Transcript Plasma Acceleration Presented by: Mark Hogan On behalf of: The E-164/E-164X Collaboration C.

Plasma Acceleration
Presented 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. Walz
Stanford 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. Oz
University of Southern California
Work supported by Department of Energy contracts DE-AC02-76SF00515 (SLAC), DE-FG03-92ER40745, DE-FG03-98DP00211, DEFG03-92ER40727, DE-AC-0376SF0098, and National Science Foundation grants No. ECS-9632735, DMS-9722121 and PHY-0078715.
1
Plasma Accelerators
Showing Great Promise!
U C L A
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?
PWFA:
Plasma Wakefield Acceleration
U C L A
 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…
Linear PWFA Theory:
Accelerating
Decelerating
-- -- -- ----- -----+----+-++ ++ ++-+--+--+--+----+--+ ++ ++ ++ ++-+--+-+--+--+---+-++
+
+-+- +++ +++ ++ ++++ +-++-+----+--+-++++ +++++++++++++--+--+++ ++++ ++++ ++
---- ------- --- -- -- -- - -- -- - ---- --- - - - -- --Ez
m
m
Ez ,linear 
N
s 2z
Fork ps r  1
 Short bunch!
andk ps z 
2
or
np 
1
s 2z
Ez: accelerating field
N: # e-/bunch
sz: gaussian bunch length
kp: plasma wave number
np: plasma density
nb: beam density
 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

PWFA Experiments @ SLAC
Share Common Apparatus
U C L A
Located in the FFTB
 FFTB
Energy
Spectrum
“X-ray”
Plasma light
eN=1.81010
sz=20-12µm
E=28.5 GeV
Li Plasma
Gas Cell: H2, Xe, NO
ne≈0-1018 cm-3
L≈2.5-20 cm
Coherent
Transition
Radiation and
Interferometer
Optical Transition
Radiators
y x
z
∫Cdt
Imaging
Cherenkov
Spectrometer Radiator
25m
X-Ray
Diagnostic,
e-/e+
Production
Dump
FFTB
Focusing e300
X-ray Generation
Wakefield Acceleration e-
s0 Plasma Entrance =50 µm
250  =1210-5 (m rad)
N
0=1.16m
200
150
100
50
0
0 51 60 ce dFIT. graph
-2
0
2
4
6
8
10
12
=K*Lne1/2L
Phase Advance   ne1/2L
Phys. Rev. Lett. 88, 154801 (2002)
Matching e-
Phys. Rev. Lett. 88, 135004 (2002)
Electron Beam Refraction
at theBPMGas–
impulse model
data
Wakefield Acceleration e+
Plasma Boundary
600
L=1.4 m
s0=14 µm
500
Plasma OFF
Plasma ON
Envelope
N=1810 m-rad
-5
1/sin
0.3
0.2
0=6.1 cm
400
0=-0.6
300
200
100
0.1
0
≈
-0.1
o
BPM Data
– Model
-0.2
BetatronFitShortBetaXPSI.grap h
0
0
2
4
6
8
Phys. Rev. Lett. 93, 014802 (2004)
05190cec+m2.txt 8:26:53 PM 6/21/00
 (mrad)
s X DS OTR (µm)
sx (µm)
Beam-Plasma Experimental Results (6 Highlights)
10
12
   n 1/2L
Phase Advance
e
Phys. Rev. Lett. 93, 014802 (2004)
14
-0.3
-8
-4
0
 (mrad)
4
8
Nature 411, 43 (3 May 2001)
Phys. Rev. Lett. 90, 214801 (2003)
Short Bunch Generation
In The SLAC Linac
50 ps
U C L A
Damping Ring
SLAC Linac
RTL
1 GeV
9 ps
0.4 ps
20-50 GeV
FFTB
<100 fs
Add 12-meter chicane compressor
in linac at 1/3-point (9 GeV)
Existing bends compress to <100 fsec
1.5%
~1 Å
30 kA
80 fsec FWHM
28 GeV
• 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.
First Measurement of SLAC Ultra-short Bunch Length!
CTR Michelson Interferometer
• Fabry-Perot resonance:
l=2d/nm, m=1,2,…, n=index of refraction
• Modulation/dips in the interferogram
• Smaller measured width:
sAutocorrelation < sbunch !
• Other issues under investigation:
- Detector response (pyro vs. Golay)
- Alternate materials:
HDPE, TPX, Si, Diamond ($$$)
1.6
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
60
SigmazMy lar12.7_3WandBS
sz ≈ 9 µm
w Filtering
50
Bunch sz (µm)
1.2
0.8
0.4
40
w/o Filtering
30
20
CombinedCTRInterferogramsSm
-50
0
50
100
0
Gaussian
Bunch
sz≈18 µm
10
0
-100
Autocorrelation:
sz≈9 µm
0
5
10 15 20 25 30 35 40
Autocorrelation sz (µm)
or
≈60 fs
Non-Invasive Energy Spectrometer
Upstream of Plasma
U C L A
Phase Space Retrieval via LiTrack*
*K.
• 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!
Bane & P. Emma
U C L A
Window
W
Plasma Source Starts with
Metal Vapor in a Heat-Pipe Oven
Optical
Window
Heater
Cooling
Cooling
Insulation
Jacket
Jacket
Boundary Layers
He
Optical
Window
Wick
U C L A
He
He
0 /m
E  6GV
N 20 100
2x1010 s r 0 s z
Pump
0
L
Ionization Rate for Li:
He

He
0
Cooling
Cooling
Insulation
Jacket
Jacket
Boundary Layers
Peak Field He
For A Gaussian
Bunch:
Li
Li
Pu
z
L
See D. Bruhwiler et al, Physics of Plasmas 2003
Space charge fields are high enough to field (tunnel) ionize - no laser!
- However, can’t just turn it off!
- No timing or alignment issues
- Ablation of the head
- Plasma recombination not an issue
z
Accelerating Gradient > 27 GeV/m!
(Sustained Over 10cm)
31.5
• Large energy spread after the
plasma is an artifact of doing single
bunch experiments
30.5
• Electrons have gained > 2.7 GeV
over maximum incoming energy in
10cm
29.5
Energy [GeV]
U C L A
• Confirmation of predicted
dramatic increase in gradient with
move to short bunches
28.5
27.5
• First time a PWFA has gained
more than 1 GeV
26.5
25.5
• Two orders of magnitude larger
than previous beam-driven results
24.5
• Future experiments will accelerate
a second “witness” bunch
No Plasma
np = 2.8 x 1017 e-/cm3
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
Test of Notch Collimator - December 2005
Exploit Position-Time Correlation on e- bunch in FFTB Dog Leg
to create separate drive and witness bunch
Access to time
coordinate
along bunch
x  DE/E  t
1.
2
Insert tantalum blade as notch
collimator
Do not compress fully to preserve
two bunches separated in time

14
Test of Notch Collimator - December 2005
Energy Spectrum Before Plasma:
High Energy
Low Energy
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
Energy Spectrum After Plasma:
Energy Gain
Ta Blade
100-300µm Wide
1.6cm Long (4 X0)
QuickTime™ and a
TIFF (Uncompressed)
decompressor
Energy Loss
are needed to see this picture.
Shot # (Time)
• Acceleration correlates with collimator location (Energy)
• No signature of temporally narrow witness bunch - yet!
• Other interesting phenomena also correlate (see next slide)
15
• Collimated spectra more complicated than anticipated
Always New Things to Look At! (Part 1)
Energy [GeV]
Narrow Energy Spread!
Always New Things to Look At! (Part 2)
Trapped Particles
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Dipole
Two Main Features
• 4 times more charge
• 104 more light!
Always New Things to Look At! (Part 2)
30cm
•
•
•
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!
20cm
10cm
Future Experiments - Part 1
(Next 2.5 months)
U C L A
•
Create two bunches via notch collimator in FFTB and
accelerate witness bunch with narrow energy spread
•
FFTB will soon be demolished to make way for LCLS
Make
Highest
Energy
Evera@bang?
SLAC!
Whatthe
should
we
do toElectrons
go out with
"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
Use ~ 1 Meter-long Plasma to
Double the Energy of Part of the Incoming Beam
28.5 GeV  57GeV
Future Experiments - Part 2
(A Couple Years)
U C L A
SABER (South Arc Beamline Experimental Region):
Short Pulse e+ Are the Frontier:
Evolution of a positron beam/wakefiled and
final energy gain in a self-ionized plasma
5.7GeV in
39cm

N b  8.79 10 9 , s r  11m, s z  19.55m, n p  1.8 1017 cm3
Plasma Wakefield Accelerator
Research Summary
U C L A
Over the past 5 years
20 Peer reviewed publications covering all aspects of beam plasma interactions: Focusing (e- &
e+), Transport, Refraction, Radiation Production, Acceleration (e- & e+)
E-164X Accomplishments
First measurement of the
SLAC Ultra-short Bunch
Length
Demonstration of Field
Ionized Plasma Source
Measured Accelerating
Gradients > 27 GeV/m
(over 30cm) in a PWFA
Autocorrelation Amplitude [a.u.]
31.5
1.6
30.5
0.8
Energy [GeV]
s z  9m
1.2

29.5
28.5
27.5
26.5
0.4
25.5
0
-100
CombinedCTRInterferogramsSm
-50
0
50
100
24.5
Position [mm]
Bright Future:
Two bunch experiment, Energy Doubler, and longer term positrons @ SABER
No Plasma
Np = 2.8x1017 e/cc