Measurements of high−current relativistic electron diode plasma properties with holographic interferometry

Abstract

Double−exposure interference holography has been used to measure the temporal and spatial dependence of plasma densities and velocities in relativistic electron beam diodes. In this paper some of the physics revealed by a detailed analysis of holograms from one such dioe is presented. Abel inversion of holograms taken on the Reba accelerator (100 kA, 1.5 MV) incorporating a 0.6−cm−diam glass rod cathode show the axial and radial structure of the diode plasmas. Finge−shift analysis has yielded densities of 5×10¹⁷−5×10¹⁹ electrons/cm³, and magnetohydrodynamic pressure balance implies a plasma temperature of about 0.3 keV. In addition, exposure variation of the fringe pattern and motion of plasmas between pictures taken at different times during the pulse have indicated plasma velocities vs spatial position that vary from 10⁶ to 10⁷ cm/sec.