UV-induced Coulomb structure in discharge plasma

A Coulomb structure of dust particles in the anode region of a dc abnormal glow discharge have been observed. A dust cloud of several tens of particle s formed above the central part of the anode. An analysis of the experiment al conditions revealed that these particles are positively charged in contr ast to other experiments on the levitation of dust particles in gas-dischar ge plasma. An estimate of the particle charge taking into account processes of photoemission and secondary electron emission from their surface shows that the general contribution to particle charging is photoemission by disc harge self-radiation in the UV region. (C) 2000 Elsevier Science B.V. All r ights reserved.