Increase in Irradiation Beam Intensity by Using a Hybrid Target System in Cyclotron-Based Neutron Capture Therapy

Abstract

A cyclotron-based epithermal neutron generator has been expected to achieve the early realization of hospital-based boron neutron capture therapy. The system using a hybrid target composed of a thin tungsten (W) layer and a thick beryllium (Be) one with 30 MeV protons and a beam-shaping assembly was previously proposed as a better generator candidate than the system using only a thick W or Be layer. In this study, to clearly show that the hybrid target system is more clinically useful than the other two, all three target systems were compared using epithermal neutron intensity as a figure of merit under an equal condition of the harmful effect of fast neutron dose. We found that the hybrid system using a W layer of appropriate thickness increased the epithermal neutron intensity by 107 and 32% compared with systems using only W or Be, respectively, with the same harmful fast neutron component. It is concluded that the hybrid target system is more useful in terms of epithermal neutron intensity than systems with either W or Be as a generator using the 30 MeV proton accelerator and beam-shaping assembly.

Conceptual design project: Accelerator complex for nuclear physics studies and boron neutron capture therapy application at the Yerevan Physics Institute (YerPhI) Yerevan, Armenia

“…To moderate fast neutrons to epithermal neutrons flux it is planned to use the Beam Shaping Assembly consist of lead, iron, aluminum and calcium fluoride [9][10][11].…”

Evaluation of the Effects of Gamma Irradiation from a 9Be Neutron Source in Digital ASIC’s with GEANT4

“…Fast neutron production by stripping/break-up reactions induced by deuteron/proton beams on a 9 Be thick target is a well-known method. 9,10) CMOS transistors are more vulnerable to radiation damages produced by gammas than those produced by neutrons.…”

“…That parasitic gammas are emmited from the 9 Be target, by means of 9 Be(p,nγ) 9 B for proton beam, and by means of 9 Be(d,nγ) 10 B and 9 Be(d,pγ) 10 Be for deuteron beam. Fast neutron production by stripping/break-up reactions induced by deuteron/proton beams on a 9 Be thick target is a well-known method.…”