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	156: Controlling the timing and evolution of L-H and H-L with 3D fields
Name:	Devon Battaglia dbattagl@pppl.gov	Affiliation:	Princeton Plasma Physics Laboratory
Research Area:	Plasma Control	Presentation time:	Requested
Co-Author(s):	--	ITPA Joint Experiment :	No
Description:	Superconducting tokamaks, such as ITER, will benefit from a controlled and slow transition in and out of H mode. Maintaining good plasma control through the H-L transition is of particular concern for ITER. This experiment would examine the effectiveness of using 3D fields to trigger L-H and H-L transitions and slowing the pedestal pressure evolution to minimize dV/dt requirements on PF coils ("soft landing").	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	1. Establish a discharge where L-H is triggered by a small increase in NBI and H-L is triggered by a decrease in NBI. This establishes baseline pedestal evolution associated with L-H and H-L. 2a. Program the n=3 to turn on right after L-H transition and then ramp to zero. Does this slow the pedestal pressure evolution? How does the evolution depend on n=3 amplitude and ramp rate to zero? 2b. Remove step down in NBI and try to trigger H-L with n=3. How does the timing and pedestal evolution following H-L change with n=3 amplitude? 3a. Try triggering L-H by applying n=3 during L-mode, increasing NBI, then notching out n=3. How long does the notch out need to be? 3b. If H-L timing is reproducible, trying reducing or removing n=3 soon after H-L transition to slow pedestal collapse.
Background:	H-L back transitions are observed on DIII-D with n=3. May be due to collapse of pedestal gradients and/or slowing the rotation. ITER will have internal non-axisymmetric coils that have faster time response than the PF coils.
Resource Requirements:	SPAs on I-coils
Diagnostic Requirements:	Profile diagnostics. L-H edge diagnostics.
Analysis Requirements:	--
Other Requirements:	The middle of the pulse (H-mode) is available for other experiments (synergistic with ELM control). Also gets good data for 3D effect on L-H, H-L.