1 - Nuclear Sciences and Applications - IAEA

660 SCOTT et al.
30
25
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I Jo
: * a
5 '- °4.8 M\
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O -^t
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R(rti)
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(a) ;
11.6 MW •
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7.3 MW :
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2.5 3.0
R(m)
FIG. 3. Profiles of (a) ion temperature and (b) toroidal rotation speed measured by CHERSfor three
discharges in a beam power scan at Ip = 1.1 MA. The solid line represents the ion temperature and
rotation speed mapped onto shifted flux surfaces for the 11.6 MW discharge. The vertical arrows
represent the location of the magnetic axis for the 11.6 MW discharge.
the plasma edge due to charge-exchange. |This perspective is supported by
the edge-heating experiments [7] which showed an inward radial diffusion of
angular momentum when torque was applied to the plasma edge only. The
rotation profile was not hollow in the inner region of the plasma during the
equilibrium phase of the discharge, implying that local damping of rotation
(e.g., due to toroidal field ripple) is a much smaller effect than radial transport.]
The steady-state momentum balance is evaluated by the 1-D radial
transport code SNAP, using v,j,(R), ne(R), TC(R), and T{(R) mapped onto
a minor radius grid using a shifted-circle equilibrium. The radial variation
of X[ r ) IS determined from the momentum balance equation [2] which includes
the deposition of beam torque calculated by a moments solution of
the Fokker-Planck equation [8]. Details of the calculation are described in
Ref. [9].
Table 1 summarizes the global momentum confinement results of the beam
power scans as calculated from the measured profiles of v^{R) and ne(R).
The thermal momentum confinement times are rather short, ranging from
29 to 56 msec, or 30-40% of the global energy confinement time. This result
is consistent with velocity profile measurements on D-III, which find
T 4> I T E ~ 0.5 in limiter discharges [10]. It should be stressed that many of
these discharges are strongly beam-dominated, in the sense that the slowingdown
beam ion population typically represents 50-65% of the stored momentum,
more than 50% of the plasma stored energy, and up to 20% of the
plasma mass. The global T$ for counter-injection is somewhat less than that