MEASUREMENTS OF THE NEUTRON YIELDS FROM LI-7(P,N)BE-7 REACTION (THICKTARGET) WITH INCIDENT ENERGIES FROM 1.885 TO 2.0 MEV

Accelerator-based neutron sources have been considered to be practical for boron neutron capture therapy (BNCT). Based on experience with th e parameters of the Brookhaven National Laboratory BMRR reactor neutro n source, which has been used in treatment experiments, the future acc elerator-based neutron source for BNCT should have the properties of l ow energy distribution (< 100 keV) and high flux (about 10(9) neutrons per second per square centimeter) in the patient zone. Using protons to bombard thick Li-7 targets, generating neutrons via the Li-7(p,n) B e-7 reaction, is one of the optimal choices for this kind of neutron s ource. Neutron yield data versus incident energy are necessary in orde r to select the proper incident energy and for estimating how high the incident proton current should be. The required proton beam current i ntensity is one of the key parameters for an accelerator useful for BN CT. In the present work, neutron yields of the Li-7(p,n) Be-7 reaction with a thick lithium target and incident energies of 1.885 and 1.9 Me V were measured at 0 degrees with respect to the incident beam directi on. The results are (3.08 +/- 0.17) x 10(12) and (5.71 +/- 0.32) x 10( 12) neutrons/C sr, respectively. Neutron yield angular distribution me asurements at 2 MeV incident energy were also performed. The proton be ams were generated by the Peking University 4.5 MV electrostatic accel erator. The emitted neutrons from these reactions have the advantages of low energy distribution and forward angular distribution, which are requirements for a BNCT neutron source. The data obtained in this wor k can be used as a reference to study the accelerator-based neutron so urces for BNCT. (C) 1998 American Association of Physicists in Medicin e.