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Benchmarking and validation are prerequisite for using simulation codes aspredictive tools. In this work, we have developed a Global Model for NegativeHydrogen Ion Source (GMNHIS) and performed benchmarking of GMNHIS againstanother independently developed code, Global Enhanced Vibrational Kinetic Model(GEVKM). This is the first study to present quite comprehensive benchmarkingtest of this kind for models of negative hydrogen ion sources (NHIS), and verygood agreement has been achieved for electron temperature, vibrationaldistribution function (VDF) of hydrogen molecules, and n_H^-/n_e ratio. Thesmall discrepancies in number densities of negative hydrogen ions, positiveions, as well as hydrogen atoms can be attributed to the differences in thepredicted electron number density for given discharge power. Higher electronnumber density obtained with GMNHIS is possibly due to fewer dissociationchannels accounted for in GMNHIS, leading to smaller energy loss. In addition,we validated GMNHIS against experimental data obtained in an electron cyclotronresonance (ECR) discharge used for H^- production. The model qualitatively (andeven quantitatively for certain conditions) reproduces the experimental H^-number density. The H^- number density as a function of pressure firstincreases at pressures below 12 mTorr, and then saturates for higher pressures.This dependence was analyzed by evaluating contributions from differentreaction pathways to the creation and loss of the H^- ions. The developed codescan be used for predicting the H^- production, improving the performance ofNHIS, and ultimately optimizing the parameters of negative ion beams for ITER.

Benchmarking and validation of global model code for negative hydrogen ion sources