SLAC ARD Test Facilities

Tor Raubenheimer

December 8th, 2010

SLAC SPC May 2010 MeetingPage 2

SLAC Accelerator Research

• SLAC is largely focused on accelerator-based research– SLAC accelerator research is key to the future of the laboratory

• Accelerator R&D focused on advancing operating facilities and the next generation of HEP and BES accelerators

• World-class research programs in Accelerator Science– High gradient acceleration: microwave structures, direct laser

acceleration, plasma wakefield acceleration– High brightness sources: Beam physics and computing– Technology programs to translate research into operations

• Laboratory has unique facilities – Experimental facilities for accelerator R&D– Technical support and fabrication capabilities to implement results

Existing Experimental Test at SLACAccelerator Research requires R&D facilities• Development has a long timeline• Important to have facilities with different energy scales• Even small facilities are expensive to operate and maintain• University participants require more of a user facility paradigm• Model for facility support is changing but support is critical for future R&D

Work supported by the U.S. DOE under Contract no. DE-AC02-76SF00515

July 8, 2008

ASTA Test Facility

From Two 50 MW Klystrons

Variable Delay line length through variable mode converter

Gate Valves

Two experimental stations inside the enclosure, one with compressed pulse and the other without the benefit of the pulse compressor.

SLAC Accelerator Research

Stanford University

Scientists,Technical Staff &

Accelerator Hardware Fabrication

ESB and NLCTA Test Facility

50 MeV capabilityRF component testingFuture photocathode R&DRapid modifications possible

400 MeV capability with L-band (10 MW), S-band (30 MW), and X-band (500 MW) RF sources RF structure and low e gun testingLow energy beam experiments Direct Laser Acceleration E-163, Echo-7, e-exchange, micro-bunching, CSR, THz, RF Undulator …Infrastructure for RF system development and laser-electron interaction experiments

FACET Test Facility20 GeV capabilityUltra high density beamsVerification of novel approachesUnique facilities only possible because of SLAC linac

FACET Experimental Region

LCLS-IIInjector

End Station Test Beam

LCLS Expansion

PossibleLCLS-IIIInjector

FACET Operation 2012 – 2017

National & International

Collaborations

Existing ARD Experimental Program

RF Linac and Technology

Development

High Gradient Acceleration

experimental research

High brightness beams and FEL

experimental research

Beam Physics, Accelerator Design,HP Computing and

Technical Infrastructure

FACET, NLCTA, ASTAFACET, NLCTA, LCLS

NLCTA, ASTA

Note: ESTB not includedas this is largely for HEPdetector R&D although itwill likely receive acceleratordiagnostic proposals as well

Introduction

• Source brightness has been increasing 1000x every decade• Future challenges to understand dynamics and time evolution• Requires improved coherence and energy bandwidth

– Short pulses and high brightness electron sources– Seeding of soft and hard x-ray FELs– Multiple pulses with timing control for pump probe

• Meeting these challenges will require advances in both fundamental accelerator concepts as well as directed development of accelerator science and technology

• Program will need a combination of quasi-parasitic use of operating facilities and a diverse set of dedicated test beds

Role of Accelerator Physics R&D Page 5

ARD Strategic Goals for Advancing XFELs

• Five strategic efforts aimed at XFEL objective1. Strong beam and FEL theory effort

2. Develop new high brightness injectors LCLS-II and upgrades

3. Development of novel beam handling and seeding techniques

4. High resolution diagnostics, timing and synchronization techniques

5. Development of high gradient and high rep rate FEL drivers

• Focus on concepts unique to SLAC – high peak brightness

• Challenge– This is research, not development or demonstration– Need correctly sized facilities to explore concepts quickly followed by

demonstrations performed at larger scale

SLAC SPC May 2010 MeetingPage 6

High Brightness Photo-Injector

• LCLS photo-injector performing better than specified:– Opens opportunity for re-optimizing FEL complexes LCLS-II– But, factor of ~2x poorer performance than simulations and next

steps for significant improvement are not clear

• Path towards a higher brightness injector:1. Improve cathode thermal emittance cathodes and laser

2. Reduce space-charge and gun aberrations electron guns

3. Manipulate beam to optimally use brightness beam dynamics

SLAC SPC May 2010 MeetingPage 7

Cathodes and Lasers

• Very hot topic with programs around the world• Most groups are focused on high average brightness

– High QE to ease laser requirements for high average current– SLAC should focus on high peak brightness, ideally, with multi-

bunch trains but low still average current

• A number of new ideas for better photocathodes– Coatings, diamond amplifiers, transparent cathodes, …– Study QE and thermal emittance performance

• Also need to explore operational limitations– Cathode lifetime, damage limits and cleaning procedures– Some of studies can be done in test chambers and some must be

done in operating rf guns

Cathode Test Facility

• Have dc cathode test chambers to study QE

• Build a facility with high rep rate laser to study thermal emittance, lifetime and in situ cleaning– Want rapid turn-around for R&D studies but include options for

accelerated lifetime testing and gun qualification– Separate thermal emittance performance from other issues

• Always want higher energy but not clear it is necessary

• Possible to utilize ASTA facility to establish CTF capability– S-band and X-band rf power is available– Shielding for 50 MeV beams but space is limited start with gun– <2M$ capital cost for lasers, PPS, test stand & controls upgrades– Operation costs ~500k/year (inc. operators, techs & consumables)

ASTA & CTF

Three goals for CTF:• Cathode research• Operational techniques • Rf gun qualification

Open path to futurecollaborations

Electron Guns

• LCLS rf gun performs extremely well

• How to improve?– Many incremental improvements (better field comp, load lock, …)– No concrete ideas for factor of 2 much less a factor of 10

• What about different approaches?– DC photo-injector (reduced space charge and emittance from gun)– Low rf frequency gun (reduced field tolerances and beam loading)– High gradient rf gun (reduced space charge and bunch length)

• X-band rf gun offers factor of 4~5 improvement in simulation but will be challenging to implement– Synergies and collaboration with other programs

Rf Gun Development

• X-band rf gun has potential to enable compact linacs– Compact single-frequency linac compared with lower rf frequency

– Higher brightness with ~ 3x higher peak currents and smaller ┴ e

– Collaboration with LLNL and UCLA on X-band gun technology

• Construct rf gun test stands in NLCTA and Cathode Test Area in ASTA Rf gun detail

Rf gun test beam line

Beam Manipulation and Seeding

• Want to manipulate the beam to optimally use the brightness, ie bunch compression, emittance exchange, etc– Study effects deleterious during bunch compression: CSR,

microbunching, …– Verify emittance exchange techniques and beam transformations

• Experiments on NLCTA linac:– Echo-7 completion and Narrow-band THz generation– COTR and micro-bunching studies– CSR catch-up / shielding measurements– Emittance exchange studies– Rf and short-period undulator demonstrations

• Upgrade Echo-7 proposal 1.8M/yr BD proposal 3.5M/yr

• 120 MeV linac with variety of L-band, S-band and X-band rf power sources, 3 laser systems and flexible beam line– Direct laser acceleration– Echo-7 seeding experiment– Microwave rf gun and structure testing– Shared between HEP and BES programs

End Station B Facility for Accelerator R&D

Class 10,000 Clean room

20 feet

Chicane -1

Echo-7 Beam line

Evolve NLCTA into ‘Injector Test Facility’ on ~ 2016 timescale LCLS-III

Flexible UV and IR laser

SLAC SPC May 2010 MeetingPage 14

NLCTA Limitations

• Would like GeV-scale beam energy and space for radiator– Present NLCTA linac energy is 120 MeV – Installed rf makes allows increasing energy to ~300 MeV– Shielding enclosure is only 50m in length

• Need to rebuild linac or extend shielding to add radiators and downstream diagnostics

– Power and water exist to support additional rf power– Largely based on 1st generation X-band rf technology

• Expensive to convert everything to S-band if that is desired

Planned Upgrades

• Improved diagnostics– Installing two X-band TCAVs for longitudinal phase space

diagnostics, energy spread control and emittance exchange studies– Installing new spectrometer with 4x better resolution

• New rf gun and capture section– Existing UCLA/SLAC/BNL S-band gun old X-band structures

1. Either install X-band rf gun and improved capture structures

2. Or improve S-band gun and add S-band capture structure– Studies at NLCTA to understand present limitations

• Modify 1st chicane (Chicane -1)– Present system very flexible but difficult to operate– Exploring options for replacement or improvement

SLAC SPC May 2010 MeetingPage 17

High Brightness Injector ProgramThree Parallel Experimental Efforts

Page 17

Cathode Test FacilityASTA Facility

Photocathode R&D aimed atunderstanding LCLS lifetime

and damage issuesTest rf gun modifications before

installation in LCLS-I or II

Longer term R&D aimedat high brightness cathodes

with lower thermal e (coatings, smoothness,

new materials)

LCLS-II InjectorIncremental upgrade ofLCLS-I with opportunity

for R&D during commissioning

Injector R&D ProgramNLCTA Facility

Simulation and experimentalprogram aimed at significantimprovement in brightness

1) Design studies on rfgun design, CSR micro-bunching and cathodes

2) Rf gun development andtesting at NLCTA in 2012

3) NLCTA R&D on injectorbeam physics

Construction in ~2014and commissioningin ~2015 to study injectorphysics before LCLS-IIoperation

Combined HB program requires ~3M/yr

new funding

Timing and Synchronization

• fs scale science requires equally stable fs scale accelerator phasing and timing information over km scale– improved stability and resolution beyond existing state of the art– Beam and radiation properties dependent on timing/synch stability

• Research fundamental technical options– Integrated systems combine RF, optical synchronization with

dynamic timing signals, integral diagnostics– Multi-drop distribution to 1000s of elements– Build on encoding techniques used in GPS and DSL (adaptive

symbol coding, orthogonal spread spectrum codes)

• Proposed joint LBL-SLAC program (Fox/Byrd)– ~500k/yr to develop options and technology

More Aggressive Approaches(in parallel or replacement)

• Want multiple facilities for different program scales– CTF/ASTA at few MeV– Injector system at 100~200 MeV– Beam dynamics studies at few hundred MeV– Dedicated seeding studies at Gev-scale– Studies at LCLS with high quality high energy beams

• Build S-band injector for rf gun and injector BD studies– Essentially the same as LCLS (LCLS-II) injector

• Build S-band injector in Sector-0 to allow GeV-scale studies– Need to understand limitations of merging beams and existing

systems and how to operate FACET.

• Build high rep rate X-band linac for GeV-class studies– Either expand NLCTA or install in new location (ESA ?)