Vacuum Insulated Tandem Accelerator for Boron Neutron Capture Therapy and Other Applications

A tandem electrostatic accelerator with an original design called a Vacuum Insulated Tandem Accelerator was proposed and developed at the Budker Institute of Nuclear Physics. Unlike conventional tandem accelerators, it does not use accelerating tubes-the high-voltage and intermediate electrodes are made in the form of nested cylinders and are fixed at a single feedthrough insulator. This design of the electrodes made it possible to provide a high rate of ion acceleration (up to 25 kV/cm). The accelerator is equipped with a set of diagnostic tools that provide the long-term stable production of a beam of protons or deuterons with an energy varying from 0.6 to 2.3 MeV and with a current varying from 0.1 to 10 mA. The ion beam is characterized by high monochromaticity, energy stability (0.1%), and high current stability (0.4%). The accelerator is used for in situ observations of the blistering of a metal irradiated with protons; for measuring the cross section of the reactions Li-7(p,p'?)Li-7, Li-7(p,a)a, and B-11(p,a)aa; for developing boron neutron capture therapy for malignant tumors by using neutrons generated in the Li-7(p,n)Li-7 reaction; for the radiation testing of promising materials using fast neutrons in the Li-7(d,n) reaction; and for other applications. The accelerator became an integral part of the medical neutron source for boron neutron capture therapy: the first facility was put into operation in one of the first six BNCT clinics in the world in Xiamen, China; the next two facilities are being made for the National Center of Oncological Hadron Therapy in Pavia (Italy) and for the Blokhin National Medical Research Center of Oncology in Moscow. In this paper, the design of the accelerator and its features and parameters, as well as the results of studies carried out using the accelerator, are presented and discussed.