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