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Accelerator Physics Summary. Paul Lebrun, (Kyioshi Kubo, Daniel Schulte). 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

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accelerator physics summary

Accelerator Physics Summary

Paul Lebrun,

(Kyioshi Kubo, Daniel Schulte)

Euro-TeV meeting

  • 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
ring to main linac rtml
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)
  • 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..
let session main linac
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
main linac comments
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.

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


main linac to do
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.
beam delivery system
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
bds tuning
BDS Tuning



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

code development
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…
code development1
Code Development
    • 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
    • ..
integration start to end
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!
ml let joint session
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..
metrology ml bds apy
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..
metrology apy joint discussion
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
focus on edr
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..
scope and tasks of our group
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.
list of 10 critical issues
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
questions comments
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…”