title: Laser-heated emissive plasma probe.
abstract: Emissive probes are standard tools in laboratory plasmas for the direct determination of the plasma potential. Usually they consist of a loop of refractory wire heated by an electric current until sufficient electron emission. Recently emissive probes were used also for measuring the radial fluctuation-induced particle flux and other essential parameters of edge turbulence in magnetized toroidal hot plasmas [R. Schrittwieser et al., Plasma Phys. Controlled Fusion 50, 055004 (2008)]. We have developed and investigated various types of emissive probes, which were heated by a focused infrared laser beam. Such a probe has several advantages: higher probe temperature without evaporation or melting and thus higher emissivity and longer lifetime, no deformation of the probe in a magnetic field, no potential drop along the probe wire, and faster time response. The probes are heated by an infrared diode laser with 808 nm wavelength and an output power up to 50 W. One probe was mounted together with the lens system on a radially movable probe shaft, and radial profiles of the plasma potential and of its oscillations were measured in a linear helicon discharge.
authors.affiliation: Institute for Ion Physics and Applied Physics, Association EURATOM-OAW, University of Innsbruck, A-6020 Innsbruck, Austria.
authors.forename: Roman
authors.initials: R
authors.lastname: Schrittwieser
authors.forename: Codrina
authors.initials: C
authors.lastname: Ionita
authors.forename: Petru
authors.initials: P
authors.lastname: Balan
authors.forename: Ramona
authors.initials: R
authors.lastname: Gstrein
authors.forename: Olaf
authors.initials: O
authors.lastname: Grulke
authors.forename: Thomas
authors.initials: T
authors.lastname: Windisch
authors.forename: Christian
authors.initials: C
authors.lastname: Brandt
authors.forename: Thomas
authors.initials: T
authors.lastname: Klinger
authors.forename: Ramin
authors.initials: R
authors.lastname: Madani
authors.forename: George
authors.initials: G
authors.lastname: Amarandei
authors.forename: Arun K
authors.initials: AK
authors.lastname: Sarma