BINP SB RAS, Novosibirsk, Russia
Budker INP & NSU, Novosibirsk, Russia
NSU, Novosibirsk, Russia
A promising method of treatment of many malignant tumors is the boron neutron capture therapy (BNCT)*. It provides a selective destruction of tumor cells by prior accumulation of a stable boron-10 isotope inside them and subsequent irradiation with epithermal neutrons. It is expected that accelerator based neutron sources will be created for the clinical practice. One such source could be an original source of epithermal neutrons**, created in BINP. To obtain proton beam a new type of particle accelerator is used - tandem accelerator with vacuum insulation. Generation of neutrons is carried out as a result of the threshold reaction 7Li(p, n)7Be. During 2015-2016 in the construction of tandem accelerator with vacuum insulation several changes were made. This allowed us to suppress the unwanted flow of charged particles in the accelerator, to improve its high-voltage stability, and to increase the proton beam current from 1.6 to 5 mA. Such current value is sufficient for BNCT. The report describes in detail the modernization of the accelerator, presents and discusses the results of experiments on obtaining the proton beam and the formation of neutron flux using lithium target, and declares our prospective plans. The obtained neutron beam meets the requirements of BNCT: the irradiation of cell cultures provides the destruction of cells with boron and preservation of cells without boron. Irradiation of immunodeficient mice with grafted glioblastoma results in their recovery.
*Neutron Capture Therapy. Principles and Applications. Eds: W. Sauerwein, A. Wittig, R. Moss, Y. Nakagawa. Springer, 2012.
**S. Taskaev. Accelerator based epithermal neutron source. Physics of Particles and Nuclei 46 (2015) 956-990.
BINP SB RAS, Novosibirsk, Russia
NSI RAS, Moscow, Russia
BINP SB RAS, Novosibirsk, Russia
BINP & NSTU, Novosibirsk, Russia
NSU, Novosibirsk, Russia
Budker INP & NSU, Novosibirsk, Russia
In the BINP SB RAS was proposed and created a source of epithermal neutrons for BNCT. The proton beam is obtained on a tandem accelerator with vacuum insulation. Sectionalized demountable feed through insulator is an integral part of the accelerator. Voltage from the high voltage source is distributed to the electrodes via resistive divider. Because of the small amount of current (hundreds of microamperes) flowing through the divider, dark currents that occur in the accelerating gaps, can significantly affect the uniform distribution of the potential along the accelerating channel, and, consequently, on the beam transportation. Therefore there is a need to change the design of the feed through insulator which will allow to set potentials at the electrodes directly from the high voltage rectifier sections. To study the feasibility of such changes has been designed and built an experimental stand, in which a single insulator with double height subjected to the same conditions as in accelerator. On the experimental stand was studied electrical strength of ceramic and polycarbonate insulators with a different shape of the surface. The paper presents the results of experimental studies of insulators. Their application will get rid of the voltage divider inside the feed through insulator and realize the scheme which allows to set potential on the electrode gaps directly from the rectifier section. This will increase the operating voltage of the accelerator and its reliability.
BINP SB RAS, Novosibirsk, Russia
In BINP the neutron source for BNCT based on proton accelerator was designed and built. It is necessary for the therapy to ensure a stable proton beam current of not less than 3 mA with energy 2 MeV. During the injection of negative hydrogen ion beam into the accelerator the unwanted charged particles are produced, affecting the stability of beam parameters. The article describes meth-ods of suppression of undesirable charged particles and the results of experiments.
Budker INP & NSU, Novosibirsk, Russia
BINP SB RAS, Novosibirsk, Russia
In The Budker Institute of Nuclear Physics the accelerator-based source of epithermal neutrons was invented and now operates to be used in the boron neutron capture therapy. For several reasons the real beam flow in the facility differs from the calculated one. To take into account this distinction it is necessary to provide continuous monitoring of the beam parameters. In order to optimize the facility operation the beam should be followed not only during the formation but also while an acceleration takes place and the proton beam is thrown on the lithium target as the proton current and energy influence on the neutron output. In this way it seems to be a significant issue to measure the current, profile and also the position of the ion beam in a low-energy part of the accelerator. This work represents the results of experiments with the D-Pace WS-30 Wire Scanner Probe, which was installed in the low-energy part of the accelerator. The experiments were carried out under various conditions to vary the position and focusing control via the system of magnetic correcting elements. To correctly interpret experimental data it was necessary to take into account physical phenomena which occur during an experiment. In this way the effects which take place when the probe interacts with the beam were thoroughly considered. The obtained results allowed to restore the ion beam profile, define its size and position.
Budker INP & NSU, Novosibirsk, Russia
BINP SB RAS, Novosibirsk, Russia
In The Budker Institute of Nuclear Physics the accelerator-based source of epithermal neutrons was invented and now operates to be used in the boron neutron capture therapy. Neutrons on the facility are generated during the threshold reaction 7Li(p, n)7Be which occurs when the proton beam is thrown on the lithium target. To control the neutron output it is necessary to monitor the parameters of the accelerated proton beam. The spatial distribution of the accelerated proton beam was measured exactly on the lithium target. Due to the interaction of protons and lithium there is an accumulation of a radioactive isotope of beryllium takes place. After experiments about neutrons generation it seems possible to track an area of beryllium storage and then restore the proton beam profile. The monitoring of gamma-quants with the energy of 0,477 MeV arising during the beryllium decay was carried out via the gamma-spectrometric complex. The main part of this complex is NaI-scintillation detector, which was pre-calibrated with energy. As a result of such kind of diagnostic the profile of the beam, its shape and characteristic size were determined and the results are depicted in this paper. Afterwards it could be used for an estimation of the total neutrons flux, its quantity, also to assess the target state and restore the proton beam profile.
BINP SB RAS, Novosibirsk, Russia
The new source of epithermal neutrons*, designed for boron neutron capture therapy (BNCT)** of cancer in oncology clinic, was proposed and developed in Budker Institute of Nuclear Physics. This method of treatment is effective against several currently incurable radioresistant tumors, such as brain glioblastoma and melanoma metastases. The neutron source includes a new type of accelerator: accelerator-tandem with vacuum insulation, lithium neutron generating target and neutron beam shaping assembly. Current accelerator produces a stationary 5 mA proton beam with 2 MeV energy, but this is not sufficient for therapy on humans. For conducting the experiment on humans it is necessary to create a new power rack for the ion source. The report summarizes results of the development and implementation of new power rack, with remote control and data collection systems, to reach 15 mA beam current. This system will increase the proton beam current and, as a result, the neutron yield, that is needed to heal people.
* S. Taskaev. Accelerator based epithermal neutron source. Physics of Particles and Nuclei, 2015, Vol. 46, No. 6, pp. 956'990.
** Neutron Capture Therapy. Principles and Applications. Eds: W. Sauerwein, A. Wittig, R. Moss, Y. Nakagawa. Springer, 2012.