DEVELOPMENT IN THE DIII-D TOKAMAK OF HYBRID OPERATION SCENARIOS FOR BURNING PLASMA EXPERIMENTS.

Download or read book DEVELOPMENT IN THE DIII-D TOKAMAK OF HYBRID OPERATION SCENARIOS FOR BURNING PLASMA EXPERIMENTS. written by and published by . This book was released on 2004 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: OAK-B135 The basic parameters of proposed burning plasma experiments such as ITER and FIRE have been chosen based on analysis of multi-machine databases of confinement, stability, and divertor operation. given these specifications, it is of interest to run discharges in present-day machines such as DIII-D to verify the design basis and evaluate the margin available to achieve the mission goals. it is especially important to operate discharges which are stationary with respect to the current relaxation time scale ([tau][sub R]) since it is well-known that higher performance can be achieved transiently. Attention has been focused on validating the baseline scenario for diverted machines--ELMing H-mode discharges with q[sub 95]= 3 with sawteeth. However, there is also interest in the ITER program to assess the feasibility of operating the tokamak in a mode to maximize the neutron fluence for the purpose of testing the design of various components critical to the nuclear fuel cycle and energy conversion systems in a fusion power plant. It was originally envisioned that these discharges would be intermediate between an inductive burn (baseline) scenario and a fully noninductive (steady state) scenario; therefore, this type of discharge has become known as a hybrid scenario. In the course of investigating these hybrid scenarios in DIII-D, two key results have been obtained. First, stationary discharges with q[sub 95]> 4 have been obtained which project to Q[sub fus][approx] 10 in ITER. The projected duration of these discharges in ITER when using the full inductive flux capability is> 4000 s. (The significant engineering issues of site heat capacity, activation, and tritium consumption are beyond the scope of this work). Second, utilizing the same plasma initiation techniques as developed for the hybrid scenario, discharges at q[sub 95]= 3.2 project to near ignition in ITER, even with reduced parameters. This indicates the ITER design has significant performance margin and possesses the physics capability to carry out an extensive nuclear testing program. These same q[sub 95]= 3.2 discharges project to Q[sub fus]> 5 in FIRE, even with pessimistic confinement scalings.