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

to handle 10 mW/m 2 , and elms with a pulsed energy density of ≤ 0.5 mJ/m 2 . Research should
include heat flux removal enhancement techniques, e.g., internal roughening, swirl tape, microjets
and porous media. design margin enhancement should also be included. innovative magnetic
configurations for high heat flux reduction, like the super X and snowflake divertor configurations,
will require development of PFcs compatible with the unique magnetic geometry and possible
differences in plasma transport.
development of solid surface PFc designs that are tolerant to a few off-normal events should continue.
This should include low-z material loaded tungsten surfaces and low-z material alloying
of tungsten-surface materials. These concepts rely on the vapor shielding effects from the low-z
material to protect the tungsten surfaces and be able to withstand a few disruptions. Real time
replenishment of the low-z surface materials will be needed for this option.
innovative refractory materials with high thermal conductivity compatible with the design of
he coolant or liquid surfaces must be developed for neutron fluence up to 15 mW-yr/m 2 . Joining
techniques compatible with he or liquid metal coolants are needed for the solid surface option
to be viable. tungsten or tungsten alloys are the leading candidates for such material because of
their high thermal conductivity, low erosion rate, and high melting point. however, neutron embrittlement
is a serious issue the innovative alloys must address.
TesTing requiremenTs To ValidaTe design issues
Can testing scenarios be developed for new plasma facing component designs on new or existing laboratory
and fusion facilities?
helium-cooled heat sinks (including fabrication methods) for high heat flux removal capacity refractory
material PFcs need to be developed and validated through rigorous testing. The joint between
the plasma facing material and the heat sink is typically a few microns thick and composed
of intermetallics. (These intermetallics have uncertain properties for which there are no measurements
after neutron irradiation.) extensive heat flux testing of new designs must be conducted on
test stands and the designs applied to long pulse fusion devices before they can be considered for
demo. This development should include different nondestructive inspection techniques. neutron
irradiation typically hardens materials while decreasing ductility and fracture toughness.
development of a database on nuclear irradiation effects on the above advanced and innovative
PFc concepts is required to address issues, including cyclic fatigue, thermal creep, fracture
toughness, and fracture mechanics at interfaces.
Results from linear machines have shown that with the impingement of edge alphas, blisters can
be created at the first-wall chamber owing to trapping of the impinging helium ions, and generation
of W-fuzz on the divertor surfaces. no explanation for the cause of the generation of the Wfuzz
is available. in general, the damage effects from edge alphas have not been systematically
studied. to address the synergistic effects, new and upgraded facilities that can allow flexibility
in the testing of PFc surface materials with the combination of simulated neutron, alphas and
plasma environment at high temperature, and operate in pulsed and steady-state modes, will be
needed.
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