HiCAT a Novel Diagnostic for Mass Loss and Species Composition Analysis

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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)

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Principle of Operation
t1 t2 t3
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
t1 t2 t3
Fast Piezo Valve
Ignitrons
Ar / He Gas
Capacitor Bank (10 kJ)
C 3 x 55 uF
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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 lt
  1017 cm-3, kTe lt 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)
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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
488nm(ArII) / 750nm(ArII). Electron
(plasma) temperature is given by the following
two equations
Ar Pressure2.5 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
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HiCAT Proof of Principle Tests
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
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UCLA Pulsed Plasma Research Facility
Z-BoxTest Chamber (Vacuum Capable Glove Box)
20 kJ Capacitor Bank
Plasma Discharge
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Z-IFE Fusion Power Plant Concept
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)