Global model for an rf hydrogen inductive plasma discharge in the deuterium negative ion source experiment including negative ions

Abstract

A study of the gas-phase kinetics and the plasma chemistry for an rf inductively coupled H 2 plasma discharge, in the deuterium negative ion source experiment (DENISE), has been carried out by means of a global model of the discharge implemented by the numerical code, Global Model Solver (GMS), which gives results for the spatially averaged densities of the species included in the model and the electron temperature in the steady state. The modelling of the discharge includes H − , with the production mechanism assumed to be dissociative attachment of H 2 (v). The effect of the magnetic filter in the source is taken into account for obtaining an estimate of the H − density also in the extraction chamber. The differences in the cross-section data assumed for some processes, between this paper and previous work, are pointed out, along with the consequences on H − density. The ratio between the H − density and the electron density obtained with GMS for the considered negative ion production mechanism is always far lower than 0.1, even with the most optimistic assumptions for H − production that can be put forward.

Global model analysis of negative ion generation in low-pressure inductively coupled hydrogen plasmas with bi-Maxwellian electron energy distributions

“…So, the H þ ion becomes the most dominant ion at RF powers exceeding a certain value, as investigated by Zorat and Vender. 15 Although the H þ density increases with pressure, its rate of increase with respect to pressure is much smaller than that of H þ 3 . This can obviously be seen in the linear-scaled Fig.…”

“…13 Global models of hydrogen plasma discharges, which are associated predominantly with negative ion sources, have been developed by several research groups. [13][14][15][16][17][18] Zorat et al developed a hydrogen plasma global model that takes into account the magnetic filter effect and compared the electron density and temperature of the model to experimental measurements collected from an ICP at 10-100 mTorr. 14,15 They emphasized that the ratio between the hydrogen negative ion (H À ) density to the electron density was far lower than 0.1 in the model under the most optimistic assumptions for H À production.…”

A Global Enhanced Vibrational Kinetic Model for High-Pressure Hydrogen RF Discharges

“…In addition to the above equations, it is necessary to link the properties at the center of the reactor to the volume averaged values in the discharge through (19) and (22) following the approximations in [16]. Additional assumptions are used in this paper.…”

“…Global models have become a standard tool in predicting main plasma parameters, such as electron temperature and number density [19], [20]. In [21] and [22], a global model with reduced chemistry was applied to the deuterium negative ion source experiment (DENISE) operating between 20-100 mtorr and absorbed power from 500-3000 W. Global models in [23] and [24] were applied to a mixture of hydrogen and argon plasmas to investigate the effect of argon dilution on hydrogen plasma. The operating pressures and absorbed power were between 20 and 60 mtorr and 120 W, respectively, in [23] and 1-100 mtorr and 600 W, respectively, in [24].…”

“…Input parameters for the GEVKM include the inlet gas flow rate to the discharge and the absorbed power. The GEVKM is validated at low pressures by comparisons with simulations and measurements in the negative hydrogen ion source DENISE [21], [22]. The high-pressure case results of the GEVKM are compared with those in [28].…”