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

due to incompatibility of the measurement physics with burning plasma parameters — e.g., large
plasma size and high density may prevent the use of diagnostics that depend on penetration of
neutral beams. Relativistic effects will significantly affect some diagnostic interpretations. some
new and difficult measurements must be identified and perfected to insure the safety of the plant
(e.g., dust accounting), and others must be perfected for the safety of the device (e.g., sensors for
disruption avoidance, tritium inventory, and first-wall ablation). however, the greatest challenge
the diagnostics will face is the hostility of the near-plasma environment and the uncertainty of
the impact of those environmental hazards. We note the following diagnostic concerns for iteR:
• no clear way to measure some desired quantities, e.g., dust and lost alpha particles.
• hazards to diagnostics close to the device: thermal excursions, irradiation-induced
damage and noise, degradation due to erosion/deposition, disruption-induced vibrations
and component displacement. lifetimes of first mirrors are a particular concern. evidence
from both modeling and experiments indicates that severe problems may exist for iteR
due to surface deposition and erosion, but understanding is limited and uncertainty is
large. iteR will require difficult trade-off decisions between measurement performance
and reliability, without well-founded guidance.
• Understanding of environmental impact to diagnostics is lacking in many areas, especially
for combined hazards.
• lifetime and performance of in-vessel sensors, cables, and connectors in the nuclear
environment.
• ability to maintain calibrations of instrumentation over long pulses.
to highlight the research needs of measurements and diagnostics for burning plasmas, we assessed
their urgency and magnitude, and constructed table 1. This table also serves to illustrate
the magnitude of the steps required when moving from present-day diagnostic capabilities,
through iteR, to a demo device.
Mostly OK
Some R&D needed
Significant R&D needed
Sufficient for present-day tokamaks
Should be sufficient for ITER
Should be sufficient for a DEMO
Measurement
readiness
Table 1. 1. Assessment Assessment of Measurement of Measurement Research Research Needs. Note Needs. that the Note “Measurement that the “Measurement
Capability” sub-issue has
been Capability” split here sub-issue into the “measurement has been split readiness” here into and “control the “measurement capable” columns. readiness” Elaboration and of “control the assessments
of capable” the “measurement columns. readiness” Elaboration and “real-time of the assessments interpretation” of the for present-day “measurement tokamaks readiness” is necessary. and Present“realdaytime tokamaks interpretation” have excellent for present-day diagnostic capability. tokamaks However, is necessary. additional Present-day research and tokamaks development have on current
devices excellent is needed diagnostic in those capability. categories to However, gain crucial additional understanding research in specific and areas development and to perform on current crucial validation
devices experiments is needed in support in those of future categories needs (see to gain text); crucial hence the understanding “striped” assessment in specific for those areas areas. and to
perform crucial validation experiments in support of future needs (see text); hence the “striped”
assessment for those areas.
60
Control capable
Compatibility
Reliability
Real-time
interpretation