ITER ELM Plasma Simulator A Promising Component of the US PFC Materials Test Program or Mark II...
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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
WQP
t
KJk
KgJC
gmt
TTkCmQ
TTktQTTCm
inthermal
p
initialfinalpin
finalininitialp
5.0
sec180
/1.1
/385.0
341.0
)()(
)()()(
:nCalculatioThermal
WP
cmA
eVT
mn
TAvn
TAP
Plasma
e
e
ePlasma
35.0
1
5.3
102
4
2
316
:nCalculatioPlasma
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
[email protected]@starfireindustries.com