Untersuchungen zur Bestimmung der Flußdichte von zerstäubtem Eisen mittels laserinduzierter Fluoreszenz

Schweer, H.-B.

Book/Report

FZJ-2018-02299

Untersuchungen zur Bestimmung der Flußdichte von zerstäubtem Eisen mittels laserinduzierter Fluoreszenz

Schweer, H.-B. (Corresponding author)FZJ*

1983
Kernforschungsanlage Jülich, Verlag Jülich

Jülich : Kernforschungsanlage Jülich, Verlag, Berichte der Kernforschungsanlage Jülich 1876, 127 p. (1983)

Please use a persistent id in citations: http://hdl.handle.net/2128/17998

Report No.: Juel-1876

Abstract: In this work investigations are described to measure the flux density of sputtered iron atoms by means of laser induced fluorescence. Sputtering of the wall material by energetic charge exchange neutrals can be a dominant process for the release of metal impurities in controlled thermonuclear fusion reactors. The conversion of the iron density in the groundstate, the quantity which is measured by laser induced fluorescence with high spatial and temporal resolution, into the total flux density of Fe-alloys is necessary. For this purpose the knowledge of the groundstate density to the total density of iron, the mean velocity and the ratio of the flux density of iron to the total flux density of the alloy is required as a function of mass and energy of light ions. In a laboratory experiment an iron target was bombarded with 10 keV Ar$^{+}$ and 2.5 keV H$^{+}$ and the population distribution of the energy levels of the groundstate a $^{5}$D and the metastable state a $^{5}$F was measured. For sputtered iron atoms the population distribution in the ground state follows a Boltzmann distribution with an excitation temperature of $\sim$ 1000 K. About 55 % of the iron atoms were found in the state a $^{5}$D$_{4}$ (excitation energy E$_{a}$ = 0) and less than 2 % with excitation energies higher than 0.86 eV. If the spectral width of the laser radiation was reduced to 0.0005 nm at 300 nm the Doppler broadened absorption profile of the excitation line of sputtered atoms could be resolved. In the groundstate a $^{5}$D$_{4}$ the velocity distributions have been measured for the bombardment of the iron target with 10 keV Ar$^{+}$, 8 keV He$^{+}$ and 2.5 keV H$^{+}$. For these cases no significant deviations have been found and the mean velocity was determined to 2.4 km/s. The conversion factor between the density in thegroundstate and the total flux density of sputtered iron atoms was calculated to 4.45 km/s using the results of the population distribution and the mean velocity. In a further experiment the flux density measured by weigth loss and the iron density in the groundstate determined by laser induced fluorescence were compared in the energy range of 100 eV to 8 keV. Over this range the conversion factor was about constant and independent of the mass of the incident ions (H$^{+}$, D$^{+}$, He$^{+}$). If the iron target was replaced by stainless steel 316 and Inconel 600 targets, respectively, the measurements give as a result that the conversion factor must be increased according to the iron concentration in the alloy. In the plasma wall region in the ISX-B tokamak at the OakRidge National Laboratory (USA) neutral iron atoms were measured the first time by laser induced fluorescence. A detection limit of 10$^{6}$ atoms/cm$^{3}$ was found and sputtered iron atoms were observed in the first 15 ms of the discharge. After the end of the discharge neutral iron atoms could be detected and showed a thermal distribution with an excitation temperature of 500 K.

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