ITER ELM Plasma ITER ELM Plasma SimulatorSimulator

A Promising Component of the A Promising Component of the US PFC Materials Test ProgramUS PFC Materials Test Program

oror

Mark II Plasma DisruptorMark II Plasma Disruptor

R. StubbersR. Stubbers11, T.K. Gray, T.K. Gray22, B.C. Masters, B.C. Masters22, D.N. , D.N. RuzicRuzic22

11Starfire Industries LLCStarfire Industries LLC22University of Illinois, Plasma-Material Interaction University of Illinois, Plasma-Material Interaction GroupGroup

OverviewOverview

Need for an ELM plasma simulatorNeed for an ELM plasma simulator Phase I proof-of-concept conical Phase I proof-of-concept conical

theta pinch ELM simulatortheta pinch ELM simulator Scaling to ITER ELMs in Phase IIScaling to ITER ELMs in Phase II Phase II-III, ELM plasma Phase II-III, ELM plasma

simulation user facilitysimulation user facility

Why Study ELMs?Why Study ELMs?

Why do we need this Why do we need this facility?facility?

Vapor barrier/macro Vapor barrier/macro particle formationparticle formation

Test plasma-material Test plasma-material interaction physicsinteraction physics

Augment and Augment and enhance existing US enhance existing US PFC programsPFC programs

Future development Future development basebase

Fits into US Fits into US Contribution to ITERContribution to ITER The NEEDThe NEED

– Advantageous tokamak H-modes accompanied by ELMsAdvantageous tokamak H-modes accompanied by ELMs– Apples-to-apples measurement of ELM Apples-to-apples measurement of ELM plasmaplasma material material

interactions is desiredinteractions is desired– Experimental facility for high-fidelity ELM plasma simulation Experimental facility for high-fidelity ELM plasma simulation

facility is needed facility is needed OpportunityOpportunity

– Complete PFC characterization suite including accurate ELM plasma Complete PFC characterization suite including accurate ELM plasma simulationsimulation

Sandia-Albuquerque has e-beam cyclic high-heat flux and lifetime Sandia-Albuquerque has e-beam cyclic high-heat flux and lifetime testing – accurate thermal loading and profile of ELMstesting – accurate thermal loading and profile of ELMs

Argonne modeling for ELM plasma surface interactionsArgonne modeling for ELM plasma surface interactions UCSD is a beryllium mixed material test bed and steady-state plasma UCSD is a beryllium mixed material test bed and steady-state plasma

exposure testsexposure tests UIUC completes picture with ELM plasma simulation facilityUIUC completes picture with ELM plasma simulation facility

– Thermal CyclingThermal Cycling– ELM event physicsELM event physics– Steady-state divertor plasma loadingSteady-state divertor plasma loading– Divertor ELM particle loading and erosionDivertor ELM particle loading and erosion

Phase I FacilityPhase I Facility

Quick and inexpensive Quick and inexpensive proof of conceptproof of concept– Use a conical theta Use a conical theta

pinch to increase pinch to increase density and temperature density and temperature of plasmaof plasma

– Use ringing PFN to get Use ringing PFN to get multiple pinches to multiple pinches to simulate what an ELM simulate what an ELM looks likelooks like

– Use multiple ringing Use multiple ringing PFNs to achieve ELM PFNs to achieve ELM durationsdurations

– Translate plasma into a Translate plasma into a target region with strong target region with strong magnetic fieldmagnetic field

On a Phase I BudgetOn a Phase I Budget

Largely built with scrap Largely built with scrap and home-made and home-made equipmentequipment– Existing coil remachined Existing coil remachined

to conical interiorto conical interior– Miscellaneous vacuum Miscellaneous vacuum

equipmentequipment– Left-over power suppliesLeft-over power supplies– Home-made trigger Home-made trigger

circuits circuits A little help from e-bay, A little help from e-bay,

Starfire equipment and Starfire equipment and some new equipmentsome new equipment– Maxwell trigger delaysMaxwell trigger delays– SpectrometerSpectrometer– High-voltage probesHigh-voltage probes– Glass pinch tubeGlass pinch tube

Phase I – Pulse Phase I – Pulse Length/StructureLength/Structure

Multiple pulses To Multiple pulses To achieve ELM envelopeachieve ELM envelope– 0.1 to 1 msec time 0.1 to 1 msec time

scale with primitive scale with primitive switchingswitching

– Easily improved with Easily improved with better switching better switching (clamping of pulse tail)(clamping of pulse tail)

Plasma blob Plasma blob subfrequencysubfrequency– ~10-100 microseconds~10-100 microseconds

Plasma blob transportPlasma blob transport– Translation onto targetTranslation onto target– Velocity ~5X10Velocity ~5X1044m/sm/s

Density and Density and TemperatureTemperature Density ScalingDensity Scaling

– Density ~5X10Density ~5X101717/m/m33 at 5kV (0.69 kJ)at 5kV (0.69 kJ)

– Measured 2X10Measured 2X101818/m/m33 at 10kV (2.75 kJ)at 10kV (2.75 kJ)

Temperature ScalingTemperature Scaling– Measured ~25eVMeasured ~25eV

Magnetic FieldsMagnetic Fields– 1-kG level Steady 1-kG level Steady

StateState– 1-Tesla pinch field1-Tesla pinch field

Approaching NSTX Approaching NSTX level ELMs in Phase Ilevel ELMs in Phase I

Thermocouple HeatingThermocouple Heating

Target PlateTarget Plate Insulated Insulated

thermocouple thermocouple embedded in embedded in copper foilcopper foil

Temperature rise Temperature rise due to RF plasma due to RF plasma has been measuredhas been measured

Provides means of Provides means of confirming heating confirming heating estimates from TLP estimates from TLP measurementmeasurement

0 1 2 3 4 50

10

20

30

40

50

60

70

80

90

100Cu Sample Heating (200 W Plasma)

Data: Data5_BModel: ExpDec1 Chi^2 = 14.12229R^2 = 0.98969 y0 98.04796 ±2.49938A1 -73.30374 ±4.3761t1 0.85608 ±0.13973C

u S

am

ple

Te

mp

. (°

C)

Time (min)

5 6 7 8 9 10 11 12 13

20

30

40

50

60

70

80

90

Cu Sample Cooling (200 W Plasma)

Data: Data1_BModel: ExpDec1 Chi^2 = 1.37617R^2 = 0.99544 y0 24.84576 ±0.31775A1 22592.2367 ±3993.32152t1 0.89894 ±0.02622

Cu

Sa

mp

le T

em

p.

(°C

)

Time (min)

Calorimetry Calorimetry Verification of TLPVerification of TLP Temperature rise Temperature rise

measurements measurements confirm TLP Plasma confirm TLP Plasma measurementsmeasurements

Both indicate Both indicate ~0.5W plasma ~0.5W plasma heating on copper heating on copper plate with only plate with only target helicon target helicon plasma presentplasma present

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Phase I SummaryPhase I Summary

Phase I effort provided good proof Phase I effort provided good proof of conceptof concept– Demonstrated subfrequency with Demonstrated subfrequency with

ringing PFNringing PFN– Demonstrated appropriate, Demonstrated appropriate,

adjustable effective pulse duration adjustable effective pulse duration using sequentially-fired PFNsusing sequentially-fired PFNs

– Demonstrated plasma heating and Demonstrated plasma heating and translation to targettranslation to target

Scaling To ITERScaling To ITER

Expected ITER ELM Expected ITER ELM Conditions (and desired Conditions (and desired ELM simulation ELM simulation parameters)parameters)– ~ 10~ 101919/m/m33

– ~1 keV temperatures~1 keV temperatures– ~1 ms duration~1 ms duration– ~5 Tesla B fields (DC)~5 Tesla B fields (DC)– ~10MJ/m~10MJ/m22

Present conditions in ELM Present conditions in ELM simulatorsimulator– 2X102X101818/m/m33

– ~25eV~25eV– 1 ms duration1 ms duration– 0.1 Tesla B fields (DC)0.1 Tesla B fields (DC)– ~10kJ/m~10kJ/m22

ELM ELM ParameterParameter

ITERITER NSTXNSTX UIUC UIUC (present)(present)

Power LoadingPower Loading ~10 MJ/m~10 MJ/m22 <1 MJ/m<1 MJ/m22 10 kJ/m10 kJ/m22

ELM Event ELM Event FrequencyFrequency

~1-10 Hz~1-10 Hz 10-20 Hz10-20 Hz Single shotSingle shot

Total ELM Total ELM DurationDuration

~0.1-1 ms~0.1-1 ms ~1 ms~1 ms 1 ms1 ms

Blob Blob SubfrequencySubfrequency

~10-100 kHz~10-100 kHz ~10 kHz~10 kHz 10 kHz10 kHz

Temperature Temperature During ELM During ELM (~T(~T

pedestalpedestal))

1-2.5 keV1-2.5 keV 100 eV100 eV 20-40 eV*20-40 eV*

Density During Density During ELM (~nELM (~n

pedestalpedestal))~10~101919/m/m33 ~10~101919/m/m33 10101818/m/m3*3*

Divertor Field Divertor Field Strength (~BStrength (~B

tt))~1-5 T~1-5 T ~0.5 T~0.5 T 0.1 T0.1 T

Theta Pinch ScalingTheta Pinch Scaling

Ideal CaseIdeal Case– For ideal magnetic-kinetic pressure balance (perfect For ideal magnetic-kinetic pressure balance (perfect

coupling), only ~700 Gauss is required to contain 1-keV coupling), only ~700 Gauss is required to contain 1-keV 10101919/m/m33 plasma plasma

– Coupling efficiency depends on dI/dt (bank inductance) and Coupling efficiency depends on dI/dt (bank inductance) and magnetic diffusion time (preionization source density and magnetic diffusion time (preionization source density and temperature)temperature)

– Therefore, field in pinch region is already adequateTherefore, field in pinch region is already adequate Energy ScalingEnergy Scaling

– Crude scaling: Energy flux out scales linearly with bank Crude scaling: Energy flux out scales linearly with bank energyenergy

– Based on this scaling and Phase I measured results, ~2MJ/mBased on this scaling and Phase I measured results, ~2MJ/m22 could be achieved with 250kJ bank (200+ times the energy could be achieved with 250kJ bank (200+ times the energy input)input)

– Present pinch field (4-10 kGauss with 10kV on bank) would Present pinch field (4-10 kGauss with 10kV on bank) would be more than enough if coupling were better be more than enough if coupling were better

– Crude scaling neglects improvements to coupling – power Crude scaling neglects improvements to coupling – power levels on target could be even better.levels on target could be even better.

Theta Pinch Scaling Theta Pinch Scaling (cont)(cont) Coupling Improvement – dI/dt ScalingCoupling Improvement – dI/dt Scaling

– Phase I current rise times are ~13-17Phase I current rise times are ~13-17s – s – veryvery long long compared to an estimated magnetic diffusion time of ~1 compared to an estimated magnetic diffusion time of ~1 s.s.

– Decreased bank inductance (~20nH/capacitor compared Decreased bank inductance (~20nH/capacitor compared to ~500nH/capacitor) will lead to a rise time less than to ~500nH/capacitor) will lead to a rise time less than 1/101/10thth present value. present value.

– dI/dt can increase further if capacitors are connected in dI/dt can increase further if capacitors are connected in parallel (likely with 2 parallel (likely with 2 F capacitors), and operated at F capacitors), and operated at higher voltage (60 kV instead of 10kV)higher voltage (60 kV instead of 10kV)

– Magnetic diffusion time can be increased with improved Magnetic diffusion time can be increased with improved preionization source.preionization source.

With pulse rise time near or less than the magnetic With pulse rise time near or less than the magnetic diffusion time, coupling should more closely resemble diffusion time, coupling should more closely resemble ideal case than linear case, and a factor of 10 or ideal case than linear case, and a factor of 10 or greater improvement can be expectedgreater improvement can be expected

Phase II – ITER ELM Phase II – ITER ELM SimulationSimulation Scale-up to reach ITER Scale-up to reach ITER

ELM demoELM demo– 250 kJ bank250 kJ bank– 56 60-kV 2-56 60-kV 2-F F

capacitors (~20nH capacitors (~20nH inductance each)inductance each)

– Bank divided into 4 Bank divided into 4 independent PFNsindependent PFNs

Expected Phase II Expected Phase II plasma parametersplasma parameters– Density ~10Density ~101919/m/m33

– Temperature ~1keVTemperature ~1keV– Duration ~0.5-1msDuration ~0.5-1ms

An ITER ELM simulator An ITER ELM simulator can be built at Illinoiscan be built at Illinois

Phase II PlanPhase II Plan

Use Installed base at Use Installed base at University of IllinoisUniversity of Illinois

Utilize existing capacitor Utilize existing capacitor bank and set it up for 60kV bank and set it up for 60kV operation at 250kJ.operation at 250kJ.– Significant undertaking to Significant undertaking to

build transmission line build transmission line system.system.

– Some transmission lines exist, Some transmission lines exist, but division of bank neededbut division of bank needed

– Switching is a challenge at 60 Switching is a challenge at 60 kVkV

New coil, magnet assembly New coil, magnet assembly and other components.and other components.– 5 Tesla field is also 5 Tesla field is also

challengingchallenging– Will likely be pulsed (slowly)Will likely be pulsed (slowly)

Two-year effort to Two-year effort to demonstrate ITER-level ELM demonstrate ITER-level ELM eventsevents

Work toward Phase III ELM Work toward Phase III ELM plasma test facilityplasma test facility

Resources Almost Resources Almost ThereThere Joint Investment byJoint Investment by

– University of IllinoisUniversity of Illinois– Starfire IndustriesStarfire Industries– STTR ProgramSTTR Program– DOEDOE

In-kind expenses In-kind expenses already committed already committed pending Phase II pending Phase II successsuccess– University of IllinoisUniversity of Illinois– Starfire IndustriesStarfire Industries

Plan for Phase II-IIIPlan for Phase II-III

Commercial ModelCommercial Model

ELM Test Facility in USELM Test Facility in US– National LabsNational Labs– AcademiaAcademia– Private IndustryPrivate Industry– International DevelopersInternational Developers

University of Illinois is an ideal locationUniversity of Illinois is an ideal location– Center for Microanalysis of Materials (DOE user Center for Microanalysis of Materials (DOE user

facility) – mutually complementary with ELM test facility) – mutually complementary with ELM test facilityfacility

– Centrally locatedCentrally located– Existing equipment and know-howExisting equipment and know-how

SummarySummary

Phase I successfully demonstrated Phase I successfully demonstrated conical theta pinch ELM simulator conical theta pinch ELM simulator conceptconcept

Phase II ITER ELM demo – Phase I data Phase II ITER ELM demo – Phase I data and scaling support ITER ELM simulation and scaling support ITER ELM simulation is possible with reasonable investmentis possible with reasonable investment

Good path toward ELM plasma Good path toward ELM plasma simulator user facility after Phase II simulator user facility after Phase II demo (Phase III)demo (Phase III)

Questions/ContactQuestions/Contact

Robert StubbersRobert Stubbers

Starfire Industries LLCStarfire Industries LLC

rstubbers@starfireindustries.comrstubbers@starfireindustries.com