Fusion Power Breakthrough: New Method for Eliminating Damaging Heat Bursts in Toroidal Tokamaks


Supreme [H]ardness
Dec 19, 2005
"Edge-localized mode (ELM) suppression by resonant magnetic perturbations (RMPs) generally occurs over very narrow ranges of the plasma current (or magnetic safety factor q95) in the DIII-D tokamak. However, wide q95 ranges of ELM suppression are needed for the safety and operational flexibility of ITER and future reactors. In DIII-D ITER similar shape plasmas with n=3 RMPs, the range of q95 for ELM suppression is found to increase with decreasing electron density. Nonlinear two-fluid MHD simulations reproduce the observed q95 windows of ELM suppression and the dependence on plasma density, based on the conditions for resonant field penetration at the top of the pedestal. When the RMP amplitude is close to the threshold for resonant field penetration, only narrow isolated magnetic islands form near the top of the pedestal, leading to narrow q95 windows of ELM suppression. However, as the threshold for field penetration decreases with decreasing density, resonant field penetration can take place over a wider range of q95. For sufficiently low density (penetration threshold) multiple magnetic islands form near the top of the pedestal giving rise to continuous q95 windows of ELM suppression. The model predicts that wide q95 windows of ELM suppression can be achieved at substantially higher pedestal pressure in DIII-D by shifting to higher toroidal mode number (n=4) RMPs."



Aug 4, 2004


[H]F Junkie
Mar 18, 2010
Cool and all, but it doesn't seem to do anything towards solving fusion's biggest problem: energy input exceeding energy output.


Supreme [H]ardness
Apr 14, 2010
COOL! Using a warp field to contain the fusion reaction -> Awesome! Nothing like collapsing the space to fool those very high energy particles into submission for mating!


Limp Gawd
May 2, 2017
I have no idea what I just read.
Basically these fusion reactors have random bursts of energy that can break through the magnetic containment field that is meant to hold the plasma in place for the fusion reaction. Obviously when the plasma breaks containment it is very bad. So in order for the fusion reactor to be viable for use, they have to have a way to suppress these bursts of energy so they don't have a containment breach. Currently, they can only suppress the plasma at certain levels of reaction. That is what they are talking about with a "narrow q95" and "wide q95 window". They can only do narrow windows of output right now, but have a theoretical way to widen that window of suppression. They do this by taking the magnetic field and make it into more of a spiral and "more rippled", which I take to mean the waveform of the magnetic field has either a larger or possibly more varied amplitude. By being able to suppress containment breaches over a larger operational range of plasma current they can have a more varied output from the reactor. This is important because power plants do not run at full power all the time, their output is varied based on grid load. The reactor must be able to ramp down so that it doesnt blow out the grid by providing tons more power than is being drawn. The most famous power reactor that was not built in a way to let it be ramped down safely is one I believe everyone knows, Chernobyl. It wasnt built well to be able to go to low power, it was expressly forbidden to go to low power, and operators did it anyway. And things went BOOM. So it is important that any power plant that is going to be put in operation must be able to work at many different outputs, and this theoretical simulation that was run shows promise to allow tokamacs to do so.


Nov 13, 2002
I can't wait for the stellarator vs tokamak purists to show up and drive this into the gutter.

Kidding (mostly), I don't care how it happens, controlled fusion will be cool!


Dec 5, 2018
Let me guess, after this development it’s 20 years away.
Yeah I remember hearing stuff like this back in 7th grade. There’s always some limitation they may overcome 10-20 years down the line.