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Polarimetry
Published in Toru Yoshizawa, Handbook of Optical Metrology, 2015
In a Tokamak, a relatively constant electric current in the toroidal coils creates a relatively constant toroidal magnetic field. The moving ions and electrons in the plasma (toroidal plasma current) create a poloidal magnetic field. The total magnetic field at any location inside the plasma is the combination of the toroidal and poloidal fields as shown in Figure 25.5. The so-called magnetic field pitch angle is defined as γp=tan−1(BpBT)
Fusion Reactor Materials
Published in C. K. Gupta, Materials in Nuclear Energy Applications, 1989
The bases for plasma confinement magnetically are shown schematically in Figure 3. The core of the system is the doughnut-shaped vacuum vessel, the torus, in which the introduced gas is heated to form a plasma by passing a large electric current through it. The metal-walled torus is wrapped with a number of equally spaced D-shaped field coils to produce a toroidal magnetic field in the direction shown by the figure. The primary coils induce a current in the plasma to generate a poloidal field. The combination of toroidal and poloidal fields is a helical or spiral magnetic field which provides the cage that prevents the hot plasma from hitting the walls of the vacuum vessel. This complex system of magnetic fields is called a TOKAMAK. In typical systems, the toroidal field has a strength about ten times greater than that of the poloidal field. Since the TOKAMAK is a low-beta device, the fusion energy per unit volume is low, and the TOKAMAK sizes must be relatively large. Beta can be increased somewhat by fattening the doughnut (i.e., reducing the ratio of the major radius to the minor radius) and by using a noncircular plasma cross section. Overall, it is necessary to balance decreased system size (increased beta) against confinement stability (favored by low beta).
Transport in Electric and Magnetic Fields and Particle Detectors
Published in Robert E. Robson, Ronald D. White, Malte Hildebrandt, Fundamentals of Charged Particle Transport in Gases and Condensed Matter, 2017
Robert E. Robson, Ronald D. White, Malte Hildebrandt
In all the applications mentioned above, transport processes are significantly influenced by short-range particle–neutral collisions. Magnetic fields are also fundamental to the operation of hot, fully ionized plasmas in toroidal fusion devices. Here, the constituent electrons and ions interact through the long-range Coulomb force and, since the Rutherford cross section Equation 4.12 decreases rapidly with energy, collisions are not so important. Thus, the early chapters of plasma physics texts are typically devoted to studying the collisionless motion of a single particle in electric and magnetic fields. Even in the present context, where collisions play a more significant role, it is instructive to say a few words about the single particle picture.
A magneto-hydrodynamic analysis of liquid metal flows in the conducting and insulating wall ducts using a finite element tool
Published in International Journal of Ambient Energy, 2023
The fusion reactor is a toroidal-shaped device, in which a plasma ring is confined by twisting the magnetic fields using vacuum vessels (Song et al. 2014a). A plasma is made up of charged particles and confinement of plasma within the walls of the vacuum vessel is achieved using a large magnetic field (Walker et al. 2020). Poloidal and toroidal coils are used to confine the plasma as it follows the magnetic flux lines. Immediately behind the first wall of the fusion reactor, blanket modules are provided through which coolant is passed (Nygren 1981), (Pironti and Walker 2005), (Sykes et al. 2014). Blanket modules have used square straight channels to flow electrically conducting fluid in it. The MHD pressure drop is a severe problem in the fusion reactor and the problems arising from the MHD effects can be interesting for the researchers. Therefore, the study of the MHD analysis in the coupled field environment is very interesting among researchers. In this paper, an extensive analysis has been carried out to reduce the MHD effect in the square channels used for the fusion reactor. A finite element analysis of MHD rotational flow of non-fluid was investigated by (Ali et al. 2020). In (Umavathi et al. 2005), the turbulent two-fluid flow and heat transfer in a horizontal channel were examined. The computational methods have been studied by increasing the field intensity with a significant influence on the fluid flow (Adesanya et al. 2015).
Confirmation of the Absence of Contact Between Edge Boundary Plasma and Inboard First Wall in LHD Discharges Based on Radial Profile Measurement of Hβ Line Emissions
Published in Fusion Science and Technology, 2022
Yasuko Kawamoto, Shigeru Morita, Gakushi Kawamura, Motoshi Goto, Tetsutarou Oishi, Tomoko Kawate, Masahiro Kobayashi, Mamoru Shoji
The LHD is a superconducting helical device with a set of helical coils (toroidally continuous winding) and three sets of poloidal coils. These coils are illustrated with the LHD toroidal plasma in Fig. 1. The cross-sectional center of the vacuum vessel and helical coils is positioned at R = 3.9 m. Magnetic surfaces can be created basically only by the helical coils. The plasma cross section is then elliptical. The poloidal coils are used for change of shape in the plasma cross section, control of the plasma axis position, and cancelation of the stray magnetic field. The helical magnetic field Bh, up to 3 T, is produced by the helical coil. Toroidal magnetic field Bt is approximately the same as Bh.