Applying scattered-ion spectroscopy to the analyzing of plasma-surface interactions

2014 International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV)

2014

Self Cite

Electric field between the plasma and the plasma faced components can be high enough for appearance of prebreakdown currents measured in the experiments on vacuum insulation. In turn, thin insulating films on plasma faced surfaces can significantly change its emission properties and generate surface-plasma instabilities. In this paper, the results of current-voltage characteristic measurement accompanied with in situ diagnostics of the surfaces covered by non-metal films and water adsorption layers by using low angle ion spectroscopy are presented.

Section: Methodsmentioning

confidence: 99%

Emission properties of the plasma faced materials covered with thin films

2014 International Symposium on Discharges and Electrical Insulation in Vacuum (ISDEIV)

2014

Self Cite

“…1. It includes diagnostic ion beam with energy range 1-15 keV generated by duoplasmatron (1), mass-separation electromagnet (2), target-cathode covered by thin-oxide film (3), movable anode (4) for in situ CVC measurement, electrostatic energy analyzer (5) for scattered ion beam diagnostic, and secondary electron multiplier (6). The setup is evacuated with turbomolecular pumps to 10 −7 torr.…”

Section: Methodsmentioning

confidence: 99%

“…A residual gas composition is controlled by Extor XT100M quadrupole mass spectrometer. The thermochemical water vapor source [6] based on Ca(OH) 2 thermal decomposition is used for experiments with water adsorption on the cathode. 0093-3813 © 2015 IEEE.…”

Section: Methodsmentioning

confidence: 99%

Prebreakdown Currents From Tungsten Samples Covered With Thin Films

IEEE Trans. Plasma Sci.

2015

Self Cite

The results of current-voltage characteristics (CVCs) of low-field emission (LFE) measurement from tungsten cathodes covered by a thin (∼10 Å) discontinuous insulator film are presented. Such characteristics have a strong hysteresis effect and can be interpreted by switch-ON model. The current density of LFE is significantly higher than that of pure tungsten and comparable with that of tungsten fuzz nanostructure-the surface with high emissivity. The influence of water adsorption layers on the emission currents demonstrates increasing hysteresis effect in the CVCs in the case of cathode exposition under the injection without voltage applying in vacuum diode.Index Terms-Ion mass spectrometry, low-field emission (LFE), metal-insulator-vacuum structure, unipolar arcs.

“…In this work first experimental results obtained at new facility based on "MEPhI mass monochromator" [1] with low and medium energy ion spectroscopy are presented.…”

mentioning

confidence: 98%

Elemental analysis of the surface during plasma irradiation

2014 Tenth International Vacuum Electron Sources Conference (IVESC)

et al. 2014

In-situ non-destructive method of surface analysis at plasma/ion treatment is presented. A differentially pumped energy analyzer is used for ion scattering and ionized recoil spectroscopy under grazing incidence conditions in automated ion mass monochromator. Build in Penning plasma source is used for plasma/ion treatment of targets.For investigation of plasma surface interaction in fusion devices it is very important to realize during plasma irradiation in situ analysis of surface layers composition and its thickness. In this work first experimental results obtained at new facility based on "MEPhI mass monochromator"[1] with low and medium energy ion spectroscopy are presented.A differentially pumped energy analyzer is used for scattered ions and ionized recoil spectroscopy under grazing incidence conditions. The mass monochromator permits to separate the ions with mass to charge ratios of up to M/Z = 100 and maximum beam energy of up to 40 keV. Ion beam with low level of impurities is produced by the duoplasmatron with an automated power supply and mass flow controller of work gases. With helium as a working gas, admixture of impurities (with hydrogen ions predominating) is less that 1% as compared to current of He + ions). The energy spread of the beam at 5 keV is~5×10 −3 , with angular divergence of~0.01 rad. Figure 1. Energy spectra of positive (top) and negative (bottom) ions knocked out from the target during bombardment with Ar + with energy of 7,5 keV at different temperatures.The interaction chamber is pumped by a TMP with pumping speed ∼10 3 l/s. A build-in plasma/ion source, with a penning discharge operating at relatively low working pressures (∼10 −4 Torr) provides a working gas (Ar) pressure in chamber less than ∼10 −3 Torr at a current density of 100mkA/cm 2 .The analyzer detects the ions scattered at angle θ = 16°. A solid angle of scattered particle is ∼1.1 ×10 −3 sr with the half width of scattering angle ∆ϑ = ±0.6°, its energy resolution is not greater than 0.8%. The ion current is detected using a secondary emission multiplier. Figure 2. Behavior of the ion C − and O − peaks sputtered from the W surface depending on the time during heating surface and irradiation Xe + and typical energy spectra positive Ar + ions reflected from the surface and/or embossed surface (small picture).Since hydrocarbons and water (hydrogen, oxygen, carbon) are the main light impurities in fusion facilities (apart from specially introduced boron or lithium), these elements (being in close affinity with an electron) can be detected via the analysis of negatively charged recoil atoms during irradiation by ions of inert gases. This allows increasing the sensitivity of the method due to the low probability of formation negative ions of inert gases. Figure 1 shows the energy spectrum of positive (top) and negative (bottom) ions obtained during bombardment of tungsten target with 7,5 keV Ar + ions. The bottom plot clearly shows two maxima corresponding to the recoils of C − and O − .Ions of heavy noble gases are more suit...