Abstract
The rise of electron temperature along the magnetic field line was clearly observed in divertor relevant recombining plasma, even though there was no additional electron heating source. Electron temperature obtained at recombination front was approximately 0.5 eV, whereas it increased up to greater than 1 eV at downstream of recombination front. Although this temperature rise is likely common in detached or recombining plasmas, the mechanism has not been understood yet. This report provides a reasonable interpretation of temperature rise along the magnetic field line, for the first time: depletion of low energy electrons due to volumetric recombination leads to deformation of electron energy distribution, resulting in an apparent increase in electron temperature. Our experiment supports this interpretation in that the experimentally observed electron temperature showed good agreement with calculated effective electron temperature.
Highlights
Volumetric recombination, the inverse process of ionization, is one of the most fundamental processes in plasmas and observed in various fields, for instance, in a supernova remnant,1 in an electric double layer like plasma,2 and in an arc plasma jet.3 Volumetric recombination is of great interest in fusion research
This report provides a reasonable interpretation of temperature rise along the magnetic field line, for the first time: depletion of low energy electrons due to volumetric recombination leads to deformation of electron energy distribution, resulting in an apparent increase in electron temperature
Continuum emission was utilized for the derivation because electron energy distributions (EEDs) in an RF plasma sometimes deviate from the Maxwellian distribution, and the use of the Boltzmann plot method leads to the underestimation of Te and ne when electrons form bi-Maxwellian one
Summary
Volumetric recombination, the inverse process of ionization, is one of the most fundamental processes in plasmas and observed in various fields, for instance, in a supernova remnant, in an electric double layer like plasma, and in an arc plasma jet. Volumetric recombination is of great interest in fusion research. Volumetric recombination, the inverse process of ionization, is one of the most fundamental processes in plasmas and observed in various fields, for instance, in a supernova remnant, in an electric double layer like plasma, and in an arc plasma jet.. Volumetric recombination is of great interest in fusion research. When heat and particles in confined plasma region move across the separatrix, they enter the scrape-off layer and eventually terminate at divertor plates. In terms of divertor protection, heat removal capability is a critical issue that determines the output of fusion reactors.. Divertor plasma detachment, which is caused by increased impurity radiation loss and volumetric recombination, is considered to be a promising solution that allows the divertor to withstand the heat flux and sputtering.. The problem is that the modeling and code development on divertor detachment are premature numerous simulations on divertor detachment have been carried out to find possible operation scenarios. In terms of divertor protection, heat removal capability is a critical issue that determines the output of fusion reactors. Divertor plasma detachment, which is caused by increased impurity radiation loss and volumetric recombination, is considered to be a promising solution that allows the divertor to withstand the heat flux and sputtering. The problem is that the modeling and code development on divertor detachment are premature numerous simulations on divertor detachment have been carried out to find possible operation scenarios.
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