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HiCAT- a Novel Diagnostic for Mass Loss and Species Composition Analysis
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)
L. Schmitz, P. Calderoni, Y. Tajima, A. YingUniversity of California, Los Angeles
Principle of Operation
1 2 3
C = 3 x 55 uF
0.25 m DualMonochromator
0.25 m DualMonochromator
PMT PMT
Target
Ion/Laser Beam
HiCAT
Fast Piezo Valve
Ignitrons
1 2 3
TimeLin
e I
nte
ns
ity
FiberOptics
CapacitorBank (10 kJ)
Ar / HeGas
Time Resolved Measurements ofAblated Species Density
HiCAT DevelopmentEmission Spectrum of > 90% Ionized
Pulsed Argon Plasma
100
300
500
700
300 400 500 600 700 800
Wavelength [nm]
Inte
nsi
ty [
a.u
.]
Ar Ion Lines
• 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.
Ar Neutral Lines
Lens
Fiber Optic
Capacitor Bank2 kJ
Dual 0.27 m Monochromators
Ocean Opticscompact
spectrometer
PMTPMT
Hollow Cathode0.5” Diameter3 ” Length
Plasma temperature and density fromspectral line ratio/continuum radiation (needed to evaluate
ablated species like Fe, Cl, Na, Mg)
Plasma Density
0
1E+16
2E+16
3E+16
4E+16
5E+16
0 1E-05 2E-05 3E-05 4E-05 5E-05
Time (s)
Den
sity
n (c
m-3
)
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
With xi: ionization energy EI, EII: Upper level energy for both transitions gI, gII: Statistical weights Aki I, Aki II : Transition probabilities
][)1032.2(
)/))(exp((
)][6.13
(
322
2
3
,
,
,
,
cmn
kTEEx
eV
kT
g
g
A
A
I
I
eIIIi
e
II
I
Iki
IIki
Iki
IIki
I
II
Pff (1.9 10 28)G ff
Z 2nine2Te
1/ 2 exp(hc
kTe)
With Pff: emission power density Gff: Gaunt factor for free-free transitions gI, gII: Statistical weights Aki I, Aki II : Transition probabilities
0.1
1
10
100
0.00E+00 1.00E-05 2.00E-05 3.00E-05 4.00E-05
time [sec]
Ar Pressure=2.5 Torr
I A
r II /
IA
r
I
Electron Temperature
00.5
11.5
22.5
33.5
0.00E+00 2.00E-05 4.00E-05
Time (s)
kTe [
eV]
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
ThermoCouple
+ HV-
Heater
ArGas
Li-AlBlock
HiCAT
Li Vapor
PlasmaDischarge
UCLA Pulsed Plasma Research Facility
Z-BoxTest Chamber(Vacuum Capable Glove Box)
PlasmaDischarge
20 kJCapacitorBank
160.00
Relative Iron Density vs. inititalfree chlorine concentration
0
0.02
0.04
0.06
0.08
0.1
0.12
0.14
40.00 80.00 120.00
nCl(t=0) [a.u.]
t =200safter breakdown
nF
e (t
=2
00
mic
ro-s
)
/nF
e(t=
0)
0
1000
2000
3000
4000
5000
300 400 500 600 700
Spectral Intensity
(nm)
Fe I
Cl II
Na I, He I
He I
Carbon steel RTL destroyed by fusion explosion is partially vaporized and ionized. Carbon steel fragments need to be recycled from molten flibe
pool.
Experimental characteri-zation of free fluorine recombination with ferritic steel needs to be performed. We use a substitute eutectic (NaCl-MgCl2)
Ferritic Fluoride(FeF3) production may cause high rate of impurities and make recycling impractical.
Z-IFE Fusion Power Plant Concept