The Third Blaise Pascal Lecture Wednesday 9th December 2009

Ecole PolytechniqueAmphi Faurre

Laser Ion Acceleration

Toshiki TajimaBlaise Pascal Chair,

Fondation Ecole Normale SupérieureInstitut de Lumière Extrême

andLMU,MPQ, Garching

Acknowledgments for Advice and Collaboration: G. Mourou, V. Malka, J. Fuchs, C. Labaune, P. Mora, F. Krausz, D. Habs, T. Esirkepov, S. Bulanov, S. Kawanishi, M. Hegelich, Y. Kishimoto, D. Jung, D. Kiefer, X. Yan, A. Henig, R. Hoerlein, S. Steinke, W. Sandner, Y. Fukuda, A. Faenov, M. Tampo, P. Bolton, Y. Ueshima, N. Rostoker, F. Mako, L. Yin, T. Pikuz, A. Pirozgkov, M. Borghesi, M. Gross

Advent of collective acceleration (1956)

Prehistoric activities (1973-75,…84)Collective acceleration suggested:

Veksler (1956)(ion energy)~ (M/m)(electron energy)

Many experimental attempts (~’70s):led to no such amplification

(ion energy)~ (several)x(electron)

Mako-Tajima analysis (1978;1984)sudden acceleration, ions untrapped,electrons return, while some run away#1 gradual acceleration necessary

#2 electron acceleration possible with trapping (with Tajima-Dawson field), more tolerant for sudden process

Professor N. Rostoker

Path once trodden

Collective accelerationof ions by electron beam

F.Mako / T. Tajima

Ions left out, while electronsshoot backward

laser electron acceleration(1979)

laser ion acceleration oflimited ion mass

(2009)

Example of solid target ca.1999

Tajima: LLNL (1999)

Toward Less Sudden Acceleration ca.1999)

Patent (Tajima) : submitted from LLNL (2002); granted (2005)

Recent breakthroughsFrom incoherent (or heating) of electrons

to Coherent drive of them

TNSA (Target Normal Sheath Acceleration)

CAIL (Coherent Acceleration of Ions by Laser)

Tajima et al., 2009

Comparison of the phase space dynamics: toward more Adiabatic Acceleration

TNSA

CAIL

(metallic boundary)

CAIL (with CP)

Rev. Accel. Sci. Tech.(Tajima, Habs, Yan, 2009)

Ion trapping width:vtr,ion ~ c a0 (m/M)

a=eE/me c

Maximal energy of protons (MeV)LLNL(redef. Ipeak )

CUOS

(rede

f. I pe

ak)

1355 (MeV)LLNL

Best s

calin

g max

a2

(T.Esirkepov et al.2006)

Optimal Thickness Scaling

Normalized thickness ~ a0

Recent Experimental Breakthroughs

Leadershipby Dieter Habs

LMU,MPQ,Max-Born Institute, LANL,RAL,PMRC

Nanometer target:DLC

Sharp contrast laserdouble plasmamirrors

More coherentelectron dynamicsin ~ a0

Recent experiments in CAIL Regime

(Henig et al, 2009;Steinke et al.)

Ultrathin film : = a0 , where = d n / nc ( = /a0 )High laser contrast: not to destroy ultrathin target

MAP + MBI

=1

Conversion efficiency of laser to ion energy

Conversion efficiency of laser energy to ion energy comparing results from thick targets and the TNSA mechanism to measurements with ultra-thin targets in the regime of CAIL (red diamonds and line).

187x10

5x1019 W/cm2

6x1019

1x1019

2x1018

7x1019

2x1020

203x10NOVA

100

10

1

0.1

0.01

Lase

r−io

n en

ergy

conv

ersi

on e

ffici

ency

[%]

10 100 103 104

Laser pulse duration [fs]

thin foil RPAthick foil TNSA

ASTRA

RAL

Two orders of magnitude higher efficiency in CAIL

Tajima, et al(2009)

Maximum energies of ions

Fig. 11. Maximum cutoff energies of ions given in MeV/u as a function of laser pulse duration. The energy gain by CAIL experiments is embedded with red dots in the predicted curves of TNSA. Note that in shorter pulses, energies by CAIL aremore than an order of magnitude higher than TNSA.

1022

1018

1021 W/cm2

7x1018

197x102x102019

10 100 103 104

Laser pulse duration [fs]

0.1

1

100

1000

10

10

10

20

19

protons, nm foil

carbon, clustercarbon, nm foil

Max

imum

cut

off i

on e

nerg

y [M

eV/u

]

ASTRAprotons, TNSA

RAL

NOVA 203x102x1020

5x10

Tajima et al.(2009)

Laser -Thin Foil Interaction

X. Yan et al., 2009

Toward monoenergy spectrum• Circularly polarized laser irradiation

more adiabatic acceleration more monoenergy

Carbon spectrum for three consecutive shots using circular polarized light at 5 *10^19 W/cm2 and a DLC foil target thickness of 5.9 nm

Coherent electron dynamics

4 6 8-180

-120

-60

0

60

120

180

Ele

ctro

n di

verg

ence

ang

le

x( )

Electron dynamics from thin foil: 3 clear patterns

Laser

Expanded target

laser transmitted

Characterization of coherent dynamics of electrons

0.1 1 100

1

2

3(c)

Coherence paramter:

Dimensionless thickness parameter normalized to a0

LP CP

Energy Gain in Laser Ion acceleration: CAIL (Coherent Acceleration of Ions by Laser) regime

• When electron dynamics by laser drive is sufficiently coherent, with coherence parameter of electrons, the ion energy in terms of electron energy is :

Electron energy = ponderomotive energy

Ion energy

(the more coherent the electron motion, the higher the ion energy)

maximizes at = 1

CAIL Theory PredictionCAIL (Coherent Acceleration of Ions by Laser) theory has definitiveprediction of max energies

Tajima et al. (2009)

For the case of LANLexperiment prediction (relative long pulse with nm targets)

Ponderomotive Bucket Formation

Gradual dynamicsof the ponderomotivebucket

PonderomotiveForce Electrostatic Trapping of ions

Yan et al. (2008)

Synchrotron oscillations in the bucket

(a,b,c)Evolution of phase space distribution for protons, the 1st, 2nd and 3rd oscillation period are 8, 8 and 10 T respectively. (d)Energy spectrum of protons.

Laser drives accelerating bucket, more adiabatic trapping structure

Monoenergy spectrum

Yan et al.(2008)

Circularly polarized laser driven

CP laser drives ions out of ultrathin (nm) foil adiabaticallyMonoenergy peak emerges

laser

Ion population

Ion mom

emntum

Ponderomotive force drives electrons,Electrostatic force nearly cancelsSlowly accelerating bucket formed

Bucket trapping ions

(X. Yan et al: 2009)

Vi,tr

Vi,tr = c (a0 m/M)

Phase space of carbon ions in 2D

Longitudinal phase space of carbon ions in 2D simulations. (a) Stable bucket structure of synchrotron oscillation; (b) Collapse of the accelerating bucket when the plasma becomes hot (due to the bending of the target)

Trapped in the bucket Bucket breaks down by runaway e-

t = 28 TL t = 40 TL

Toward more adiabatic acceleration(4)

0 10 20 30 40 50 60 70 80

0

200

400

600

800

1000

CP LP

Max

. Ene

rgy(

MeV

)

Normalized laser amplitude a0

The more adiabatic, the longer accelerated, the higher energy

Energy by CP tends to increase as ~ a02

100TW

1PW

Monoenergetic electron bunch

(Kiefer et al, 2009)

MAP + MBI

Ultrathin (2nm) foil irradiation drives monoenergetic electronsCP

Adiabatic (Gradual) Acceleration from #1 lesson of Mako-Tajima problem

Inefficient if suddenly

accelerated

Efficient when

gradually accelerated

Accelerating structure

protonsAccelerating structure

Lesson #1: gradual acceleration Relevant for ions

(cf.human trapping width:vtr,human ~ 1m/s << cs )

c

c

Adiabatic acceleration (2) Thick metal target

laser protons electrons

Graded, thin (nm), or clustered target and/or circular polarization

Most experimental configurations of

proton acceleration(2000-2009)

Innovation (“Adiabatic Acceleration”)

(2009-)= Method to make the electrons

within ion trapping width

However, in ELI automaticvtr, ion ~ c a0 (m/M) ~ c

(ultrarelativistic a0 ~ M/m )

An optimization toward adiabatic acceleration

0pl

cr cr

ndl nla

n n

,||0

la sla

,lasl R

2 2 ( )( ) pe

g

xv x c

1/ 2

0( ) exp e

i

m x Rn x nm

(Tajima, Bulanov, Esirkepov, 2007)

Laser Pulse Conditions

Adiabatic laser-plasma interaction

Relativity Helps Acceleration (for Ions, too!)

In relativistic regime,photon electronsand even protonscouple stronger.

(Tajima, 1999 @LLNL; Esirkepov et al.,PRL,2004)

Strong fields:rectifies laserto longitudinal fields

code

Monoenergy beam from double layer target

Esirkepov et al.(2002)

Laser Piston (radiation pressure) Acceleration

Esirkepov et al. (2004)

Radiation dominant regime

Nanostructured target

(Habs, 2009)

Main laser

CO2 clusterBackground gas (He)

Three-stepconical nozzle

Target gas:60-bar He(90%) + CO2 (10%)

Probe Laser

CR39 stack

2 mm

Nozzle output

Main laser

Shadowgraph

Cluster Target Irradiation

Order of magnitude energy gainWith a modest (140mJ) laser, to go beyond 15MeV/nucleon by cluster

target

Fukuda et al. (PRL 2009)

FSSR

Laser beam

Off axis

parabola

Cluster jet x�’

X Y

Z

20

to shadowgraphimaging optics

Probe beam

Z = 0.7 mm

Z = 1.5 mm

Z = 3.5 mm

Z = 5.5 mm

Z = 8.5 mm

2 mm

Orifice output

x = 6.5 mm

4.0 mm

3.8 mm

2.1 mm

1.8 mm

1.3 mm

X =

18.627 Å 18.627 Å

Ly

O VIIIHe

OVII

(a)

(c)

(b)

Fig.15

Laser beamLaserbe

am

Faenov et al., 2009

-0.006 -0.003 0.000 0.003 0.006

1E-3

0.01

0.1

f(v)*

107

v/c

1010100 100Ei (keV)

200 200

Ly

Side

Front

-0.006 -0.003 0.000 0.003 0.006

1E-3

0.01

0.1

f(v)*

107

v/c

1010100 100Ei (keV)

200 200

He

Side

Front

(b)

z�’

FSSR(Side)

FSSR( Front)

Laser beamOff axis

parabola

Clusterjet

CR 39 (Side)

1 µm C3

H6

foil

x�’

X Y

Z

2020

1 µm C3

H6

foil

CR 39 (Front)

(a)

Fig.11

20

Faenov et al.,2009

Cluster ions strongly energized

Laser-carbon cluster interaction

a0 =4

ion

electron

laser

Ion energy~ pulse length(laser energy)

Kishimoto (2009)

Pulse Strength

Maximum energy vs. laser intensity

20max 112 aQ

Consistent to the Theory by Yan et al. (2009),though it is based on thin film case

Cluster target scaling

Ion Energy spectrum r=125 m

150.98MeV 178.84MeV114.9MeV 171.71MeV

Ion Energy vs. Cluster Radius

Radius [nm]

Cluster target scaling: ion energy ~1/(cluster radius)

Kishimoto,Tajima(2009)

Toward Compact Laser-Driven Ion Therapy

Laser particle therapy (image-guided diagnosis irradiation dose verification)targeting at smaller pre-metastasis tumors with more accuracy

PET or ray image of autoradioactivation

Proton accelerator+gantry

laser

prostate cancerrectum

X-ray IMRT Proton IMRT

Merci Beaucoup et a la Prochaine Fois!

January 20, 2010: “Relativistic Engineering”February: “High Field Science”March: “Photonuclear Physics”April: “Medical Applications”

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