1Work supported by Department of Energy contracts DE-AC02-76SF00515 (SLAC), DE-FG03-92ER40745, DE-FG03-98DP00211, DE-FG03-92ER40727, DE-AC-0376SF0098, and National Science Foundation grants No. ECS-9632735, DMS-9722121 and PHY-0078715.

Work supported by Department of Energy contracts DE-AC02-76SF00515 (SLAC), DE-FG03-92ER40745, DE-FG03-98DP00211, DE-FG03-92ER40727, DE-AC-0376SF0098, and National Science Foundation grants No. ECS-9632735, DMS-9722121 and PHY-0078715.

Plasma AccelerationPresented by: Mark Hogan

On behalf of: The E-164/E-164X Collaboration

C. D. Barnes, I. Blumenfeld, F.J. Decker, P. Emma, M.J. Hogan*, R. Ischebeck, R. Iverson,

N. Kirby, P. Krejcik, C. L. O'Connell, R.H. Siemann and D. WalzStanford Linear Accelerator Center

C. E. Clayton, C. Huang, D. K. Johnson, C. Joshi*, W. Lu, K. A. Marsh, W. B. Mori and M. Zhou

University of California, Los Angeles

S. Deng, T. Katsouleas*, P. Muggli and E. OzUniversity of Southern California

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Laser Driven Plasma Accelerators:

• Accelerating Gradients > 100GeV/m (measured)• Narrow Energy Spread Bunches• Interaction Length limited to mm’s

Beam Driven Plasma Accelerators:

Large Gradients:• Accelerating Gradients > 30 GeV/m (measured!)• Interaction Length not limited

Unique SLAC Facilities:• FFTB• High Beam Energy• Short Bunch Length• High Peak Current• Power Density• e- & e+

Scientific Question:• Can one make & sustain high gradients in plasmas for lengths that give significant energy gain?

Laser Driven Plasma Accelerators:

• Accelerating Gradients > 100GeV/m (measured)• Narrow Energy Spread Bunches• Interaction Length limited to mm’s

Beam Driven Plasma Accelerators:

Large Gradients:• Accelerating Gradients > 30 GeV/m (measured!)• Interaction Length not limited

Unique SLAC Facilities:• FFTB• High Beam Energy• Short Bunch Length• High Peak Current• Power Density• e- & e+

Scientific Question:• Can one make & sustain high gradients in plasmas for lengths that give significant energy gain?

Plasma AcceleratorsShowing Great Promise!

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PWFA:Plasma Wakefield Acceleration

Ez: accelerating fieldN: # e-/bunchz: gaussian bunch lengthkp: plasma wave numbernp: plasma densitynb: beam density

Ez,linear∝Nσ z

2

kpσz ≅ 2 or np ∝1σ z

2For and

++++++++++++++ ++++++++++++++++

----- -------------------

---- -----------

----------------------------------- --

-

---- ------

-------- -- --------- --

---- - --- - - --- --

- -- - -- - -

---------

------

electron beam

+ + + + + + + + + + ++ + + + + + + + + + + + + + ++ + + + + + + + + + + + + + +

+ + + + + + + + + + + + + + +-

- --

--- --

EzEz

AcceleratingDecelerating

Short bunch!

€

kpσ r <<1

Linear PWFA Theory:

Looking at issues associated with applying the large focusing (MT/m) and

accelerating (GeV/m) gradients in plasmas to high energy physics and colliders Built on E-157 & E-162 which observed a wide range of phenomena with both

electron and positron drive beams: focusing, acceleration/de-acceleration, X-ray

emission, refraction, tests for hose instability…

A single bunch from the linac drives a large amplitude plasma wave which focus and accelerates particles For a single bunch the plasma works as an energy transformer and transfers energy from the head to the tail

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Located in the FFTB

FFTB

PWFA Experiments @ SLACShare Common Apparatus

e-

N=1.81010

z=20-12µmE=28.5 GeV

Optical TransitionRadiators

Li Plasma Gas Cell: H2, Xe, NO

ne≈0-1018 cm-3

L≈2.5-20 cmPlasma light

X-RayDiagnostic,

e-/e+

Production

CherenkovRadiator Dump

∫Cdt

ImagingSpectrometer

xz

y

EnergySpectrum“X-ray”

25m

CoherentTransition

Radiation andInterferometer

FFTB

Wakefield Acceleration e-

Focusing e-

Phys. Rev. Lett. 88, 154801 (2002)

Beam-Plasma Experimental Results (6 Highlights)

X-ray Generation

Phys. Rev. Lett. 88, 135004 (2002)

0

50

100

150

200

250

300

-2 0 2 4 6 8 10 12

05160cedFIT.graph

ψ= *K L∝ne1/2L

0 Plasma Entrance

=50µm

εN=12×10-5( )m rad

β0=1.16m

0

100

200

300

400

500

600

0 2 4 6 8 10 12 14

BetatronFitShortBetaXPSI.graph

Plasma OFF

Plasma ON

Envelope

Ψ

=1.4L m0=14µm

εN=18×10-5 -m rad

β0=6.1cm

α0=-0.6

Phase Advance Ψ ne1/2L

Matching e-

Phase Advance Ψ ne1/2L

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

-8 -4 0 4 8

05190cec+m2.txt 8:26:53 PM 6/21/00impulse model

BPM data

θ

( )mrad

φ( )mrad

θ1/sin

θ≈o BPM Data– Model

Electron Beam Refraction at the Gas–Plasma Boundary

Nature 411, 43 (3 May 2001)

Wakefield Acceleration e+

Phys. Rev. Lett. 90, 214801 (2003)Phys. Rev. Lett. 93, 014802 (2004)

Phys. Rev. Lett. 93, 014802 (2004)

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28 GeV28 GeV

Existing bends compress to Existing bends compress to <100 fsec<100 fsec

~1 Å~1 Å

Add 12-meter chicane compressor Add 12-meter chicane compressor in linac at 1/3-point (9 GeV)in linac at 1/3-point (9 GeV)

Add 12-meter chicane compressor Add 12-meter chicane compressor in linac at 1/3-point (9 GeV)in linac at 1/3-point (9 GeV)

Damping RingDamping Ring

9 ps9 ps 0.4 ps0.4 ps<100 fs<100 fs

50 ps50 ps

SLAC LinacSLAC Linac

1 GeV1 GeV 20-50 GeV20-50 GeV

FFTBFFTBRTLRTL

30 kA30 kA

80 fsec FWHM80 fsec FWHM

1.5%1.5%

Short Bunch GenerationIn The SLAC Linac

• Bunch length/current profile is the convolution of an incoming energy spectrum and the magnetic compression• Dial FFTB R56 & linac phase, then measure incoming energy spectrum.

0

0.4

0.8

1.2

1.6

-100 -50 0 50 100CombinedCTRInterferogramsSm 0

10

20

30

40

50

60

0 5 10 15 20 25 30 35 40

SigmazMylar12.7_3WandBS

Autocorrelationz( )µm

/ w o Filtering

w Filtering

z≈9 µm

≈60 fs

z ≈ 9 µm

z≈18 µm

GaussianBunch

or

First Measurement of SLAC Ultra-short Bunch Length!

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Autocorrelation:

CTR Michelson Interferometer• Fabry-Perot resonance:=2d/nm, m=1,2,…, n=index of refraction• Modulation/dips in the interferogram• Smaller measured width:Autocorrelation < bunch !• Other issues under investigation:- Detector response (pyro vs. Golay)- Alternate materials:HDPE, TPX, Si, Diamond ($$$)

CTR Michelson Interferometer• Fabry-Perot resonance:=2d/nm, m=1,2,…, n=index of refraction• Modulation/dips in the interferogram• Smaller measured width:Autocorrelation < bunch !• Other issues under investigation:- Detector response (pyro vs. Golay)- Alternate materials:HDPE, TPX, Si, Diamond ($$$)

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Non-Invasive Energy SpectrometerUpstream of Plasma

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Phase Space Retrieval via LiTrack*

*K. Bane & P. Emma

• Extension of previous work on SLC- More compression stages- More free parameters- Shorter bunches• Requires good measurements, good intuition or really good guessing!• Not automated (yet!)• Single shot and non-destructive!

• Extension of previous work on SLC- More compression stages- More free parameters- Shorter bunches• Requires good measurements, good intuition or really good guessing!• Not automated (yet!)• Single shot and non-destructive!

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Plasma Source Starts withMetal Vapor in a Heat-Pipe Oven

€

E = 6GV /mN

2x1010

20μ

σ r

100μ

σ z

Peak Field For A Gaussian Bunch: Ionization Rate for Li:

See D. Bruhwiler et al, Physics of Plasmas 2003

Space charge fields are high enough to field (tunnel) ionize - no laser!- No timing or alignment issues- Plasma recombination not an issue

- However, can’t just turn it off! - Ablation of the head

0 0Pressure

zLi HeHe

Boundary Layers

OpticalWindowCoolingJacketCoolingJacket

HeaterWick

InsulationPumpHe

OpticalWindow

L

0 0 zLi HeHe

Boundary Layers

OpticalWindowCoolingJacketCoolingJacket

HeaterWick

InsulationPumpHe

OpticalWindow

L

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Accelerating Gradient > 27 GeV/m!(Sustained Over 10cm)

No Plasma np = 2.8 x 1017 e-/cm3

Ene

rgy

[GeV

]

31.5

30.5

29.5

28.5

27.5

26.5

25.5

24.5

• Large energy spread after the plasma is an artifact of doing single bunch experiments

• Electrons have gained > 2.7 GeV over maximum incoming energy in 10cm

• Confirmation of predicted dramatic increase in gradient with move to short bunches

• First time a PWFA has gained more than 1 GeV

• Two orders of magnitude larger than previous beam-driven results

• Future experiments will accelerate a second “witness” bunch

• Large energy spread after the plasma is an artifact of doing single bunch experiments

• Electrons have gained > 2.7 GeV over maximum incoming energy in 10cm

• Confirmation of predicted dramatic increase in gradient with move to short bunches

• First time a PWFA has gained more than 1 GeV

• Two orders of magnitude larger than previous beam-driven results

• Future experiments will accelerate a second “witness” bunch

M.J. Hogan et al. Phys. Rev. Lett. 95, 054802 (2005)

Summer 2004:

• Results Recently

Published

• Outdated within two

weeks!

Summer 2005:

• Increased beamline

apertures

• Plasma Length increased

from

10 to 30 cm

Summer 2004:

• Results Recently

Published

• Outdated within two

weeks!

Summer 2005:

• Increased beamline

apertures

• Plasma Length increased

from

10 to 30 cm

• Energy Gain > 10GeV!

…but spectrometer

redesign necessary to

transport more of the

low energy electrons

14

Access to Access to timetime coordinate coordinate along bunchalong bunch

Exploit Exploit Position-TimePosition-Time Correlation on Correlation on ee-- bunch in FFTB Dog Leg bunch in FFTB Dog Legto create separate drive and witness bunchto create separate drive and witness bunch

x E/E t

1. Insert tantalum blade as notch collimator

2 Do not compress fully to preserve two bunches separated in time

Test of Notch Collimator - December 2005

15

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

QuickTime™ and aTIFF (Uncompressed) decompressor

are needed to see this picture.

Low Energy

High Energy

Energy Spectrum Before Plasma:

Energy Spectrum After Plasma:

Shot # (Time)

Ta Blade100-300µm Wide1.6cm Long (4 X0)

• Acceleration correlates with collimator location (Energy)• No signature of temporally narrow witness bunch - yet!• Other interesting phenomena also correlate (see next slide)• Collimated spectra more complicated than anticipated

• Acceleration correlates with collimator location (Energy)• No signature of temporally narrow witness bunch - yet!• Other interesting phenomena also correlate (see next slide)• Collimated spectra more complicated than anticipated

Energy Loss

Energy Gain

Test of Notch Collimator - December 2005

Always New Things to Look At! (Part 1)

Narrow Energy Spread!

En

erg

y [G

eV]

QuickTime™ and aTIFF (LZW) decompressor

are needed to see this picture.

Trapped Particles Two Main Features• 4 times more charge• 104 more light!

Two Main Features• 4 times more charge• 104 more light!

Always New Things to Look At! (Part 2)

Dipole

10cm

30cm 20cm

• Particles are trapped and accelerated out of the plasma

• Trapped particle energy scales with plasma length: 5GeV @ 30cm

• Primary beam (28.5GeV) is also radiating after the plasma!

• Particles are trapped and accelerated out of the plasma

• Trapped particle energy scales with plasma length: 5GeV @ 30cm

• Primary beam (28.5GeV) is also radiating after the plasma!

Always New Things to Look At! (Part 2)

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• Create two bunches via notch collimator in FFTB and accelerate witness bunch with narrow energy spread

Future Experiments - Part 1(Next 2.5 months)

"Far better is it to dare mighty things, to win glorious triumphs, even though checkered by failure, than to take rank with those poor spirits who neither enjoy much nor suffer much, because they live in the gray twilight that knows not victory or defeat."

Theodore Roosevelt, 1899

• FFTB will soon be demolished to make way for LCLS

Use ~ 1 Meter-long Plasma toDouble the Energy of Part of the

Incoming Beam28.5 GeV 57GeV

What should we do to go out with a bang?Make the Highest Energy Electrons Ever @ SLAC!

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Future Experiments - Part 2(A Couple Years)

SABER (South Arc Beamline Experimental Region):

5.7GeV in 39cm

Evolution of a positron beam/wakefiled and final energy gain in a self-ionized plasma

€

N b = 8.79 ×109,σ r = 11μm, σ z = 19.55μm, np = 1.8 ×1017cm−3

Short Pulse e+ Are the Frontier:

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Over the past 5 years20 Peer reviewed publications covering all aspects of beam plasma interactions: Focusing (e- & e+), Transport, Refraction, Radiation Production, Acceleration (e- & e+)

E-164X Accomplishments

Demonstration of Field Ionized Plasma Source

En

erg

y [G

eV

]

31.5

30.5

29.5

28.5

27.5

26.5

25.5

24.5

No Plasma Np = 2.8x1017 e-/cc

Measured Accelerating Gradients > 27 GeV/m (over 30cm) in a PWFA

€

z ≈ 9μm

0

0.4

0.8

1.2

1.6

-100 -50 0 50 100CombinedCTRInterferogramsSm

First measurement of the SLAC Ultra-short Bunch

Length

Position [mm]

Au

toco

rre

latio

n A

mp

litu

de

[a

.u.]

Plasma Wakefield AcceleratorResearch Summary

Bright Future:Two bunch experiment, Energy Doubler, and longer term positrons @ SABER