Paper presents the results of experiments on multicapillary carbon-epoxy as a candidate material for a cathode of a pulsed electron accelerator. A high voltage pulse of 350 kV, 350 ns (FWHM) was applied to the cathode. The pulse repetition rate was 20 pps. The optical image of the cathode surface after 4×104 shots of electron beam was changed as well as electrical characteristics of the electron diode.
A review of methods for diagnosing the most important parameters of pulsed beams of electrons, ions, and accelerated atoms, such as the current density, fluence, total energy per pulse, the energy density distribution over the cross section, the composition of the beam, and its energy spectrum, is presented. The main attention is paid to the methods of diagnostics of beams intended for technological applications with a particle energy of 0.01–1 MeV and an energy density of 0.1–10 J/cm2. This paper contains a description of each diagnostic method, its scope of application, and systematic errors. The thermal imaging diagnostics of the total energy of a particle beam, the energy-density distribution over the cross section, the beam movement in the focal plane in a series of pulses, and the beam divergence during its transport to the target are considered. The time-of-flight diagnostics of ion beams is presented, which allows determining the beam composition, the fluence, and the energy spectrum of each type of ion in a beam of a complex composition (ions with different masses and degrees of ionization). The acoustic (thermoradiation) diagnostics based on the detection of acoustic waves, which are generated by a particle beam in a metal target by a piezoelectric transducer, is described.
The algorithm and results of calculating the integral and differential energy spectra of a pulsed electron beam (350–500 keV, 80 ns), generated by direct-action accelerators, are presented. The electron spectrum was calculated using the oscillograms of the accelerating voltage, electron current, total current of the diode, and the one-dimensional Child–Langmuir (1D CL) ratio. It was found that the discrepancy in the integrated electron beam energy spectrum, when measured using the total current in the diode and using the electron beam current, did not exceed 15% for 80%–95% of the electrons generated in a diode with graphite, carbon fabric, and multipoint cathodes. When calculating the electron spectrum using the 1D CL, the error was much higher.
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