Hydrogen plasma induced photoelectron emission from metal surfaces
Low temperature hydrogen plasmas are strong sources of vacuum ultraviolet radiation. The properties of laboratory plasmas can be inﬂuenced by surface processes induced by photons with their energies exceeding the surface work function of the wall material. In this work, the plasma induced photoelectron emission has been studied with different ion sources. The emission depends on the mechanical design of the plasma device, plasma heating method and the discharge power (density). Parametric studies include the quantifying of the emission from different metal surfaces, commonly used as plasma facing materials in ion sources, as well as alkali metal covered surfaces. Experimental studies suggest that low temperature hydrogen plasma induced photoelectron emission from metal surfaces can reach an order of magnitude of 1 A per kW of plasma heating power. Furthermore, the emission can increase 2–3.5 times when the metal surface is coated with a thin layer of alkali metal reducing the work function. The free electrons produced by the photoelectron emission can inﬂuence various plasma processes and especially the plasma sheath structure, which has been studied using a one-dimensional analytical model. ...
PublisherUniversity of Jyväskylä
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Komppula, Jani (University of Jyväskylä, 2015)
Laulainen, Janne; Kalvas, Taneli; Koivisto, Hannu; Kronholm, Risto; Tarvainen, Olli (AIP Publishing, 2018)Experimental results of low temperature hydrogen plasma induced photoelectron emission measurements comparing two different plasma heating methods are summarized. By exposing the samples to the vacuum ultraviolet radiation ...
Koivisto, Hannu; Suominen, Pekka; Tarvainen, Olli; Spädtke, P. (American Institute of Physics, 2012)The main limitation to further improve the performance of ECR ion sources is set by the magnet technology related to the multipole magnet field used for the closed minimum-B structure. The JYFL ion source group has sought ...
Study of gasdynamic electron cyclotron resonance plasma vacuum ultraviolet emission to optimize negative hydrogen ion production efficiency Lapin, R. L.; Skalyga, V. A.; Izotov, I.; Razin, S. V.; Shaposhnikov, R. A.; Vybin, S. S.; Bokhanov, A. F.; Kazakov, M. Yu.; Tarvainen, O. (American Institute of Physics, 2020)Negative hydrogen ion sources are used as injectors into accelerators and drive the neutral beam heating in ITER. Certain processes in low-temperature hydrogen plasmas are accompanied by the emission of vacuum ultraviolet ...
Hydrogen plasma induced photoelectron emission from low work function cesium covered metal surfaces Laulainen, Janne; Aleiferis, S.; Kalvas, Taneli; Koivisto, Hannu; Kronholm, Risto; Tarvainen, Olli (AIP Publishing LLC, 2017)Experimental results of hydrogen plasma induced photoelectron emission from cesium covered metal surfaces under ion source relevant conditions are reported. The transient photoelectron current during the Cs deposition ...