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Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.
Plans for addressing MagLIF hypotheses in 2017 and beyond
Patrick Knapp representing the MagLIF teamNISP Working GroupWashington D.C.September 13, 2016
2
As always, many people contributed to this talk….Matt Gomez1, Chris Jennings1, Stephanie Hansen1, Steve Slutz1, Kelly Hahn1, Eric Harding1, Paul Schmit1, Brian Hutsel1, Dean Rovang1, Gordon Chandler1, Edward Norris7, Adam Sefkow6, Dan Sinars1, Kyle Peterson1, Mike Cuneo1, Ryan McBride1, Tom Awe1, Matt Martin1, Dave Ampleford1, Carlos Ruiz1, Gary Cooper1, Bill Stygar1, Mark Savage1, Mark Herrmann3, Gregory Rochau1, John Porter1, Ian Smith1, Matthias Geisel1, Patrick Rambo1, Jens Schwarz1, Mike Campbell6, Brent Blue3, Kurt Tomlinson2, Diana Schroen2, Robert Stamm4, Ray Leeper5, Charlie Nakleh5
… And many many more1Sandia National Laboratories, Albuquerque, NM2General Atomics, San Diego, CA3Lawrence Livermore National Laboratory, Livermore, CA4Raytheon Ktech, Albuquerque, NM5Los Alamos National Laboratory, Los Alamos, NM6 Laboratory of Laser Energetics, Rochester, NY7 Missouri Univ. of Science and Technology, Rolla, MO
Thebroadthemeforaddressingexistinghypothesesisenergybalance
§ Howmuchenergyisabsorbed§ Howmuchenergyisscattered§ Howmuchmixisgenerated,
wheredoesitgo
4
Radial Posi tion [mm]
AxialPosition[m
m]
z2839: Ar Imager
−2 −1 0 1 2−10
−9
−8
−7
−6
−5
−4
−3
−2
−1
0
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
§ Whatisthehot-spotpressure,mass,volume
§ Whatisthedrivepressurenearstagnation
§ Howwellisthelinerconfiningthefuel
§ Isthereresidualkineticenergy
§ Whatistheradiationlossinflight§ Howeffectiveismagneticinsulation§ Whataretheend-losses
Detailed accounting of the energy in the system at each phase is critical to distinguish
between hypotheses
ElaserPdV PdV
LradLcond
Lend
Thebroadthemeforaddressingexistinghypothesesisenergybalance
§ Howmuchenergyisabsorbed§ Howmuchenergyisscattered§ Howmuchmixisgenerated,
wheredoesitgo
5
Radial Posi tion [mm]
AxialPosition[m
m]
z2839: Ar Imager
−2 −1 0 1 2−10
−9
−8
−7
−6
−5
−4
−3
−2
−1
0
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
§ Whatisthehot-spotpressure,mass,volume
§ Whatisthedrivepressurenearstagnation
§ Howwellisthelinerconfiningthefuel
§ Whatistheradiationlossinflight§ Howeffectiveismagneticinsulation§ Whataretheend-losses
Detailed accounting of the energy in the system at each phase is critical to distinguish
between hypotheses
Laser Heating
Recently,progresshasbeenmadeinresolvingthelaserenergydepositionproblem
§ Acombinedapproachoflasertransmissionstudiesandgas-cell studiesisbeingusednow
§ Wehavealreadymadetremendousprogressinunderstandingtransmittedandscatteredenergy
§ Moreworkneededonunderstandingenergydeposited
6
Gas cell experiments
ZBL
LEH foil (1.5 µm polyimide)
53 psi He gas fillProbe laser
Heated plasma
Backward scatter Laser shadowgram
Heated plasmaLEH foil
Gas cell
LEH transmission studies
Forward scatterBackward scatter
Transmitted energy measurement
LEH foil
1.5 µm polyimide
ZBL
Material courtesy Matthias Geissel and Adam Harvey-Thompson
Wewilldevelopthecapabilitytomeasurethegastemperatureasafunctionoftime
§ Neonisbelieved tobesensitivetosufficiently lowtemperatures totracktheincreaseinTe andsubsequentdecayastheenergy redistributesandradiatesaway
§ Thespectrometerwillviewtheheatedgasthrough theLEH
§ Theproposed instrument iscompatiblewithdownlineaswellasZBLonlyshotsonZandinPECOS
7
ZBL
LEH foil (1.5 µm polyimide)
Heated plasma
Backward scatter
Gas cell
Time resolved Ne spectroscopy
D2+Ne
Material courtesy Matthias Geissel and Adam Harvey-Thompson
Wearealsodevelopingnewtargetdesignstoenableside-onimagingandspectroscopyofNeemission
8
LEH appears in FOVWindows for x-ray transmission
End-plug overlap (required for pressure)
Gas fill
Mounting holes to anode
LEH washer
Anode
Different window designs for different applicationsCompatible with a variety of in-chamber imaging and spectroscopy diagnostics
Material courtesy Adam Harvey-Thompson and Matt Gomez
Weareexploringvariouspump/probeexperimentstotracktheevolutionofmixgeneratedduringpreheat
§ Theideaofexternallyprobingthepreheatedplasmaisbeingexplored§ Inprinciple,thiscanbedonewithaseparatelaserorx-raysource§ Lettheplasmaevolve,thenexcitethecontaminantstoproduceKα emission§ Byspatiallyresolvingtheemission,wecantrackwherethemixgoesasafunctionoftime§ Doesnotrelyonmaterialbeinghotinordertodetectit
9
Heated plasma
D2
t0 +�tX-ray source
Gas cell
D2 D2
Heating beam
Optical Probe beam
t0 t0 +�t
or
Characteristic x-rays from contaminants
Characteristic x-rays from contaminants
Space resolving x-ray spectrometer
AdditionalongoingeffortonmitigationstrategiesCryogenicGasfillplatform
10
~100 nm window è allows cushionless“thick-end” liner
Initial radiography campaign showed agreement with early time behavior, but some problems with shots
Twohighriskwindowlessdesignsarebeingexploredatalowlevel
Cryo-pool
11
D2 Liq/Ice
Nowindow
Form a pool of liquid, or disk of iceUse the preheat laser to create a plume that dynamically generates your hot spot fuelFoam shot on EP to scope this
Use a thick membraneMechanically burst the membrane ~1µs before preheatHeating beam propagates through the gas rarefaction, into the imploding region
Thick Membrane
Thebroadthemeforaddressingexistinghypothesesisenergybalance
§ Howmuchenergyisabsorbed§ Howmuchenergyisscattered§ Howmuchmixisgenerated,
wheredoesitgo
12
Radial Posi tion [mm]
AxialPosition[m
m]
z2839: Ar Imager
−2 −1 0 1 2−10
−9
−8
−7
−6
−5
−4
−3
−2
−1
0
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
§ Whatisthehot-spotpressure,mass,volume
§ Whatisthedrivepressurenearstagnation
§ Howwellisthelinerconfiningthefuel
§ Whatistheradiationlossinflight§ Howeffectiveismagneticinsulation§ Whataretheend-losses
Detailed accounting of the energy in the system at each phase is critical to distinguish
between hypotheses
Implosion/Compression
InCY17wewillextendpreviousworkonthestagnationdynamicstomagnetizedliners
§ Wehavedemonstratedtheabilitytoradiographicallymapoutstagnationinmoderateconvergence(CR~8)implosionswithunmagnetized liners
§ Wewillapplythismethodologyto liquidD2-filledMagLIF linersw/appliedBz§ ”standard”AR=6liner§ Mass-matchedlinerwithETImitigation
13
Powerfeedmodificationsarebeingpursuedtoimprovedriverenergycoupling
§ Thepowerfeedinductancehasadramaticinfluenceoncouplingdriverenergytothe load
§ Higherinductancefeedsdroptheavailablecurrentandincreasethevoltageattheconvolute,exacerbatinglosses
§ Lowerinductancefeedlikelyneedstobeaccompaniedbytargetmodificationstofullyrealizethebenefits
§ Increasingcurrentisimportanttotestscaling 14
Lincoln feed – 4 mm minimum gap Conical feed – 3 mm minimum gapReturn can
Field Coil
convolute post
Standard Feed Low Inductance Alternatives**Target
Calculated* Load Currents
*Circuit model developed by Brian Hutsel, **power feeds designed by Matt Gomez
Wewillbetestingtheeffectivenessofmodifyingthetargetdiameteratincreasingcurrentdelivery
§ IncreasingtargetODatfixedARhasaparadoxicaleffect§ Initiallyslowstheimplosion
(bad)§ Thisreducesthedynamic
(dL/dt)voltage(good)§ Thisinturn increasesthedrive
current,allowingthepeakvelocitytobelargelyrecovered
§ Alsomoves innersurfaceawayfromlaserinteractionregion
§ Neteffectisthatthedriverisabletomoreeffectivelycoupletotheload(bettermatchedimpedance)
15
Circuit model predictions* for new Low-L design with various diameter targets
“inductive dip” caused by large dL/dt near stagnation
*Circuit model developed by Brian Hutsel
Wearealsoexploringseveralwaystoaccuratelycharacterizecurrentdelivery
§ Wehavedevelopedthecylindrical analogtotheNIF“key-hole”experiments tocompliment electricaldiagnostics
§ Multi-point radialPDV(MPDV*)allowsustomeasurethelinervelocityatupto6azimuths
§ Currently goesto~40km/s, butextension to>100km/sinprogress
§ Thevelocity historyisadirectprobeofthedrivepressure history
§ CanbeconvertedtodrivecurrentthroughMHDsimulation
16
Probes
Example Velocity Spectrumfibers
liner
*MPDV developed by Dan Dolan in conjunction w/ Ray Lemke, Matt Martin and Patrick Knapp
Example Velocity Compared to Simulation
InadditiontoincreasingPdV work,weaimtomeasureandmitigatelosses
§ Early-timemixfromlaser-windowandlaser-wall interactionscanbedevastating:webelieve that~0.1%endcapmixandfew-%windowmixare introducedduringpreheat
§ Mixnearstagnation(~1%wallmix)ismuchlessharmful§ Spectroscopic tracershavebeenusedtotrackendcapmaterial§ Time-resolvedheating,windowmix,andradlossdiagnosticsare
possiblewith100ppmAr andchlorinatedplastic;time-resolvedspectrometers required forfieldingonintegratedshots
Co tracer
Cl tracer
Ardopant
*Calculations courtesy Steve Slutz
Thebroadthemeforaddressingexistinghypothesesisenergybalance
§ Howmuchenergyisabsorbed§ Howmuchenergyisscattered§ Howmuchmixisgenerated,
wheredoesitgo
18
Radial Posi tion [mm]
AxialPosition[m
m]
z2839: Ar Imager
−2 −1 0 1 2−10
−9
−8
−7
−6
−5
−4
−3
−2
−1
0
0
1000
2000
3000
4000
5000
6000
7000
8000
9000
10000
§ Whatisthehot-spotpressure,mass,volume
§ Whatisthedrivepressurenearstagnation
§ Howwellisthelinerconfiningthefuel
§ Whatistheradiationlossinflight§ Howeffectiveismagneticinsulation§ Whataretheend-losses
Detailed accounting of the energy in the system at each phase is critical to distinguish
between hypotheses
Stagnation
PHS =
vuuute
⌫⇢l`(h⌫)1/3Y⌫
8⇡2m
2p�hR
2⌧(1 +
Pi xiZi)
R 1
0r̃dr̃
e�h⌫/Te
T 2e
✓1 +
Pi xi
jijD
◆
Wearedevelopingthemeanstomeasurethefuelpressureusingindependentmethods
19
X-rays
PHS = (Z + 1)
s2YDD
⌧2VR 1
0r̃dr̃h�viDD/T 2
i
Neutrons
Necessary MeasurementsNeutron Yield
Total X-ray yieldFuel volume
Ion temperatureElectron temperatureLiner areal densityEmission duration
Mix (Z)Must improve uncertainties to discern trends
ThereisasignificantongoingefforttomodeltheZenvironmentinordertoimprovetheprecisionofouryieldandTi measurements
§ MCNPmodeling ofvariousnTOF LOS’s§ Exploringexperimental campaignsto
calibratethemodels§ AbsolutecalibrationofnTOF
detectors
20
Modeled scatter*
*Model for LOS50 developed by Edward Norris and Kelly Hahn
Same LOS, different detectors see different signal
These discrepancies contribute significantly to uncertainty in Ti
FilteredpinholeimagescanbeusedtoreconstructfuelTe,linerarealdensityandtotalx-rayyield
§ Existinginstrumenthaspoorspatialresolution (~100µm)§ Imagesareintegrated radially,butresolvedaxially§ Withabsolutex-rayyield,mix,andemissionradius, canalsoget§ Workingonformalizing parameterestimationanddefining uncertainties 21
hP i, �P (z)
hP i
Te [keV]⇢`R [g/cm2]
Images provided by Matt Gomez
- Measured intensity
- Simulated intensity
- Filter transmission & detector response
Xj
Fj
⇣j
�2r =
1
N �m
X
j
✓Xj � ⇣j
�j
◆2
⇣j = 8⇡2m
2pP
2HS(1 +
X
i
xiZi)⌧�hR2
Z 1
0
d⌫Fje�⌫⇢l`
Z 1
0
r̃dr̃
✓1 +
X
i
xiji
jD
◆e
�h⌫/Te
T
2e h⌫
1/3
1 2 3 4
1011
1012
1013
DD
NeutronYield
I on Temperature [keV]
Be (Ta l l , t hi n)
A l (Ta l l , t hi n)
B e ( Sho r t , t hi ck )
A l ( Sho r t , t hi ck )
∝ ⟨σv ⟩
Wehaveshownadependenceoftargetperformanceonmix,butsignificantuncertaintiesremain
§ Wehaveclearindicationsofthepresenceofhotcontaminants§ Uncertainhowmuchistrulymixedintheparticipatingfuel§ ObservedhotFeemission* couldbefromhotspot,orcould
belaterintime§ Uncertainhowmuchwindowmaterialismixedin
§ Indications thatthisamountscaleswithlaserenergydeposition
§ Potentialsolutions aredegeneratewithrespecttowindowmixandpreheatenergy
22
0 0.5 1 1.5 2 2.5 3 3.5x 1012
Tall
Short
Neutron Yield
Targ
et
AluminumBeryl l ium
0 0.5 1 1.5 2 2.5 3 3.5x 1012
Tall
Short
Neutron Yield
Targ
et
AluminumBeryl l ium
50%
10x
-1 -0.5 0 0.5 1
Horiz. Pos. [mm]
-6
-4
-2
0
2
4
6
Ve
rtic
al P
ositio
n [
mm
]
z2850
-1 -0.5 0 0.5 1
6500 7000 7500 8000
Energy [eV]
-6
-4
-2
0
2
4
6
z2850 XRS3-AR
0
100
200
300
400
500
0
100
200
300
400
500
Counts
He-like Fe + sats.Fe Kα1,2
He-like Ni + sats
Fe He-βNi Kα1,2
Fe K-edge
-1 -0.5 0 0.5 1
Horiz. Pos. [mm]
-6
-4
-2
0
2
4
6
Ve
rtic
al P
ositio
n [
mm
]
z2850
-1 -0.5 0 0.5 1
6500 7000 7500 8000
Energy [eV]
-6
-4
-2
0
2
4
6
z2850 XRS3-AR
0
100
200
300
400
500
0
100
200
300
400
500
Counts
Spectra processing and analysis courtesy Eric Harding and Stephanie Hansen
Mix is measured by impurity line emissionand absolute x-ray yields
23
§ X-ray yields from filtered silicon diodes indicate ρf ~ 0.3 g/cc (with mix), dependent on Δt and volume
§ XRS3 and CRITR impurity line emission intensities indicate ~few % Be believed to be from late-time instability driven mixing
§ Ratios of neutron to x-ray yields indicate that endcap and possibly window mix increase with preheat energy
Wehavedemonstratedtheabilitytoimpactthestagnationmorphologythroughcontrollingtheimplosion
24
w/ dielectric coating
No coating ”spotty” emissionHot Fe emission
Little Hot Fe emissionUniform K-α Fe emission
Helical columnHighly variable intensity
Much straighter columnUniform brightness
Despite ”improved” morphology, neutron yield and ion temperature decreased
X-ray Spectrum
X-ray Spectrum
Implosion only experimentsIntegrated experiments
Radiographs provided by Tom Awe and Dave Ampleford
Wearecurrentlydesigningandbuildinganin-chambertimeresolvedPHCforstudyinghot-spotevolution
2558 59 60 61
16
17
18
19
20
21
22
23
24
25
Posi t i on [mm]
Position[m
m]
z 2839 MLM-C Frame 6
0.02
0.04
0.06
0.08
0.1
0.12
0.14
0.16
40 41 42 43
16
17
18
19
20
21
22
23
24
25
Posi t i on [mm]
Position[m
m]
z 2839 MLM-C Frame 7
0.1
0.2
0.3
0.4
0.5
0.6
0.7
22 23 24 25
16
17
18
19
20
21
22
23
24
25
Posi t i on [mm]
Position[m
m]
z 2839 MLM-C Frame 8
0.05
0.1
0.15
0.2
0.25
0.3
3.095 3.1 3.105 3.11 3.115
0
5
10
time [µs]
Signal[V
]
XRBT-t5MA≈101 ns
1 mils Kapton10 mils Kapton
Previous measurements hint at important features in hot spot evolution, but instrument did not have sufficient resolution or sensitivity
target
pinholes
W MCP Enclosure
M = 0.5, 1 or 3
�x � 25 µm�t � 250 ps8 frames
Independent vacuum
Instrument design by Christopher Ball and Matt Gomez
TheCY17Zshotallocationreflectsthesepriorities
26*Preconditioning shot allocation does not include PECOS or OMEGA/OMEGA-EP experiments
10 days: split between lowering inductance to increase drive current and better diagnosing current delivery
5 days: MagLIF Cryo8 days: Develop and characterize new baseline2 days: Calibration1 days: Electron temperature measurement
4 days: Stagnation Hydrodynamics8 days: Mix techniques/characterization/mitigation2 days: Liner diameter scan1 days: Tritium development
5 days: Integration of new platforms
Driver/ Target coupling
Target Preconditioning*
Implosion/ Stagnation
Int.
MagLIF Relevant Shot days: 48
Focusing heavily on preconditioning as interpretation of stagnation is predicated on understanding initial conditions