Development of a regenerated Beryllium target and a thermal test facility for Compact Accelerator-based Neutron Sources

Abstract

Recently, the possibility to use compact accelerators coupled to high current ion sources for the production of intense low energy proton or deuteron beams has motivated many research laboratories to develop accelerator based neutrons sources for several purposes, including Neutron Capture Therapy (NCT). The NCT needs a high flux, about 10 9 n.cm-2.s-1, of thermal neutrons (E<10 keV) at the tumour site. Up to now, the NCT required neutron flux was mainly delivered by nuclear reactors. However, the production of such neutron flux is now possible using proton or deuteron beams on specific targets able to stand a high pow er (~15- 30 kW) on a small area (~10 cm2). This specific target design, materials and supports, has to cope with extreme physical constraints . The LPSC team has conceived an original solution formed by a thin (8 μm) rotating beryllium target depos ited on a graphite wheel and coupled with a beryllium sputtering device for periodic 9Be layer restoration. By means of 9Be (d,n) 10B nuclear reaction, this target irradiated by a 10- -20 mA deuteron beam (1.45 MeV) should produce the required neutron flux. In order to validate the target design of the neutron flux production and the beryllium target thermal capabilities, we built a 30 cm diameter rotating Beryllium target prototype and a compact electron beam line able to deliver a power density of 3kW/cm2.

On the Eptihermal Neutron Energy Limit for Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT): Study and Impact of New Energy Limits

“…• 14 N(n,p) 14 C to the called proton dose D p , considering the ionisation energy released by the proton and the carbon nucleus,…”

“…The weight is a value allocated to a particle that is calculated at each step of its track according to the probability of the current event to happen. In general, the 7 Li, 14 N(n,p) 14 weight of the tracked particle is reduced at each interaction (scattering or capture) until a default threshold is reached below which the particle is killed. This implicit mode, used for tally computations to obtain capture rates and total absorbed dose from a specified particle type in users specified volumes, allows computing time reduction for simulations and uncertainty calculations.…”

“…The absorbed proton dose D p was evaluated for healthy tissues. The absorbed proton dose D p results from ionisation of protons produced by the 14 N(n,p) 14 C reaction. Table 5 shows the relative difference in percentage with respect to 10 keV values of results obtained for lower epithermal energies.…”

“…It is interesting to note that the relative gap of the absorbed proton dose D p in healthy tissues of energies in [10 eV; 100 eV; 1 keV] with respect to results obtained at 10 keV is similar to the one obtained considering the 10 B(n,α) 7 Li reaction rate normalized per unit mass. This can be explained by the fact that the 14 N(n,p) 14 C reaction used in the computation of the absorbed proton dose D p and the 10 B(n,α) 7 Li reaction have both analogous cross section variation in the epithermal range. The study of the absolute values shows that the brain is the healthy tissue receiving the highest value of dose from 14 N(n,p) 14 C reaction for all energies.…”

“…The use of low energy particle compact accelerators and targets adapted to cope with high power (15 to 30 kW) for neutron production led to the development of Accelerator-Based BNCT (AB-BCNT) facilit- 10 B + n −→ [ 11 B * ] 4 He + 7 Li Q = 2.792MeV (1a) 4 He + 7 Li Q = 2.310MeV + γ[0.48MeV] (1b) 6% 94% ies [12]. In this context, an AB-BNCT facility project was launched at the Laboratory of Subatomic Physics and Cosmology (LPSC) in France [13,14]. The purpose is to use a compact accelerator coupled to a beryllium target using the 9 Be(d(1.45MeV),n) 10 B reaction as a neutron source [15].…”