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Injector Target ChamberBeam transportsolenoids

FinalFocus

solenoid

Bunching module

FCAPS

IonIon--beambeam--driven warm dense matter driven warm dense matter experimentsexperiments

Frank Bieniosek1, John Barnard2, Alex Friedman2, Enrique Henestroza1, Jin-Young Jung1, Matthaeus Leitner1, Steve Lidia1,

Grant Logan1, Richard More1, Pavel Ni1, Prabir Roy1, Peter Seidl1, Will Waldron1

1LBNL, 2LLNL, and HIFS-VNL

The Heavy Ion Fusion Science Virtual National Laboratory

This work was performed under the auspices of the U.S. Department of Energy by LLNL under contract DE-AC52-07NA27344, the University of California, LBNL under Contract Number DE-AC02-05CH1123 and PPPL under contract DEFG0295ER40919 .

NDCX-I NDCX-II

IFSA 2009, San Francisco, CASep. 9, 2009

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NDCX facility and HIFS-VNL staff at LBNL

NDCX-I

NDCX-II test stand

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The WDM regime is at the meeting point of several distinct physical regimes - a scientifically rich area of High Energy Density Physics.

tem

pera

ture

density

Unknown properties:EOS (p(ρ,T), E(ρ,T))Liquid-vapor boundaryLatent heat of evaporationEvaporation rateSurface tensionWork functionElectrical conductivitydE/dX for hot targets

Phenomena:Metal-insulator transitionPhase transitions? Plasma composition?Interesting phenomena at: 0.01 ρsolid < ρ < 1.0 ρsolid

and 0.1 eV < T < 10 eV

From R. More, Warm Dense Matter School, LBNL, Jan. 10-16, 2008. http://hifweb.lbl.gov/wdmschool/

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Ion beams provide a tool for generating homogeneous warm dense matter.

Short pulseion beam

Enter targetExit target

Al target• Warm dense matter (WDM)

– T ~ 0.1 to 10 eV– ρ ~ 0.01 -1 * solid density

• Uniform energy deposition near flat portion of dE/dx curve, e.g. nuclear stopping plateau (NDCX-I); Bragg peak (NDCX-II)

• Characteristics include– Precise control of energy

deposition– Sample size ~micron depth, 1 mm

diameter– Ability to heat any target

material – Benign environment for

diagnostics

GSINDCX-1

NDCX-2

L.C Northcliffe and R.F.Schilling, Nuclear Data Tables, A7, 233 (1970)

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Injector Target ChamberBeam transportsolenoids

FinalFocus

solenoid

Bunching module

FCAPS

NDCX II

3 - 6 MeV, 0.03 μC

1 ns

Completion date: 2012

NDCX I

0.35 MeV,

0.003 μC

2 ns

Now

NDCX I is laying the groundwork for NDCX II.

•Bragg peak heating•T ~1-2 eV in planar targets(higher in cylindrical/spherical Implosions)•Ion+/Ion- plasmas•Critical point; complete liquid/vapor boundary•Transport physics•HIF coupling and beam physics

•Explore liquid/vaporboundaries at T ~ 0.4 eV•Evaporation rates/ bubble and droplet formation •Test beam compression physics•Develop diagnostics

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Warm dense matter target chamber contains target, neutralizing plasma, and target diagnostics.

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Experiments include WDM target and beam diagnostics.

Initial diagnostics include– Optical emission, especially

high speed optical pyrometer – High speed I-CCD cameras– Streak camera – Optical spectrometer– Beam transmission– VISAR probe– Electrostatic energy analyzer

Probe laser

Optical emission

Probe laser transmission

ION BEAM

Target holder

Target foilProbe laser specular reflection

Initial set of targets (foils with mesh backing)– 350-nm Al– 150 nm Au– 120 nm Pt

– 400 nm Si– 400 nm C

VISAR

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1

1.2

1.4

1.6

1.8

2

2.2

1 2 3 4 5 6 7 8

γ = Entrance Aperture Radius / Target Radius

η =

Con

e En

ergy

Gai

n

Gold cone concentrates ion beam energy density on target.

• Cone acts as grazing incidence mirror. Enhanced ion intensity using cone has been demonstrated.

• Space charge neutralization of beam electric field by presence of walls, electron production may improve final focus on target.

• Cone shields target from unwanted heating by edge of beam.

Scattering K+ on gold

0

0.2

0.4

0.6

0.8

1

1 10 100 1000Angle of Incidence (mrad)

Part

icle

refle

ctio

n co

effi

1-MeV0.1-MeV10-MeV

WDMTarget

Gold cone

Ion beam

TRIM calculations for a single reflection

300-keV K+ on gold cone

simple cone

paraboloid

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Equilibrium model predicts target heating using NDCX-I beam at 500 kW/cm2.

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Model of target heating predicts T ~ 0.3 – 0.6 eV using NDCX-I beam; T ~ 1 - 2 eV using NDCX-II beam.

compresseduncompressedNDCX -I

NDCX-II:

power/unit area x 100 power/unit volume x 10

For gold:

1 MW/cm2 = 3.45 kJ/g/μs

Times indicate time required to reach equilibrium.

Energy Flux (W/cm2)

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Heated sample

Fiber bundle

Streak camera+spectrometerPyrometer:Doppler-shift interferometer (VISAR):

Target chamber:

Optical probing of target

Probing of target:

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Typical data in foil targets shows heating from the prepulse and compressed pulse.

Streak - spectrometer data in Au target showing transition from continuum emission to emission lines from heated gold

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Gold targets are initially heated to about 3000 K and show drop in brightness temperature after ~3 μs.

Au

Actual beam power ≥ 200 kW /cm2

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Carbon foil streak-spectrometer data and comparison with simple model.

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Shot#51, compressed pulse delay 1 μs

Platinum foil streak-spectrometer data

EmissivityBeam Flux

Brightness Temperature

Measured Color Temperature

Calculated Temperature

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Shower of hot debris fragments after end of shot suggests droplet formation.

5.5 us 100 us

200 us 500 us

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NDCX-II driver for >1 eV WDM target heating.

TARGET FOIL

Thickness (for <5% ΔT):~3 micron, solid density foil~25 micron, 10% solid density

TYPICAL DESIGN PARAMETERS FOR LITHIUM ION BEAM BUNCH

Final Beam Energy: 2.8 MeVFinal Spot Size : <1 mm diameterFinal Bunch Length: <1 ns (≅ <1 cm)Total Charge Delivered: 0.03 micro-Coulomb (~ 2x1011 particles or Imax ~ 42 A)Normalized Emittance: 0.4 pi-mm-mrad

•Ion+/Ion- plasmas•Critical point; complete liquid/vapor boundary•HIF coupling and driver physics•Cylindrical/spherical implosions •Beam physics

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Summary

• Ion beams provide a new tool with unique properties to generate homogeneous WDM.

• We have developed and tested targets, target diagnostics, and a target chamber, as part of a new HEDLP user facility for studying WDM physics.

• NDCX-I provides a test bed for target physics studies, target diagnostics development, and ion beam compression studies.

• Upgrades in beam tuning, bunch compression, etc. are expected toyield higher temperature in NDCX-I WDM targets.

• Future experiments with NDCX-I and NDCX-II will explore aspects of WDM physics including high electron affinity targets, porous targets, beam-target coupling, etc.

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Extra slides

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Iodine, 0.1 g/cm3

1.E+14

1.E+16

1.E+18

1.E+20

1.E+22

0.1 1.0 10.0

Temperature, eV

Den

sity

, cm

-3 nen0n-n+n20n2-n2+

Experiment in high electron affinity targets (halogen)

• Unusual material – dominated by +/- ions• narrow temperature range; e.g. 0.4 to 0.7 eV for iodine at 0.1 g/cc.• radiation from charge exchange• expect conduction by charge transfer• unequal mobility for electrons and holes• Other: optical behavior, metal-insulator transition

Electron affinity:

Au 2.3 eV

I 3.1

Br 3.4

neutral

- ion

+ ion

electron

H Yoneda, et al., Phys. Rev. Lett. 2003, 91, 75004. R. More

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Formation of droplets during expansion of foil is being investigated using a kinetic code

(Ref: J. Armijo, master's internship report, ENS, Paris, 2006; Armijo et al APS DDP 2006, and in prep.)Density (g/cm3)

Tem

pera

ture

(eV)

gas

2-phase

liquid

Example of evolution of foil in ρ and T

DPC result

0 ns

0.2 ns

0.4 ns

0.6 ns0.8 ns

1 ns

Vgas= Vliquid

Foil is first entirely liquid thenenters two phase regime.

1 ns

10 ns

100 ns1000 ns

Log[initial radius r0 (cm)]

r f/r 0

R0= 40 nm dV/dx= 109

Tl0=Tg0=9000K

tf=100 ns

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We are investigating the polarization of optical emission, for possible application to improved pyrometer diagnostic.

Optical polarization experiment using a hot tungsten filament.