Major Radius Compression Research Articles

Radial Compression to Transiently Achieve Higher Beta Poloidal in a Tokamak

An increase in the magnetic strength of the vertical field will, in general, compress and heat plasmas, which thus allows high temperature, high density, and high beta to be reached. In this paper, according to the scaling laws for the magnetic compression, the scaling range of both the major-radius compression and the minor-radius compression is figured out. Then, the comparison between the major-radius compression and the minor-radius compression is carried out. It demonstrates that the minor-radius compression can obtain higher ${\beta }_{p}$ of plasma. Consequently, we try to significantly enhance discharge parameters by the minor-radius compression by inserting the sets of the vertical-field coils in the experimental advanced superconducting tokamak (EAST) vacuum chamber. Afterward, the minor-radius compression based on EAST shot #34128 is deduced with ${C}_{a}=1.5$ and ${C}_{R}=0.925$ , which increases ${\beta }_{p}$ by 76.19%. It notes that the minor-radius compression is a promising way to effectively improve ${\beta }_{p}$ in a tokamak. Finally, the preliminary design of the minor-radius compression, which includes the control system, the in-vessel vertical-field coils, and its fast-control power supply, is described.

Kinetic theory of plasma adiabatic major radius compression in tokamaks

In order to understand the individual charged particle behavior as well as plasma macroparameters (temperature, density, etc.) during the adiabatic major radius compression (R-compression) in a tokamak, a kinetic approach is used. The perpendicular electric field from the Ohm’s law at zero resistivity is made use of in order to describe particle motion during the R-compression. Expressions for both passing and trapped particle energy and pitch angle change are derived for a plasma with high aspect ratio and circular magnetic surfaces. The particle behavior near the passing trapped boundary during the compression is studied to simulate the compression-induced collisional losses of alpha particles. Qualitative agreement is obtained with the alphas loss measurements in deuterium-tritium (D-T) experiments in the Tokamak Fusion Test Reactor (TFTR) [World Survey of Activities in Controlled Fusion Research [Nucl. Fusion special supplement (1991)] (International Atomic Energy Agency, Vienna, 1991)]. The plasma macroparameters evolution at the R-compression is calculated by solving the gyroaveraged drift kinetic equation.

Measurements of the toroidal plasma rotation velocity in TFTR major-radius compression experiments with auxiliary neutral beam heating

The time history of the central toroidal plasma rotation velocity in Tokamak Fusion Test Reactor (TFTR) experiments [Phys. Rev. Lett. 55, 2587 (1985)] with auxiliary heating by neutral deuterium beam injection and major-radius compression has been measured from the Doppler shift of the emitted Ti XXI Kα line radiation. The experiments were conducted for neutral beam powers in the range 2.1–3.8 MW and line-averaged densities in the range 1.8–3.0×1019 m−2. The observed rotation velocity increase during compression is consistent with theoretical estimates.

Electron Energy Increase of a REB-Ring by Major Radius Compression

Measurement of X-ray bremsstrahlung emitted from REB rings formed in SPAC-Vl toroidal device elucidated that major radius compression of the ring raises energies of the ring electrons. At the compression ratio of 2.0, the ring current rose from 24 kA to 50 kA. The highest energy of electrons that was estimated by hard X-ray spectrum measurement increased from ∼1 MeV to ∼2 MeV. The energy distribution of REB was broadly spread. During the compression, the current of ring I R and the major radius R are governed by the relation I R · R =const. Some discussions on this relation are given in which energy spread of the beam electrons and the change in the magnetic flux enclosed by the ring are taken into consideration.

Conceptual Design of a Movingring Reactor: Karin-I

A 650-MW(electric) deuterium-tritium fusion reactor, KARIN-I, has ten moving plasma rings, which are produced by relativistic electron beam injection, heated by a major radius compression, and transported into a linear cylindrical burning section by annularly flowing liquid lithium outside the silicon carbide first wall. The liquid lithium not only stabilizes the tilting motion of the rings but also works as the tritium breeder and the main coolant. Energy from the ash-accumulated rings is efficiently recovered at the exit during the major radius expansion. The linear alignment of reactor components ensures easy assembly and disassembly, and also provides for easy maintenance. These features of the reactor result in a net electric output power of 650 MW(electric) with overall plant efficiency of 30%.

Acceleration of beam ions during major-radius compression in the tokamak fusion test reactor.

Tangentially coinjected deuterium beam ions were accelerated from 82 up to 150 keV during a major-radius compression experiment in the tokamak fusion test reactor. The ion energy spectra and the variation in fusion yield were in good agreement with Fokker-Planck code simulations. In addition, the plasma rotation velocity was observed to rise during compression.Received 26 July 1985DOI:https://doi.org/10.1103/PhysRevLett.55.2587©1985 American Physical Society

The ATC tokamak

The Adiabatic Toroidal Compressor (ATC) successfully demonstrated major-radius compression of Ohmic and auxiliary heated tokamak plasmas. Plasma densities well above 1014 cm−3 were reached, together with central ion and electron temperatures above 1 keV.

The investigation of adiabatic compression in Tokamaks

The results of magnetic compression investigation in tokamaks are discussed. The latest experiments on minor and major radius compression on Tuman-3 tokamak are described in more detail.

Adiabatic equilibrium calculations of major-radius compression in a tokamak

Equilibrium calculations which conserve adiabatic quantities (magnetic fluxes, particle number and entropy) during major-radius compression in a tokamak have been made by using a flux-surface-averaged description of the plasma behaviour in order to solve the two-dimensional plasma equilibrium equation. Boundary conditions are chosen to avoid skin current formation during compression, and the changes of the Ohmic-heating flux required to maintain this condition are determined. Comparisons are made between the plasma parameter variations determined from these computations and the scaling behaviour predicted by a large-aspect-ratio approximation to the adiabatic constraints.

Neutral-beam requirements for compression-boosted ignited tokamak plasmas

Neutral-beam energies of 200 to 500-keV D0 may be required to ensure adequate penetration into the centre of ignition-sized tokamak plasmas. However, the beam energy requirement can be reduced by using a start-up scenario in which the final plasma is formed by major-radius compression of a beam-heated plasma whose density-radius product, na, is determined by satisfactory neutral-beam penetration. “Compression boosting” is attractive only for plasmas in which nτE increases with na, because a major-radius compression C increases na by C3/2. This paper analyses the dependence on C of beam energy and beam power for plasmas which obey “empirical scaling laws” of the type nτE∝(na)2. The dependences on C of stored magnetic energy and TF-coil power dissipation are also determined. It is found that a compression ratio of 1.5 to attain the ignited plasma permits adequate penetration by ·150-keV D0 beams.

Major radius compression in a large Tokamak

In the presence of certain plasma loss mechanisms, major radius compression of a plasma of reduced size may give higher temperatures than those obtainable in full aperture Tokamak operation. The authors give compression scaling laws of temperature for various loss mechanisms and identify situations where major radius compression may be usefully applied.

Adiabatic Compression of Plasma in Trapped-Particle-Free Stellarator

The combination of the toroidal h.f. electric field and the stellarators with stellarator winding located on the major radius side is exhibited to be a possible stationary fusion reactor. The fusion ignition condition is attainable by the major radius compression of toroidal plasma.

Effect of Detrapping on Trapped-Particle Instabilities in Tokamaks

The effect of weak detrapping of magnetically trapped particles on low-frequency, trapped-particle modes in sheared magnetic configurations is considered; such detrapping can be imposed by oscillation of the magnetic configuration, e.g., by major-radius compression. Detrapping has a dynamical effect analogous to collisions. In particular, it is shown that trapped-particle instabilities in tokamaks can be dynamically stabilized by weak oscillation of the aspect ratio with frequency Ω and relative amplitude λ, thus imitating ion collisions with ion detrapping. In the intermediate regime of the collisional trappedparticle instability, where νi/e≪ω∼ε1/2ω*≪νe/ε, stabilization is found if ω≪Ω<λνe/ε, where ε = r/R. The stabilizing effect (surprisingly of order λ) arises from oscillation of the field strength near its maximum, where detrapping occurs. These results are for simple models of the geometry.