Electron Bernstein wave assisted plasma current start-up in MAST

Shevchenko, V. F.; O’Brien, M.R.; Taylor, D.; Saveliev, A. N.; Team, Mast

doi:10.1088/0029-5515/50/2/022004

Cited by 94 publications

(94 citation statements)

References 14 publications

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“…Such plasmas are similar in nature to those also observed in LATE [5], QUEST [6], and MAST [7]. Calculation of such equilibrium will help understand the electron and ion fluid force balance properties in these plasmas, and provide an equilibrium basis for further studies of particle orbits, plasma stability, transport, current drive, boundary, and the plasma-wall interface.…”

Section: Introductionmentioning

confidence: 63%

Two-Fluid Equilibrium Considerations of Te/Ti ≫ 1, Collisionless ST Plasmas Sustained by RF Electron Heating

Peng

Ishida²,

Takase

et al. 2014

Plasma and Fusion Research

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A solution of two-fluid (electron and ion), axisymmetric equilibrium is presented that approximates solenoidfree plasmas sustained only by RF electron heating that are recently studied in TST-2, LATE, QUEST. These plasmas indicate presence of orbit-confined energetic electrons carrying substantial toroidal current outside the last closed flux surface (LCFS); T e /T i 1 and low collisionality at modest densities within LCFS; and likely a positive plasma potential relative to the conductive vacuum vessel. A system of nonlinear second-order partial differential and algebraic equations constraining six functionals of poloidal magnetic flux or canonical angular momentum are solved. An example plasma measured in TST-2 is used to guide, by trial and error, the selection of these functionals to find appropriate solutions, while assuming peaked plasma profiles and 60% toroidal current within the LCFS. The numerical equilibrium obtained indicates a substantial ion toroidal flow and electrostatic potential so that the ion ∇p i , centrifugal, and electrostatic forces of nearly equal magnitudes combine to balance the J i × B force, differently from the massless electron fluid that satisfies ∇p e = J e × B. The calculated properties suggest additional measurements needed to refine the choices of the functional forms and improve the two-fluid equilibrium fit to such plasmas.

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Section: Introductionmentioning

confidence: 63%

Two-Fluid Equilibrium Considerations of Te/Ti ≫ 1, Collisionless ST Plasmas Sustained by RF Electron Heating

Peng

Ishida²,

Takase

et al. 2014

Plasma and Fusion Research

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show abstract

“…It was designed to explore the operational regime for spherical tokamaks with high toroidal beta plasmas in the limit of A → 1 10 . EBW heating can assist during the startup phase of Pegasus as it has been done in MAST 17 . The plasma core can be heated-up and EBW heating can provide a tool to control the current profile.…”

Section: A General Propertiesmentioning

confidence: 99%

Full-wave modeling of the O–X mode conversion in the Pegasus toroidal experiment

et al. 2011

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The ordinary-extraordinary (O-X) mode conversion is modeled with the aid of a 2D full-wave code in the Pegasus Toroidal Experiment as a function of the launch angles. It is shown how the shape of the plasma density profile in front of the antenna can significantly influence the mode conversion efficiency and, thus, the generation of electron Bernstein waves (EBW). It is therefore desirable to control the density profile in front of the antenna for successful operation of an EBW heating and current drive system. On the other hand, the conversion efficiency is shown to be resilient to vertical displacements of the plasma as large as ±10 cm.

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“…On the other hand, establishment of an efficient and reliable non-inductive plasma start-up method is an active area of research [4][5][6][7][8][9][10][11]. Since neutral beam current drive requires finite plasma current for confinement of fast ions, plasma current ramp-up from no current needs to be performed by other means such as coaxial helicity injection [4] or radio frequency (RF) waves [5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Fully non-inductive plasma start-up with lower-hybrid waves using the outboard-launch and top-launch antennas on the TST-2 spherical tokamak

et al. 2017

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Abstract. Removal of the central solenoid is essential to realize an economical spherical tokamak fusion reactor, but non-inductive plasma start-up is a challenge. On the TST-2 spherical tokamak, non-inductive plasma start-up using lower-hybrid (LH) waves has been investigated. Using the capacitively-coupled combline (CCC) antenna installed at the outboard midplane, fully non-inductive plasma current ramp-up up to a quarter of that of the typical Ohmic discharges has been achieved. Although it was desirable to keep the density low during the plasma current ramp-up to avoid the LH density limit, it was recognized that there was a maximum current density that could be carried by a given electron density. Since the density needed to increase as the plasma current was ramped-up, the achievable plasma current was limited by the maximum operational toroidal field of TST-2. The top-launch CCC antenna was installed to access higher density with up-shift of the parallel index of refraction. Numerical analysis of LH current drive with the outboard-launch and top-launch antennas was performed and the results were qualitatively consistent with the experimental observations.

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Electron Bernstein wave assisted plasma current start-up in MAST

Cited by 94 publications

References 14 publications

Two-Fluid Equilibrium Considerations of <i>T</i><sub>e</sub>/<i>T</i><sub>i </sub>≫ 1, Collisionless ST Plasmas Sustained by RF Electron Heating

Two-Fluid Equilibrium Considerations of <i>T</i><sub>e</sub>/<i>T</i><sub>i </sub>≫ 1, Collisionless ST Plasmas Sustained by RF Electron Heating

Full-wave modeling of the O–X mode conversion in the Pegasus toroidal experiment

Fully non-inductive plasma start-up with lower-hybrid waves using the outboard-launch and top-launch antennas on the TST-2 spherical tokamak

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