Technical Paper Abstract

Compact, Inexpensive Epithermal Neutron Source for BNCT

D.A. Swenson,

A new rf-focused linac structure, designed specifically to increase the acceleration efficiency and reduce the cost of
linac structures in the few-MeV range, may win the role as the optimum accelerator-based epithermal neutron source for
the BNCT application. This new linac structure resembles a drift tube linac (DTL) with radio frequency quadrupole (RFQ)
focusing incorporated into each "drift tube", hence the name, Rf-Focused Drift tube (or RFD) Linac.
It promises superior acceleration properties, focusing properties and CW capabilities.

We have a proposal under consideration for the development of an epithermal neutron source, based on the 2.5 MeV RFD linac
system with an average current of 10 mA, having the following components: an ion source, a short low-energy beam transport
system, a short RFQ linac section, an RFD linac section, an rf power system, a high-energy beam transport system, a proton
beam target, and a neutron beam moderator system. We propose to develop a solid lithium target for this application in the
form of a thin lithium layer on the inner surface of a truncated aluminum cone, cooled by the heavy water moderator, where
the proton beam is expanded to a diameter of 3 cm and scanned along a circular path, striking the lithium later at the
cone's half-angle of 30 degrees. We propose to develop a moderator assembly designed to transmit a large fraction of the
source neutrons from the target to the patient treatment port, while shifting the neutron energies to an appropriate
epithermal energy spectrum and minimizing the gamma-ray dose. The status of this proposal and these plans are presented.