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HiCAT - a Novel Diagnostic for Mass Loss and Species Composition Analysis. L. Schmitz, P. Calderoni, Y. Tajima, A. Ying University of California, Los Angeles.
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HiCAT- a Novel Diagnostic for Mass Loss and Species Composition Analysis L. Schmitz, P. Calderoni, Y. Tajima, A. Ying University of California, Los Angeles Goal:Provide In-situ, real time characterization of ablated/ vaporized materials (density, species composition) Principle of HiCAT: • Ablated/vaporized material is ionized/excited in a well controlled pulsed plasma discharge. The species densities and composition are determined by quantitative emission spectroscopy. Advantages compared to conventional surface analysis (Coupons, Weight loss measurements, SEM): • In situ, real-time measurements with high time resolution (down to ns range depending on vapor density) • Compact (1/2” diameter x 3” length) • Quantitative mass loss can be determined with appropriate geometry and/or modeling)
Principle of Operation t1 t2t3 Time Resolved Measurements of Ablated Species Density Line Intensity Target Time PMT PMT Ion/Laser Beam 0.25 m Dual Monochromator 0.25 m Dual Monochromator HiCAT FiberOptics t1t2t3 Fast Piezo Valve Ignitrons Ar / He Gas Capacitor Bank (10 kJ) C = 3 x 55 uF
PMT PMT HiCAT Development Ocean Optics compact spectrometer Fiber Optic Ar Ion Lines Lens Dual 0.27 m Monochromators Ar Neutral Lines Hollow Cathode 0.5” Diameter 3 ” Length Capacitor Bank 2 kJ • A compact (~15 mm diam.), high power pulsed hollow cathode discharge has been developed to ionize vaporized/ablated material. • High density, nearly fully ionized plasma (n < 1017 cm-3, kTe < 2 eV) with local thermodynamic equilibrium (LTE) allows simplified spectroscopic determination of plasma parameters needed to interpret materials spectra. • Operation in Argon/Helium background gas or (0.01-5 torr) or as vacuum arc. Z-BoxTest Chamber (Vacuum Capable Glove Box)
Plasma temperature and density fromspectral line ratio/continuum radiation (needed to evaluate ablated species like Fe, Cl, Na, Mg) Line ratio of two Ar ion lines is measured [488[nm](ArII) / 750[nm](ArII)]. Electron (plasma) temperature is given by the following two equations Ar Pressure=2.5 Torr I Ar II / IAr I With xi: ionization energy EI, EII: Upper level energy for both transitions gI, gII:Statistical weights Aki I, Aki II : Transition probabilities With Pff: emission power density Gff: Gaunt factor for free-free transitions gI, gII:Statistical weights Aki I, Aki II : Transition probabilities
HiCAT Proof of Principle Tests + HV - HiCAT Ar Gas Li Vapor Heater Li-Al Block ThermoCouple Measured Lithium density compared to vapor pressure equilibrium density (pAr= 0.3 torr) L. Schmitz et al., J Nucl. Mat. 337-339 (2005) 1096 Plasma Discharge
UCLA Pulsed Plasma Research Facility Z-BoxTest Chamber (Vacuum Capable Glove Box) 20 kJ Capacitor Bank Plasma Discharge
Z-IFE Fusion Power Plant Concept Relative Iron Density vs. initital free chlorine concentration Spectral Intensity t =200 ms after breakdown Na I, He I 0.14 nFe (t=200 micro-s)/nFe(t=0) 0.12 Cl II 0.1 He I 0.08 Fe I 0.06 0.04 0.02 l (nm) 0 40.00 80.00 120.00 nCl(t=0) [a.u.] 160.00 Carbon steel RTL destroyed by fusion explosion is partially vaporized and ionized. Carbon steel fragments need to be recycled from molten flibe pool. Ferritic Fluoride(FeF3) production may cause high rate of impurities and make recycling impractical. Experimental characteri-zation of free fluorine recombination with ferritic steel needs to be performed. We use a substitute eutectic (NaCl-MgCl2)
