Electron scraping and electron temperature reduction by bias electrode at the extraction region of a large negative ion source

Alm of this work is presenting the first numerical results obtained with a 2D 3V PIC MCC code applied to investigate the effect of the bias electrodes on the plasma properties at the extraction region of a SPIDER like negative ion source. Why investigating the bias electrodes effect? In the SPIDER source, the bias electrodes can be independently biased with respect to the source itself, influencing the uniformity of the extracted beam, the amount of co extracted electrons. The plasma facing electrode (Bias Plate) might act as a scrape off layer for the electrons, possibly reducing their density along the direction parallel to the filter field. Why a 2D simulation code? The model is intrinsically two dimensional since, the magnetic filter field hinders electron transport along the direction perpendicular to the field itself, the Bias Plate causes an electron flux along the direction parallel to the filter field.