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  • 1.
    Brunsell, Per
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Bergsåker, Henric
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Cecconello, Marco
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Drake, James Robert
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Gravestijn, Robert
    KTH, Tidigare Institutioner, Fysik.
    Hedqvist, Anders
    KTH, Tidigare Institutioner, Fysik.
    Malmberg, Jenny A.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Initial results from the rebuilt EXTRAP T2R RFP device2001Ingår i: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 43, nr 11, s. 1457-1470Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The EXTRAP T2R thin shell reversed-field pinch (RFP) device has recently resumed operation after a major rebuild including the replacement of the graphite armour with molybdenum limiters, a fourfold increase of the shell time constant, and the replacement of the helical coil used for the toroidal field with a conventional solenoid-type coil. Wall-conditioning using hydrogen glow discharge cleaning was instrumental for successful RFP operation. Carbon was permanently removed from the walls during the first week of operation. The initial results from RFP operation with relatively low plasma currents in the range I-p = 70-100 kA are reported. RFP discharges are sustained for more than three shell times. Significant improvements in plasma parameters are observed, compared to operation before the rebuild. There is a substantial reduction in the carbon impurity level. The electron density behaviour is more shot-to-shot reproducible. The typical density is n(e) = 0.5-1 x 10(19) m(-3). Monitors of H-alpha line radiation indicate that the plasma wall interaction is more toroidally symmetric and that there is less transient gas release from the wall. The minimum loop voltage is in the range V-t = 28-35 V, corresponding to a reduction by a factor of two to three compared to the value before the rebuild.

  • 2.
    Cecconello, Marco
    et al.
    KTH, Tidigare Institutioner                               , Alfvénlaboratoriet.
    Brzozowski, Jerzy
    KTH, Tidigare Institutioner                               , Alfvénlaboratoriet.
    Gravestijn, Robert
    KTH, Tidigare Institutioner                               , Fysik.
    Murari, A
    Total radiation losses studies in EXTRAP T2R2001Ingår i: Proceedings of the 28th European Physical Society Conference on Controlled Fusion and Plasma Physics, Madeira, 2001Konferensbidrag (Övrigt vetenskapligt)
  • 3.
    Cecconello, Marco
    et al.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Malmberg, Jenny A.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Spizzo, G.
    Chapman, B. E.
    Gravestjin, Robert M.
    KTH, Tidigare Institutioner, Fysik.
    Franz, P.
    Piovesan, P.
    Martin, P.
    Drake, James R.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Current profile modification experiments in EXTRAP T2R2004Ingår i: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 46, nr 1, s. 145-161Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    Pulsed poloidal current drive (PPCD) experiments have been conducted in the resistive shell EXTRAP T2R reversed-field pinch experiment. During the current profile modification phase, the fluctuation level of the m = 1 internally resonant tearing modes decreases, and the velocity of these modes increases. The m = 0 modes are not affected during PPCD, although termination occurs with a burst in the m = 0 amplitude. The PPCD phase is characterized by an increase in the central electron temperature (up to 380 eV) and in the soft x-ray signal. Spectroscopic observations confirm an increase in the central electron temperature. During PPCD, the plasma poloidal beta increases to 14%, and the estimated energy confinement time doubles, reaching 380 mus. The reduction in the fluctuation level and the corresponding increase in the energy confinement time are qualitatively consistent with a reduction in parallel transport along stochastic magnetic field lines.

  • 4.
    Cecconello, Marco
    et al.
    KTH, Tidigare Institutioner                               , Alfvénlaboratoriet.
    Malmberg, Jenny-Ann
    KTH, Tidigare Institutioner                               , Alfvénlaboratoriet.
    Spizzo, G
    Gravestijn, Robert
    KTH, Tidigare Institutioner                               , Fysik.
    Franz, P
    Martin, P
    Chapman, B
    Drake, James Robert
    KTH, Tidigare Institutioner                               , Alfvénlaboratoriet.
    Current profile control experiments in EXTRAP T2RManuskript (preprint) (Övrigt vetenskapligt)
  • 5.
    Gravestijn, Robert
    et al.
    KTH, Tidigare Institutioner, Fysik.
    Drake, James R.
    KTH, Tidigare Institutioner, Alfvénlaboratoriet.
    Hedqvist, Anders
    KTH, Tidigare Institutioner, Fysik.
    Rachlew, Elisabeth
    KTH, Tidigare Institutioner, Fysik.
    Comparison of confinement in resistive-shell reversed-field pinch devices with two different magnetic shell penetration times2004Ingår i: Plasma Physics and Controlled Fusion, ISSN 0741-3335, E-ISSN 1361-6587, Vol. 46, nr 1, s. 11-22Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    A loop voltage is required to sustain the reversed-field pinch (RFP) equilibrium. The configuration is characterized by redistribution of magnetic helicity but with the condition that the total helicity is maintained constant. The magnetic field shell penetration time, tau(s), has a critical role in the stability and performance of the RFP Confinement in the EXTRAP device has been studied with two values of tau(s), first (EXTRAP-T2) with tau(s), of the order of the typical relaxation cycle timescale and then (EXTRAP-T2R) with tau(s), much longer than the relaxation cycle timescale, but still much shorter than the pulse length. Plasma parameters show significant improvements in confinement in EXTRAP-T2R. The typical loop voltage required to sustain comparable electron poloidal beta values is a factor of 3 lower in the EXTRAP-T2R device. The improvement is attributed to reduced magnetic turbulence.

  • 6.
    Kuldkepp, Mattias
    et al.
    KTH, Tidigare Institutioner                               , Fysik.
    Gravestijn, Robert
    KTH, Tidigare Institutioner                               , Fysik.
    Cecconello, Marco
    KTH, Tidigare Institutioner                               , Alfvénlaboratoriet.
    Rachlew, E.lisabeth
    KTH, Tidigare Institutioner                               , Fysik.
    A Spectroscopic Method To Determine Changes In The Temperature Profile2003Ingår i: 30th EPS Conference on Contr. Fusion and Plasma Phys / [ed] R. Koch, S. Lebedev, Mulhouse: European Physical Society , 2003Konferensbidrag (Refereegranskat)
1 - 6 av 6
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