A magnetic field free plasma was separated into a region with discharge filaments and the one without by inserting a metallic grid between them. Effects due to bias voltage applied to the plasma separation grid upon the electron temperature, electron density, and the hydrogen negative ion (H-) density were investigated with the direct current laser photodetachment method. The electron temperature at the center of the chamber without the filaments decreased from 6.0 to 0.7 eV, while the electron density increased from 1.2 x 10(9) to 8.0 x 10(9) cm(-3) by varying the grid bias from +20 to - 60 V The ratio of the H- density to the electron density increased from 2.5% to 12% by applying +5 V to the plasma separation grid. (c) 2005 Published by Elsevier B.V.