Title: Beam-induced Back-streaming Electron Suppression Analysis for Accelerator Type Neutron Generators,
Abstract: A facility based on a next-generation, high-flux D-D neutron generator has
been commissioned and it is now operational at the University of California,
Berkeley. The current generator design produces near monoenergetic 2.45 MeV
neutrons at outputs of 10^8 n/s. Calculations provided show that future
conditioning at higher currents and voltages will allow for a production rate
over 10^10 n/s. A significant problem encountered was beam-induced electron
backstreaming, that needed to be resolved to achieve meaningful beam currents.
Two methods of suppressing secondary electrons resulting from the deuterium
beam striking the target were tested: the application of static electric and
magnetic fields. Computational simulations of both techniques were done using a
finite element analysis in COMSOL Multiphysics. Experimental tests verified
these simulation results. The most reliable suppression was achieved via the
implementation of an electrostatic shroud with a voltage offset of -800 V
relative to the target.