Chapter 8
PMI in Large Tokamaks
8.1 Power Load
As shown in Chap. 2, research targets have been changing with improvement of
plasma confinement. Now, targeting the establishment of a fusion reactor as an energy
source, durability of plasma-facing materials (PFM) to steady and transient power
load are main concerns. Nevertheless, no tokamaks could have given such highpower load as expected in a reactor. Only JET is now working to give power load a
little less than that expected in the reactor. However, after changing its plasma-facing
wall from carbon-based materials to ITER like Wall, i.e. Be for first wall and W for
divertor, the power loads are carefully controlled not to destroy the W divertor. In this
respect, the previous carbon-based divertor allowed higher power load and PMI data
including effects of giant ELM and disruption are used for design base for ITER.
Recent large power linear plasma machines are also useful to examine material
responses to the high-power loads as already noted in Chap. 2 and in reviews [1,
2]. However, owing to their different geometrical structure from divertor and lack of
strong magnetic field, it is questionable to use them as a divertor simulator except
power load tests. In this respect, data obtained in presently running plasma machines
under well-designed program for studying plasma material interactions (PMI) would
be useful. In this chapter, PMI observed in large tokamaks, in particular, JET and
JT-60U are mainly summarized.
8.1.1 Power Load in JET
To ensure sufficient divertor target lifetime, the loss of plasma stored energy due
to ELMs in ITER should be restricted to W ELM 1 MJ. Only in JET, by virtue
of its size, can such energies be approached. And the impact of large type I ELMs
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
T. Tanabe, Plasma-Material Interactions in a Controlled Fusion Reactor, Springer Series
in Plasma Science and Technology, https://doi.org/10.1007/978-981-16-0328-0_8
133
PMI in Large Tokamaks
8.1 Power Load
As shown in Chap. 2, research targets have been changing with improvement of
plasma confinement. Now, targeting the establishment of a fusion reactor as an energy
source, durability of plasma-facing materials (PFM) to steady and transient power
load are main concerns. Nevertheless, no tokamaks could have given such highpower load as expected in a reactor. Only JET is now working to give power load a
little less than that expected in the reactor. However, after changing its plasma-facing
wall from carbon-based materials to ITER like Wall, i.e. Be for first wall and W for
divertor, the power loads are carefully controlled not to destroy the W divertor. In this
respect, the previous carbon-based divertor allowed higher power load and PMI data
including effects of giant ELM and disruption are used for design base for ITER.
Recent large power linear plasma machines are also useful to examine material
responses to the high-power loads as already noted in Chap. 2 and in reviews [1,
2]. However, owing to their different geometrical structure from divertor and lack of
strong magnetic field, it is questionable to use them as a divertor simulator except
power load tests. In this respect, data obtained in presently running plasma machines
under well-designed program for studying plasma material interactions (PMI) would
be useful. In this chapter, PMI observed in large tokamaks, in particular, JET and
JT-60U are mainly summarized.
8.1.1 Power Load in JET
To ensure sufficient divertor target lifetime, the loss of plasma stored energy due
to ELMs in ITER should be restricted to W ELM 1 MJ. Only in JET, by virtue
of its size, can such energies be approached. And the impact of large type I ELMs
© The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2021
T. Tanabe, Plasma-Material Interactions in a Controlled Fusion Reactor, Springer Series
in Plasma Science and Technology, https://doi.org/10.1007/978-981-16-0328-0_8
133