This paper describes the mechanism of efficientH−production in a high-density hydrogen plasma produced by helicon wave discharge. AnH−source using helicon wave discharge has been developed. Spatial and temporal variations ofH−density in the helicon plasma were measured by laser photodetachment technique. A steep increase inH−density was observed in the afterglow. TheH−ions were efficiently produced for the first 20&mgr;s after the termination of the discharge and mainly lost by mutual neutralization with positive ions. In the outer region of the plasma column, 20&percent; of the negatively charged particles wereH−ions. In the region ofTe=1.5−2&hthinsp;eV,the effective attachment rate coefficient defined as the average value for hydrogen molecules of all energy levels was evaluated to be0.5−1.3×10−11&hthinsp;cm3/s,of which the value is 3-order higher than that for attachment to thev=0level of the ground state molecules. ©1998 American Institute of Physics.