ion density by adding argon into a low-pressure hydrogen discharge is probably due to the increase of the low-energy electron density.

Study of argon additive in a beam injection type negative ion source using VUV emission spectroscopy

“…3-5, have the same tendencies as ones in DC and ECR plasmas [2 -4]. In DC plasmas, Ar addition does not affect VUV emission [2], and the cause of decrease in H À ion production at high base pressure is written nothing. But we think that decrease in I H À at high base pressure in DC and ECR plasmas is also caused by decrease in H 2 (vW) production.…”

“…The value of T e is suitable for H À ion production at both low and high base pressures. Increase in n e is caused by the higher ionization cross section of Ar gas compared with that of H 2 gas [2]. Fig.…”

“…Concerning enhancement of negative ion production, effects of Ar addition have been studied by several authors [2 -4]. In DC [2] and ECR [3,4] plasmas, with adding Ar gas to low or high base H 2 pressure, electron density: n e goes up and electron temperature: T e is kept under 1 eV. That is to say, plasma parameters (n e and T e ) are suitable for negative ion production.…”

Vibrational States of Hydrogen Molecules in One Third LHD Negative Ion Source

“…The Argon admixture in the hydrogen negative ion source does not enhance the Lyman and Werner bands. The H -density in low gas pressure region (less than 0.1 Pa) is enhanced because the electron density is increased due to Ar additive in hydrogen plasmas, and it leads to the enhancement of dissociative electron attachment to H 2 molecules [5,6]. A large size negative ion source for NBI usually uses cesium vapor admixture in it to enhance negative ion beam currents.…”

Effect of argon additive on H− density and temperature in volume negative ion source

“…Previous experiments showed various results depending on the type of source and the plasma conditions. [1][2][3][4] Several parameters of hydrogen-argon plasma were measured in the multicusp filament volume source Camembert III, described in Refs. 5 and 6.…”