HEATING OF A CURRENT FILAMENT AND FORMATION OF CONSTRICTIONS IN A PULSED VACUUM DISCHARGE

It is shown that a rapid current rise in a pulsed vacuum discharge is accompanied by enhanced compression of the current filament by its sel f-induced magnetic field. As a result, a constriction forms at a dista nce L similar or equal to 1 mm from the cathode and the electron tempe rature increases to 10(2)-10(3) eV at currents of order 1 kA. This beh avior explains the observed increase in the degree of ion charge and t he appearance of x-rays as the current pulse length decreases. The cri terion for a rapid rise is the condition tau < L/V = 10(-7) s, where t au is the characteristic current amplification time and V similar or e qual to 10(6) is the velocity of the cathode plasma. (C) 1998 American Institute of Physics. [S1063-7850(98)02309-X].