david n. ruzic , j. norman, j.p. allain, m. boaz, and n. li

L I M I TLiquid Metal Illinois Toroidal Test

Facility

Toroidally Symmetric Liquid Metal J X B ExperimentsDavid N. Ruzic, J. Norman,

J.P. Allain, M. Boaz, and N. Li

Department of Nuclear, Plasma and Radiological Engineering, University of Illinois

at Urbana-Champaign

APS / DPP October 26, 2000

Outline

Motivation Experiment Pool Experiments Flow Experiments Analysis Future Work Acknowledgments

Motivation

Flowing liquid metal walls can… withstand high heat fluxes rapidly remove heat withstand disruptions reduce impurity influx introduce new operating regimes

Will they work as we expect? Build a device and test the LIMITs

LIMIT -- LIquid Metal Illinois Toroidal test facility

40 Coils

Pyrex reservoir

Ga reservoir

Pyrex center column

SS support structure

40

cm

height

LIMIT --- Top view

50 cm diameter

LIMIT -- LIquid Metal Illinois Toroidal test facility

LIMIT Characteristics

40 coils of 12 Gage wire. R=0.13 Ohms 27 V creates 200 Amps and produces

1000 Gauss at outside radius of center column

5 kW of heat limits duration of experiments

200 A available to pass through liquid metal Resistance of Gallium pool plus contact resistance is 0.015 Ohms.

Magnetic Field at 190 Amps

B Field

0

200

400

600

800

1000

1200

0 1 2 3 4 5 6 7 8 9 10r(cm)

B(G

)

Electrodes

Copper tape Striped and flattened magnet wire

leads Two concentric circles at bottom of

pool to produce a uniform radial current

Current density will decease as R increases, but pool depth will decrease too near edge.

LIMIT --- with electrodes and pool of gallium

Power Supplies Courtesy of

PPPL and INTEL

Tokamak First Wall :self propelled metal concept

RB

1

externally supplied current

may cause metal to flow up outboard

wall

J X B up, J=200 A, B raised to 1000 Gauss

J X B down, J=200 A, B raised to 1000 Gauss

J X B down, J=200 A, B raised to 1000 Gauss

J X B up, J=200 A, B raised to 1000 Gauss

Force Calculation

0

2

4

6

8

10

12

0 1 2 3 4 5 6 7 8 9 10

r(cm)

B(*100 G)

J(A/cm^3)

F(*10^3 N/m^3)

How Big is this Force ?

On inner most 5 mm Force of Gravity = 0.3 N J X B Force = 0.09 N 30%

On inner most 1 mm Force of Gravity = 0.05 N J X B Force = 0.02 N 40%

Flow down the central column

One electrode near top One electrode near bottom Flow Ga down center column Current path created when Ga

reaches bottom J X B can be radially in or out

Electrodes after Ga wetting

Flow down center post, J X B radially inward

Flow is thinned and boring

Flow down center post, J X B radially outward Flow is bunched and explosive

Side view of J X B force radially outward

Ejected Material !

Close up of ejected gallium from central column

Analysis

200 A flows through a small cross section

Force of gravity downward = 0.0026 N

Force outward = 0.325 N

125 times gravity Ballistic droplets of Ga result and

impinge on far wall.

Conclusions Surface instabilities still arise in toroidally

symmetric configuration Magnetic propulsion not observed Expansion against free surface boundary is

seen Center stack flowing liquid metal can be

severely thinned Care must be exercised in center stack eddy

current formation to avoid injecting liquid metal into a plasma

Future Work

More experiments More galium to wet entire center

stack Secondary current configurations Comparison to theory Investigation of ripples

Acknowledgments

PPPL for equipment and funding DOE, APEX program Undergraduates:

Collen Marron-Beebe Hussain Nomanbhai Shadi Beidas