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| Hauptseite > Publikationsdatenbank > Entwicklung und Einsatzverhalten von aktiv gekühlten Testlimitern für das Fusionsexperiment TEXTOR |
| Hauptseite > Publikationsdatenbank > Entwicklung und Einsatzverhalten von aktiv gekühlten Testlimitern für das Fusionsexperiment TEXTOR |
| Book/Report | FZJ-2019-01705 |
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1996
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag
Jülich
Please use a persistent id in citations: http://hdl.handle.net/2128/21747
Report No.: Juel-3312
Abstract: To investigate aspects of the plama-wall-interaction in fusion devices, TEXTOR ($\underline{T}$oroidal$\underline{E }$xperiment for $\underline{T}$echnology $\underline{O}$rientated $\underline{R}$esearch) provides a favourable testbed. The enhanced possibilities of TEXTOR-94 enable to study typical erosion- and redeposition phenomena on plasma exposed surfaces under stationary, technology relevant conditions. For these purposes actively cooled test limiters are developed and described in their experimental behaviour. Compared to the maximum length of plama discharges in TEXTOR of 10 s, these limiters reach a stationary state within 5,5 s. The detailed analysis of the thermal load conditions led to an optimized geometry of the test limiters. The use of the new load lock system "TEXTOR-Schleuse-III" limits the maximum diameter of the inserted structures to 120 mm. Both, the heat load distribution at the limiter surface and the restrictions of the load lock system, led to the selection of a hemispherical shape with a maximum diameter of 80 mm at the top of the test limiters. They where realized in two technological variants. The first variant was a brazed compound of a metallic heat sink (TZM) with carbon materials as the two directional C/C material SEPCARB-N11 or the fine grain graphite IG 610. The second one was a TZM heat sink, coated with thermally sprayed tungsten. The choosen braze was CulCr. The used thermal spray technology was LPPS ($\underline{L}$ow $\underline{P}$ressure $\underline{P}$lasma $\underline{S}$praying). For the analysis of the thermomechanical conditions in the joined hemispherical test limiter, analytical as well as numerical estimations of the transient spatial tempmeratures were done. Both methods predicted a stationary temperature on the C/C surface is 1150$^{\circ}$ C. In the joining zone 630 $^{\circ}$ C. are reached, at the cooling surface 220 $^{\circ}$ C. For the coated test liiter the calculations predicted stationary conditions after 2 s and a maximum hot spot temperature of 550 $^{\circ}$ C. A qualitative, numerical analysis of the von Mises equivalent stress was done for the C/C-TZM brazing compound. In the hot spot zone moderate stress levels as weIl as stress amplitudes appear. Maximum stress levels and stress amplitudes were predicted in the equatorial area of the hemispherical test limiter. Stress levels in the TZM structure are approximately four times higher than in the carbon materials. Mismatches in the elastomechanical properties of the joining partners locally generate high stress levels. They were reduced by the use of the ductile Cu1Cr braze and an optimized interface design. High heat flux tests with prototype test limiters in the ion beam test facility MARION($\underline{M}$aterial $\underline{R}$esearch $\underline{I}$on Beam Test Facility) confirmed the calculated cooling behaviour and the application reliability of the components under high vacuum conditions and high heat loads. An optimized brazed test limiter was inserted in TEXTOR for 101 plasma discharges. Experimental results with heat loads of up to 12 MW/m$^{2}$ are in excellent agreement with the mathematical models and confirmed the structural integrity of the joined structure. Physical and chemical erosion of carbon from the limiter surface could be observed. Erosion and redeposition phenomena led to an optical change of the C/C surface, but no significant loss of C/C material was detectable.
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