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

enormous strides have been made in theory and predictive modeling, enabled by advances in
massively parallel computing, in concert with a strong basic theory effort, and validation with
new and detailed measurements. in the area of auxiliary systems, much of the complex interaction
of radiofrequency waves with core plasmas, leading to heating and current drive, is now
understood and can be accurately modeled. as one example of many during the past decade, significant
improvements have been made in simulating wave-particle interactions in the ion cyclotron
range of frequencies (icRF). it is now possible to simulate icRF mode conversion to ion
bernstein wave (ibW) and ion cyclotron wave (icW), which have wavelengths much shorter than
that of the incident fast magnetosonic wave (Figure 1). a short wavelength mode detected using
a Phase contrast imaging technique on alcator c-mod was first expected to be an ibW, but appeared
at the wrong wave number and spatial position. Theory and simulation, including comparison
with a synthetic diagnostic in the code, led to the discovery of the first observation of an ion
cyclotron wave. very recently, the use of spectral full-wave solvers in the lower hybrid (lh) range
of frequencies has made it possible to study focusing and diffraction effects in this regime. accurate
prediction of electron cyclotron resonance heating and current drive has been carried out
and validated extensively on the diii-d tokamak. validation of ion-scale turbulence and transport
models with new turbulence diagnostics has similarly increased our understanding in the
transport area.
Re (Ez )
Z (cm)
20
0
-20
-20 -10 0 10 20
X (cm)
75
1.3
0.27
0.055
0.011
0.0023
-0.0034
-0.015
-0.066
-0.29
Figure 1. Simulation of mode conversion of incident ICRF waves to shorter wavelength modes with the TO-
RIC full wave code. From J.C. Wright et al, Phys. Plasmas, 11(5) (2004) 2473.
building on the measurement, prediction and control tools described above, integrated scenarios
have been produced on many tokamaks that achieve many of the normalized parameters envisaged
for attractive and economic tokamak reactors. in advanced tokamaks such as diii-d in the
Us, and Jt60-U in Japan, fully noninductive discharges have been produced with neutral beam
and electron cyclotron current drive, and about 60% bootstrap current. in other discharges, up
to 100% bootstrap fraction has been obtained. normalized pressures well above passive stabil-
-1.3