The negative hydrogen ions (H^-) are formed by dissociateve attachment of slow electron to the vibrationally excited molecules which is attributed to electron-impact excitation of molecules by the fast primary electron in the plasma. We have been carried out the control of H^- ion density at the circumference of the hydrogen sheet plasma by an electron emitter which is changed the density and the energy of slow electron. The hydrogen sheet plasma was produced in the linear plasma simulator, TPD-SheetIV (Test Plasma produced by Direct current for Sheet plasma IV)[1]. The H^- ion densities were measured by a probe-assisted laser photodetachment method. The space potential was measured by an emissive probe. At a secondary hydrogen gas puffing into a hydrogen plasma, H^- ion density n_H^- have a maximum value (n_H- = 2×10¹⁷ m^-3) at the gas pressure of 0.15 Pa×m³/s and peak position of n_H^- appears at the circumference of the sheet plasma. Under these conditions, n_H^- increases when the current of electron emitter I_E increases from 0 to 25 A. Also, n_H^- reached a peak value at the applying bias voltage of the electron emitter against the plasma potential V_E = 1-2 V. Above this bias voltage, n_H^- is smoothly decreasing function of V_E. The bias voltage V_E at the peak value of n_H^- is related to the cross section for dissociative attachment of electrons to vibrationally excited hydrogen molecules.

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