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A numerical investigation of the radio-frequency hydrogen discharge in the high current negative hydrogen ion source (HCNHIS) is presented using a global enhanced vibrational kinetic model (GEVKM). The HCNHIS consists of a high-pressure (2–65 torr) radio-frequency discharge chamber where the main production of high-lying vibrational states of the hydrogen molecules occurs. The hydrogen plasma flow in the discharge chamber is reduced by a series of bypass tubes and enters through a nozzle into a low-pressure (1–15 mtorr) negative hydrogen ion production chamber where H− are generated mainly by the dissociative attachment of low-energy electrons to rovibrationally excited hydrogen molecules. The GEVKM is applied to the HCNHIS discharge and involves volume-averaged equations for 21 hydrogen species (atoms, ions, and molecules in excited states) and electrons. The GEVKM is supplemented with outlet boundary conditions for the nozzle and bypass tubes of the HCNHIS and accounts for compressibility, viscous, and rarefaction effects. GEVKM simulations of the RF discharge are performed with inlet flow rates of 5–1000 sccm and absorbed powers of 200–1000 W using the HCNHIS-2 design which is configured with an extractor grid attached to a short negative ion production region. These simulations investigate the effects of the absorbed power and the inlet flow rate on the chemical composition, electron and heavy particles temperature, wall temperature, the maximum extractable H− current in the discharge chamber, as well as optimum operational parameters of HCNHIS-2. GEVKM simulations of the HCNHIS-2 discharge are used to obtain estimates of the H− current and compared with Faraday cup measurements taken at the extraction grid. [ABSTRACT FROM PUBLISHER]

A global enhanced vibrational kinetic model (GEVKM) is developed for multitemperature, chemically reacting hydrogen plasmas in inductively coupled cylindrical discharges for low- to high-pressure regimes. The species in a GEVKM are ground-state hydrogen atoms H and molecules H2, 14 vibrationally excited hydrogen molecules \textrm H2 (v) , v=1-14 , electronically excited hydrogen atoms H(2) and H(3), ground-state positive ions H+, H2+, and H3+, ground-state negative ions H− and electrons e. The GEVKM involves volume-averaged steady-state continuity equations for the plasma species, an electron energy equation, a total energy equation, a heat transfer equation to the chamber walls, and a comprehensive set of surface and volumetric chemical processes governing vibrational and ionization kinetics of hydrogen plasmas. The GEVKM is verified and validated by comparisons with previous numerical simulations and experimental measurements of a negative hydrogen ion source in the low-pressure (20–100 mtorr), low-absorbed-power-density (0.053–0.32 W/cm ^{3}) regime and of a microwave plasma reactor in the intermediate- to high-pressure (1–100 torr), high-absorbed-power-density (8.26–22 W/cm ^{3})$ regime. The GEVKM is applied to the simulation of a high-current negative hydrogen ion source (HCNHIS). The HCNHIS consists of a high-pressure (20–65 torr) radio-frequency discharge chamber in which the main production of high-lying vibrational states of the hydrogen molecules occurs, a bypass system, and a low-pressure (0.1–0.4 torr) negative hydrogen ion production region where negative ions are generated by the dissociative attachment of low-energy electrons to rovibrationally excited hydrogen molecules. The discharge pressure and negative hydrogen ion current predicted by the GEVKM compare well with the measurements in the HCNHIS. [ABSTRACT FROM PUBLISHER]