Discharges analised pellet by mikeholy

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									               Particle transport and density
                 profile behaviour on JET
                                          L. Garzotti
                                with contributions from
            G. Corrigan, X. Garbet, D. Heading,
             T. T. C. Jones, P. Lang, P. Mantica,
       H. Nordman, V. Parail, B. Pégourié, G. Saibene,
        J. Spence, P. Strand, M. Valovič, J. Weiland
                  (work performed within the JET TF-T
                    particle transport working group)

9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   1
                        Motivation of the work
    • Study particle transport in different
      scenarios
    • Investigate the mechanisms leading to
      density profile peaking (in particular the
      existence of an anomalous pinch velocity)
    • Compare with predictions of existing
      theories


9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   2
                       Description of the work
    • Many scenarios analysed: L-modes, H
      modes both stationary, quasi-stationary
      and transient
    • JETTO transport code with different
      models employed: completely empirical,
      semi-empirical (mixed Bohm/gyro-Bohm)
      and physics based (Weiland’s ITG and TE
      modes)
    • Particular attention paid to the density
      profile peaking and possible effects of an
      anomalous pinch
9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   3
                            Discharges analysed
                          PNBI        PICRH
              Pulse      (MW)        (MW)        Mode         *                Notes


              51034         -           4          L         0.03               Only RF


              49030         1          4.5         L         0.15       HFS deep pellet injection


              55804        3.2         3.5         L         0.07       Shallow pellet standard q


              51084        7.6          5          L         0.03      Shallow pellet optimised q


              47744        1.2         10          H         0.05                Mainly RF


              52979       10.4          -          H         0.25      Slow puffing sawtoothing



9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002       Luca Garzotti    4
                         Model description (1)
                        mixed Bohm gyro-Bohm
    electron/ion thermal conductivity
                     e,i   Be ,i   gBe ,i
                                 cTe *1 2                       pe
                     Be   B      Lp q ;            L* e 
                                                       p             ;     Bi  2  Be
                                 eBt e                         a pe
                           cT                              M 1 2cTe1 2
                 gB   gB e L*1 *;
                               T                        
                                                         *
                           eBt e                             Zi eBt
    particle diffusivity
                                  e i
                    D  S (r )            ;       S (0)  1;      S (a)  0.3
                                  e  i
    pinch velocity (Ware pinch always present)

                   V  cT D T T                or     V  cq D q q

    (trapped electron modes, turbulence equipartition)
9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002        Luca Garzotti   5
                          Model description (2)
                               Weiland’s
    • ITG and trapped electron instabilities
    • growth rate for each point of the radial
      mesh
    • transport matrix obtained by quasi-linear
      theory combined with saturation level
      estimate
    • the presence of terms like T/T, n/n and
      B/B introduces off-diagonals elements in
      the transport matrix
9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   6
                                         L-mode

          51034 - Steady state plasma heated
                  by radio-frequency only

          49030 - Multiple deep pellet injection

          51084 - shallow pellet, optimised shear

          55804 - shallow pellet, non-optimised shear

9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   7
                 Shot 51034 only RF heating

Mixed Bohm/gyro-Bohm:
 V = Ware pinch
 V = cT D T/T cT = -0.25
 V = cq D q/q cq = 0.75

Weiland’s + off-diagonal
elements

Similar results are obtained
for shot 49030
(deep pellet fuelling).




9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   8
               Shot 55804 - standard shear
    Analytical D (~ 0.6 m2/s)
     V = Ware pinch
     V = -cT D T/T cT = 0.25
     V = cq D q/q     cq = 0.5

    Weiland’s + off-diagonal
    elements

    × Interferometer (KG1)
     Thomson scattering (LIDAR)

   Simulation of shot 51084
   (shallow pellet, optimised                                 JPN 55804
   shear) doesn’t need any pinch
   velocity.

9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   9
     Comments on the analysis of L-modes
                                                       •   Equivalence between: mixed Bohm
                                                           gyro-Bohm + anomalous pinch
                Mixed     Weiland’s
Pulse                                                           Weiland’s + off-diagonals
           Bohm/gyro-Bohm off-diagonal
                          elements                         elements
             cT       cq
                                                       •   Compatibility with pinch velocity:
51034        0.25        0.75             yes              V = -DcTT/T 0.125 < cT < 0.25
                                                           V = Dcqq/q      0.25 < cq < 0.75
49030       0.125        0.25             yes              (5 to 10 times larger than the Ware
                                                           pinch)
55804        0.25         0.5             yes
                                                       •   Off-diagonals elements in Weiland’s
51084          -            -             no               model provide the correct particle
                                                           convection


9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   10
                                         H-modes

       47744 - steady state sawtoothing plasma,
              mainly radio frequency heated

       52979 - steady state sawtoothing plasma,
              mainly NBI heated, slow puffing




9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   11
               Shot 47744 mainly RF heating
  Weiland’s:
   without off-diagonals elements
   with off-diagonals elements


  Mixed Bohm/gyro-Bohm:
   V = Ware pinch
   V = -cT D T/T cT = 0.125
   V = cq D q/q  cq = 0.125




9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   12
         Shot 52979 slow puffing sawteeth
  Weiland’s:
   without off-diagonals elements
   with off-diagonals elements


  Mixed Bohm/gyro-Bohm:
   V = Ware pinch
   V = -cT D T/T cT = 0.125
   V = cq D q/q  cq = 0.25




9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   13
    Comments on the analysis of H-modes
    • In the mixed Bohm/gyro-Bohm model, due to the fact that D
      is much lower than in L-mode, the effect of the pinch
      velocity is strongly reduced. Particle convection becomes
      compatible with neo-classical Ware convection. In some case
      this is in agreement with the experiment in some other it is
      not. Why?
    • A similar effect is observed in the Weiland’s model. The
      effect of the off-diagonal elements is not clear. Sometimes
      they are needed sometimes they aren’t. Why?
    • In general Weiland’s model seems to do better than the
      mixed Bohm/gyro-Bohm in the gradient zone (0.5 < r/a < 0.9)



9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   14
                                   Conclusions (1)
    • Particle transport has been analysed in different
      scenarios.
    • The JETTO code has been employed with
      analytical, semi-empirical and physics based
      transport model.
    • The semi-empirical mixed Bohm gyro-Bohm works
      well in L-mode.
    • The physics based Weiland’s model is as good as
      mixed Bohm gyro-Bohm and gives a better
      reproduction of the gradient zone in H-mode
      (although the role of the off-diagonal elements is
      still not clear)
9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   15
                                   Conclusions (2)
    • Convective velocity
       – L-mode simulations are compatible with an
         anomalous pinch velocity 5 to 10 times greater
         than the neo-classical Ware pinch. (Reasonably
         well established)
       – Dependence on q-profile detected in shallow
         pellet simulations
       – H-mode simulations are less clear: sometimes
         the expected lower convection (comparable
         with the Ware pinch) is in agreement with
         experiments sometimes it is not

9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   16
                  Shot 49030 pellet injection




     Mixed Bohm/gyro-Bohm:
        V = Ware pinch
        V = -cT D T/T cT = 0.125
        V = cq D q/q  cq = 0.25
     Weiland’s

9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   17
              Shot 51084 - optimised shear
• Simulation with analytical
  D and without anomalous
  pinch
• D (~ 0.3 m2/s) fitted to
  have a density profile
  evolution compatible:
     – with the temperature pulse
       propagation
     – with the integral line
       density measured by the                                                 JPN 51034
       interferometers chords


9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002     Luca Garzotti   18
       Shot 52961 slow puffing no sawteeth




   Mixed Bohm/gyro-Bohm:
    V = Ware pinch
    V = -cT D T/T cT = 0.125
    V = cq D q/q  cq = 0.25
   Weiland’s
9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   19
          Partial conclusions for cold pulses

    • Optimised shear. No anomalous pinch.
         (As in H-mode).
    • Standard shear. Anomalous pinch (5-10
      times the Ware pinch).
         (As in L-mode).



9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   20
                         Model description (1)
                        mixed Bohm gyro-Bohm
    electron/ion thermal conductivity




    particle diffusivity
                                  e i
                    D  S (r )            ;    S (0)  1;     S (a)  0.3
                                  e  i
    pinch velocity (Ware pinch always present)

                   V  cT D T T             or     V  cq D q q

    (trapped electron modes, turbulence equipartition)
9th EU-US Transport Task Force Workshop, Córdoba, Spain, 9-12 September 2002   Luca Garzotti   21

								
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