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Research Needs for Magnetic Fusion Energy Sciences - US Burning ...

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The Us d-t facility, studied in 1b, would per<strong>for</strong>m focused research on creating high-per<strong>for</strong>mance<br />

fusion plasmas in the strongly coupled regime to provide the core plasma physics approaching<br />

demo conditions. The coupled plasma transport and mhd at high pressure, high density, and<br />

high self-driven current, exceeding that possible on iteR, would be explored. The heating and<br />

current drive sources would be used to establish these plasmas, and new and more effective control<br />

tools would be sought and developed. The demo parameters would be pursued simultaneously<br />

to the extent possible. self-consistent core/scrape-off layer/divertor plasmas would be established,<br />

potentially at higher flux densities than those in iteR, and the supporting elements of<br />

fueling and pumping <strong>for</strong> particle control, power handling, multi-level feedback control with disruption<br />

avoidance would be established on the multiple current profile redistribution time scale.<br />

The studies in 1b would determine the possible extensions of this facility to other fusion nuclear<br />

science missions.<br />

2. Existing program activities that contribute to this Thrust and should be supported and<br />

expanded.<br />

Activity 2a: Continue to pursue the program on <strong>US</strong> tokamak (and ST) facilities to establish<br />

the simultaneous high-per<strong>for</strong>mance plasma parameters (b N , f BS , P rad,core , etc.) in nonburning<br />

D-D plasma.<br />

in the very near-term, present tokamaks in the Us should pursue upgrades to heating and current<br />

drive systems, as well as pulse extension to a few current profile redistribution times. These<br />

non-burning d-d plasma devices should identify attractive plasma configurations <strong>for</strong> iteR and<br />

beyond. The access to combinations of high beta, high noninductive plasma current, high bootstrap<br />

fraction, high fast particle content, long pulse lengths, other dimensionless plasma parameters,<br />

and a mix of external control tools varies among the Us tokamaks. The results of the Us (and<br />

international) experiments will need to be combined to establish a more universal physics basis.<br />

Using the varied tools on the Us devices, the requirements <strong>for</strong> plasma current profile and radiated<br />

power fraction control can be explored (Thrust 5).<br />

Activity 2b: Take advantage of the Asian long pulse non-burning D-D tokamaks <strong>for</strong><br />

longer pulse lengths, all four heating and current drive sources <strong>for</strong> flexibility in plasma<br />

configurations, and control system development. Examine areas where existing device<br />

program plans <strong>for</strong> the Asian devices could be enhanced or expanded to provide a greater<br />

physics database, and seek to establish a strong collaboration to pursue this.<br />

The main new d-d devices planned over the next 20 years are the long pulse asian tokamaks —<br />

kstaR (korea), east (china), and Jt-60sa (Japan). The focus of the asian tokamaks is d-d operation<br />

<strong>for</strong> pulses ranging from 100 to 1000 s, which provides > 2-5 current relaxation times. in<br />

addition, the plasma configurations of interest are high noninductive current fraction plasmas<br />

(targeting 100%, and high bootstrap current fraction), and high beta pushing above the no-wall<br />

limit. kstaR and east will utilize all four main tokamak heating and current drive systems<br />

(neutral beams, ion cyclotron, electron cyclotron, and lower hybrid), which will give them considerably<br />

greater flexibility than any single Us tokamak in exploring plasma configurations, while<br />

Jt-60sa will use neutral beams and electron cyclotron sources only. development of more so-<br />

298

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