| Abstract: | Results are presented from experimental and numerical studies of the spatial and temporal microstructure of a relativistic
heavy-current electron beam of nanosecond duration. The beam is formed in a magnetically insulated coaxial diode with an edge-emitting
cathode. Microcurrent oscillations and azimuthal nonuniformity of the beam are seen, the scale of the latter depending on
the maximum cyclotron radius of the electrons. Two- and three-dimensional numerical calculations performed by the macroparticle
method show that space-charge oscillations near the cathode produce these phenomena even in the case of a uniform emission
surface. It is shown that the increase in the full current of the beam that occurs during the pulse in a weak magnetic field
is connected with the gradual propagation of emission to the cylindrical outside surface of the cathode. A study is made of
the effect of the discreteness of the emission surface on the impedance and current of the vacuum diode. The linear increase
seen in current during the pulse with a small number of emission centers is attributed to an increase in their size as a result
of expansion of the cathode plasma.
Institute of Heavy-Current Electronics, Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh
Uchebnykh Zavedenii, No. 12, pp. 31–48, December, 1996. |
