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Title	164: Produce fNI = 1 discharges at q_min near 1.5 using off-axis injection and a model guided approach
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:	Focus on producing discharges which robustly have fNI = 1 with good current profile alignment. Run these discharges for as long as possible in order to allow good nvloop analysis of the electric field profile. Make use of a new empirical model that extrapolates from the existing database of steady-state scenario discharges in order to predict a self consistent set of parameters with fNI = 1. Use the long pulse discharge 147634 as the starting point, but operate at higher betaN and higher input power. Use the fNI = 1 discharge 133103 as a comparison point.	ITER IO Urgent Research Task :	No
Experimental Approach/Plan:	Most of the approach is described in the description paragraph. The starting point would be discharge 147634. Scans in beam power (to raise betaN) and Bt (at constant betaN, thus increasing beam power) would be used to find the fNI = 1 operating point that is most tearing mode stable. The results from the scan would provide additional data to contribute to our understanding of the scaling of fNI = 1 operating regimes. 147634 had q_min = 1.5 where confinement is good enough to perform this experiment with the available beam power and off-axis injection.
Background:	Recently, there has been a better understanding of the necessity to choose a self-consistent set of parameters in order to obtain fNI = fBS + fCD = 1. In particular, many of the steady-state scenario experiments that have been run in the past have been run under conditions that require too little beam power (e.g. good confinement or low betaN target). As a result, the beam-driven current fraction was not high enough to reach fully noninductive conditions. Discharges in fall 2011 were operated at betaN = 3.5 with relatively low fNI = 0.7 and relatively low beam power (in order to achieve a long pulse). These discharges should be scaled up, either in betaN or Bt in order to increase the necessary beam power and reach fNI = 1 (although at shorter pulse length).
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