laser produced positron research at lawrence livermore...

LLNL-PRES-737787This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under contract DE-AC52-07NA27344. Lawrence Livermore National Security, LLC

HuiChen

May 24, 2017

LaserProducedPositronResearchatLawrenceLivermoreNationalLaboratoryPresenttothe2ndConferenceonExtremelyHigh-IntensityLaserPhysics,September5-8,2017,LisbonPortugal

LLNL-PRES-7377872

JaebumParkN. Brejnholt, M-A. Descalle, A. Hazi, R. Heeter, A. Kemp, G. E. Kemp, A. Link, B. Pollock, E. Marley, S. R. Nagel, J. Park,

M. Schneider, R. Shepherd, M. Sherlock, R. Tommasini, S. C. Wilks, G. J. Williams - Lawrence Livermore National Lab

F. Fiuza, J. Sheppard - SLAC

D. Barnak, P-Y. Chang, G. Fiksel, V. Glebov, D. D. Meyerhofer, J. F. Myatt, C. Stoeckel – LLE and Uni. of Rochester

G. Grigori – Oxford University

E. d’Humieres, University of Bordeaux

R. Fedosejevs, S. Kerr – University of Alberta

F. Beg, B. Edghill, C. Krauland, C. Mcguffey, J. Peebles, M-S Wei - UCSD

C. Kuranz, M. Manuel, L. Willingale – University of Michigan

A. Spitkovsky - Princeton University

Y. Arikawa, H. Azechi, S. Fujioka, , H. Hosoda, S. Kojima, N. Miyanaga, T. Morita, T. Moritaka, T. Nagai, M. Nakai,

T. Namimoto, H. Nishimura, T. Ozaki, Y. Sentoku, Y. Sakawa, H. Takabe, Z. Zhang - ILE, Osaka University

P. Audebert – LULI, École Polytechnique

M. Hill, D. Hoarty, L. Hobbs, S. James - AWE

Acknowledgement:TeammemberandCollaborations

*Complete list of names are included in the publications citedMany thanks to the JLF, Omega EP, LFEX and Orion laser facilities for their support.Weacknowledge the LLNL LDRD funding (10-ERD-044 and 12-ERD-062, 17-ERD-010) for this project.

JacksonWilliams

ShaunKerr Brandon

Edghill

LLNL-PRES-7377873

AtLLNL,wehavebeeninvestigatinglaserproducedpositronsthroughexperimentsandmodeling

1. Positronjetcharacterization:• Absolutepositronnumberandenergies• Emittance• Yielddependencetolaser&target

2. Relativisticlaser-plasmainteractionphysics:• Sheathfieldacceleration• Effectofelectromagneticfield

3. Applications:• Positronradiography– APSDPP2017• Relativisticelectron-positronpairplasma –

APSDPP2017

Simulationtools:• Particle-in-cell:PICLS• Particlecode:GEANT4;EGS4• Hydrodynamiccode:HYDRA

• OSIRIS; LSP

LLNL-PRES-7377874

Majorityofexperimentswereperformedonlargelaserfacilitieswith1-10ps,100Jto1500Jenergypershot

Titan laser (LLNL)1-10 ps, 100-350 J5-10 shots/day

LFEX (ILE)2-4 beams 1-2 ps, ~0.5-1 kJ/beam

ORION (AWE)2 beams0.5-1 ps, up to 500 J/beam

Omega EP (LLE)2 beams1-10 psup to 1.3 kJ/beamUp to 16 shots/day

LLNL-PRES-7377875

Ineachexperiments,e-,e+,p+andg fromgoldtargetsweremeasuredbyvariousdiagnostics

Experimental setup at Titan

Short-pulse laser

EPPS-1

EPPS-2 Radiation spectrometers

EPPS-3

18o

++++-

-

--

-

-

-

-

-

Positron/ionAcceleration

Escaping electrons

Sheath formation

Preformedplasma

++

+

Au Target

High-energy gamma diagnostics

GCS: Seely et al. HEDP 2011Chen, et al., RSI 2012

Step Wedge image

Electron positron proton spectrometer

EPPS: Chen, et al., RSI 2008

Particle energy

Gamma-crystal spectrometer

Protons Positrons

Electrons

EPPS raw images

LLNL-PRES-7377876

Thelaserintensitiesusedexperimentallywerefrom1018 to1020 W/cm2

Prior references on making positrons using wake-field accelerated electrons:Gahn et al. (2002) and Sarri et al., (2013)

Prior experiment laser produced positrons:T. Cowan et al., Laser Particle Beams (1999)

Directpairproduction(laserongoldtarget)

Indirectpairproduction(wake-fieldelectronsongoldtarget)

Williams et al. Physics of Plasmas (2015)

f/8

OAP

Callisto Target Chamber

Laser Parameters

800 nm, 60fs

Up to 10 J

Gas Cell Parameters

3 mm He gas cell

Pressure = 550 Torr

ne = 9x1018 cm-3

B. B. Pollock et al. Phys. Rev. Lett., 107:045001 (2011).

F. Albert et al. Phys. Rev. Lett., 111:235004 (2013).

Gas Cell

e+/e-

Spec

Converter

Target

LLNL-PRES-7377877

Weexperimentedwithindirectpairproductionusingwake-fieldgeneratedelectronbeams






f/8

OAP


Laser Parameters

800 nm, 60fs

Up to 10 J

Gas Cell Parameters

3 mm He gas cell

Pressure = 550 Torr

ne = 9x1018 cm-3



Gas Cell

e+/e-

Spec

Converter

Target

LLNL-PRES-7377878

Charged particle spectrometer

He gas cell

60 fs6-10 J

e-

e-

4 cm 4 cm

Electronswereacceleratedanddrivenintoaconvertertargettoproducepositrons

e+

1.5 mm Tantalum

Williams, et al. Phys. Plasmas (2015)

LLNL-PRES-7377879

0 50 100 150 200 250 300 3500

1

2

3

4

5

6

7

8 x 106

Energy (MeV)

Elec

trons

/MeV

EL = 6.5 JEL = 10 J

0 50 100 150 200 250 300 3500

1

2

3

4

5

6

7

8 x 106

Energy (MeV)

Elec

trons

/MeV

EL = 6.5 JEL = 10 J

Sarri et al

InitialElectronDistributions

Positronsignalwasnotobservedforeitherahighenergyorhighfluxelectronsource

Ne- =19pCEe- =2.3mJ

Ne- =56pCEe- =2.8mJ

Ne- =50pC

Positive-sideimageplateforelectronsourceinredcurve

Energy (MeV)1 10 25 50 100 200

Geant4 modeling may provide explanation of null result


LLNL-PRES-73778710

Beamdivergenceislargerthanexpected,andisdominatedbyCoulombscattering

Initial electron divergence from LWFA sources is a negligible contribution

Energy-ResolvedDivergenceofEmittedPositrons

40<Ee+ (MeV)<60

180<Ee+ (MeV)<200MeanDivergenceSim w/oCoulomb

ScatteringWilliams, et al. Phys. Plasmas (2015)

LLNL-PRES-73778711

Pulsedurationofpositronscanbesignificantlylonger

thanelectronsource

§ τe- >10fs

§ τe+ ≥13-50fs

Simulationalsoshowsthatthepositronbeamislongerthantheelectronpulseduetostragglinginsidethetarget

Timehistoryofpositronemission

0

0.5

1 40 < E (MeV) < 60

0 20 40 60 800

0.5

1

Positron Breakout Time (fs)Posi

tron

Flux

at T

arge

t Rea

r (a.

u.)

180 < E (MeV) < 200


LLNL-PRES-73778712






f/8

OAP


Laser Parameters

800 nm, 60fs

Up to 10 J

Gas Cell Parameters

3 mm He gas cell

Pressure = 550 Torr

ne = 9x1018 cm-3



Gas Cell

e+/e-

Spec

Converter

Target

Directpairproductionwasinvestigatedextensivelyforlaserintensitiesfrom1018 to1020 W/cm2

LLNL-PRES-73778713

Bethe-Heitler processwasverifiedasthedominantpairgenerationmechanismsthroughdetailedmeasurements

Titan Laser~300 J, 10 ps

~I

~B

Target

EPPS

Positron and electron jets

Shot 17 − Ta disc, Ø 6.3mm x 518um

Electron Energy (MeV)

Elec

trons

/MeV

/SR

× 1

09

E = 224 J

Sig.Width = 0 pxEPPS Distance = 0 cm

Slinky = 6 kV @ 12.7 mmEPPS @ 0°

filename = 20140429−EPPS4−s17.img

0 10 20 30 40 50 60 700

2

4

6

8

10

Shot 19 − Ta disc, Ø 6.3mm x 792um

Electron Energy (MeV)

Elec

trons

/MeV

/SR

× 1

09

E = 268 J

Sig.Width = 0 pxEPPS Distance = 0 cm

Slinky = 2 kV @ 12.7 mmEPPS @ 0°

filename = 20140429−EPPS4−s19.img

0 10 20 30 40 50 60 700

10

20

30

B=2.2T

B=6.5T

RawPositronData

IncreasingEnergy

0 10 20 30 40 50 60 700

0.5

1

1.5

2

2.5

Z2 × ρ × d × A−1 (cm2 mol)

Posi

trons

/SR

(× 1

010)

CuMoSnTaWAu

SimulationFit

Bethe-Heitler hasaneffectivescaling~Z2

0 20 40 60 80 100

0.6

0.8

1

1.2

1.4

1.6

Electron Temperature (MeV)

Scal

ing

pow

er, n

YBH ∝Z 2ρA

"

#$

%

&'

n

Target dependence of laser-produced positrons were measured, aided by magnetic collimation of the pair jets

Williams et al. Phys. Plasmas (2016)

LLNL-PRES-73778714

Quasi-monoenergetic,highflux,relativisticpositronsareproducedinps timescale

Titan and Omega EP positron data*

* More details see Chen et al., PRL 2009, PRL2010, HEDP 2011

Pair number: 1010 – 1012 Peak energy: 4 - 30 MeV Flux duration: ~10 - 100 psE conversion>2x10-4 Pair rate: ~1022 /s Peak flux: >1025 cm-2s-1

Sim. e+ width for 10 ps exp. (LSP )**

20

15

10

5

0

Num

ber/M

eV/S

r (x1

09 )

252015105

A - 20 mm target; 312J, 10 psB - 6.4 mm target; 130J, 1psC - 2 mm target; 305 J, 10 psD - 2 mm target; 280 J, 10 psE - 2 mm target; 323 J, 10 psF - 2 mm target; 812 J, 10ps

Energy (MeV)

A B C D E F

Positron energy (MeV)

Titan(100-300 J)

Omega EP(800J)

35x1012

30

25

20

15

10

5

0

Posit

ron

num

ber

50403020100

Time (ps)

FWHM ~ 8ps

**Chen et al, POP 2015

Posi

tron

num

ber

x1012

0

10

20

30

Posi

tron

num

ber/M

eV (x

109 )

0

10

20

10 20155 25Time (ps)

10 40200 5030

LLNL-PRES-73778715

Positronsareacceleratedto10s’ofMeV,whichfarexceedtheirbirthenergy

* Particle code GEANT4 was developed by CEAN (www. geant4.cern.ch)

Positron peak energy vs laser energy35x103

30

25

20

15

10

5

0

Posit

ron

Peak

ene

rgy

(MeV

)

2000150010005000

Laser energy (J)

y=9000+10x

Birth peak energy (from GEANT4*)

Measurements

0

10

20

30

0 500 1000 1500 2000

* Chen, et al, Phys. Plasmas 2015

Sheath acceleration

Sheath acceleration of protons

+++++++

--

---

-

p+p+p+

-

Short-pulse Laser

Au Target SheathField

ProtonAcceleration

Snavely, et al., PRL 2000 Wilks, et al., PoP 2001………….

This feature is unique and it is the result of intense laser target interaction

LLNL-PRES-73778716

Detailedpositronspectrumrevealsphysicsinsheathacceleration

E&P pectra at 3 laser energies

106

107

108

109

Num

ber/

keV/

sr

50x10340302010Energy (keV)

10 ps laser; Au target (1mm x 2mm dia.)

Black - 247 JGreen - 800 J Red - 1500J

e-

e+


LLNL-PRES-73778717

Time evolution of the spectrum (LSP)


Shaun Kerr, APS DPP 2017

106

107

108

109

Num

ber/

keV/

sr

50x10340302010Energy (keV)



e-

e+


E&P pectra at 3 laser energies

LLNL-PRES-73778718

Laserproducedrelativisticpairsformjetsatthebackofthetarget

Jet angular spread: 10-30 degrees. The jets are shaped by the E and B fields of the target. Its direction is controlled by the laser parameters and target.

e+ and e- angular distributions

1.0

0.5

0.0

Nor

mal

ized

Num

ber o

f Pos

itron

s

100806040200-20-40-60Angle (Degrees)

1.2

0.8

0.4

0Ral

. num

ber o

f ele

ctro

ns

-40 0 40Angle (degree)

EPPS RCF Fit EGS

Data Fit EGS

Lase

r dire

ctio

n

Targ

et n

orm

al

Chen et al., PRL 2010

Jets simulated by LSP*

e+

e-

*Tony Link

LLNL-PRES-73778719

Theemittance oflaser-positronsiscomparableto,orsmaller,thanthatobtainedonlargeaccelerators

Exp. on Titan & OMEGA EP, in collaboration with SLAC

Our pairs can be called a jet; as they are not sufficiently collimated to be a ”beam”.

Simulated positron emittance using LSPMeasured positron emittance

600

500

400

300

200

100

0

Posit

ron

emitt

ance

(mm

.mra

d)

35302520151050

Positron energy (MeV)

Accelerator (SLAC)

Chen, Sheppard, Gronberg et al., POP 2013

LLNL-PRES-73778720

Wefoundthatthepairyieldscalesas~E2 basedondatafromTitan,EPandOrionexperiments

Positron number ~ E2

800x109

600

400

200

0

Posit

ron

num

ber/

sr

1600140012001000800600400200Laser energy (J)

Orion(1ps)

Omega EP(10ps)

Titan (1, 10 ps)

Positron number shows a ~E2 dependence for both 1 ps and 10 ps shots.

Norm. positrons ~ Ilaser1.1

1010

1011

1012

Numb

er of

posit

rons p

er KJ

lase

r ene

rgy

1018 1019 1020

Laser intensity (W/cm2)

Orion(1ps)

Omega EP(10ps)

Titan (10 ps)

Titan (1 ps)

Chen, Fiuza, Sentoku et al. PRL, 2015Chen, Link, et al, PoP, 2015Myatt, et al. PRE 2009

LLNL-PRES-73778721

Relativistic,non-neutralelectron-positronplasmajetshavebeenproduced

Parameter Exp. Value*

T// 0.5 - 4 MeV

T┴ 0.2-1 MeV

ne+ ~1011-13 cm-3

ne- ~1012-15 cm-3

tJet 5 – 30 ps

The most obvious needs are to (1) increase the density of the pair jets and (2) reduce the electron/positron density ratio.

*Chen, et al. PRL 2010; HEDP 2011; POP 2014

LLNL-PRES-73778722

109

1010

1011

1012

25201510

Particle energy (MeV)

Num

bers

/MeV

/Sr Electrons

Positrons

Ref. shot(no B-fields)

Shot with B-fieldsby MIFEDS

MIFEDS setup on OMEGA EP e- & e+ spectra after collimationR

adiu

s (m

m)

Distance to beam source (mm)20 40 600

0

2

4

6

8

10

Particle trajectory

B-field lines

Coil Exp. setup

Chen, Fiksel, Barnak, et al., POP 2014

Posi

tron

num

ber/M

eV/s

r

109

1010

1011

1012

Energy (MeV)10 15 20 25

Electrons

Positrons

Electrons

Positrons

• The effective divergence of the beam reduced from 30 deg FWHM to 5 deg; • The charge (e-/e+) ratio in the beam reduced from ~100 to 5.

Wehavedemonstratedeffectivecollimationoflaser-producedrelativisticelectron-positronpairjets

LLNL-PRES-73778723

109

1010

1011

1012

1013Po

sitro

n nu

mbe

r/sr

8

1022 3 4 5 6 7 8

1032 3 4 5 6 7 8

104

Laser energy (J)

Titan_number_1ps_635 Orion_number_1ps Titan_numb_10ps EP_posNum 'fit_Titan&EP_number_10ps' 'fit_Titan&Orion_number_1ps'

ThepositronscalingindicatesthatARCenergymayprovideveryhighpositronyield

We have been awarded NIF Discovery Science shot time using ARC – these questions will be answered soon.

ARC energy results in high e+ yield

ARC

To determine the actual yield, we need:(1) Laser intensity;(2) Pulse contrast;(3) Focal quality.

Furthermore, ARC is unique relative to the Titan, Omega EP and Orion lasers:

Titan parabola – f/3Omega EP – f/2Orion – f/3NIF ARC – f/60

The long focal length parabola is favored by wake-field acceleration experiments; its effect to laser plasma interaction needs to be determined.

ARC resultsHui Chen, APS DPP 2017

LLNL-PRES-73778724

Date Published

Primary Author

Laser Energy/J Intensity/𝑊𝑐𝑚$%

Pulse Duration/fs

Target Diameter/mm

Thickness/mm

Beste+/e- ratio

Best e+ Number Best e+

DensityDominant Production Method

9/14/2015 E. Liang Texas Petawatt ~100 3×10%+− 1.9×20%0

128-245 Au: Disk/Rod 2-4.5/2-3

0.1-5/4-10 15%/37% ~1.8×100+ 1.6×1003𝑐𝑚$4

Bethe-Heitler/Direct Process

Pt: Disk/Rod 2-4.5/2-3

0.1-6/4-6 33%/52% ±10%

10/23/2000 C. Gahn Table-Top at ATLAS .22 130 Pb 2 (slab) ~2×108 Bethe-Heitler/Indirect Process

3/15/2017 Yonghong Yan XingGuang ᴵᴵᴵ laser facility 100-200 ~2×1009 800 Ta 1-10 1 2.8 ±0.3×109𝑠𝑡𝑟$0


3/12/2017 Yuchi Wu XingGuang ᴵᴵᴵ laser facility 1-10 2.8×109𝑠𝑡𝑟$0

3/7/2016 Tongjun Xu Petawatt at Shanghai Institute of Optics and Fine Mechanics

3.75 3.5×1009 45 Cu and Pb 2-20 48% 3.5×10> 3×100%𝑐𝑚$4

Bethe-Heitler/Indirect Process

6/20/2013 G. Sarri HERCULES at Center for Ultrafast Optical Science

0.8 6×100> 30 Cu, Sn, Ta and Pb

1.4-6.4 3.5×108 2×100?𝑐𝑚$4

Bethe-Heitler/

4/23/2015 G. Sarri ASTRA-GEMINI at Rutherford Appleton Laboratory

14 3×1009 42 ± 4 Pb 5-40 49% of the beam is 𝑒B

3×108 1003𝑐𝑚$4 Bethe-Heitler/Indirect Process

12/23/2009 H. Chen Titan at the Jupiter Laser Facility 120-250 ~1×10%+ 700-10000 Au, Ta, Sn, Cu, Al

6.4 0.1-3.1 2×100+𝑠$0 Bethe-Heitler/Direct Process

7/1/2010 H. Chen Titan at the Jupiter Laser Facility and OMEGA EP at the Laboratory for Laser Energetics

100-850 1×1009− 5×10%+

1000-10000 Au 1-20 1 100+ − 1000 ~1004 Bethe-Heitler/Direct Process

4/24/2014 H. Chen OMEGA EP at the Laboratory for Laser Energetics

830 ± 30 5×100> 10000 Au 2 1 2.5 = DE

DF 1.9×109 Bethe-Heitler/Direct

Process – Magnetic Collimation

1/31/2013 H. Chen Titan at the Jupiter Laser Facility and OMEGA EP at the Laboratory for Laser Energetics

200-850 5×100>− 6×1009

10000 Au 1 100+− 100%𝑝𝑒𝑟𝑏𝑢𝑛𝑐ℎ


12/6/2016 G. Williams Titan at the Jupiter Laser Facility 270 1.2×1009 10000 Cu, Mo, Sn, Ta, W, Au

6.3 0.538-2.36 ≈ 108 − 109 Bethe-Heitler/Direct Process – Target Dependence

10/21/2015 G. Williams Calisto at the Jupiter Laser Facility 6.5-10 60 Ta 0.25-4.2 None Measured above background

Bethe-Heitler/Indirect Process

Brandon Edghill, APS DPP 2017

LLNL-PRES-73778725

ü Pairjetcharacterization:• Absolutepositronnumberandenergies• Emittance• Yielddependencetolaser&target

ü Relativisticlaser-plasmainteractionphysics:• Sheathfieldacceleration• Effectofelectromagneticfield

Ø Applications:• Positronradiography– APSDPP2017• Relativisticelectron-positronpairplasma –

APSDPP2017

Simulationtools:Ø Particle-in-cell:PICLSü Particlecode:GEANT4;EGS4Ø Hydrodynamiccode:HYDRA

ü OSIRIS; LSP

AtLLNL,wehavebeeninvestigatinglaserproducedpositronsthroughexperimentsandmodeling

LLNL-PRES-73778727

Arelativisticpairplasmabypairconfinement?

In theory mirror machine works for both charges

Gibsonetal,PRL1960Pedersenetal,J.Phys.B2003Myatt,etal,PRE2009

The first step: one coil has been demonstrated

Chenetal.PoP(2014)R

adiu

s (m

m)

Distance to beam source (mm)20 40 600

0

2

4

6

8

10

Particle trajectory

B-field lines

Coil Exp. setup

Theory and preliminary simulations show that using mirror fields, it is possible to trap MeV electrons and positrons produced from the laser-solid interactions.

A double-coil system will form a mirror field

coilcoil

B-fields

LLNL-PRES-73778728

Time evolution of the spectrum (LSP)


Positron spectra at 3 laser energies

Shaun Kerr, APS DPP 2017

106

107

108

109

Num

ber/

keV/

sr

50x10340302010Energy (keV)



e-

e+


laser produced positron research at lawrence livermore...

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