Attenuation of secondary electron emission from divertor plates due to magnetic field inclination

The effect of the magnetic field inclination to the divertor/limiter plate on the efficiency of secondary electron emission has been analysed. The dep endence of the emission current on the magnetic field angle and the sheath potential is considered in a self-consistent manner. It is shown that for s mall inclination angles the electric field at the sheath cannot effectively pull out the emitted electrons from the plate, thus protecting them from b eing captured back to the plate. The reason for this is a weakness of the e lectric field due to the widening of the sheath at shallow inclination angl es and the reduction of the positive charge in the sheath layer. (C) 2001 E lsevier Science B.V. All rights reserved.