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Tungsten-Steel Composites and FGMs Produced by Hot Pressing
Matějíček, Jiří ; Boldyryeva, Hanna ; Brožek, Vlastimil ; Čižmárová, E. ; Pala, Zdeněk
Tungsten-steel composites and FGMs are being developed for potential application in plasma facing components of fusion devices. In this study, uniform composites and graded layers produced from tungsten and steel powders by hot pressing were investigated. Formation of dense composites with uniform distribution and good bonding of the phases was observed. A thin layer of intermetallic phase Fe7W6 formed at the interfaces. Thermal and mechanical properties of the composites in the as-produced and annealed state were characterized.
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Korekce optických vad astronomických zrcadel
Rail, Zdeněk ; Jareš, Daniel ; Tomka, David ; Doleček, Roman
Velká a světelná astronomická zrcadla vykazují značné mimoosové vady. Aby je bylo možné použít pro fotografování oblohy, je nutné použít ke korekci jejich vad korektory. S nimi je možné dosáhnout radikálního zlepšení obrazů hvězd na rovinném poli o velkém úhlovém průměru a v širokém spektrálním oboru. Korektory jsou napočítány jak pro zrcadla o sférickém, paraboloidickém i hyperboloidickém tvaru. Korekce vad je předvedana jak pro sférické,tak pro paraboloidickéi hzperboloidické zrcadlo.
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Dynamics of cavitation induced by focused tandem shock waves in water
Hoffer, Petr ; Šunka, Pavel ; Lukeš, Petr
Cavitation associated with the generation of shock waves in water was examined. To study these processes, a tandem shock wave generator, which generates two cylindrical pressure waves focused by a metallic parabolic reflector to a common focal region, was developed. The temporal evolution of cavitation generated by shock waves at the focal region was determined experimentally using high-temporal-resolution microphotography for a certain time delay between the first and second shock waves. Observation of the focal area also showed jetting cavitation bubbles with diameters of 100 m without presence of any rigid boundary. A theoretical model that provides analytical expressions for the temporal evolution of the pressure inside the cavitation bubbles and parameters of the pressure waveform of the second shock wave at the focal area was used to improve the same measurement by PVDF sensor gauges. On the basis of this model, the amplitudes of the compression and rarefaction parts
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Keramické povlaky připravené metodou LPPS
Brožek, Vlastimil ; Kutílek, Zdeněk ; Bertolissi, Gabriele ; Mastný, L.
Metodou LPPS (Liquid precursor plasma spraying) byly z vodných roztoků chromanu a vanadičnanu amonného připraveny keramické nanokrystalické povlaky na ocelových i keramických substrátech, byla studována jejich struktura a ověřovány podmínky vnášení kapalných prekurzorů do proudu vodou stabilizovaného plazmatu. Nano-povlaky a jejich dokonalé pokrytí povrchu substrátů je nepřímo úměrné koncentraci prekurzoru a především závislé na geometrickém uspořádání depozičního zařízení, v němž dochází ke složitému vícestupňovému procesu zpracování prekurzoru v průběhu jednotek milisekund.
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Simulations of Runaway Electrons
Papřok, R. ; Krlín, Ladislav ; Cahyna, Pavel
In this paper we discuss current knowledge of phenomena of runaway electrons in tokamaks. We summarize experimental facts and investigate theoretical understanding of runaway electrons. We also present result of our recent work concerning influence of JET’s Error Filed Correction Coils on runaway electrons dynamics. At the end of our paper we describe our plan to study runaway electrons dynamic in time and space varying magnetic field during plasma disruption as obtained from global MHD code JOREK.
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U-probe for the COMPASS Tokamak
Kovařík, Karel ; Ďuran, Ivan ; Stöckel, Jan ; Seidl, Jakub ; Šesták, David ; Brotánková, J. ; Spolaore, M. ; Martines, E. ; Vianello, N. ; Hidalgo, C. ; Pedrosa, M. A.
A complex electrostatic-magnetic probe diagnostics, baptized as 'U-probe', is being prepared for measurement of properties of the filamentary structures in the edge plasmas of COMPASS tokamak. Probe will be composed of two identical towers. Each tower will house 3 sets of 3D coils, balanced triple probe and six single Langmuir probes each. The design of the probe is based on that of U-probe used on reversed field pinch RFX-mod and our combined electromagnetic probe at TJ-II stellarator. This new COMPASS diagnostic will measure vorticity and longitudial electric current of the plasma filaments. Analysis of the properties and, particularly, the correlation between filament vorticity and its current is expected to shed light into physics of filamentary structures in the tokamak plasma edge. The simulation of the probe surface temperature evolution as a function of expected incident heat loads within the COMPASS edge plasmas is presented.
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