The Budker Institute of Nuclear Physics in worldwide collaboration has developed a project of a 14 MeV neutron source for fusion material studies and other applications. The projected neutron source ...of the plasma type is based on the gas dynamic trap (GDT), which is a special magnetic mirror system for plasma confinement. Essential progress in plasma parameters has been achieved in recent experiments at the GDT facility in the Budker Institute, which is a hydrogen (deuterium) prototype of the source. Stable confinement of hot-ion plasmas with the relative pressure exceeding 0.5 was demonstrated. The electron temperature was increased up to 0.9 keV in the regime with additional electron cyclotron resonance heating (ECRH) of a moderate power. These parameters are the record for axisymmetric open mirror traps. These achievements elevate the projects of a GDT-based neutron source on a higher level of competitive ability and make it possible to construct a source with parameters suitable for materials testing today. The paper presents the progress in experimental studies and numerical simulations of the mirror-based fusion neutron source and its possible applications including a fusion material test facility and a fusion-fission hybrid system.
The low-magnetic-field feature in the magnetic field dependence of the luminescence of negatively charged nitrogen-vacancy (NV−) centers in diamond has been experimentally observed for the first ...time. This feature, centered at the zero magnetic field-henceforth the zero field line-and observed with a magnetic field sweep of NV− center luminescence (magnetic spectrum), is quite narrow. The properties of this line are considerably different from those of other narrow NV− magnetic spectrum lines. Its amplitude is weakly dependent on the orientation of the single-crystal sample with respect to the external magnetic field. This line is also observed in a powdered sample. The shape of the line changes drastically with a change in the polarization of excitation light. The amplitude of the line non-linearly depends on excitation light intensity. For low intensities this dependence is close to the square law. We attribute the occurrence of this line to the dipole-dipole interaction between different NV− centers.
The diagnostic complex of the Globus-M2 spherical tokamak (
R
= 36 cm,
a
= 24 cm), the only operating tokamak in Russia with a divertor plasma configuration, which operates in the range of ...subthermonuclear temperatures (
T
e
to 1.6 keV,
T
i
to 4.5 keV) and densities (
n
e
to 2 × 10
20
m
–3
), is described. The Globus‑M2 tokamak is the unique scientific facility, which is a part of the Federal Center for Collective Use of the Ioffe Institute, Russian Academy of Sciences “Materials Science and Diagnostics in Advanced Technologies.” This allows third parties to perform their research using it. The work contains a list of all diagnostics currently available on the tokamak. The description of the diagnostics is structured in such a way that the reader gets an idea of their capabilities for measuring plasma parameters with an emphasis on the limits and accuracy of the measured values, and also spatial and time resolution. At the same time, many technical details are omitted in order to save space; references are given to papers with a more detailed description of individual diagnostics.
This Letter describes plasma discharges with a high temperature of bulk electrons in the axially symmetric high-mirror-ratio (R=35) open magnetic system gas dynamic trap (GDT) in the Budker Institute ...(Novosibirsk). According to Thomson scattering measurements, the on-axis electron temperature averaged over a number of sequential shots is 660±50 eV with the plasma density being 0.7×10^{19} m^{-3}; in few shots, electron temperature exceeds 900 eV. This corresponds to at least a threefold increase with respect to previous experiments both at GDT and at other comparable machines, thus, demonstrating the highest quasistationary (about 1 ms) electron temperature achieved in open traps. The breakthrough is made possible by application of a new 0.7 MW/54.5 GHz electron cyclotron resonance heating system in addition to standard 5 MW heating by neutral beams, and application of a radial electric field to mitigate the flute instability.
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•Radiation-induced fluorescence from frozen tricosane doped with a luminophore was studied.•Magnetic field effect in the fluorescence showed Δg-quantum beats on a nanosecond ...timescale.•The frequency of the beats increased upon going from the liquid to the crystal phase.•Effect of the g-tensor and hyperfine coupling anisotropy was analysed.•Fast hole migration in the tricosane crystal favoured observation of the beats.
The effect of an external magnetic field on the radiation-induced fluorescence of tricosane (n-C23H48), doped with luminophore, was studied on the nanosecond timescale. It was found that the characteristic frequency of quantum beats caused by the difference between the Zeeman interactions of dopant radical anions and tricosane radical cations increased substantially upon transition from the liquid to the crystal phase. Experimental data were in agreement with both the quantum-chemical calculations and theoretical spin evolution simulations, assuming that hyperfine couplings and transverse components of the tricosane radical cation g-tensor were averaged out by degenerate positive charge transfer in the tricosane crystal.
► GENESYS code was developed to model plasma processes in gas-dynamic mirror devices. ► NMC code was developed for modelling neutron processes in fuel blankets. ► Source's maximum emission intensity ...was estimated at 2×1018neutrons/s. ► Multiplicity dependence on buffer zone thickness was determined for a MA blanket.
A task of long-lived transuranic isotopes utilization is considered to be one of the urgent problems for the nuclear reactor technology. Using sub-critical hybrid systems is a possible solution of the problem. Budker Institute of Nuclear Physics SB RAS together with Nuclear Safety Institute RAS is working on a hybrid system with a neutron source based on the gas dynamic trap and sub-critical fuel blanket. This article presents the results obtained from a series of numerical experiments aimed at estimating the optimal system. Particularly, maximum neutron source emission rate has been estimated to reach 1×1018–2×1018neutrons/s at the input parameters typical for such a system. Pb–Bi buffer zone impact on integral characteristics of fuel blanket has been considered. Decrease in amount of secondary fission neutrons as the result of buffer zone thickening has been revealed.
The codes developed to conduct the investigations are also described in the article. The first one, GENESYS, is a zero-dimensional code aimed at modelling plasma processes in the gas dynamic trap. The second one, NMC (Neutron Monte-Carlo), is a Monte-Carlo particle transport code and is developed as a multipurpose tool for neutron transport calculation.
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•Charge transfer from radical ion to molecule changes magnetic interactions of the unpaired electron.•The spin evolution of the spin-correlated radical ion pair, involving the radical ...ion, is sensitive to such changes.•The external magnetic field allows the monitoring of both spin evolution and charge transfer.•The reaction rate is determined from magnetic field curve analysis with an acceptable accuracy.
The capabilities of the method of time-resolved magnetic field effect in determining the rates of charge transfer reactions between radical ions and molecules on a nanosecond time scale have been investigated. The approach relies on the electron spin coherence in radical pair’s partners generated by ionizing radiation. The spin evolution of the pair is sensitive to the reaction since the latter results in changing magnetic interactions of the unpaired electron. This process can be monitored by magnetic-field-sensitive fluorescence from an irradiated sample that is illustrated using reactions involving alkane radical cations. The accuracy and limitations of the approach are discussed.
•We propose use of radical triads for verification of spin-chemistry master equation.•Spin-selective reaction of radicals B and C modifies spin state of radical pair AB.•Various forms of the master ...equation predict various spin state populations of AB.
The problem of verifying various approaches to account for the effect of spin-selective recombination of radicals on the quantum state of the radical pairs escaping recombination is discussed. Here we propose the use of radical triads for the verification. It is shown that in radical triads ABC a spin-selective reaction between radicals B and C modifies spin correlation between radicals A and B. Different approaches predict different time dependences for these changes, e.g., the population of the singlet spin state of the radical pair AB decays with different rates. Possible experimental checks of these predictions are discussed.
Axisymmetric magnetic mirrors are capable of confining high-β plasma and, at the same time, enable provision of higher magnetic field in the confinement region compared to non-axisymmetric systems. ...These advantages and their technical simplicity make them rather attractive as high-flux volumetric neutron sources, fission-fusion hybrids, and in the longer term as pure fusion reactors. The specific issues that still have to be further studied are plasma MHD stability at plasma parameters relevant to fusion applications, too-high plasma end losses, and the relatively low electron temperatures obtained so far in the experiments. These main physics issues were successfully addressed in the recent experiments in the GDT and GOL-3 devices in Novosibirsk. The review concludes with an update of the experimental results from both experimental devices and a discussion about the limiting factors in the current experiments. Specifically, we report on an almost twofold increase of the electron temperature with application of ECR heating, which was obtained in the experiments on the GDT device, and control of plasma rotation profile by injection of an electron beam at the end of the device, which was demonstrated in the GOL-3 device.
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