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

elevant plasmas for very long pulses. The larger existing and near-future devices (Jet and Jt-
60sa) are an essential element of extrapolation from present devices to iteR, and techniques for
avoidance of elms and disruptions must be tested to the fullest possible extent in these as well
as the medium-size devices.
Ultimately, a burning plasma experiment such as iteR is required to develop and demonstrate
avoidance of transient events in a fusion environment. The thermal and magnetic energy,
heat flux, and potential for runaway electron generation during disruptions all become greater as
the device size and toroidal field increase. on the other hand, the presence of strong plasma selfheating
reduces the influence of external control. These conditions cannot be fully simulated in
any existing facility, and continuing development in iteR will be an essential element in this research
Thrust.
The Us is well positioned to make a major contribution to this area of research with existing facilities.
however, to address a meaningful fraction of these elements on the time scale needed for
iteR will require a large commitment of resources, including:
• significant increase in operating time for:
developing and testing individual elements of instability avoidance and control.
demonstration of integrated stability control under a wide range of conditions.
• significant increase in staffing for:
analysis and modeling for prediction of disruptions and elms.
modeling and experimental tests of avoidance and mitigation strategies.
validation of models suitable for extrapolation of these strategies to iteR.
testing of systems to predict, avoid and mitigate disruptions on iteR.
• modest facility upgrades:
diagnostics, e.g., for runaway electrons and 3-d field effects.
auxiliary systems for avoidance and mitigation, e.g., gyrotrons for localized current
drive, mass injection systems for disruption mitigation, non-axisymmetric coils with
improved spectrum flexibility.
digital control systems, e.g., for more diagnostic inputs and greater real-time
computing power.
Readiness
Disruption characterization can take advantage of a large existing database in present facilities.
Further progress can be made in the near future, making use of non-linear 3-d mhd modeling
codes and new diagnostics for high-speed imaging, halo currents, and runaway electron detection.
Disruption prediction in empirical forms for detection of growing tearing modes is employed
at many facilities. magnetohydrodynamic spectroscopy has been successfully used in off-line
analysis of specialized experiments, and development toward its routine use in real time is need-
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