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The reason I mention this is that one can differentiate between the natural pressure of the plasma and the pressure applied by a magnetic field. The ratio of these two, called beta, is an important parameter in fusion reactors. Essentially, the efficiency of fusion goes up rapidly as beta approaches one, so magnetic compression aims to get beta as close to that level as possible.
Recent experiments on the Lithium Tokamak Experiment (LTX), the first facility to fully surround plasma with liquid lithium, showed that lithium coatings can produce temperatures that stay constant all the way from the hot central core of the plasma to the normally cool outer edge. The findings confirmed predictions that high edge temperatures and constant or nearly constant temperature profiles would result from the ability of lithium to keep stray plasma particles from kicking—or recycling—cold gas from the walls of a tokamak back into the edge of the plasma.
Researchers performed this set of experiments with solid lithium, Boyle explained, but a coating of liquid lithium could produce similar results. Physicists have long used both forms of lithium to coat the walls of LTX. Since flowing liquid lithium could absorb hot particles but wouldn't wear down or crack when struck by them, it also would reduce damage to tokamak walls - another critical challenge for fusion.
China's Experimental Advanced Superconducting Tokamak (EAST) made an important advance by achieving a stable 101.2-second steady-state high confinement plasma, setting a world record in long-pulse H-mode operation on the night of July 3rd.
All the plasma parameters, including recycling, and particle and heat fluxes, reached a truly steady state after 20 seconds—the wall saturation time for the W divertor—and remained stable until the end of the discharge.
The stellarator Wendelstein 7-X has received its first divertor. Just one step closer towards realising plasma pulse lengths of half an hour without breaking the machine
“The higher heat handling capabilities of the divertor allows us to make longer pulses with higher energy input”, says Arturo Alonso, W7-X‘s task force leader. A divertor takes the energy that is split out from the main plasma. It diverts waste particles directly into the trash with the help of magnetic field lines. For the first operational period of Wendelstein 7-X (from 10th December 2015 to 10th March 2016) a limiter had to do the job of the actual divertor, but its performance was quite “limited”.
Now that the divertor is in place and the wall elements made of copper-chromium-zirconium have been covered by graphite tiles, researchers expect extended pulse lengths of about one minute, as the permitted energy input per discharge moves from 4 Megajoule up to 80 Megajoule, a 20 fold increase in terms of renergy input!