Transcript E - Indico

FACET: A Facility for Advanced
Accelerator Research at SLAC
U. Wienands, SLAC
at CERN until 12-Nov.
on a LARP-sponsored Long Term Visit
Division Head for FACET Linac
I am indebted to Mark Hogan for providing material on plasma acceleration
U. Wienands, SLAC
UA9 Workshop, 27-Oct-10
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Overall Thrust of FACET
• The primary goal of FACET is proof in principle
that plasma acceleration can accelerate a bunch
– characterize the mechanism under beam loading
– estimate beam parameters (witness)
– estimate the efficiency and gradient reachable in
practice
– demonstrate acceleration of a positron bunch
• Beyond that, FACET will provide a facility to
explore other accelerator physics issues
– Wakefield measurements (ILC, CLIC)
– Matter in extreme fields
U. Wienands, SLAC
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–
new
radiation
sources
using crystals
UA9 Workshop, 27-Oct-10
The FACET Facility
• Driven by first 2/3rd of the SLAC 2-mile linac
–
–
–
–
U. Wienands, SLAC
UA9 Workshop, 27-Oct-10
new exp. area in Sec. 19-20.
new compressor chicane in Sec. 10 for e+
new compressor chicanes in Sec. 19.
e– and slightly later also e+
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The FACET Facility
• Beam Parameters:
Energy
23 GeV
Charge
3 nC
Sigma z
14 µm
Sigma r
10 µm
Peak Current
22 kAmps
Species
e- & e+
– many of these can be tuned to match requirements
– 30 Hz repetition rate
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UA9 Workshop, 27-Oct-10
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Staged Bunch Compression
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S10 Compressor Chicane
QuickTime™ and a
TIFF (Uncompressed) decompressor
are needed to see this picture.
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“Sailboat” Chicane (S20)
• 3rd-stage bunch compression
• precision timing e+ and e– bunches wrt. each other
– allow e+ bunch to sample wake from e– bunch
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Linac Removed from FACET Expt. Area
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Some of the Beam Diagnostics
SLAC linac:
BPM’s, Toroids,
Feedbacks, GADCs,
triggers
U. Wienands, SLAC
UA9 Workshop, 27-Oct-10
FACET IP
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FACET Status
• Construction expected to finish early Summer 2011
– accelerator and beam commissioning soon after.
• Experimental program to begin early Fall 2011
• First Users Workshop @ SLAC March 18-19, 2010
– http://www-conf.slac.stanford.edu/facetusers/spring2010/
– 40 people, 9 institutions
•
Argonne, Brookhaven, Euclid Techlabs, Fermilab, SLAC,
Stanford, UCLA, USC, UT Austin
– 4 Working groups considered ideas for first experiments:
•
•
•
•
Plasma Wakefield Acceleration
Dielectric Wakefield Acceleration
Materials in Extreme Conditions
Crystals & Novel Sources of Radiation
• Beamtime allocated12in a proposal driven process
U. Wienands, SLAC
UA9 Workshop, 27-Oct-10
PWFA: Particle to Beam
Acceleration
• Collimation system to craft drive/witness bunch from single
bunch (similar to BNL ATF wire system)
Disperse the beam in energy
x  E/E  t
dp/p [%]
Adjust final compression
Witness
Bunch
dp/p [%]
z [mm]
80cm
Plasma
Drive
Bunch
x [mm]
...selectively collimate

Vary charge ratio, bunch lengths, spacing by changing collimators and linac phase, R56

Study wake loading in the non-linear regime for the first time
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Beam Loading & Wake Evolution
Energy [GeV]
QuickPIC simulation, D: z=30µm, N=3x1010e-, W: z=10µm, N=1x1010e-, r0=3µm, ∆z=115µm, ne=1017cm-3
Propagation Distance
[cm]
•
•
•
•
•
Beam loading at 37GeV/m (z = 0)
After 80 cm plasma, gain 25 GeV with 3% E/E
Wake evolution due to bunch head erosion, but no dephasing
Wake evolution “bends” energy gain but preserves low ∆E/E
Drive to witness Energy 14
transfer efficiency ~ 30%
U. Wienands, SLAC
UA9 Workshop, 27-Oct-10
PWFA Collider
• Concept for a beam-driven PWFA collider (1TeV)
– R&D: e+, emittance, efficiency
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FACET Beam is Well Suited for Studying
DWA
A ‘‘drive’’ beam excites wake-fields in the tube, while a subsequent
witness beam (not shown) would be accelerated by the Ez component of
the reflected wakefields (bands of color).
For large wakes want high charge, short bunches and narrow tubes,
e.g. 2E10 e-, σz=20µm, Si with 200µm ID get 85GV/m surface fields!
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Other Proposed Research
These are
submitted
proposals or
LOIs
•
•
•
•
•
Ultrafast processes in magnetic solids.
Wakefield measurements of CLIC structures
Optical diffraction radiation tests
Time profile of 50 fs bunches
Test of advanced Feedback Algorithms (CLIC).
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Other Research Considered
• Crystal Accelerator:
– idea has been around for a while, inverse FEL process
– at FACET could be done with high-energy photons
• Crystal collimation and X-ray generation
– use the strong bending in channeling to make Xrays
– some work at other facilities (mostly e–)
– at FACET can use e+, higher energies & non-negligible intensities
• Beam collimation studies
• Bragg diagnostics.
• High-gradient structure tests.
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Crystal Channeling @ FACET
Noble, Ng,
Stupakov,
Seryi et al.
• Study of volume reflection of e+ and e–
– test continuum model of VR for light particles
– study effect of multiple scattering on vr
– possible application for halo cleaning in lin. colliders
• Physics of volume-reflection radiation by e+ & e–
– test radiation models for channeled light particles in
region of undulator parameter K = E/m* ≈ 1.
– possible application as new photon source
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VR Simulation for FACET
But
FACET can
make
divergence
< 1 µr at ≈
100 µm
Noble et al.,
CERN, 2009
QuickTime™ and a
decompressor
are needed to see this picture.
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Carrigan,
Channeling 2008
QuickTime™ and a
decompressor
are needed to see this picture.
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X-ray Generation
Bolognini, Thesis
180 GeV e– and e+
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Undulator Radiation possible?
QuickTime™ and a
decompressor
are needed to see this picture.
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Crystal Accelerator
• Idea: intense Xrays (40 keV, 109 W) shone on
crystal at Bragg angle setup accelerating field
– channeled µ+ see accelerating field of GV/m
– (Tajima & Cavenago 1987)
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Summary
• FACET will be a unique facility to advance the
high-gradient acceleration research with plasmas
and dielectrica
• Beyond this, FACET will allow a number of
advanced experiments in solid-state physics and
the study of particle interaction with matter.
• An open, proposal-driven process of experiment
approval will allow equitable access to the facility
to fore-front experiments
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Apply Now!
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Backup Slides
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1 GeV
1.5 TeV
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Outline
• The FACET Project
• The Experimental Program
• Conclusion
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Primary Challenges for Accelerator
R&D
• Beam Power
– directly relates to (average) luminosity & energy
– MW scale, technical and physical limitations
• Beam brightness (intensity/phase-space volume)
– directly relates to peak luminosity (for given power)
– important parameter for light & X-ray sources
• Beam energy
– Energy reach in HEP, wavelength reach in X-ray
sources
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Primary Challenges for Accelerator R&D
• Presently most radical new mechanisms:
– Plasma wave acceleration
– Dielectric wake acceleration
– other schemes based on the inverse FEL process
• These clearly need demonstration of capability
– not just accelerate tail-particles, need to create and
accelerate a beam (bunch)
– ability to accelerate both polarities
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Dielectric Wake Accelerator
 Material limited breakdown (metal < dielectric < plasma)
 Nearly symmetric response for positrons
DWA Experimental History: Argonne / BNL experiments
•
Proof-of-principle experiments
E vs. witness delay
(W. Gai, et al.)
–
•
ANL AATF
Mode superposition
(J. Power, et al. and S. Shchelkunov, et al.)
–
•
ANL AWA, BNL
Transformer ratio improvement
(J. Power, et al.)
– Beam shaping
Tunable permittivity structures
– For external feeding
•
(A. Kanareykin, et al.)
Gradients ~100 MV/m, limited by available beam
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Tunable permittivity
Summary of non-WFA expts.
• At FACET, we can
– Study collimation schemes for a linear collider
• e+ and in particular e– as well
• crystals may offer important advantages
• extension of proton expts. at FNAL and CERN (UA9)
– behaviour of crystals at high intensities
– Study the generation of X-rays by the extreme fields
• equivalent to kTesla of magnetic fields
• use e+: stronger effects than with e–
• Possible to get coherent light?
– with sizeable intensities??
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