Transcript 090716 SLUO meeting Raubenheimer

SLAC Accelerator Research
Program
Tor Raubenheimer
SLUO Meeting, July 17, 2009
What is Accelerator Research?
• Accelerators are throughout medicine, science, & industry
– Accelerator research is basis for future development
• Analogous to laser research
– Motivated by the applications as well as the science
• The R&D is broad both in topic and timescale
– Materials surface physics, magnet design, Hamiltonian dynamics
– Direct accelerator improvements to concept exploration with
application more than 20-years in the future
• Accelerator R&D is usually directed towards applications
– Results can have broad impact, e.g. L-band & C-band linear
collider R&D provided the basis for DESY and Spring-8 XFEL’s
– High Energy Physics is one of the greatest challenges
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Key Challenges in Accelerator Physics
• Beam brightness and control  peak luminosity and
radiation source brightness
– Brightness is flux divided by 6-D phase space volume (emittance)
which should be conserved after beam creation
• Beam energy  energy reach or radiation wavelength
– Critical problem for HEP requiring new cost-effective concepts
– Novel concepts will enable new applications elsewhere as well
• Beam power  average luminosity or brightness
– Power (average current times energy) is frequently measured in
megawatts and has both technical and physical limitations
• SLAC Accelerator Research group has effort in all areas
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SLAC Experimental Facilities
• SLAC has extensive experimental facilities to enable
accelerator R&D
LCLS Undulator 2
End Station Test Beam
– SLAC Linac and infrastructure  FACET, Injector Test Facility
(ITF), ESTB, PEP-X, and SLC Arcs
Important to have different
– NLC Test Accelerator
facilities with different energy
– Accelerator Structure Test Area (ASTA)
scales.
– GTF (SSRL), GTF (ILC), CTF, …
– End Station A, End Station B, Klystron Test Lab
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SLAC Accelerator Research Program
• Broad program
– Working on LCLS, SPEAR-III, and LHC
– Efforts on upgrades for LCLS and LHC; Design efforts on ILC, CLIC,
Super-B, Project-X, PEP-X, and test facilities
– R&D towards higher brightness, higher gradient, and higher power
• Program takes advantage of SLAC facilities, expertise and
core competencies
– High power RF; beam theory and computing; Stanford University
• Strong programs at international facilities
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CERN on CLIC / CTF3 and LHC
KEK on ATF / ATF2
INFN on Super-B
Smaller collaborations with IHEP, DESY, …
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LHC R&D (Subject of later talks)
• Novel collimators (building prototype LHC collimator)
– Spin off of Linear Collider R&D program
– R&D uses Klystron Department and beam theory expertise
– Engagement has led to R&D on new concepts such as crystal
collimation which may have impact for LC and future rad. sources
• Electron Cloud and E-cloud Feedback
– Application of R&D on e+/e- colliders
• Low level RF
– Application of concepts and technologies developed for PEP-II
• Crab cavity design
– Synergistic with LC; utilizes beam theory expertise; broad use
• Program keeps engagement in premier HEP accelerator
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SLAC ILC Program
Most developed near-term option for a TeV-scale collider
• Focus on R&D synergistic with rest of the program
• 1.3 GHz RF power source R&D
– Modulators
– Klystrons
– RF distribution and couplers
Synergistic with Project-X R&D,
future LC R&D, and CW light
source R&D
• Electron source R&D
– Photocathode development
• Beam delivery system R&D
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FFS optics and tuning design
Collimation and beam dump design
MDI design with FD and crab cavity
ATF / ATF2 Test facility
Synergistic with future LC
R&D and with Super
B-factory & PEP-X R&D
• Damping ring & e-cloud R&D
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Marx Modulator and 10MW Klystron
Marx Modulator installed in ESB and
powering Toshiba 10 MW klystron
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ATF2 Final Focus
ATF2 commissioning in Dec 2008
ATF2 is aiming for 35 nm spots
SLAC provided magnets, movers,
power supplies, BPMs, diagnostics
Has led the effort building tuning
tools for commissioning
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RF Distribution and Couplers
Coupler class-10
clean room
ILC Rf distribution system
Coupler processing results
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Accelerator Science Program
• Beam theory and Computing
– Echo-enhanced harmonic gain; EM design of LHC crab cavity
• High gradient X-band program
– RF testing of CLIC PETS structure in ASTA
– Tested two high gradient structures in NLCTA
– Study of materials for high gradient performance
• Direct laser acceleration
– Reconfiguring experiment for the PBG fiber experiment
• Plasma wakefield effort is focused on the FACET project
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Echo-Enhanced Harmonic Generation
• Novel approach to harmonic generation that potentially seeds
harmonics as high as a few 100
– Seeding increases the temporal coherence and spectral brightness
and shortens the required undulator length
1
2
4
3
Evolution of the longitudinal phase space (one
laser period is shown):
1. Energy modulation after
first modulator
2. Tilted beamlets in the
phase space after the
first chicane
3. Energy modulation after
the second modulator
4. Phase space after the
second chicane
Planning experiment to verify EEHG at NLC Test Accelerator this year
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High Gradient R&D
• P5 noted that a future lepton collider will be a necessary
complement to the LHC
– The science case remains strong
• SLAC has been developing LC concepts for 30 years
• Many options for the next-generation collider with different
levels of risk and different costs
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ILC: most developed, lowest risk but high cost
High gradient klystron: medium risk with significant cost savings
Drive-beam microwave: higher risk with probably greater savings
Dielectric or Plasma acceleration: much higher risk but with
potential for much lower costs
• R&D programs on these different options have broad
applicability across Office of Science
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High Gradient Microwave Acceleration
• Extensive R&D on breakdown limitations in microwave
structures
– US High Gradient Collaboration
– CERN and Japan
• In the last few years:
– X-band gradients have gone from ~50 MV/m loaded to
demonstrations of ~150 MV/m loaded with ~100 MV/m expected
– Greatly improved understanding of breakdown and limits
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NLC Test Accelerator: RF Testing
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3 x RF stations
2 x pulse compressors (240ns - 300MW
max), driven each by 2 x 50MW X-band
klystrons
1 x pulse compressors (400ns – 300MW
/200ns – 500MW variable), driven by 2 x
50MW X-band klystrons.
1 x Injector: 65MeV, ~0.3 nC / bunch
In the accelerator housing:
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2 x 2.5m slots for structures
Shielding Enclosure:
suitable up to 1 GeV
For operation:
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Can run 24/7 using automated
controls
(Gain = 3.1)
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ASTA Test Facility
•Designed for economical testing of TW, SW
accelerator structures, and waveguides.
•Add an electron gun to test gradients next year
•Versatile structure for future applications
(beyond high gradient work)
Gate Valves
Variable iris
Variable Delay line length
through variable mode
converter
From Two 50 MW Klystrons
Two experimental stations inside the enclosure,
one with compressed pulse and the other without
the benefit of the pulse compressor.
July 8, 2008
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High Gradient Acceleration with Lasers
• Laser capability improving rapidly
– Billion $ industrial development effort
• Two acceleration approaches using lasers:
– Laser wakefield (plasma) acceleration, i.e BELLA (10 GV/m)
– Direct laser (dielectric) acceleration, i.e. E-163
(1 GV/m)
• Real challenges for both approaches
• Very different laser requirements
– Both require high average power  must generate beam power
• Laser-wakefield acceleration requires high peak laser power
– Lasers are most efficient and cost effective near CW operation
• CW operation is best use of expensive amplification medium
 SLAC is pursuing direct laser acceleration with ~10,000 times
lower peak power requirements  more favorable cost scaling
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The E-163 Facility at the NLCTA
(Commissioned in March 2007)
E
S
B
Counting Room
(b. 225)
Ti:Sapphire Laser
System
Cl. 10,000 Clean Room
E-163
RF PhotoInjector
Optical Microbuncher
Gun Spectrometer
Next Linear ColliderNext
Test Accelerator
Linear Collider Test Accelerator
The E163 program has advanced rapidly due to three factors:
Experimental Hall
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A decade of experience conducting this type of experiment at LEAP
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Extensive NLCTA infrastructure required modest extension to make a functioning facility
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Experienced help from the Test Facilities staff at every step
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Staged Laser Acceleration Experiment
Accelerator
Buncher
Energy
Spectrometer
e
Total Mach-Zender Interferometer
path length: ~19 feet = 7.2x106 l !!
All-passive stabilization used (high-mass, highrigidity mounts, protection from air currents)
3 feet
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New SLAC Experimental Facility: FACET
• New FACET facility will provide high quality 25 GeV e+ & ebeams for studies of plasma wakefield acceleration
– Plasma wakefield acceleration could reduce cost/GeV significantly for
linear colliders and could provide an easy upgrade for FEL facilities
– FACET will also be used to develop beam-driven dielectric acceleration
and plasma focusing concepts as well as other beam physics studies
• Beams of e+ / e- at 25 GeV with 20kA and 10x10 um spot sizes
LCLS Undulator 2
End Station Test Beam
FACET timescale
2010 – 2017
Scheduling CD1
Review in June
– Unique facility is only possible because of SLAC linac
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Promise of Plasma Acceleration
(Beam-driven or Laser-driven)
• 50 GV/m in FFTB
experiments
– Potential use for linear
colliders and radiation
sources
Simulation of 25
GeV PWFA stage
Witness
bunch
Drive bunch
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Broad Research Capability
• Unique science opportunities in many fields:
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Plasma beam source for LC concepts or radiation source
Plasma lens for compact focusing
Bent crystal for beam collimation or photon source
e+ and e- acceleration study essential for LWFA & PWFA
Dielectric wakefield acceleration
Energy-doubling for existing
facilities such as FEL’s
– Generation of THz radiation
for materials studies
Short bunches and their Tera-Hz radiation
open new possibilities to study ultrafast
magnetization switching
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FACET Program Development
• FACET is aimed at R&D on Plasma Wakefield Acceleration
however unique beams will be used for broader research
– Originally proposed a 3:1 ratio between PWFA and other programs
• Present PWFA collaboration (UCLA, USC, SLAC) is
developing new formal collaboration structure
– Will grow collaborations to support full PWFA R&D program
• Two workshops planned on Advanced Accelerator / PWFA
– ICFA Mini-Workshop on Novel Concepts for Linear Accelerators and
Colliders, July 8-10, 2009
– Workshop on PWFA and FACET Research Opportunities, Feb 2010
• Creating external advisory committee to review the SLAC
Accelerator Research program as well as FACET
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http://FACET.slac.stanford.edu
Summary of SLAC Accelerator Research
• Excellent research programs in Accelerator Science:
– High gradient acceleration: microwave structures, direct laser
acceleration, plasma wakefield acceleration
– High brightness sources; Beam physics and computing
• Strong programs on existing and next generation
accelerators at SLAC and world-wide
• Laboratory has unique experimental facilities
– End Stations A and B, SLAC Linac, ASTA, Klystron Test stations,
NLC Test Accelerator with FACET and ITF in the future
• Excellent technical support and fabrication capabilities
and strong ties to Stanford University
• SLAC accelerator research is key to the future of the
laboratory and to the international accelerator program
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Backup
• END OF TALK
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Potential for Near-term Development
• ASTA  photo cathode test facility as well as rf test facility
– Supports high brightness source development and LCLS upgrades
• NLCTA  support quick Acc Science experiments as well as
rf testing and DLA programs
– Not planning to convert NLCTA into full fledged user facility
• SLAC Linac  FACET and Injector Test Facility (ITF)
– FACET will support plasma acceleration and intense beam R&D
– ITF will be able to support a broad program of beam manipulation
• LCLS  End Station Test Beams and LCLS Undulator #2
– User facility for HEP and BES using End Station A
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SLAC Linac Sectors 0-20
• Plans for the SLAC Linac include FACET, ITF, and LCLS
Undulator 3
– SLAC linac is a unique resource
– Cost to maintain the linac in a warm state: ~7 M$ / year
– FACET and ITF operations would invest another 6~7 M$ / year
– Critical to maintain linac in operation state to ensure future capability
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Injector Test Facility
• Injector Test Facility (ITF)
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Use SLAC linac to characterize the beam emittance
Develop cathodes and rf gun technology
Will be placed to serve as the injector for LCLS upgrades
Dramatically reduces risks on LCLS upgrades to harder x-rays
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SLAC Research Yard
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End Station A – ESTB & LCLS U2
• End Station A is proposed to house Undulator 2
– Undulator 2 and parasitic HEP test beam to be developed
• Optimization of Undulator 2: seeding options, ESASE, …
– Need to develop pulse sharing mechanism with Undulator 1
• Operate with multibunch trains
• Alternate pulses
End Station A:
Undulator 2
Secondary Target
and Undulator
Beam Switch Yard
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End Station B
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Direct Laser Acceleration (E-163)
Experiment Layout
Permanent Magnet Quadrupoles
4 commercial fiber candidates:
l
(telecom
)
2R
(defect)
(µm)
a (pitch)
(µm)
lattice
dia. (µm)
cladding
dia.
(µm)
1550
10.9
3.8
70
120
1060
9.7
2.75
50
123
633
5.1
1.77
33.5
101
830
9.2/9.5
2.3
40
135
• Completed April 2009
• 8-wedge Halbach geometry
• Material: NdFeB
• Remote actuation:
- intra-quad spacings
- z position of assembly
- insert/remove from beam path
• String encoder position read-back
• In-vacuum assembly
b* = 0.5 mm
fiber aperture
HC-1060 Fiber
simulation of accelerating mode
10 µm
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SEM scan of fiber
Simulated Field Strengths (RADIA)
PMQ
B’(T/m)
Bint(T)
Leff(mm)
1
501
4.5
8.97
2
594
9.3
15.7
9.3
15.7
Page
33595
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3
EEHG Demonstration at NLCTA
• Use 120 MeV beam from rf gun with 20 pC and
ge < 8 mm-mrad
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