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Numerical investigations on high flux neutron production from a high-current pulsed ion device

Perrakis Konstantinos, Moustaizis Stavros, Lalousis, Paraskevas

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Summary

High-current pulsed ion accelerators operate on the principle of slow energy storage in the primary accumulator circuit and of fast transfer to the accelerating diode configuration, increasing by many orders of magnitude the current of the generated ion beam. Particular interest exists for the Magnetically Insulated Diode (MID) configurations used for high power generation of negative or positive ion beams. Our previous work [1-3] regarding numerical simulations using 1-D multi-fluid code [4] in cylindrical geometry enable us to investigate both the spatio-temporal evolution of the plasma species in MID configurations and the high power extracted negative ion beam (H- or D-). The code allows evaluating theextracted high-current beam for different initial, physical parameters of the MID (externally applied electric and magnetic fields), of the plasma (density, species, temperature) and geometrical parameters. The interaction of high current ion beam with suitable targets enables producing relative high neutron flux for material tests or other industrial applications (e. g. radionuclides of different species). In the present work numerical investigations using the elaborated version of the 1-D multi-fluid code enables to improve the diode operation by studying the spatio-temporal evolution of the ion specie for different initial parameters of the diode in order to optimize the extracted high current. This parametric study allows toincrease both the pulse duration of the ion beam up to 0.5 μs - 1 μs and the final extracted current (protons or deuterons) up to 14 kA. The accelerating voltage could vary from 400 keV to 1.2 MeV. The ion source is originated from plasmas formed by ionizing a gas or clusters (by electric discharge or laser beam) closeto the diode electrode and feeds the pulse duration of the MID operation, in order to extract the long pulse high current ion beam (typically protons or deuterons). For the neutron production we use the extracted high current deuteron (d) beam to interact with a Be target [9Be (d, n) 10B] which presents a relatively highyield up to 3x10-5 n/d, comparing to other targets and with neutron energy spectrum similar to nuclear reactors. The above parameters of the proposed device enable to produce a relatively high neutron flux up 1012–1014 n/cm2 for an operation of several minutes of at a rep. rate of 20 Hz. Alternatively, the use of theproposed high-current deuteron beam with targets implanted with deuterons or 3H (tritium) increase the spectrum of the produced neutrons to energies with interest to test materials for Tokamak blankets.

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