Electric probe systems for Diversified Plasma Simulator (DiPS)

Abstract

DiPS (Diversified Plasma Simulator), a new versatile linear machine (length=3400 mm, diameter=200-600 mm), is developed for the simulations of divertor, space and processing plasmas with various electric probes: fast-scanning systems with single, triple, and Mach Probes, slow-scanning water-cooled single probe, gridded-energy analyzer (GEA), and several fixed single probes. For the verification of current probe theories and the development of new theories with magnetic vector field, collisional effects, various particle sources, and wide range of plasma parameters, two different plasma sources are installed: (1) For a stable high density dc plasma, a LaB6 disk is used as the thermal electron emission source with 5 kW graphite heater. Initial plasma density of the LaB6 source is 5 x 10(12) cm(-3), electron temperature is 8-10 eV with magnetic field around 1 kG. The electron density would be decreased severely, i.e., to 10(6) - 10(8) cm(-3) with grid, and expanded into space simulation region without magnetic field; (2) Helicon plasma source is also installed for a processing simulation in DiPS and for the space propulsion study with magnetic expansion, which generates the plasma with density of 2 x 10(13) cm(-3) and electron temperature 3-4 eV for the rf power of 2.5 kW at optimum pressure of 7.5 mTorr. As a unique feature for the diversified uses of sources and divertor simulator experiments, space and processing simulation chambers can be detached from and attached to the divertor simulation chamber on the rail. Initial data of various electric probes (single, triple, emissive, mach probes, GEA, etc.) are introduced for the the following conditions of DiPS with B = 1 kG, P = 130 mTorr at source region, P = 2 mTorr at divertor simulation region, n(e) = 1 x 10(12) - 1 x 10(14) cm(-3), T-3 = 2 - 3 eV, T-i = 0.2 eV with laser induced fluorescence (LIF) (Ar gas), n(e) = 1 x 10(12) - 1 x 10(13) cm(-3), T-e =5 - 6 eV (He gas) at divertor simulation region, T-i = 0.47 - 0.74 eV with GEA at space simulation region and v(d) = 500 - 600 m/s.