caa a22 4500 386368252 CHVBK 20180307111944.0 cr unu---uuuuu 161130e198910 xx s 000 0 eng 10.1017/S0022377800014380 doi S0022377800014380 pii (NATIONALLICENCE)cambridge-10.1017/S0022377800014380 Free double layers in mercury-arc discharges [Elektronische Daten] A study has been carried out of free double layers formed within the plasma volume of a low-pressure mercury-arc discharge at high current densities. The free double layer is observed to form as a visible boundary, which drifts slowly from the central section of the discharge. Current-driven instabilities are observed as the discharge current is gradually increased to a critical value, at which current limitation is observed to occur. This process, which is accompanied by high-current spikes, ceases when the free double layer becomes visible as a sharp boundary dividing the discharge column into two regions of different luminosities. The layer is observed to form in the later stages of current limitation, the onset of which occurs for a ratio of drift to thermal speed of electrons of about unity. Electrical energy is converted by the layer into kinetic energy of the charged particles. Accordingly, high-energy ions were measured by means of an electrostatic energy analyser. The multiple-sheath character of the free ‘double layer', which is inferred from probe measurements of potential profiles, is discussed and comparisons with other space-charge structures with the same topology are made. Copyright © Cambridge University Press 1989 Maciel Homero Santiago Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, U.K. Allen J. E. Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, U.K. Journal of Plasma Physics Cambridge University Press 42/2(1989-10), 321-352 0022-3778 42:2<321 1989 42 PLA https://doi.org/10.1017/S0022377800014380 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1017/S0022377800014380 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Maciel Homero Santiago Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, U.K NATIONALLICENCE 700 1- Allen J. E. Department of Engineering Science, University of Oxford, Oxford OX1 3PJ, U.K NATIONALLICENCE 773 0- Journal of Plasma Physics Cambridge University Press 42/2(1989-10), 321-352 0022-3778 42:2<321 1989 42 PLA CC0 http://creativecommons.org/publicdomain/zero/1.0 nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-cambridge