Terawatt Ultrafast High Field Facility: Using Photons …...Facility: Using Photons to Accelerate...

A U.S. Department of EnergyOffice of Science LaboratoryOperated by The University of Chicago

Argonne National Laboratory

Office of ScienceU.S. Department of Energy

Terawatt Ultrafast High Field Facility: Using Photons to

Accelerate ElectronsRobert A. Crowell

Radiation and Photochemistry GroupChemistry Division

June 26, 2004

2

Pioneering Science andTechnology

Office of ScienceU.S. Department

of Energy

Outline• Why? Already covered in numerous workshops/meetings

D. Bartels will discuss some of these tomorrow

• Physics under extreme conditions

• Terawatt Ultrafast High Field Facility

• Table(s)-Top Terawatt Laser – T3

• Generation/Characterization of electron pulses

• Future will include coherent fs hard x-rays

• Advantages and disadvantages of our approach

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Acknowledgments

Dave GosztolaEli ShkrobDmitri OulianovOleg KorovyankoYuelin Li (Advanced Photon

Source)

Prof. Don Umstadter (U. Mich.)Stanislaus Pommeret (Saclay)Prof. Edward Kibblewhite(U. Chicago)

DOE-BESInside of the TUHFF Target Chamber

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Generation of Ultrahigh Peak Powers: Chirped Pulse Amplification

1960 1970 1980 1990 2000

1010

1015

1020

1025

Year

Focu

ssed

Inte

nsity

(W/c

m2 )

Q-switchingMode locking

CPA

Bound electrons

Nonlinear relativistic optics(large pondermotive forces)

Laser intensity limit Recent advances in laser technology that have opened up new areas of research in physics and chemical physics

and radiation chemistry?

K. Yamanouchi Science, 295 1659 (2002)

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In the relativistic regime it becomespossible to generate subps e- pulses

Requires

- >1018W/cm2

⇒ terawatt laser systeme.g., .5J in 50fs = 10TW

Pulse charges as high as 8nC have been achieved using T3

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Terawatt Ultrafast High Field Facility

Control Room

Amplifier#3

Amplifier#2

PulseStretcher

Oscillator

Amplifier#1

Amplifier#1

VacuumPulse

Compressor

VacuumInteractionChamber

Radiation shielding

Single- ShotDetection

E- BeamDiagnostics

LIN

AC

5-20MeV30ps

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T3 Specifications

Wavelength Rep. Pulsewidth Energy

Oscillator 780nm 100MHz 15fs 2nJ

Amp 1 800nm 10Hz ~350ps 2mJ

Amp 2 805nm 10Hz ~350ps .35J

30fs .15J (5TW)Amp 3 805nm 10Hz ~350ps 1.3J

30fs .6J ( 20TW )

Future upgrade will increase the power to 50TW

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T3

Sometime ago

Present

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Inside T3

AMP 1 AMP 2

AMP 3

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VacuumCompressor

Target Chamber

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Unique Aspects of T3

• Pulse contrast ratio- Need better than 1:108 (1012W/cm2 in pedestal)

• Stretcher/Compressor- Very large aperture high quality optics- Must compensate for high order dispersive effects

• Spatial Beam Quality- Critical to prevent catastrophic failure

• Incorporation of adaptive optics- Continuous real time control over various laser parameters to

optimize electron beam and prevent optical failure- AOPDF, DM etc.

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Correcting for Spatial Aberrations

From 1st pass

To 2nd pass

Beam profile inversion

Beam profile monitors

Ti:Sapphirerod

90° Spatial Inversion during amplification offers some relief

Full correction will be realized via deformable mirrors and adaptive learning software

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Laser In

He Jet

e- out

Al Foil MagnetScintillation

Screen

PMT

Jet

PMT

MagnetAl foil

Scintillation screen

Parabola mirror

Laser beam

Laser Generation of Electron Pulses

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The full angle beam divergence goes from ~15º at low power (2TW) to ~3º at higher power (7TW). At the highest laser power (23TW) the divergence is expected to be on the order of 1º.

2TW

Electron Beam Spatial Profile2TW 7TW

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Measurement of Charge

-1.2

-0.8

-0.4

0.0V

olts

-15 -10 -5 0 5 10 15Time (ns)

Faraday Cup(40pC e- pulse)

RF Noise

Figure 5. Response of the Faraday cup using 10TW of laser power. From our calibration factor of 21pC/ns·V the charge is estimated to be 40pC

We have measured charges as high as 0.1nC, enough to start experiments with ~5ps resolution!

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Scintillator Signal

0 5 10 15 20 25

Time (µs)

PMT

Sign

al

1MeV filter

5 MeV filter

~30% of electrons >5MeVUp to 0.1nC using <10TW

Accelerates electrons to 2MeV in .75mm=>3GeV/cm acceleration gradient1MeV/cm traditional accelerator

ThTh

The broad energy dispersionwill limit the initial time resolution to 1-2ps

Enter presentation date [Your Presentation Title] 17

Malka et. Al, Science 298 (2002) 1596

Energy Spectrum

Large energy dispersion is a definite disadvantageDispersion = .5ps/cm

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Gas jet

PMT

MagnetAl foil

Scintillation screen

Parabolic mirror

Terawatt laser beam

e- beam TS x-ray beam

TS probe beam

Laser In

He Jet

e- out

Al FoilMagnet

e-

x-ray

TS probe

Thomson scattering x-ray source in TUHFFTUHFF = Terawatt Ultra High Field Facility

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Electron Pulse Longitudinal Profile

?!

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Thomson scattering x-ray source based on laser wakefieldaccelerators (calculations)*

* P Catravas, et al Meas. Sci. Technol. 12 (2001) 1828–1834

Has recently been demonstrated, 108ph/eV up to 2keV

LOA U. Mich. collaboration

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Summary• T3 Version 1 at TUHFF is complete• Generation of 0.1nC electron pulses achieved• Next 5ps radiolysis experiments and electron beam temporal

characterization• Continue plans for coherent hard X-ray generation

Advantages/Disadvantages

• More than electron pulses (i.e., physics)• Can also be used as X-ray source• Complicated laser system, but…..• Energy dispersion• Synchronization• No linac

Terawatt Ultrafast High Field Facility: Using Photons …...Facility: Using Photons to Accelerate...

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