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

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

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

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

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

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

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

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

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

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)

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

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

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

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

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

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

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

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

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, 061301, (2008). July 8, 2008 SLAC Annual Program Review

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

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

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

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

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

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

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

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.)

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

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

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

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

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

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

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