Plasma detachment study of high density helium plasmas in the Pilot-PSI device

Abstract

We have investigated plasma detachment phenomena of high-density helium plasmas in \u3cbr/\u3ethe linear plasma device Pilot-PSI, which can realize a relevant ITER SOL/Divertor plasma \u3cbr/\u3econdition. The experiment clearly indicated plasma detachment features such as drops in the \u3cbr/\u3eplasma pressure and particle flux along the magnetic field lines that were observed under the \u3cbr/\u3econdition of high neutral pressure; a feature of flux drop was parameterized using the degree \u3cbr/\u3eof detachment (DOD) index. Fundamental plasma parameters such as electron temperature (Te) and electron density in the detached recombining plasmas were measured by different \u3cbr/\u3emethods: reciprocating electrostatic probes, Thomson scattering (TS), and optical emission spectroscopy (OES). The Te measured using single and double probes corresponded to the TS measurement. No anomalies in the single probe I – V\u3cbr/\u3echaracteristics, observed in other linear plasma devices [ 16, 17,36], appeared under the present condition in the Pilot-PSI device. \u3cbr/\u3eA possible reason for this difference is discussed by comparing the different linear devices. \u3cbr/\u3eThe OES results are also compared with the simulation results of a collisional radiative (CR) model. Further, we demonstrated more than 90% of parallel particle and heat fluxes were \u3cbr/\u3edissipated in a short length of 0.5 m under the high neutral pressure condition in Pilot-PSI