Investigating the effect of different impurities on plasma detachment in linear plasma machine Magnum-PSI

R. Perillo (Corresponding author), Ray Chandra, G.R.A. Akkermans, I.G.J. Classen, S.Q. Korving

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

To achieve a tolerable heat and particle flux to the divertor target of fusion reactors, the so-called plasma detachment is essential to be set up and controlled. Impurity seeding facilitates the achievement of such a regime, mostly due to the enhanced plasma radiation led by the excitation-relaxation cycle of such species. Little is known about the impurity-induced plasma chemical processes occurring in the divertor region during detachment operation. In this work, the influence of three different impurities, i.e., N2, Ar, and He, on detachment performance is studied. To do so, experimental campaigns on the linear plasma machine Magnum-PSI have been carried out. Results highlight the beneficial role of N2 + H2 seeding, decreasing the plasma pressure in front of the target, leading to a reduced heat load compared to the pure H2 seeding case. An opposite trend has been found concerning He and Ar puffing. In fact, injection of H2 + He and H2 + Ar gas mixtures led to an increased heat flux. To address the importance of different plasma-chemical reaction paths, global plasma models have been used. The resulting reduced reaction schemes for Ar + H2, He + H2, and N2 + H2 have been implemented in B2.5-Eunomia, a coupled code consisting of a Monte Carlo code treating the transport of neutrals and a fluid code solving plasma equations. Simulation results qualitatively reproduce the favorable effect of N2, while confirming the deteriorating effect of He and Ar on a detachedlike hydrogen plasma. We point the synergetic role of H2 + N2 to be due to molecular-driven ion recombination, i.e., N-molecular-assisted recombination (MAR). A direct comparison of the collision frequency between N-MAR and MAR is showed, highlighting the crucial importance of the former in reducing the ion and heat flux to the target plate.

Original languageEnglish
Article number102502
Number of pages15
JournalPhysics of Plasmas
Volume26
Issue number10
DOIs
Publication statusPublished - 1 Oct 2019

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detachment
impurities
inoculation
heat flux
ion recombination
plasma radiation
plasma pressure
fusion reactors
hydrogen plasma
flux (rate)
gas mixtures
chemical reactions
injection
trends
heat
cycles
collisions
fluids
excitation
ions

Cite this

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title = "Investigating the effect of different impurities on plasma detachment in linear plasma machine Magnum-PSI",
abstract = "To achieve a tolerable heat and particle flux to the divertor target of fusion reactors, the so-called plasma detachment is essential to be set up and controlled. Impurity seeding facilitates the achievement of such a regime, mostly due to the enhanced plasma radiation led by the excitation-relaxation cycle of such species. Little is known about the impurity-induced plasma chemical processes occurring in the divertor region during detachment operation. In this work, the influence of three different impurities, i.e., N2, Ar, and He, on detachment performance is studied. To do so, experimental campaigns on the linear plasma machine Magnum-PSI have been carried out. Results highlight the beneficial role of N2 + H2 seeding, decreasing the plasma pressure in front of the target, leading to a reduced heat load compared to the pure H2 seeding case. An opposite trend has been found concerning He and Ar puffing. In fact, injection of H2 + He and H2 + Ar gas mixtures led to an increased heat flux. To address the importance of different plasma-chemical reaction paths, global plasma models have been used. The resulting reduced reaction schemes for Ar + H2, He + H2, and N2 + H2 have been implemented in B2.5-Eunomia, a coupled code consisting of a Monte Carlo code treating the transport of neutrals and a fluid code solving plasma equations. Simulation results qualitatively reproduce the favorable effect of N2, while confirming the deteriorating effect of He and Ar on a detachedlike hydrogen plasma. We point the synergetic role of H2 + N2 to be due to molecular-driven ion recombination, i.e., N-molecular-assisted recombination (MAR). A direct comparison of the collision frequency between N-MAR and MAR is showed, highlighting the crucial importance of the former in reducing the ion and heat flux to the target plate.",
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Investigating the effect of different impurities on plasma detachment in linear plasma machine Magnum-PSI. / Perillo, R. (Corresponding author); Chandra, Ray; Akkermans, G.R.A.; Classen, I.G.J.; Korving, S.Q.

In: Physics of Plasmas, Vol. 26, No. 10, 102502, 01.10.2019.

Research output: Contribution to journalArticleAcademicpeer-review

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T1 - Investigating the effect of different impurities on plasma detachment in linear plasma machine Magnum-PSI

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AU - Korving, S.Q.

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Y1 - 2019/10/1

N2 - To achieve a tolerable heat and particle flux to the divertor target of fusion reactors, the so-called plasma detachment is essential to be set up and controlled. Impurity seeding facilitates the achievement of such a regime, mostly due to the enhanced plasma radiation led by the excitation-relaxation cycle of such species. Little is known about the impurity-induced plasma chemical processes occurring in the divertor region during detachment operation. In this work, the influence of three different impurities, i.e., N2, Ar, and He, on detachment performance is studied. To do so, experimental campaigns on the linear plasma machine Magnum-PSI have been carried out. Results highlight the beneficial role of N2 + H2 seeding, decreasing the plasma pressure in front of the target, leading to a reduced heat load compared to the pure H2 seeding case. An opposite trend has been found concerning He and Ar puffing. In fact, injection of H2 + He and H2 + Ar gas mixtures led to an increased heat flux. To address the importance of different plasma-chemical reaction paths, global plasma models have been used. The resulting reduced reaction schemes for Ar + H2, He + H2, and N2 + H2 have been implemented in B2.5-Eunomia, a coupled code consisting of a Monte Carlo code treating the transport of neutrals and a fluid code solving plasma equations. Simulation results qualitatively reproduce the favorable effect of N2, while confirming the deteriorating effect of He and Ar on a detachedlike hydrogen plasma. We point the synergetic role of H2 + N2 to be due to molecular-driven ion recombination, i.e., N-molecular-assisted recombination (MAR). A direct comparison of the collision frequency between N-MAR and MAR is showed, highlighting the crucial importance of the former in reducing the ion and heat flux to the target plate.

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