1. Present and Future Program for Accelerator Research at SLAC
Tor Raubenheimer
SLAC DOE HEP Review
July 7 – 9, 2008

2. SLAC Annual Program Review
ARD Mission
Develop accelerator science and technology that will enable new accelerators in photon science and high energy physics as well as other fields of science, medicine and industry with R&D aimed at near-term, mid-term, and long-term development
Requires broad spectrum of R&D activities focused on different timescales and ranging from theory aimed at fundamental questions to experiments directed towards immediate or near-term applications
Need to determine the balance between long-term, mid-term, and near-term R&D
Where applicable, support a national and international user program in accelerator R&D
July 8, 2008
SLAC Annual Program Review

3. ARD Departments & Functions
Accelerator Beam Physics
Supports operating accelerators and R&D groups with optics designs and understanding of collective effects
Accelerator Computation
Develop computational solutions for accelerator design and operation using massively parallel computing
Test Facilities
Operate and support test facilities including NLC Test Accelerator, ESB, ESA, ATF & ATF2, and FACET R&D
LHC R&D
Contribute to the LHC operation and upgrades
Linear Collider R&D
Develop linear collider designs and technology for NC and SC options
Advanced Microwave Tech.
Develop advanced rf structures and sources
Advanced Accelerator R&D
Research options for ultra-high gradient acceleration using technologies such as lasers and plasmas
July 8, 2008
SLAC Annual Program Review

4. Overview of Financial Data – FY2008
SLAC ARD program was badly hit by December Omnibus bill  21 PPA positions cut
July 8, 2008
SLAC Annual Program Review

5. Overview of Financial Data 2007-2010
July 8, 2008
SLAC Annual Program Review

6. SLAC Annual Program Review
Linear Collider R&D
P5 noted that a future lepton collider will be a necessary complement to the LHC
A linear collider can provide this capability
SLAC has been developing LC concepts for 30 years
Many options for the next-generation collider with different levels of risk and different costs
ILC: lowest risk but high cost
X-band klystron: medium risk but significant cost savings
X-band Two-beam: higher risk but probably greater savings
Plasma wakefield or laser acceleration: much higher risk but potential for much lower costs
Strong R&D programs on these different options
Need to understand systems issues and cost scales to direct R&D
July 8, 2008
SLAC Annual Program Review

7. A Roadmap for Multi-TeV Lepton Colliders
Normal conducting - Two-Beam-based
Multi-TeV LC
Normal conducting – Klystron-based
350 GeV LC
Plasma Acc
Multi-TeV LC
4th Generation
SR Sources
5th Generation SR Sources?
Superconducting RF
500 GeV LC
The LC roadmap illustrates options and connections between them. Selecting a path requires additional information such as LHC results and technology status
Neutrino source
Neutrino ring
Muon collider (few TeV)
Timescale (personal guess)
2010
2020
2030
2040
2050
July 8, 2008
SLAC Annual Program Review

8. Conventional rf Linear Collider R&D
Strong leadership in ILC GDE
Working on 1.3 GHz RF power sources, beam delivery system, electron source, and systems integration
Efforts have broad applicability – not just ILC
Want to re-invigorate X-band (11~12 GHz) R&D
Provides more conservative solution to normal conducting LC
Excellent High Gradient effort but need power source studies
Collaboration with CERN and KEK on CLIC
Accelerator structure development and testing
CLIC structures based on SLAC/KEK work at 11 GHz
Future collaborations on beam delivery, e+/e- sources, and collective effects (impedance, electron cloud, ion instabilities)
Building 12 GHz klystrons for CERN testing program
July 8, 2008
SLAC Annual Program Review

9. SLAC Annual Program Review
High Gradient R&D
Long history of X-band rf development
Achieved >400 MW 11.GHz rf power in 400 ns pulses
Modulators, klystrons, and rf pulse compression
1000 hours operation of ~5m X-band structures at 65 MV/m
Strong collaboration with CERN and KEK
Improved understanding of gradient limitations
Theoretical and experimental studies
Studying rf power flow, arc formation, pulsed heating , …
Significant improvements in X-band structure capability
>100 MV/m (unloaded) in traveling wave structures
Collaborating with CERN to develop structures for 120MV/m
~150 MV/m in single cell standing wave structures
Potential for very high gradient normal conducting linacs
July 8, 2008
SLAC Annual Program Review

10. Understanding the Gradient Choice
Cost optimum is a balance between costs proportional to length, i.e. tunnel & structures and costs proportional to the rf power sources
G ~ A sqrt(P * Rs) P = rf power / meter Rs = shunt imp. / m
Have to reduce rf power cost per MW by 2x or double Rs to increase G by 40%
GLC/NLC X-band
At low gradient, cost increases due to larger length costs
Relative TPC
At high gradient, cost increases due to higher rf power costs
July 8, 2008
SLAC Annual Program Review
Unloaded Gradient (MV/m)

11. GLC/NLC RF Power Sources (2004)
Good success with modulator, pulse compression and rf distribution development. Klystrons achieved peak power and pulse length specs but breakdown rate was too high
Output Power
(Gain = 3.1, Goal = 3.25)
Combined Klystron Power

12. X-band RF Power Source R&D
Developing novel rf power sources:
Marx solid state modulator – broad applicability of technology
Sheet beam klystron – broad applicability of SBK concept
Developed rf power source for GLC/NLC:
SLED-II system delivered >500 MW
Two-Pac modulator fabricated but not fully tested – halted in 2004
X-band klystrons worked at 75 MW / 1.5 us but many breakdowns
Consider new output structures or reduced power levels using knowledge from high gradient studies
Future program to complete X-band rf source development
Could provide a more conservative option to X-band design
Broad applicability: power sources for compact radiation sources and other compact linacs (complements High Gradient Program)
July 8, 2008
SLAC Annual Program Review

13. Linear Collider Cost Studies
Linac cost studies are needed to set X-band gradient and optimize between Two-Beam and Klystron options
Working with GDE on ILC design and costing
Tried to engage GDE in CLIC/X-band effort and costing as well
Detailed X-band costs will be needed to optimize between X-band and other technical options
Use the GDE costing methodology – common basis
Performing cost studies in collaboration with CERN
May consider a broader X-band collaboration for these efforts
High-level costing is needed to help direct R&D efforts
Options for X-band, plasma or laser acceleration
July 8, 2008
SLAC Annual Program Review

14. Future X-band Test Facilities (>2012)
After initial R&D, need a new test facility if either X-band klystron-based or TBA-based collider are to be pursued
3 GeV X-band Test Facility
10 rf units with 100 MV/m X-band linac
Demonstrate emittance preservation, rf stability, and reliability
Completed facility could deliver beams for AARD or BES programs
Two-Beam Demonstration (STF4 ??)
Next step beyond CTF3 at CERN
Use ~150 SLAC linac klystrons to generate 10 Amp 1 GeV few us drive beam (share rf with FACET and LCLS-II)
8x combiner using SLC damping ring complex  80 Amps
Drive beam would power 40 GeV of TBA linac
July 8, 2008
SLAC Annual Program Review

15. Advanced Accelerator R&D
Program to find cost-effective solution to accelerate e-
Need to generate multi-MW beams with low emittance
Plasma-Wakefield Acceleration (PWFA)
Use drive beam to excite plasma wave and accelerate a trailing beam  no material breakdown limits
Excellent power transfer efficiency >30% in simulation
Possible to generate drive beam with high efficiency like CLIC
Emittance preservation possible in simulation
Needs experimental demonstration  new FACET facility
Direct Laser Acceleration
Use high electric fields of laser beam to directly accelerate e-
Does NOT require esoteric PetaWatt lasers
Capitalize on B$ laser industry pushing cost, efficiency and size
R&D program is making great progress
July 8, 2008
SLAC Annual Program Review

16. PWFA-Linear Collider Concept
Developed a concept for a 1 TeV plasma wakefield-based linear collider
Use conventional Linear Collider concepts for main beam and drive beam generation and focusing and PWFA for acceleration
Makes best use of PWFA R&D and 30 years of conventional rf R&D
Concept illustrates focus of PWFA R&D program
High efficiency
Emittance pres.
Positrons
Allows study of cost-scales for further optimization
July 8, 2008
SLAC Annual Program Review

17. FACET PWFA Experimental Facility
Progress on PWFA requires new facility to demonstrate single-stage e- acceleration and understand e+ acceleration
New FACET facility will provide high quality e+ & e- beams for studies of drive-witness studies of e-/e-, e+/e+ & e-/e+ acceleration
Developed an R&D program at FACET to determine all parameters of a PWFA-LC from 2010  2016
Followed by pre-construction multi-stage PWFA demonstration: FACET-II (~100M$ scale similar to current rf LC test facilities)
July 8, 2008
SLAC Annual Program Review

18. Laser Acceleration R&D
High gradient (~GV/m) and high efficiency are possible
Capitalize on large diode-pumped solid state laser industry and on semiconductor fabrication technology
Structures for High-Gradient Laser Accelerators
Photonic Crystal Fiber (Silica)
Photonic Crystal Woodpile (Silicon)
Transmission Grating (Silica)
Possible to generate a reasonable set of parameters for a TeV-scale linear collider
Luminosity from a laser-driven linear collider must come from high bunch repetition rate and smaller spot sizes, which naturally follow from the small emittances required
July 8, 2008
SLAC Annual Program Review

19. Laser Acceleration — Bunch Train Attosecond Bunch Train Generation
Inferred Electron Pulse Train Structure
Bunching parameters: b1=0.52, b2=0.39
800 nm
400 nm
l=800 nm
First- and Second-Harmonic COTR Output as a function of Energy Modulation Depth (“bunching voltage”)
400 nm
800 nm
Left: First- and Second-Harmonic COTR output as a function of temporal dispersion (R56)
C. M. Sears, et al, “Production and Characterization of Attosecond Electron Bunch Trains“, Phys. Rev. ST-AB, 11, , (2008).
July 8, 2008
SLAC Annual Program Review

20. SLAC Annual Program Review
LHC / LARP Activities
Participate in the LHC accelerator physics program:
Contributing in areas where SLAC has expertise & experience
Enhance SLAC’s areas of core excellence:
collective effects, RF cavity design, collimation systems,…
Educate SLAC staff on HEP’s only energy frontier machine
Collimation
Rotatable Collimator and crystal collimation
Instrumentation and LLRF diagnostics
Long-term visitor to work on instrumentation projects
Accelerator Physics
Ecloud; Beam-Beam Studies; Crab Cavity; PS2 Studies
Management
LARP Level-2 Accelerator Systems leader
July 8, 2008
SLAC Annual Program Review

21. LHC Phase II Collimators
Stable
Unstable
Errant LHC beams will destroy most materials except Carbon
Carbon has a large resistance and impacts the beam
CERN Carbon-Jaw Collimator
SLAC Prototype Jaw
SLAC Design

22. SLAC Annual Program Review
Super B-Factory R&D
SLAC could collaborate with Frascati on Super-B design
Possible to consider L ~ 1036 using results from PEP-II with some improvements: crab waist scheme, improved beam control (very small emittances), e-cloud control, powerful feedback
Beam control concepts from SRS and LC damping rings
Crab waist tested at DAFNE
Frascati ring would reuse much PEP-II hardware allowing an inexpensive path for a strong US contribution
Also possible to collaborate with KEK on KEKB upgrade
Design path with very high currents seems more challenging but KEK team has demonstrated capability
US role less evident: SLAC could contribute vacuum system, feedback systems, …
July 8, 2008
SLAC Annual Program Review

23. SLAC Annual Program Review
Accelerator Physics
Strong Accelerator Physics group
Optics design
ILC Beam Delivery, Bunch Compressor, Damping Rings, e+/e- Sources
Design of PEP-II and upgrade options
FACET facility
Collective effects
Conventional impedance issues
Electron cloud and beam ion instabilities
Feedback and LLRF system design
Pioneered bunch-by-bunch feedbacks and diagnostics
Colliding beam accelerator design
Strong experience with e+/e- IR and systems design
Massively parallel computation
Leader of EM accelerator computation
July 8, 2008
SLAC Annual Program Review

24. Beam Physics and Computing
A Trapped Mode in ILC Cryomodule -
Electric fields calculated by Omega3P
TM-like mode localized in beampipe between 2 ILC TDR cavities
Damping required to avoid deleterious effects on beam dynamics and excessive heat loads
Similar techniques were applied to study the beam breakup problem in the cryomodule of the JLab 12 GeV upgrade
TM mode

25. L-Band Sheet Beam Klystron
LBSK DC gun –
Simulated using Gun3P, a parallel, 3D, high order finite-element electron trajectory code
Benchmarked against Michelle
Parallel computation speeds up runtime by an order of magnitude
Input: 115 kV
Output: 129 A
Gun3P
144K tets
4.5M DOF’s
Michelle
Beam profile at cathode

26. Microwave Fabrication
High precision machining, brazing and cleaning of rf components is a core capability at SLAC
Supports SLAC efforts in rf development as well as world-wide HEP community
SLAC asked to build 12 GHz klystrons for European labs
SLAC / KEK / CERN collaboration built best high gradient structures
SLAC PEP-II klystrons needed to replace industry-built devices
SLAC regularly consulted on structure fabrication and supports external user base
Capability is at risk in transition from HEP to BES funding
BES demands and vision for rf development are narrower
Need to work with HEP and BES to develop plan to keep this core capability
July 8, 2008
SLAC Annual Program Review

27. Electron cloud effect – R&D at SLAC
Intense R&D by many groups
Complicated problem
Our strategy: eliminate low energy electrons  no cloud
Focused on measuring and understanding SEY in acc. environment
TiN-coated aluminum chamber demonstrated consistently low SEY
Other options add further improvement but may not be necessary
Key collaborations and experiments at other labs:
KEK: grooved chamber and clearing electrodes
CESR-TA: grooved chamber in dipole magnet and simulations
FNAL: effect of SEY in Project-X proton ring
SPS/LHC: grooved chamber in dipoles, simulations and measurements
Continue to investigate remaining issues with TiN (long term durability, SEY in magnetic regions, etc.)

28. SLAC Annual Program Review
PEP-II chambers dedicated to electron-cloud research
3nd INSTALLATION: chicane magnetic field tests
1ST INSTALLATION: in situ SEY measurements
2nd INSTALLATION: groove chambers
PEP-II Low Energy Ring LER
1.5% of the ring
July 8, 2008
SLAC Annual Program Review

29. PEP-II E-cloud Results
SEY #1
SEY #2
Before installation in beam line
After beam conditioning
SEY #3
SEY #3
TiN coated Al
1000x smaller scale
Uncoated Al

30. Test Facilities for ARD
Accelerator Research has four main test facilities:
NLC Test Accelerator and End Station B
E-163, X-band & L-band rf development
End Station A
Future test beam and beam physics program
FACET
PWFA experimental program; user program
Klystron Test Lab
X-band and L-band rf development; rf gun development
Also ATF/ATF2 at KEK in which we have a large role
Test facilities are critical for ongoing advancement of accelerator science and technology
Need to provide support in era when HEP facilities are closing
July 8, 2008
SLAC Annual Program Review

31. Future plans for ARD Test Facilities
FACET:
>20 GeV; 2x1010 e+ or e-; >20kA; <10 um spot sizes
Planned to be dedicated 75% to the directed PWFA-LC program and 25% for a user program
External advisory committee to recommend experiments
End Station A
~10 GeV; ~1x1010 e- or few 107 hadron beams
Proposal for test beam facility for detector and IR instrumentation development; requires new PPS system and BES agreement
NLC Test Accelerator
<350 MeV; ~1x1010 e-; sz < 1 mm (100 um); ge < 5 mm-mrad
Laser acceleration; L-band and X-band rf development
Soliciting proposals for new experiments but not to support as a user facility
July 8, 2008
SLAC Annual Program Review

32. Contributions to Project-X
SLAC has been collaborating with Fermilab on the L-band rf system – essential for ILC and Project-X
Planning to deliver rf distribution systems; fundamental mode couplers; 10 MW klystron
Would play a large role in the rf system design and construction
Planning to work on electron-cloud issues for Project-X
Simulation and modeling studies
Electron cloud experimental apparatus for use in Main Injector
Could take additional roles:
Beam optics and nonlinear dynamics
Detailed impedance model and instability calculations
Complete model for beam losses and collimation including nonlinear optics, space charge, and collimators
July 8, 2008
SLAC Annual Program Review

33. SLAC Annual Program Review
Summary
Excellent accelerator research program
World-class beam theory and computation group and world-class rf design, fabrication, and testing facilities
Host to US High Gradient collaboration and forming a PWFA-LC collaboration
Options to collaborate on Super B-factory
Leverage US investment in PEP-II and SLAC expertise
Broad program to advance energy frontier
Superconducting LC, X-band LC, PWFA and laser acceleration
Different timescales, risks and costs
Want to increase efforts on alternates to ILC to provide options
Linear collider Roadmap – document available in September
July 8, 2008
SLAC Annual Program Review

34. SLAC Annual Program Review
ARD Talks Agenda
July 8, 2008
SLAC Annual Program Review