Neutron producing target for accelerator based neutron capture therapy

Abstract

Pilot innovative accelerator based neutron source for neutron capture therapy of cancer is under construction now at the Budker Institute. One of the main elements of the facility is lithium target producing neutrons via threshold 7 Li(p,n) 7 Be reaction at 10 mA proton beam with energies of 1.915 MeV or 2.5 MeV. In the present report, choice of target was substantiated. The main problems of lithium target were determined to be: 7 Be radioactive isotope activation, keeping lithium layer solid, presence of photons resulted from proton inelastic scattering on lithium nuclei, and radiation blistering. The results of thermal testing of target prototype, investigation of radiation blistering and several simulations are presented. It becomes clear that water is preferable for cooling this target, and that the lithium target 10 cm in diameter is able to run up to 25 kW proton beam before melting. The conception of optimal target is proposed: thin and easy to detach metal disk 10 cm in diameter, evaporated with thin layer of pure lithium from the side of proton beam exposure: its back is intensively cooled with turbulent water flow to maintain lithium layer solid. Design of target for the neutron source constructed at BINP is shown. Conceptions of radiation protection and neutrons, γ-rays and αparticles diagnostics are presented. The immediate plans on obtaining epithermal neutron beam are declared.

Measuring the neutron spectrum of the accelerator-based source using the time-of-flight method

“…Neutrons generated in a thin lithium layer pass thereafter through the target assembly proving effi cient heat pickup. The target assembly with a thickness of 6 cm is made of stainless steel and has water supply channels with a characteristic size as large as 2.2 cm [9]. Passing of neutrons through the target assembly is followed by their scattering and moderation by elastic scattering in the water.…”

In Situ Observations of Blistering of a Metal Irradiated with 2-MeV Protons

“…Neutrons are generated as a result of a 7 Li(p,n) 7 Be threshold reaction by directing a proton beam, with an energy of 2 MeV and a current of up to 5 mA obtained in a tandem accelerator with vacuum insulation, to a lithium target with a diameter of 10 cm. The target is made of a thin lithium layer deposited on an efficiently-cooled substrate (in this study, copper) [5,6]. The thickness of the neutron-generating lithium layer is chosen so that the proton energy coming out from the layer is slightly below 1.882 MeV (the 7 Li(p,n) 7 Be reaction threshold).…”

Characterization of neutrons from a thick target 9Be(p, n) reaction by multiple foil activation technique for practical applications: measurement of integral cross sections and their comparison with integrated data from data files

“…Those neutron sources can play an important role in imaging applications [1]. Neutron imaging provides an efficient tool for investigations in the field of non-destructive testing as well as in many applications related to fundamental research.…”