Research Thrust on disruptions/runaways
Overarching goal: eliminate disruptions as a threat to the viability of fusion energy
If this thrust is not pursued and the goal not achieved, fusion power in magnetically confined plasmas will not be
reliable or economical. The thrust has elements requiring immediate attention to benefit ITER (Theme I), and
longer term elements to address the challenge more comprehensively (Theme II). Within these two themes, the
thrust is most strongly linked to the issues of control, and also to measurement, and integration. The thrust also
connects directly to issues of PFCs (Theme III), RAMI (Theme IV), and magnetic configurations without
disruptions (Theme V).
Thrust elements organized by
1. Prediction
 Can the onset of most disruptions be predicted?
2. Avoidance
 What level of steady-state tokamak performance can be achieved while avoiding disruptions?
 Can the stellarator remain free of disruptions at the beta and collisionality characteristic of a reactor?
3. Mitigation
 Can the potential damage from major disruptions in future high performance discharges be largely
avoided?
4. Characterization of consequences
All goals listed contribute to Theme II. Many have explicit connection to Theme I.
Goal relating to
gap or issue
1(a). Predict onset
of disruptions in
tokamaks with
sufficient accuracy
to enable active
avoidance or
controlled
shutdown
Time
frame
Short:
Theme I
1(b). Validate
models of runaway
electron
generation,
confinement, and
loss
1(c). Compile
comprehensive
disruption
statistics
Short:
Theme I
Work
description
Develop suite of diagnostics and realtime analysis to predict onset of VDEs
and disruptions arising from multiple
causes including equipment failure.
Benefit to fusion
Cross-links
with control,
measurement,
integration
panels
Evaluate compatibility of above with
high performance, burning plasmas.
Understanding
physics of
disruptions and
their precursors
improves
prospect for
better avoidance
in ITER, DEMO
Compare the prediction of runway
electron currents with experimental
data to provide a reliable means for
projecting to ITER and Demo.
Understanding of
single-event
catastrophes in
ITER, DEMO
with control,
integration
panels;
Themes 3 & 4
Short, and Compile single-machine and multicontinuing machine data on disruptions, VDEs,
in ITER
runaway events, forces and thermal
loads: frequency of occurrence,
‘types’, ‘causes’ (physics +
hardware), correlations with device,
FW material, plasma configuration,
ops mode, effect of ‘control’,
deployment of avoidance or
mitigation measures, ….
Statisical
knowledge
provides
operational
guidance in
ITER, DEMO
2(a). Avoid
Short:
disruptions in
Theme I
tokamaks by active Medium
means
Develop set of control methods to
avoid onset of disruption or VDE
and/or lead to safe shutdown; apply
to ITER.
2(b). Advance
magnetic
configurations
immune to major
disruptions
Extend stellarator research to
integrated high performance (long
pulse, reactor-like values of , Ti, ne
obtained in stellarators but not
simultaneously)
Medium
to Long
2(c). Demonstrate Short,
potential of various medium,
levels of nonand long
axisymmetric
shaping to avoid
disruptions
Design non-axisymmetric shaping
schemes for disruption control
Evaluate integrated consequences of
NA-shaping of axis-symmetric
systems
Minimize
interruption of
operation and
damage
requiring repair
Robustly
eliminate
disruption as
show-stopper in
fusion energy
system
Reliably
eliminate
disruptions with
minimum
deviation from
tokamak
experience and
technology
with control,
measurement,
integration
panels
With Theme
V
With Theme
V
3(a). Develop
reliable mitigation
schemes for
unavoidable
disruptions in
tokamaks
3(b). Provide
additional
mitigation of
runaway electron
avalanche should it
occur
Short
Expand MGI activities on present
Theme I,
devices to assess
to medium feasibility for ITER and DEMO
Improved
survivability of
ITER and
DEMO
with control
panel
Short to
long
Eliminate
consequences of
potentially
catastrophic
runaway beam
With control
panel
Develop tools to provide the density
required to collisionally damp the
runaway electrons.
Assess suppression of runaways by
stochastic magnetic fields both
intrinsic and externally applied.
Assess control and rampdown of
runaway-dominated discharges
4(a). Develop
Short,
validated models of Theme I
disruption
medium
dynamics
4 (b). Develop
Medium
disruption-tolerant to long
PFCs
4 (c). Develop
after-disruption
recovery strategies
Medium
to long
Compare experiment with
computational models that predict
the electromagnetic and thermal heat
loads due to disruptions to develop a
predictive model.
Conceive, develop and test innovative
PFC materials or concepts, e.g.,
liquids, capable of in-situ repair;
special recovery measures
Explore wall-conditioning techniques
and in-situ dust removal for optimal
recovery
Prediction of
disruption
consequences in
ITER, DEMO,
and others
Hardening of
fusion facility
(CTF, DEMO)
against
unmitigated
disruptions
Enable recovery
from disruption
damage is as
routine as
possible
With Theme
III
With Themes
III and IV