EFFECT OF THE POLOIDAL FIELD-COIL SYSTEM ON THE RAMP-UP SCENARIO WITHL H TRANSITION/

Improved confinement is indispensable for designing an attractive fusi on reactor, and an H-mode is one of the most prominent candidates for a fusion reactor plasma. It is experimentally clear that there exists a minimum heating power so as to access the H-mode confinement region. This threshold power has been investigated in many tokamak devices, a nd recently compiled with some plasma parameters. We simulated the pla sma ramp-up of the International Thermonuclear Experiment Reactor, Eng ineering Design Activity (ITER EDA) by using a global model simulation based on a power balance equation and a helium particle balance equat ion with L- to H- and H- to L-mode transitions. A new ramp-up method w as adopted, whereby the surface area of the plasma is varied during th e ramp-up phase to save the auxiliary heating power for ignition or fo r operating at an elevated density. This method reduces the heating po wer from 100 to 30 MW or increases the initial density from 0.5 x 10(2 0) to 0.9 x 10(20) m(-3) when the threshold power is in proportion to the plasma surface. The PF coil system is discussed with this ramp-up method and a plasma equilibrium code, and it is found that when the pl asma is ramped up from the outer-side of the torus such as in the ITER -EDA design, the power supply of 1.7 GW is sufficient for PF coil syst em, being independent of the winding method of the central solenoid (C S) coil. However the inner-side ramp-up, which is preferable for reduc ing L/H transition power, can be realized only when the flexibility of the CS coil is preserved with a pancake winding. (C) 1998 Elsevier Sc ience S.A. All rights reserved.