Title: Drivers for Low Cost, Ultra-Compact, Epithermal Neutron Sources for BNCT

The focus of this study is the indentification of key feasibility issues for the use of non-reactor neutron sources for Boron Neutron Capture Therapy (BNCT). Of the non-reactor neutron sources surveyed, the /sup 7/Li(p,n) reaction appears to be the most favorable for producing epithermal neutrons for BNCT, and RFQ accelerators are best for producing the desired proton beam. At a proton energy of 2.5 MeV, the total neutron yield is 1.49 /times/ 10/sup /minus/4/ neutrons/proton, with a forward energy spectrum extending up to 780 keV and peaked at 500-600 keV. At I = 20 mA, the total neutron yield wouldmore » be about 1.86 /times/ 10/sup 13/ neutrons/s. In comparison with a medical therapy fission reactor, the 20 mA accelerator system has a flux intensity at least 5 times lower, requiring an irradiation time at least 5 times longer, a much higher gamma intensity, which would probably require additional shielding, further reducing the neutron intensity, 30% of the neutrons above 15 keV, resulting in a higher fast neutron dose to healthy tissue, poorer spatial uniformity of the neutron beam, and greater angular divergence of the neutron beam, resulting in a rapid decrease of flux with distance from the filter. The possibility of overcoming these limitations by using more shielding and a higher beam current needs further study. RFQ accelerator technology is being developed to provide the desired proton beam parameters. The effects of neutron beam energy spectra, beam contaminants, angular divergence, spatial variation, and beam rotation around the tumor need to be studied in detail, in order to evaluate the feasibility of accelerator-produced neutrons for BNCT. 41 refs., 20 figs., 8 tabs.« less

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 R lowbar f F lowbar ocused D lowbar TL, or RFD. 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 themore » 2.5-MeV RFD linac system with an average current of 10 mA, having the following components: an ion source, a short low-energy 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 layer 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.« less

This report describes a new algorithm for the joint estimation of carrier phase, symbol timing and data in a Turbo coded phase shift keyed (PSK) digital communications system. Jointly estimating phase, timing and data can give processing gains of several dB over conventional processing, which consists of joint estimation of carrier phase and symbol timing followed by estimation of the Turbo-coded data. The new joint estimator allows delay and phase locked loops (DLL/PLL) to work at lower bit energies where Turbo codes are most useful. Performance results of software simulations and of a field test are given, as are detailsmore » of a field programmable gate array (FPGA) implementation that is currently in design.« less