Title :
A flat-cathode thermionic injector for the PHERMEX radiographic facility
Author :
Kauppila, T. ; Builta, L. ; Burns, M. ; Gregory, W. ; Honaberger, D. ; Watson, S. ; Hughes, T.
Author_Institution :
Los Alamos Nat. Lab., NM, USA
Abstract :
The PHERMEX (Pulsed High-Energy Radiographic Machine Emitting X-rays) standing-wave linear accelerator is a high- current electron beam generator used for flash-radiography. An improved electron gun has been designed employing a flat-thermionic cathode to replace the existing Pierce-geometry gun. The flat cathode yields increased current with the same applied voltage and cathode area as the Pierce gun. The ISIS code simulations indicate a beam current of 1.5 kA at 600 kV vs. 500 A for the old gun. The new geometry also reduces the probability for high voltage breakdown in the A-K gap. A re-entrant magnet captures the expanding electron beam and a bucking coil nulls cathode-fringe field. A third coil is used to optimize the extraction field profile and reduce the effect of nonlinear space charge on the beam emittance. Time-resolved measurements of beam current and voltage have been made. In addition, a streak camera was used to measure beam emittance and spatial profile. Comparisons of measurements with simulations are presented
Keywords :
electron guns; particle beam diagnostics; space charge; thermionic cathodes; voltage measurement; 600 V; ISIS code simulation; PHERMEX; beam current; beam emittance; beam profile; beam voltage; breakdown; electron gun; flash-radiography; flat-cathode thermionic injector; high voltage breakdown; nonlinear space charge; re-entrant magnet; Cathodes; Coils; Electron beams; Intersymbol interference; Linear accelerators; Magnetic field measurement; Pulse generation; Radiography; Voltage; X-rays;
Conference_Titel :
Particle Accelerator Conference, 1993., Proceedings of the 1993
Conference_Location :
Washington, DC
Print_ISBN :
0-7803-1203-1
DOI :
10.1109/PAC.1993.309549
