1. SLAC ILC Accelerator: Luminosity Production Peter Tenenbaum HEP Program Review June 15, 2005

2. Peter Tenenbaum2 Introduction: SLC and ILC  SLC luminosity in 1998: 2 x 10 30  ILC luminosity targets: Instantaneous: 2 x 10 34 Integrated: 500 fb -1 in 4 years  Implications High beam power (10 MW) Small beam sizes everywhere Deliver luminosity ~75% of the time Do not allow beam to damage accelerator

3. June 15, 2005Peter Tenenbaum3 Luminosity Production  Luminosity goals ↔ ILC operation Algorithms, instruments, correction devices for emittance tuning and feedback Design and operations approach which minimize unwanted downtime System which prevents beam damage but permits luminosity operation  Approach: put these operational issues into the design on equal footing with cost and CM Energy Design requires quantitative and realistic studies which show that emittance preservation, stabilization, availability, machine protection goals will be achieved Tolerances and specifications of components will be driven by these operational requirements  What have we done so far and what are we doing now?

4. June 15, 2005Peter Tenenbaum4 Tuning and Stabilization Studies: Tools  Developed simulation tools to permit modeling of beam transport from Damping Ring exit to IP Beam optics, acceleration, wakefields, beam-beam interaction Misalignments, errors, beam instrumentation (with realistic limitations), ground motion, feedbacks  In regular use to model tuning and operation of ILC and estimate luminosity performance Understand how varying parameters impacts luminosity Compare tuning and feedback algorithms Determine required performance from beam instrumentation Model interactions between subsystems and regions, escape “tyranny of the Gaussian”  SLAC in collaboration with CERN, Cornell, DESY, LBL, Queen Mary University London (QMUL)

5. June 15, 2005Peter Tenenbaum5 ILC Bunch Compressor Design  TESLA TDR called for compression from 6 mm to 300 µm in 1 stage Marginal performance – large energy spread drives BC and linac emittance growth No margin for longer bunch in damping ring No path to shorter final bunch lengths  Solution: multi-stage BC with acceleration between the stages Studied a first set of candidate designs  @ 300 µm final length, emittance growth reduced by ~50% compared to TDR design  150 µm final length achievable Developing optimized 2-stage design using results from first study  SLAC in collaboration with LBL Cornell coming on board this month

6. June 15, 2005Peter Tenenbaum6 Main Linac Emittance Tuning  CW in 2001: Emittance preservation trivial in low-frequency, SC main linac Result: not carefully studied  CW in 2005: Main linac emittance goals hard to achieve Large energy spread from BC Large apertures  poor BPM resolution Component alignment in cryomodules poor  Major effort developing and evaluating emittance tuning procedures Several candidates which have ~desired performance Different approaches have different limitations and make different demands on main linac hardware  Pushing the algorithms for better performance  Studying the limits of each algorithm  Considering implications on linac design (Stronger or weaker lattice desired? BPM resolution? Laser-straight linac required? Tolerance to stray fields? Benefits from RF cavity “HOM BPMs”?)  Initiating experimental study of SC quadrupole center stability  SLAC in collaboration with Cornell, FNAL, KEK CERN and DESY involvement in past, maybe again in future

7. June 15, 2005Peter Tenenbaum7 BDS Tuning and Feedback  Tuning and alignment issues more complicated than in BC or linac  Feedback: orbit through collimators and sextupoles, colliding nanobeams  Lots of experience at SLAC (SLC FF and FFTB)  Performed simulation studies of extremely sophisticated collision feedback Optimizes IP offset/angle vs lumi within 1 train  Beginning studies on static alignment and tuning of BDS  Work on more complete feedback Several components (steering, optics, energy, collision) Several timescales (microseconds to minutes) Extends back into BC and linac  SLAC in collaboration with QMUL

8. June 15, 2005Peter Tenenbaum8 Availability and Downtime Modeling  More to it than just MTBF and MTTR  Written a time-domain simulation MTBF and MTTR Impact of failure (down for repairs, colliding at reduced luminosity, need to spend time tuning around, etc) Impact of accelerator segmentation Availability of people to perform repairs Lumi recovery/tuning time after repairs  Recovery sequence Impact of machine development (MD) programs

9. June 15, 2005Peter Tenenbaum9 Availability and Downtime (2)  Applied program to study “big ticket” issues and get quantitative answers Impact of putting “repairable” items like klystrons in accelerator tunnel DR and linac in same tunnel vs separate tunnels Conventional vs undulator vs undulator + weak conventional e+ source What sorts of MTBF and MTTR values needed for magnet power supplies etc? How much improvement in uptime for given level of redundancy in RF system? How much penalty for lack of redundancy where impractical?  SLAC in collaboration with DESY

10. June 15, 2005Peter Tenenbaum10 Machine Protection  Studied extensively for NLC design  Just getting started on ILC studies Already have good understanding of the main issues from NLC work  Current work: classifying scenarios which lead to single-pulse or single-train damage Starting point to determine mitigation strategies Results will influence ILC design  Special instrumentation or algorithms to trap faults?  Sacrificial collimators?  Balance between beam signals, other signals, and passive protection  SLAC in collaboration with DESY

11. June 15, 2005Peter Tenenbaum11 SLAC Role in ILC Luminosity Production Study  SLAC has a lot of experience in this area SLC and FFTB  Intense area of study for NLC Led to current approach  operations issues are part of the design on equal footing with cost and energy reach  Strong early participants in ILC design  SLAC group is leading collaborations with worldwide membership Still growing Several regular phone / video meetings on various topics