Accelerator Physics Summary

1. Accelerator Physics Summary Paul Lebrun, (Kyioshi Kubo, Daniel Schulte) Euro-TeV meeting

2. Overview • Organization: APY sessions + joints sessions • Topics are presented out of order with respect to the agenda of the workshop • Starting with LET studies • Lessons learned from ML+APY, MET + APY • (Apologies for possible repeats) • Essential part of our “service” function • Numerous Beam Studies are done within system areas. • ending with key session: discussion on EDR • Progress on: • Checks, depth, details on “classical” LET simulations: • Moving from static to dynamics • Integration…---> Interface, matching, X-talk between feedback loops, S2E. • New problems

3. Ring To Main Linac (RTML) • No formal session on RTML, but an in depth talk by PT, Andrea Latina and Kiyoshi Kubo on the state of the RTML • Re-design during RDR process, prompted by: • Move of the Damping Rings (DR) -> long transfer line. • LET performance not optimal though turn-around, spin rotator, bunch compressor. • Bunch from DR length longer, momentum compaction in turn-around. • Improvements • Optic design upstream of BC • Matching to the site (vertical + horizontal bends &XY couplings) (on going effort..) • Reducing the number of r.f. stations for bunch compressor..(cost saving)

4. RTML • Possible remaining concern(s): • Time dependent stray fields in Return line : tolerance of ~2 nT, comparable to measurement at end of StationB, SLAC • Space charge (> 10 km line @ 5 GeV) • Turn-around and spin rotator tuning, coupling & Dispersion … Considering having complete, “4D”, emittance measurement system. (2D is baseline..) • Overall performance of Bunch Compressor 1, with current cavity tilt tolerances. • Moving to 2007 optics..

5. LET Session, Main Linac • Lattice Studies: Realistic (cryo system), matching RTML, BDS • lattice files are version controlled, in a formal repository. • Main Linac Undulator: Difficult problem, ongoing ! • Dynamical Studies: • Maintaining performance via 1-to-1, or better, Adaptive alignment, post 1rst steering .. Now done on single desktop and on FermiGrid • Progress on Dynamical Dispersion “Free” Steering on the Main Linac using CHEF • 1st Steering, as the machine moves. • Ground Motion based on standard “ATL” model, or real data, at Minos and/or Aurora mine tunnel

6. Main Linac, Comments • Cross-Checks: Running multiple codes, mainly Lucretia & CHEF (FNAL), Merlin (DESY), PLACET (Cern),.. • Benchmarks (2006 saga completed… Must be ongoing when new code or physics introduced..) • Static alignment of Main Linac satisfactory, albeit “bumps” (i.e., non-local corrections) are currently used.

7. Short Lattice: 2 Dispersion and 1 Wake Bumps After DFS 1st dispersion bump 2nd dispersion bump Projected y-emittance (nm) 1st Wake bump 1st dispersion bump : Corrector # 3 2nd dispersion bump : Corrector # 36 1st Wake bump : Corrector # 63 BPM #

8. Main Linac, To Do Dynamical Studies: progress, still on going. • Model improvements.. • Multiple feedback loops (e.g. 5Hz adaptive while re-steering via DFS, downstream..) • Undulator, steering ( static & Dynamics) • 1TeV: synchrotron radiation budget thermal budge, while curving & steering.

9. Beam Delivery System • CERN: Offset & angle tuning at the IP • Checks of previous Tesla studies. • Orbit feedback • SLAC: Tuning studies, dynamic re-steering • Mature studies, advanced algorithms

10. BDS Tuning dK tilt Disp, Waist, <x’y>, <xy> Two views – effectiveness of tuning sextupole mover knobs (dispersions, waists, couplings), then sextupole strengths and tilts From PT’s talk, work done by Glenn White

11. Code Development • From LIAR to Lucretia • Relatively new code.. Benchmark phase, looks good. • Customer base growing: code running at Fermilab as well. • More physics capabilities for • Beam Delivery System (BDS) being implemented. • Better Ground Motion interface • Field map tracking…

12. Code Development • PLACET: • Parallelism • Embedded Analysis tool (Octave) • … • Guinea-Pig ++ (Beam-beam at IP) • C++, Parallelism, .. • CHEF development @ Fermilab • r.f. cavity transport accuracy • Faster implementation of wake kicks • Parsers • ..

13. Integration & “Start-to-End” • Progress!! : • Beam Delivery System: BDSIM (S. Malton) • G4 in, switch between fast, and (slower)…. • Ongoing.. • Start to End: ML -> IP • Tools : Merlin & Guinea-Pig • Code + inputs, old recent.. • Mirror tracking.. • Recent Placet results (A. Latina) • Covering BC, ML and BDS • It’s the process that matter, not the final answer!

14. ML & LET joint session. • Coupler Wakes : • Advanced computation of the wake potential in Tesla style cavities, with the three couplers (Input, HOM) • New problem, need beam dynamic simulation! • New Quadrupole Vibration data • Relatively flat transfer function • Yet, some amplification from stands -> quad • Scale matters: motion of ~ 500 nm observed, improvements on stands foreseen..

15. Metrology, ML, BDS & APY • MonaLisa project • Nanometer Position measurement for Final Focus (FF) • Position Measurement device for the FF quads, without direct line of site through the IP (Also an MDI issue..) • LICAS simulation status. • Looking forward to the upcoming system test at DESY! • Discussion on Jitter tolerance and mitigation between ML and BDS, impacting the BDS feedback systems. Need extra length.. Cost impact..

16. Metrology, APY joint Discussion. • Specs and understanding of procedures • Detail model of alignment errors, more than one number! E.g., Systematic vs random • Quad jitter through an entire Linac, at 2 K., under normal operating conditions (i..e, Helium and Nitrogen flowing at design rate) • Rely on simulation for now.. XFEL will bring real data.. • More discussion and, small dedicated task force needed

17. Focus on EDR • Three ~1.5 hour sessions were dedicated to: • Review where we are in terms of organization, scope etc.. • Planning, one with EDR management. • Yesterday late afternoon, we wrote the following slides..

18. Scope and Tasks of our group • Three main objectives • Definitions or agreement on specifications • Preparation for high performance • Finding problems • The first goal is quite demanding • Establish interfaces with lots of specializations • Perform studies to answer questions, define tolerances • Some specifications depend on beam-based correction procedures • Need to maintain core activity across subsystems • Not all issues can be solved locally • Some problems are common • Flexibility to find problems • Draft tasks list written. • Specification & Models • Simulation studies.

19. List of 10 Critical Issues • Define critical specifications for components .. e.g. for BPMs not only resolution but stability in time • Document specifications and rational/results • Helical undulator integration • RTML alignment and tuning • Machine protection • Dynamic imperfections and feedback • Locally and globally • e.g. can be a problem at noisy sites, feedback design and performance • Putting fires out: .. e.g space charge, coupler wakefields, crab cavities • Investigate alternatives .. e.g. different main linac cavity designs • Heat load (dark current) • Think about unexpected problems

20. Questions / Comments? (last slide of PT’s talk on RTML) “Watch out, you can’t ignore what’s going on When your visions are drying out Like the oceans from the underworld…” -Alphaville