Heavy ion beam probing—diagnostics to study potential and turbulence in toroidal plasmas. (10th March 2017)

• Record Type: Journal Article
• Authors: Melnikov, A.V.; Krupnik, L.I.; Eliseev, L.G.; Barcala, J.M.; Bravo, A.; Chmyga, A.A.; Deshko, G.N.; Drabinskij, M.A.; Hidalgo, C.; Khabanov, P.O.; Khrebtov, S.M.; Kharchev, N.K.; Komarov, A.D.; Kozachek, A.S.; Lopez, J.; Lysenko, S.E.; Martin, G.; Molinero, A.; de Pablos, J.L.; Soleto, A.; Ufimtsev, M.V.; Zenin, V.N.; Zhezhera, A.I.
• Other Names: collab.; collab.
• Is Part Of: Nuclear fusion. Volume 57:Number 7(2017:Jul.)
• Publication Date: 2017-03-10
• Subjects: heavy ion beam probe -- diagnostics -- turbulence; Nuclear fusion -- Periodicals; 621.48405
• DOI: 10.1088/1741-4326/aa5382
• Languages: English
• ISSNs: 0029-5515

Abstract

Abstract: Heavy ion beam probing (HIBP) is a unique diagnostics to study the core plasma potential and turbulence. Advanced HIBPs operate in the T-10 tokamak and TJ-II flexible heliac with fine focused (<1 cm) and intense (100 µ A) beams. They provide measurements in the wide density interval n ¯ e = (0.3–5) × 10 19 m −3, in a wide range of Ohmic and electron cyclotron resonance heated (ECRH) discharges with various currents at T-10, and in the wide range of magnetic configurations with ECR and neutral beam injection (NBI) heating at TJ-II. Time evolution of the radial profiles and/or local values of plasma parameters from high field side (HFS) to low field side (LFS), −1 < ρ < 1, is observed in TJ-II by 125 keV Cs + ions in a single shot, while LFS (+0.2 < ρ < 1) is observed in T-10 by 300 keV Tl + ions. Multi-slit energy analyzers provide simultaneously data on the plasma potential ϕ (by the beam extra energy), plasma density n e (by the beam current), poloidal magnetic field B pol (by the beam toroidal shift), poloidal electric filed E pol that allows one to derive the electrostatic turbulent particle flux ΓE×B . The cross-phase of density oscillations produces the phase velocity of their poloidal propagation or rotation; also it gives the poloidal mode number. Dual HIBP, consisting of two identical HIBPs located ¼ torus apart provide the long-range correlations of core plasma parameters. Low-noise high-gain electronics allows us to study broadband turbulence and quasi-coherent modes like geodesic acoustic modes and Alfvén eigenmodes.