The effect of copper doping of ZnSe:Fe crystals on the kinetics of luminescence of iron ions is investigated in this work. It has been discovered that doping with copper leads to a sharp decrease in ...the radiative recombination of iron ions at a temperature of 77 K. The obtained results are explained based on the model of nonradiative relaxation of iron ions due to Auger recombination with the participation of electrons in the conduction band.
The applicability of neutral particle diagnostics for studying plasma parameters and additional methods of heating in the Tokamak with Reactor Technologies is analyzed. Options for the arrangement of ...diagnostic equipment, which includes three analyzers of charge-exchange atoms (neutral particle analyzers) for different energy ranges of recorded atomic fluxes, are given. It is shown that the diagnostic complex of analyzers makes it possible to measure the distribution functions of plasma thermal ions and to obtain information on the isotopic ratio of the main plasma ion component in the deuterium–tritium mode of facility operation. In addition, the proposed geometry of the analyzer arrangement makes it possible to measure the energy distribution of fast ions, which arise during neutral beam injection and ion cyclotron heating of plasma.
A neutron collimator is developed to attenuate the neutron flux and reduce the residual induced activity in the interportal space of the diagnostic system of neutral particle analyzers of the ITER ...tokamak reactor. The collimator is installed in the port plug of the ITER vacuum vessel in front of an inlet to the vacuum pipeline of the diagnostic system. The collimator design has a cellular structure with 80% transparency for the neutral atom beam that goes out of the plasma and is recorded by the analyzers. However, because of increased scattering of neutrons in the collimator, their flux in the interportal room in the service zone of diagnostic systems of equatorial port no. 11 is significantly reduced and allows the equivalent dose rate in this zone to be decreased by several times. Thermal analysis showed that, during the reactor operation in modes with generation of the maximum power of 500 MW, the plasma radiation will cause the heating of the collimating grid to a temperature not exceeding 250°C, which makes it possible to select the stainless steel (316L(N)-ITER grade) as a material for manufacturing the collimator. In this case the cyclic strength of the collimator meets the ITER requirements, and it can be used without replacement during the entire deuterium-tritium experiment of the tokamak reactor.
A scheme of a multichannel time-of-flight atomic analyzer with an electrostatic deflection system that provides two-dimensional focusing of the ion beam in the transverse direction is described. A ...thin carbon film with a thickness of 100 Å is used to ionize the incoming flow of atoms. The results of numerical simulation of the main parameters of the analyzer, such as the energy values in the channels, their energy resolution, and permeability, are given. An example of the possible use of such an atomic analyzer for measuring the energy distribution function of thermal plasma ions and fast ions of heating beams in the deuterium–tritium operating regime of the TRT facility is considered. The efficiency of radiation background suppression in the analyzer detection system by the coincidence circuit has been analyzed.
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The article addresses general matters concerned with the occurrence of low-frequency vibration (LFV) in turbine units. It is pointed out that, despite the level of knowledge that has been achieved ...in regard to LFV, it still arises from time to time in power plant turbine units. Along with LFV caused by aero- and hydrodynamic excitation, LFV can also bear a subharmonic pattern. It is emphasized that the measures taken to remove LFV depend on the LFV occurrence origin. The article presents LFV occurrence and removal examples, including those relating to the use of honeycomb seals in high-pressure cylinders. With honeycomb seals, decreased sizes of channels and an increased channel component of overshroud forces caused by aerodynamic excitation are typically observed. It is pointed out that, in some cases that involve rotor rubbing against the stator, a multicomponent LFV with subharmonic and self-oscillation components is observed. It is shown that the regulatory documents do not contain criteria for estimating a multicomponent vibration in the low-frequency band. It is pointed out that multicomponent LFV can be a diagnostic indicator pointing to rubbing of the rotor against the babbit or seals. Recommendations on removing LFV of various origins are suggested. A diagnostic table that helps determine factors causing the LFV and that produces recommendations on increasing the turbine units operational reliability is given. It is stated for the first time that the turbine thrust bearing can behave as a source of oil excitation. It is also noted that the conditions under which a self-oscillation type LFV occur and its suppression methods should differ from the methods for suppressing self-excited LFV of a subharmonic nature.
Academician A. D. Sakharov’s idea concerning the emission of atomic flux from hot plasma (1951) inspired scientists of A. F. Ioffe Physico-Technical Institute to create the first in the world ...instrument called Neutral Atom Analyzer in 1960 and then in 1961 to use it successfully on the Alpha device (USSR, 1958–1963). Now the analysis of fluxes of fast atoms referred to as Neutral Particle Analysis (NPA) is one of the main diagnostic methods for the ion component of plasma in tokamaks, stellarators, and other devices. NPA provides a unique opportunity for studying the ion distribution functions, ion temperatures and hydrogen isotope ratio in hot plasma. Neutral particle analyzers developed at the Ioffe Institute were widely used in the USSR until the late 1970s, and afterwards began to be employed worldwide. Since then, most of the information on the ion distribution functions and the behavior of fast ions in fusion plasma is obtained from NPA measurements on all leading magnetic confinement fusion systems worldwide. The specialized complex of atom analyzers currently being created at the Ioffe Institute is included in the primary list of ITER diagnostics. The integration of this complex on ITER is expected to begin in 2025.
The possibilities of using active neutral particle diagnostics for measuring local ion temperatures and isotopic ratio of deuterium-tritium plasma at the tokamak with reactor technologies are ...considered. Options for positioning the neutral particle analyzer relative to the diagnostic injector are presented. The fluxes of deuterium and tritium atoms escaping out of plasma were simulated in a wide range of plasma densities and temperatures. It is shown that the neutral particle analyzer active diagnostics will make it possible to measure the plasma parameters mentioned with the spatial and time resolutions of ~14 cm and ~0.01–0.1 s, respectively.
The control of the deuterium–tritium (DT) fuel isotopic ratio has to ensure the best performance of the ITER thermonuclear fusion reactor. The diagnostic system described in this paper allows the ...measurement of this ratio analyzing the hydrogen isotope fluxes (performing neutral particle analysis (NPA)). The development and supply of the NPA diagnostics for ITER was delegated to the Russian Federation. The diagnostics is being developed at the Ioffe Institute. The system consists of two analyzers, viz., LENPA (Low Energy Neutral Particle Analyzer) with 10–200 keV energy range and HENPA (High Energy Neutral Particle Analyzer) with 0.1–4.0MeV energy range. Simultaneous operation of both analyzers in different energy ranges enables researchers to measure the DT fuel ratio both in the central burning plasma (thermonuclear burn zone) and at the edge as well. When developing the diagnostic complex, it was necessary to account for the impact of several factors: high levels of neutron and gamma radiation, the direct vacuum connection to the ITER vessel, implying high tritium containment, strict requirements on reliability of all units and mechanisms, and the limited space available for accommodation of the diagnostic hardware at the ITER tokamak. The paper describes the design of the diagnostic complex and the engineering solutions that make it possible to conduct measurements under tokamak reactor conditions. The proposed engineering solutions provide a safe—with respect to thermal and mechanical loads—common vacuum channel for hydrogen isotope atoms to pass to the analyzers; ensure efficient shielding of the analyzers from the ITER stray magnetic field (up to 1 kG); provide the remote control of the NPA diagnostic complex, in particular, connection/disconnection of the NPA vacuum beamline from the ITER vessel; meet the ITER radiation safety requirements; and ensure measurements of the fuel isotopic ratio under high levels of neutron and gamma radiation.
The plasmaphysical code is presented that makes it possible to simulate the energy distributions of atoms escaping from plasma of the toroidal facilities. The code includes calculations of the ...particle spatial distributions in the charge-exchange plasma target consisting of atoms and hydrogen-like impurity ions. The calculations of the charge-exchange target are performed in two ways: using the Monte Carlo method and solving the ionization balance equation in the coronal approximation. The code can be used to interpret the neutral particle analyzers (NPAs) data. In particular, with its help, the ion temperatures determined using the NPAs can be corrected. The code can be also used to estimate the atomic fluxes from plasma onto the first wall expected at the currently designed fusion facilities.
