Docstoc

AT_ITER_CRONOS

Document Sample
AT_ITER_CRONOS Powered By Docstoc
					                                                                    Association
                                                                    Euratom-Cea




                             CRONOS simulations of

                                   ITER AT scenarios



        F. Imbeaux, J.F. Artaud, V. Basiuk, L.G. Eriksson, G. Giruzzi,
                 G. Huysmans, X. Litaudon, M. Schneider




ITPA CDBM group meeting, St Petersburg, October 2005                       1
                                               Outline           Association
                                                                 Euratom-Cea


• Main assumptions
• Hybrid scenario (presented at EPS 2005, joint with TP group)
        • Projections using various models / scalings
        • Current drive issues
• Steady-state scenario : demonstration of new feedback algorithm
• Database submission




ITPA CDBM group meeting, St Petersburg, October 2005                    2
                              Simulation parameters                      Association
                                                                         Euratom-Cea


• Hybrid (q95 = 4) scenarios
• Thermal transport + current diffusion
• Density prescribed (flat Zeff profile, ne flat or peaked)
        • fD = fT = 37.5 % (nD/ne), fHe = 2 %, fBe = 0.5 %, fC = 4.5 %
• 53 / 73 MW of additional power
        • 33 MW NBI @ 900 keV (SINBAD)
        • 20 MW ICRH (PION, 2nd harmonic of T, f = 55 MHz)
        • 0 / 20 MW of LHCD (DELPHINE, f = 5 GHz, n// = 2.0)




ITPA CDBM group meeting, St Petersburg, October 2005                            3
          Transport model based on 2-terms scaling                                              Association
                                                                                                Euratom-Cea

•    1D model with a profile dependence :                                q 2 Te,i
            c e,i  C. f ( s, ,  ExB ).Re,i (Ti , ne )                             Ptot
                                                                               ne
•    Most important point : C is a normalisation factor calculated at each time step so
     that the total energy content follows a global scaling law (IPB98(y,2) or DS03).
•    If Pin > PL-H, then a pedestal is added (fixed width). Constant c in the pedestal,
     pedestal energy content renormalised to a specific scaling law (2-terms approach,
     [Cordey et al NF 2003, 670])

             P                                             c
                tot
                                                                ccore


                      Wcore                                             link

                         Wped               Pcrit
                                                               cneo                      cped
           W0
                                                                                                 
                                     ped   max                                ped   max
ITPA CDBM group meeting, St Petersburg, October 2005                                                   4
                             Scaling expressions used                            Association
                                                                                 Euratom-Cea

•    Scaling set A (global IPB98 + core 96-L):
 E ,th, IPB98( y , 2)  0.0562I 0.93 B 0.15 P 0.69 n 0.41 M 0.19 R 1.97  0.58 a .78
                                                                                  0


       E ,th,96 L  0.0231I 0.96 B 0.03 P 0.73 n 0.40 M 0.20 R 1.83 0.06 a .64 0


•    Scaling set A’ with reduced pedestal (global IPB98 + enhanced 96-L), more
     consistent with official ITER reference H mode projections




•    Scaling set B (DS03 + pedestal scaling), no b degradation

           E,th,DS 03  0.028I 0.83B0.07 P0.55n0.49 M 0.14 R1.81a0.3 a .75
                                                                        0



              Eped,th  0.0209I 1.6 P 0.4 n 0.16 M 0.20 R1.03 0.26

                                                  HH = 1
•    One example using GLF23 for  < 0.8, with edge given by scaling set B
ITPA CDBM group meeting, St Petersburg, October 2005                                      5
              Hybrid scenario for ITER, for various
                        scalings / models                                 Association
                                                                          Euratom-Cea


•      Ip = 13 MA only slightly lower than reference scenario (15 MA) (not lose too
       much on energy confinement). Paux = 53 MW (NBI + ICRH)
•      Density peaking ne0/ne,ped = 1.5
•      Greenwald fraction = 0.92
                                                                        [CRONOS]
•      No enhancement w.r.t. scaling laws
    Model   Ip  ne 0 / ne (   0.95)   Q      bN
           (MA)
DS03        13          1.0             10    2.65
DS03        13          1.5             13    3.0
GLF23       13          1.5             13    3.0
IPB98,high 13           1.5             4     1.8
pedestal
IPB98, low  13          1.5             5      1.8
pedestal


    NB : the GLF23 result uses same
    pedestal condition as DS03
ITPA CDBM group meeting, St Petersburg, October 2005                            6
            Off-axis current drive needed for high bN
                     and extended duration ?                                    Association
                                                                                Euratom-Cea

                                                                             [CRONOS]
•      Sustaining high bN ~ 3 requires no or
       small q = 1 surface
•      In spite of reduced Ip, q = 1 finally
       occurs … and might trigger deleterious
       NTMs ?




DS03 scaling
   Ip n / n (   0.95)   Q           INI/IP PLH Time of
                                                                               LH
       e0 e                     bN
 (MA)                                  (%) (MW)    q=1                  
  11.3     1.0            4.9   2.2     45    0    490
  11.3     1.0            4.7   2.5     68   20    925
                                                           20 MW LHCD delay
   13      1.5            13    3.0     59    0    650
                                                           significantly the occurrence
   13      1.5            11    3.5     77   20   1040
                                                           of q = 1
ITPA CDBM group meeting, St Petersburg, October 2005                                   7
                      Conclusions for hybrid scenario
                                                                                        Association
                                                                                        Euratom-Cea

   •     The Hybrid scenario achieves Q = 10 at 13 MA (using DS03 scaling
         more favorable at high bN)
   •     If only 33 MW NBI and 20 MW ICRH, q = 1 appears at ~ 650 s

   •     Additional off-axis current drive might be needed to
         reduce the size of the q = 1 surface and delay its
         occurrence
   •     20 MW LHCD allow to delay the occurrence of the q = 1 surface until
         1040 s
   •     40 MW LHCD allows to get rid completely of q = 1 surface
   •     RWM stabilisation needed (bN > 4li)
           Ip      ne 0 / ne (     0.95 )
                                              Q   bN   No-wall   INI/IP PLH   Time of
          (MA)                                          limit     (%) (MW)      q=1
                                                        (4*li)
          13           1.5            13        3.0      2.7     59    0        650
          13           1.5            11        3.5      2.4     77    20      1040
          13           1.5           10.5      3.65      1.76    88    30      1470
ITPA CDBM 13
          group meeting, St Petersburg, October 2005
                       1.5            10        3.8      1.66    95    40                     8
                                                          Association
                                                          Euratom-Cea




                                  Steady-state scenario




ITPA CDBM group meeting, St Petersburg, October 2005             9
                                 Steady-state scenario                        Association
                                                                              Euratom-Cea


•      Multi feedback control on the steady-state scenario (9 MA) : aim at
       sustaining internal transport barrier without going beyond operational
       limits




•      A rather optimistic transport model is used :
         • 2-terms scaling model, using scaling set B (DS03)
                                                           q 2 Te,i
                  c e,i  C. f ( s, ).Re,i (Ti , ne )              Ptot
                                                              ne
         • Shear function to produce an ITB (improvement w.r.t. global
           scaling)
                  f ( s,  )  exp( ( s  3 / 5  0.5) 2 / 2)

ITPA CDBM group meeting, St Petersburg, October 2005                                 10
                   The « try, wait and see » feedback
                               algorithm                                    Association
                                                                            Euratom-Cea


•      Philosophy : control a given parameter without a priori knowledge of
       the physics of the system
•      Aim : maximize a given parameter (here : look for maximum Pfus)
•      Try : modify one of the actuators (here, PNBI, PICRH, ne) (add or
       substract a given incremental value)
•      Wait : let the plasma evolve during a given time scale (here : energy
       confinement time)
•      See : has the modification of the actuator fullfilled the aim ?
         • Yes  take another incremental step on the actuator
         • No  if it was the first variation of actuator, try variation in the
           opposite direction; otherwise, step back and skip to next actuator




ITPA CDBM group meeting, St Petersburg, October 2005                               11
                               Additional constraints                         Association
                                                                              Euratom-Cea


•      The « try, wait and see » feedback algorithm is used with additional
       constraints, corresponding to physical limits and/or the desired
       operation space
•      bN < 4.li : otherwise, reduce PNBI and PICRH
•      frmin  n/nG  frmax : otherwise :
         • n/nG < frmin : increase density
         • n/nG > frmax : increase PNBI and PICRH (will increase Ip)
•      Aim at Vloop = 0 :
         • Start at low Ip (550 kA, fixed), and let IP vary as an actuator of the
           « try, wait and see » feedback algorithm
         • As soon as full non-inductive current drive is reached (following the
           increase of the heating power), transition to constant edge flux  Ip
           is left floating and removed from the list of TWS actuators

ITPA CDBM group meeting, St Petersburg, October 2005                                 12
                                              Example                       Association
                                                                            Euratom-Cea


   •     Current, Te and Ti are simulated, as well as heat sources and current
         drive
   •     Heat transport model : 2-terms scaling model, using scaling set B
         (DS03), with shear function (s,)
   •     The line-averaged density is considered directly as an actuator (no
         particle transport calculation). The whole density profile keeps a
         constant shape with peaking factor = 1.2
            – Constraint on operational space : 0.55 < Greenwald fraction < 0.85
   •     Injected Power
            – PLH fixed at 20 MW, with a fixed profile (center = 0.5, width = 0.2
              and a fixed efficiency 2.5 1019 W/A/m² and scaling dependences)
            – PICRH between 10 to 20 MW
            – PNBI between 0 to 32 MW
   •     « try, wait and see » feedback algorithm aiming at maximize Pfus
ITPA CDBM group meeting, St Petersburg, October 2005                                13
                                              Currents                           Association
                                                                                 Euratom-Cea




                                      Transition to constant
                                      edge flux




                                                       Spikes are consequences
                                                       of the TWS actuators
                                                       dynamics




ITPA CDBM group meeting, St Petersburg, October 2005                                    14
                                       Heating powers                                     Association
                                                                                          Euratom-Cea




                                     Transition to constant              P
                                     edge flux
                                                                  PLH
                                           PICRH
                                                           PNBI

                                                            PNBI drops because of operational limit




                                                       time (s)
ITPA CDBM group meeting, St Petersburg, October 2005                                             15
                              Operational constraints                       Association
                                                                            Euratom-Cea


   •     Constraint bN < 4li prevents from increasing PNBI
   •     As li slowly increases, bN is also allowed to increase slowly (via the
         density)  slow increase of fusion power
                           4li

                              bN



                                     Transition to constant         P
                                     edge flux
                                                              PLH
                                           PICRH
                                                       PNBI

ITPA CDBM group meeting, St Petersburg, October 2005                               16
                 Bootstrap and Greenwald fractions                       Association
                                                                         Euratom-Cea


   •     Greenwald fraction increases slowly with bN limit, within the
         operational space : 0.55 < fGR < 0.85




                                                   time (s)
ITPA CDBM group meeting, St Petersburg, October 2005                            17
                                        ITB dynamics                     Association
                                                                         Euratom-Cea


   •     Until 400 s, the ITB shrinks owing to misalignment with bootstrap
         current
   •     To be continued …




ITPA CDBM group meeting, St Petersburg, October 2005                            18
               Conclusions for steady-state scenario                      Association
                                                                          Euratom-Cea

   •     « Try, wait and see » feedback algorithm allows to maximise fusion
         power while keeping the system in a safe operational domain
   •     Does not require a priori knowledge of the system.
   •     Very useful for transient phases of the steady-state scenario (owing to
         the non-linearities due to the ITB)
   •     Can be applied too much more subtle optimisation problems




ITPA CDBM group meeting, St Petersburg, October 2005                               19
                        Conclusions and perspectives                      Association
                                                                          Euratom-Cea

   •     The Hybrid scenario achieves Q = 10 at 13 MA (using DS03 scaling
         more favorable at high bN)
   •     If only 33 MW NBI and 20 MW ICRH, q = 1 appears at ~ 650 s

   •     Additional off-axis current drive might be needed to
         reduce the size of the q = 1 surface and delay its
         occurrence
   •     20 MW LHCD allow to delay the occurrence of the q = 1 surface until
         1040 s
   •     « Try, wait and see » feedback algorithm allows to maximise fusion
         power while keeping the system in a safe operational domain
   •     Very useful for transient phases of the steady-state scenario (owing to
         the non-linearities due to the ITB)
   •     CRONOS is now able to write ITER simulations in Profile DB 
         strategy to discuss
ITPA CDBM group meeting, St Petersburg, October 2005                               20

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:3
posted:12/4/2011
language:English
pages:20