A. Makarov

STATUS AND PROSPECTS OF GOL-3 MULTIPLE-MIRROR TRAP

Abstract The paper reviews recent experimental results from GOL-3. Currently efforts are focused on further development of a physical database for multiple-mirror confinement systems and also on an upgrade of plasma heating systems of GOL-3 device. In general, current GOL-3 parameters demonstrate good prospects of a multiple-mirror trap as a fusion reactor.

Plasma Heating and Confinement in GOL-3 Multi Mirror Trap

Recent results of the experiments at GOL-3 facility are presented. In present configuration of the device, plasma with a density of 1014[divided by]1016 cm-3 is confined in a 12-meter-long solenoid, which comprises 55 corrugation cells with mirror ratio Bmax/Bmin=4.8/3.2 T. The plasma in the solenoid is heated up to 2-4 keV temperature by a high power relativistic electron beam (˜1 MeV, ˜30 kA, ˜8 μs, ˜120 kJ) injected through one of the ends. Mechanism of experimentally observed fast ion heating, issues of plasma stability and confinement are discussed.

Progress on the Multimirror Trap GOL-3

Main results of researches on plasma heating and confinement of dense plasma in the multimirror trap GOL-3 are presented. Recently magnetic system of the facility was converted into completely multimirror one. This results in further improvement of energy confinement time of plasma with ion temperature ~1 keV. Collective plasma heating by ~120 kJ (~8 ɷs) relativistic electron beam results in Te ~ 2 keV at ~1021 m-3 density. High Te exists for ~10 μs. To this time Ti reaches ~2 keV. Ion temperature keeps at the high level during ~1 ms. The energy confinement time sufficiently increases and a value of nτE = (1.5 [divide] 3)·1018 m-3s.

BINP accelerator based epithermal neutron source.

Innovative facility for neutron capture therapy has been built at BINP. This facility is based on compact vacuum insulation tandem accelerator designed to produce proton current up to 10 mA. Epithermal neutrons are proposed to be generated by 1.915-2.5 MeV protons bombarding a lithium target using (7)Li(p,n)(7)Be threshold reaction. In the article, diagnostic techniques for proton beam and neutrons developed are described, results of experiments on proton beam transport and neutron generation are shown, discussed, and plans are presented.

Proton beam of 2 MeV 1.6 mA on a tandem accelerator with vacuum insulation

A source of epithermal neutrons based on a tandem accelerator with vacuum insulation for boron neutron capture therapy of malignant tumors was proposed and constructed. Stationary proton beam with 2 MeV energy, 1.6 mA current, 0.1% energy monochromaticity and 0.5% current stability has just been obtained.

Current progress and future prospects of the VITA based neutron source

At the BINP, a pilot accelerator based epithermal neutron source is now in use. Most recent investigations on the facility are related with studying the dark current, X-ray radiation measuring, optimization of H(-)-beam injection and new gas stripping target calibrating. The results of these studies, ways of providing stability to the accelerator are presented and discussed, as well as the ways of creating the therapeutic beam and strategies of applying the facility for clinical use.

New technical solution for using the time-of-flight technique to measure neutron spectra

New technical solution is proposed for using the time-of-flight technique to measure neutron spectra on VITA-facility. During 200 ns the energy of protons increases from 1.865 up to 1.915 MeV by supplying the square pulse of 50 kV on the neutron-generating target, which is isolated from facility body. During these 200 ns the generation of neutrons is performed. The spectrum can be obtained measuring the time of flight by a remote neutron detector.

Suppression of an unwanted flow of charged particles in a tandem accelerator with vacuum insulation

In the construction of a 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 mA to 5 mA.

Readiness for boron neutron capture therap

A source of epithermal neutrons based on a tandem accelerator with vacuum insulation and a lithium neutron producing target was proposed and created to develop boron neutron capture therapy of malignant tumors. A laboratory was created in 2014 to be prepared for practical implementation of the therapy using the accelerator neutron source. To achieve this goal it is necessary to increase the current and the energy of the proton beam, to create a new neutron producing target, neutron beam shaping assembly and so on. The article provides a description of the created source of epithermal neutrons, presents and discusses the results of experiments and declares future plans.

Modification of the argon stripping target of the tandem accelerator.

The tandem accelerator with vacuum insulation has been proposed and developed in Budker Institute of Nuclear Physics. Negative hydrogen ions are accelerated by the positive 1MV potential of the high-voltage electrode, converted into protons in the gas stripping target inside the electrode, and then protons are accelerated again by the same potential. A stationary proton beam with 2 MeV energy, 1.6 mA current, 0.1% energy monochromaticity, and 0.5% current stability is obtained now. To conduct Boron Neutron Capture Therapy it is planned to increase the proton beam current to at least 3 mA. The paper presents the results of experimental studies clarifying the reasons for limiting the current, and gives suggestions for modifying the gas stripping target in order to increase the proton beam current along with the stability of the accelerator.