Energy deposition measurements of a large-diameter, intense relativistic electron beam for high-power gas laser excitation

Measurements of electron-beam (e-beam) energy deposition in gaseous medium by a segmented totally stopping calorimeter and a pressure jump method are described, both of which gave the same values. Typical e-beam parameters are 2 MV, 80 kA, and 65 ns (FWHM). The e-beam cross-sectional area is 10 cm in diameter. First, the radial distribution of the e-beam current generated from the field-emission diode as a function of the axial magnetic field was measured. Next, for applications to longitudinal excitation of the high-power gas lasers, the e-beam energy deposition characteristics are measured in N₂ for the propagation distance up to 2.3 m in terms of the axial magnetic field, the N₂ gas pressure, and the radial e-beam distribution. As a result, the axial field equivalent to the self-magnetic field of the electron beam can acceptably control the e-beam generation and propagation uniformities.