High-power critical electron emission from dielectric induced by high-current-density electron beam injection and its transition to vacuum breakdown

Abstract

Since 1975 our lab has been investigating the critical electron emission from dielectrics into vacuum with nanosecond time resolution using highcurrent-density electron accelerators. It allowed us to clear up some intrinsic properties of the critical electron emission induced by electron beam injection: (1) The emission pulse is delayed for several nanoseconds from the injection one. (2) The peak value of the emission current reaches 100 -1000 A. (3) The direct experimental evidence is obtained for intense electron-hole generation by superhigh electric field in subsurface layer of dielectric. And this process is discovered to be the main reason of the transition to critical electron emission. (4) Critical emission is not uniform and accompanied by point explosions on the dielectric surface and by injections of ion plasmas from these points into vacuum. (5) Transition of critical emission to vacuum breakdown has been observed.

The thermostimulated exoelectron emission of NaF:U,Me compounds after electron beam irradiation

“…So we suppose that some impurities can play important role in TAEE process. TAEE phenomenon is similar to known explosive electronic emission phenomenon (EEE) from metals [6] and critical electronic emission (CEE) from insulators [4] by number of features. EEE are connected with formation of strong electron streams at super-strong local electrical field, which creates a high concentration of energy on surface of cathode and which is stimulated by explosive conversion of the condensed substance of cathode into dense plasma during the initial heating of local regions of the cathode by proper emission stream.…”

“…CEE impulse is observed after impulse of injection of a primary beam (in 23-30 ns). The heating of a crystal could lead to EEE, if intensity of electric field on the micro-spike during thermoactivation reaches value 1.2·10 6 V/cm [4,6]. The heating of a crystal is connected with formation of micro-spike centers of emission, which appear in a shape of typical craters.…”

“…Super-strong local electrical field stimulate avalanche-like growth of electronic emission. It is known [4], that CEE is observed when intensity of the field of injected charge reaches some critical value. CEE impulse is observed after impulse of injection of a primary beam (in 23-30 ns).…”