Construction of an Accelerator-based BNCT Facility at yhe Ibaraki Neutron Medical Research Center

An accelerator-based BNCT (Boron Neutron Capture Therapy) facility is being constructed at the Ibaraki Neutron Medical Research Center. It consists of a proton linac of 80kW beam power with 8 MeV energy, a beryllium target, and a moderator system to provide an epithermal neutron flux sufficient for patient treatment. The technology choices for this present system were driven by the need to house the facility in a hospital where low residual activity is essential. OUTLINE OF THE PROJECT An accelerator-based BNCT facility, (hereafter, i-BNCT [1]) is being constructed at the Ibaraki Neutron Medical Research Center (INMRC) with broad a collaboration coming from universities and organizations: KEK, Tsukuba University, Hokkaido University, JAEA; and commercial enterprises: Mitsubishi Heavy Industries, NAT, ATOX and COSYLAB. It consists of a high-power proton linac of 80 kW beam power with 8 MeV energy (3MeV RFQ + 5MeV DTL), a beryllium target, and a moderator system to provide a high enough epi-thermal neutron flux for patient treatment. The main parameters of the i-BNCT are summarized in Table 1 and the layout and a block diagram are shown in Figures 1 and 2, respectively. The basis for the technology choices will be described in the next section. Presently the construction of the accelerator system has been completed and RF conditioning of the RFQ and DTL is in progress. The first phase beam commissioning will be carried out this fall with a small beam current (a few A) by using a target without a beryllium layer and the second phase full beam commissioning is scheduled for next year with a beryllium target and moderator system to provide the epi-thermal neutron flux. Since the INMRC is a retrofit into an existing building, the layout of the irradiation room, accelerator and klystron modulator is not optimum as can be seen in Figure 1. In particular, the design of the beam transport line optics is made complex because of the 1.8 m floor level difference between the accelerator and irradiation room. Table 1: Main Parameters of the 80 kW Linac Beam energy 8 MeV (50kV ion source, 3MeV RFQ and 5MeV DTL)