Promising computer simulations for stellarator plasmas

Because the precise computational description of plasma turbulence would require the answer of extremely advanced methods of equations and the execution of numerous computational steps, the code improvement course of is aimed toward attaining affordable simplifications. The GENE code developed at IPP is predicated on a set of simplified, so-called gyrokinetic equations. They disregard all phenomena within the plasma which don’t play a significant position in turbulent transport. Though the computational effort will be decreased by many orders of magnitude on this approach, the world’s quickest and strongest supercomputers have at all times been wanted to additional develop the code. Within the meantime, GENE is ready to describe the formation and propagation of small low-frequency plasma eddies within the plasma inside nicely and to breed and clarify the experimental outcomes — however initially just for the merely constructed, as a result of axisymmetric fusion methods of the tokamak kind.

For instance, calculations with GENE confirmed that quick ions can vastly cut back turbulent transport in tokamak plasmas. Experiments on the ASDEX Improve tokamak at Garching confirmed this outcome. The required quick ions had been offered by plasma heating utilizing radio waves of the ion cyclotron frequency.

A tokamak code for stellarators

In stellarators, this turbulence suppression by quick ions had not been noticed experimentally thus far. Nevertheless, the newest calculations with GENE now counsel that this impact must also exist in stellarator plasmas: Within the Wendelstein 7-X stellarator at IPP at Greifswald, it might theoretically cut back turbulence by greater than half. As IPP scientists Alessandro Di Siena, Alejandro Bañón Navarro and Frank Jenko present within the journal Bodily Assessment Letters, the optimum ion temperature relies upon strongly on the form of the magnetic subject. Professor Frank Jenko, head of the Tokamak Idea division at IPP in Garching: “If this calculated result’s confirmed in future experiments with Wendelstein 7-X in Greifswald, this might open up a path to attention-grabbing high-performance plasmas.”

With a purpose to use GENE for turbulence calculation within the extra sophisticated formed plasmas of stellarators, main code changes had been needed. With out the axial symmetry of the tokamaks, one has to deal with a way more advanced geometry for stellarators.

For Professor Per Helander, head of the Stellarator Idea division at IPP in Greifswald, the stellarator simulations carried out with GENE are “very thrilling physics.” He hopes that the outcomes will be verified within the Wendelstein 7-X stellarator at Greifswald. “Whether or not the plasma values in Wendelstein 7-X are appropriate for such experiments will be investigated when, within the coming experimental interval, the radio wave heating system might be put into operation along with the present microwave and particle heating,” says Professor Robert Wolf, whose division is answerable for plasma heating.

GENE turns into GENE-3D

In response to Frank Jenko, it was one other “monumental step” to make GENE not solely roughly, however utterly match for the advanced, three-dimensional form of stellarators. After virtually 5 years of improvement work, the code GENE-3D, now offered within the “Journal of Computational Physics” by Maurice Maurer and co-authors, offers a “quick and but practical turbulence calculation additionally for stellarators,” says Frank Jenko. In distinction to different stellarator turbulence codes, GENE-3D describes the total dynamics of the system, i.e. the turbulent movement of the ions and likewise of the electrons over the complete internal quantity of the plasma, together with the ensuing fluctuations of the magnetic subject.

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Materials offered by Max-Planck-Institut für Plasmaphysik (IPP). Observe: Content material could also be edited for model and size.