SLAC ARD Test Facilities

SLAC ARD Test Facilities Tor Raubenheimer December 8th, 2010

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 SLAC SPC May 2010 Meeting Page 2

Existing Experimental Test at SLAC • Accelerator 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 ASTA Test Facility 50 MeV capability RF component testing Future photocathode R&D Rapid modifications possible Variable Delay line length through variable mode converter Gate Valves Scientists, Technical Staff & Accelerator Hardware Fabrication ESB and NLCTA Test Facility 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 testing Low 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 July 8, 2008 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. FACET Test Facility SLAC Accelerator Research 20 GeV capability Ultra high density beams Verification of novel approaches Unique facilities only possible because of SLAC linac FACET Operation 2012 – 2017 Stanford University National & International Collaborations Work supported by the U.S. DOE under Contract no. DE-AC02-76SF00515 End Station Test Beam PossibleLCLS-IIIInjector LCLS-IIInjector LCLS Expansion FACET Experimental Region

Existing ARD Experimental Program High brightness beams and FEL experimental research High Gradient Acceleration experimental research FACET, NLCTA, LCLS FACET, NLCTA, ASTA Beam Physics, Accelerator Design, HP Computing and Technical Infrastructure Note: ESTB not includedas this is largely for HEPdetector R&D although itwill likely receive acceleratordiagnostic proposals as well NLCTA, ASTA RF Linac and Technology Development

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 objective • Strong beam and FEL theory effort • Develop new high brightness injectors  LCLS-II and upgrades • Development of novel beam handling and seeding techniques • High resolution diagnostics, timing and synchronization techniques • 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 Meeting Page 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: • Improve cathode thermal emittance cathodes and laser • Reduce space-charge and gun aberrations  electron guns • Manipulate beam to optimally use brightness  beam dynamics SLAC SPC May 2010 Meeting Page 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 Rf gun detail Rf gun test beam line • 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

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 Evolve NLCTA into ‘Injector Test Facility’ on ~ 2016 timescale  LCLS-III Flexible UV and IR laser Class 10,000 Clean room Chicane -1 20 feet Echo-7 Beam line SLAC SPC May 2010 Meeting Page 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 • Either install X-band rf gun and improved capture structures • 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

High Brightness Injector ProgramThree Parallel Experimental Efforts Cathode Test Facility ASTA FacilityPhotocathode R&D aimed atunderstanding LCLS lifetime and damage issues Test rf gun modifications before installation in LCLS-I or II LCLS-II InjectorIncremental upgrade ofLCLS-I with opportunityfor R&D during commissioning Injector R&D Program NLCTA FacilitySimulation and experimentalprogram aimed at significantimprovement in brightness Longer term R&D aimedat high brightness cathodes with lower thermal e (coatings, smoothness, new materials) Construction in ~2014and commissioningin ~2015 to study injectorphysics before LCLS-IIoperation • Design studies on rfgun design, CSR micro-bunching and cathodes • Rfgun development andtesting at NLCTA in 2012 • NLCTA R&D on injectorbeam physics Combined HB program requires ~3M/yrnew funding SLAC SPC May 2010 Meeting Page 17 Page 17

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 ?)

SLAC ARD Test Facilities