DIII-D RESEARCH OPPORTUNITIES FORUM FOR THE 2013 EXPERIMENTAL CAMPAIGN Review | Direct submission with log-in | Request submission without log-in
Print this page

Print this page
Title	178: Beta limit and bootstrap current fraction in ITER steady-state scenario discharges
Name:	John Ferron ferron@fusion.gat.com	Affiliation:	General Atomics
Research Area:	Steady State Heating and Current Drive	Presentation time:	Not requested
Co-Author(s):		ITPA Joint Experiment :	No
Description:	Study the performance of steady-state scenario discharges in the ITER discharge shape in order to establish the physics basis and optimum operating scenario for the ITER steady-state mission. Determine the beta limit and bootstrap current density as a function of q_min. Make comparisons between performance in the single null ITER shape and the double null DIII-D AT shape in order to establish the physics basis for the evolution between ITER and DEMO and for optimization of steady-state scenario discharges in DIII-D. The portion of this work would be relevant to the IOS ITPA group. Increase the plasma current over what has been used previously to push q95 down to 5 in order to reach conditions that project to Q = 5 in ITER. Test both NCS and weak shear q profiles in order to determine how to achieve fNI = 1 at moderate betaN.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Reproduce the fNI = 1 discharges produced in 2008 and vary q_min, the central shear, beta and density gradient in order to test the effect on the achieved bootstrap current and beta limit. Use the ECCD to better advantage to avoid 2/1 tearing modes in order to either raise the achievable betaN or establish the maximum betaN value as determined by ideal stability. Do this in a discharge shape that better matches the ITER scaled shape in the outer, lower squareness. Using shape adjustments, modify the density by taking advantage of the divertor cryopump. As conditions are varied, test the effect of the outside gap on the betaN limit. Make use of the off-axis beams to improve the capability to reach elevated values of q_min.
Background:	During 2008 the first attempts were made at making a fNI = 1 discharge in a scaled ITER shape in DIII-D. FNI = 1 was successfully obtained at relatively low betaN = 3.1 with fBS = 0.7. The beta limiting instability was a 2/1 NTM and the outside gap seemed to have a moderate effect on the achievable beta. This contrasts with the double null shape steady-state scenario discharges which had less density gradient and correspondingly less bootstrap current but which have been operated at betaN = 3.7 without a 2/1 NTM. The discharge shape that was used doesn't quite match the intended ITER scaled shape.
Resource Requirements:
Diagnostic Requirements:
Analysis Requirements:
Other Requirements: