Study of hydrogen plasma affected by strong outer electric field

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We calculate potential spatial structure at extraction region in a negative ion source with two dimensional Particle-In-Cell(PIC) method. It is confirmed that extraction electric field produced by high beam extraction voltage invades into the ion source plasma though a beam extraction hole. Besides, H^- extraction probability is calculated with H^- trajectory calculation in Monte Carlo method. Then, potential structure needed for the H^- extraction model is assumed by the calculation result of the PIC code. A calculation result with the extraction model is in good agreement with experimental result in H^- extraction probability. From some calculation results with the model, we conclude that potential structure for perpendicular direction to H^- beam axis is a key factor for H^- extraction from a negative ion source.