Study of boron neutron capture therapy used neutron source with protons bombarding a thick 9Be target

Abstract

Neutron sources created by 4-, 3.5-, and 3-MeV protons striking a thick beryllium target were studied via the time-of-flight technique. Protons were accelerated by the Peking University 4.5 MV electrostatic accelerator. Two disk-shaped 9Be targets with thickness 1.5 and 3 mm were used in the measurements. The time-of-flight spectra were observed at zero degrees with respect to the incident proton beam. The analysis to these time-of-flight spectra is given. The time-of-flight spectra were converted to the energy spectra and compared to a neutron spectrum of 7Li(p, n)7 Be reaction with incident energy 2.5 MeV, which was also measured in this work. Restricted by the spectrometer itself, the threshold of the measurements is 400 keV. The results show that by using several MeV protons bombarding a thick beryllium target, reactions other than 9Be(p, n)9B produce significant contributions to the neutron yield with energy less than 1 MeV.

Measurements of low‐energy (d,n) reactions for BNCT

“…Currently, two reactions are being considered for use in the first generation of accelerator-based neutron sources for BNCT: the 7 Li(p,n) 7 Be reaction at an energy around 2.5 MeV, 2-4 and the 9 Be(p,n) 9 B at energies approaching 4 MeV. [5][6][7] Both reactions produce neutrons with adequate energy and yield, but their use is complicated by the low melting point of the Li target ͑180°C͒ and production of the radioactive 7 Be residue (T 1/2 ϭ53 days͒ for the first reaction, and the higher proton energy and poorer neutron beam quality for the second one.…”

“…[5][6][7] Both reactions produce neutrons with adequate energy and yield, but their use is complicated by the low melting point of the Li target ͑180°C͒ and production of the radioactive 7 Be residue (T 1/2 ϭ53 days͒ for the first reaction, and the higher proton energy and poorer neutron beam quality for the second one. In order to investigate whether alternative reactions exist for neutron production in BNCT, we have performed measurements of several (d,n) reactions.…”

The experimental determination of the fraction of neutrons below 1.5MeV for the Chinese-made Am–Be neutron source

“…directly coupled to a XP2040 photomultiplier tube. The main detector was placed inside a massive shield [11] with a double-truncated conical collimator made of copper for optimum transmission of the neutron flux of interest. The neutron flight path was 186.6 cm.…”

Investigating a multi-purpose target for electron linac based photoneutron sources for BNCT of deep-seated tumors

“…The recommended criteria for the optimal beam for BNCT, including the beam intensity and beam quality, are given in a document published by IAEA [3]. Based on these criteria, the minimum beam intensity of the epithermal neutrons should be 5 Â 10 8 should be 2 Â 10 À13 Gy cm 2 , the target number for the ratio of the thermal flux to the epithermal flux should be 0.05, and the maximum beam size should be 12-14 cm. In order to satisfy the IAEA recommended neutron beam intensity, various neutron sources have been suggested so far, and detailed discussions of them can be found in the literature [4][5][6][7][8][9][10][11]. Of special interest are so-called photoneutron sources based on linear electron accelerators (linac) [12][13][14].…”