B. F. Bayanov¹, V. P. Belov¹, E. D. Bender¹, M. V. Bokhovko²,G. I. Dimov¹,
V. N. Kononov², O. E. Kononov², N. K. Kuksanov¹, V. E. Palchikov¹, V. A. Pivovarov²,
R. A. Salimov¹, G. I. Silvestrov¹, A. N. Skrinsky¹, N. A. Soloviov², S. Yu. Taskaev^1*

Physical project of accelerator-based neutron source for the neutron-capture and fast neutron therapy at hospital appropriate for commercial use is proposed [1].

At present, the beam therapy is one of the basic methods for curing malignant tumors. Recently, the ever increasing attention in therapy was drawn to the use of neutron beams. The neutron therapy is realized in two versions: a neutron-capture therapy (NCT) and fast neutron therapy (FNT). At present, the mostly promising is the version of boron neutron capture therapy (BNCT). Boron containing compounds enriched in the isotope ¹⁰B are synthesized. This compound introduced into the patient's blood produce in the tumor cell the ¹⁰B isotope concentration three times larger than in a normal tissue cell. This allows to destroy selectively the malignant tumors.

In this project, neutron generation is proposed to be carried out by dropping an intensive proton beam onto lithium target using ⁷Li(p,n)⁷Be threshold reaction. Two modes of operation of the complex is characteristic for this project. The first provides neutron beam kinematically collimated with good forward direction in 25° and average energy of 30 keV, directly applicable for neutron-capture therapy with high efficiency of proton beam use. The proton energy in this mode is 1.883 ¸  1.890 MeV that is near the threshold of the reaction. In the second mode, at proton energy of 2.5 MeV, the complex produces neutron beam with maximum energy board of 790 keV which can be used directly for fast neutron therapy and for neutron-capture therapy after moderation. Other characteristic features of the project are: i) production of 40 mA proton beam for providing treatment time of tens of minutes necessary to achieve absorbed dose of 20 Gy; ii) use of tandem accelerator with vacuum insulation instead of direct accelerator.

This project is based on wide experience. At BINP original electrostatic vacuum insulation tandem accelerator was develop which used sectionalized rectifier from electron accelerator of ELV type as a powerful source of high voltage. Specifics of geometry of accelerating electrodes and tandem optics allows to reach maximum reliability. It was tested on 1 MeV prototype which was used as an injector in a synchrotron. The reliability of high voltage ELV rectifier was confirmed by many years of operation of such accelerators in industry. A surface plasma technique for negative ion generation was proposed and realized in BINP, basic modifications of surface plasma sources operating at most of the large proton accelerators all over the world were developed. Cylindrical lenses with solid or liquid lithium and liquid metal targets applied in high energy physics for secondary particles beam generation were produced. IPPE has wide experience in investigation of distribution of produced neutrons and absorbed doses.

After investments and necessary research and design works the proposed accelerator complex can be created and transferred for use in clinics within 2 y.