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

systems include neutral beams, ion cyclotron range of frequencies and electron cyclotron range of
frequencies. The use of lower-hybrid current drive (lhcd) is only considered an option. The flexibility
of this mixture of sources on iteR is in question, and it is not clear that a wide range of
burning plasmas can be explored, or whether steady-state scenarios can be sustained. iteR will
provide an initial look at the control of plasmas with alpha power and ≥ 50% bootstrap current,
along with self-consistent pedestal and edge/divertor plasmas.
itER-at aRiES-i aRiES-at
bn (%) 3.0 3.2 5.4
i bootstrap /i plasma 0.48-0.68 0.68 0.89
n/n gr 1.0 1.04 0.95
q cyl , q 95 3.8-4.5 4.4 3.0
z eff 1.4-2.0 1.73 1.83
P rad core /Pinput 0.2-0.3 0.48 0.36
P rad div /Pinput 0.43
(P alpha + P input – P rad core ) /a p , MW/m 2 0.14 0.45 0.56
(P alpha + P input – P rad core ) /P input 1.36 2.52 6.25
P alpha /P input 1 3.8 8.8
, MW/m 2 0.6 2.5 3.3
t j , s 200-400 300 275
Duration, s 3000 ~3x10 7 ~3x10 7
Table 2. Comparative parameters of ITER AT and some projected power plant target plasmas.
to increase the contributions of iteR to this Thrust, the Us should encourage the expansion of
the heating and current drive mix on iteR, potentially including lower hybrid and upgrades of
one or more of the planned sources to enable greater flexibility in producing a range of plasma
configurations. The capability to significantly exceed the no-wall beta limit through mhd feedback
control, including plasma rotation, should also be pursued. in addition, it may be possible
to attain higher P alpha /P input by reducing the input power, if the plasma-generated bootstrap current
can compensate for the lost externally driven current. The acceleration of advanced tokamak
experiments and high P alpha /P input operating modes in the iteR research plan would allow more
rapid identification of underlying physics for operation at high core performance. These possibilities
should be assessed in detail, through predictive simulations enabled by Thrust 6, and plasma
operating scenarios identified for enhanced performance in iteR.
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