Measurements of hydrogen negative ion and its comparison with the molecular hydrogen spectra in divertor simulator MAP-II

Diagnostics of Recombining Plasmas in Divertor Simulator MAP-II

“…[33] and the references therein). Recently, since much attention has been paid to the role of negative ions in plasma recombination, the LPD method has also been applied to the divertor simulators such as MAP-II [34] and TPDSHEET-IV [15]. A common characteristic of the negative ions in the divertor-simulating discharge plasmas is that they localize in the peripheral region of the plasma column where the electron temperature is low (the details are described in Sec.…”

“…Both results indicate that the ratio of the negative ion density to the electron density is almost constant during this MAR phase. In order to clarify the behaviors of the negative ions in the H 2 -MAR plasmas, we evaluated the negative ion density from a steady state solution of the following simple rate equation [34,38]:…”

“…On the other hand, in the attached condition, reported in ref. [34], transport loss from the peripheral region should be taken into consideration to reproduce the negative ion density.…”

“…The data in both conditions have been reported in refs. [34] and [38], respectively. Even at the same pressure in the gas target chamber, the electron density and temperature are different depending on the operation conditions.…”

“…Fig. 9 Comparison of the destruction rate of the negative ions produced at the center of the plasma column between attached [34] and detached [38] conditions. The reciprocal of the value represents the lifetime of the negative ions.…”