December 6 2006 Ground Motion Group Global Design Effort 1

LET Status report, December 06

Paul Lebrun

Fermilab CD/AMR

December 6 2006 Ground Motion Group 2

Status, I

• Benchmark CHEF/Merlin, Misaligned and Steered Tesla design. – Tracking:

• Completed, results send to Jeff Smith, month(s) ago.• Writing internal FNAL memo..

- DFS Steering:- Coding completed, analysis mostly done.- Documenting.

• DFS Steering Studies in CHEF • On the above Linac, finishing up studies,

documenting.

December 6 2006 Ground Motion Group 3

Benchmark, Fixed dipole setting

Non trivial emit emittance growth!

Ups and down because D taken out.. and coming back..

Agreement not perfect, sensitivity to small local difference in tracking.. Improves if Dispersion if corrected.

December 6 2006 Ground Motion Group 4

Status, I, II : DFS, in depth.

• DFS Steering Tricky if…

• Many variants of the basic DFS have been proposed, with not always good agreement between what works and does not work. • A lot of dedicated software is needed, to duplicate these

algorithms. • Tedious to document ( rarely done!) • Semi-Qualitative agreement between codes on the

performance (Emittance vs S), substantial disagreement on what the “best” solution (dipole corrector settings) really is..

December 6 2006 Ground Motion Group 5

Benchmark, Fixed dipole setting

Sorting this out took considerable amount of time…

December 6 2006 Ground Motion Group 6

Status, I, II : DFS, in depth.

• DFS Steering Tricky, one “root” cause• Many perturbations of the orbit occurs with

too few “knobs”, or dipole corrector.• Cavity tilts: 24 of them per dipole correctors.

• Individual cavity tilts : ~200 micro-radiants • Quadrupole displacements: ~ 350 microns• At ~5 GeV, integrated kicks over 2 cryo-modules (24

cav.) delta y’ about the same size as the kick given by the quadrupole..

December 6 2006 Ground Motion Group 7

Kicks, Cavity vs Quadrupole.

Plot has been produced, hopefully correctly.

No time to included in this talk..

December 6 2006 Ground Motion Group 8

Accurate tracking through Cavities

If cavity rotation matter, Shouldn’t be worried about tracking accuracy..

With rotated fieldsWith realistic field map (kick depends on XY)

A solution (Lynn Garren):

G4 Runge Kutta integration G4/CHEF integration: allows to simulate halo, and

interaction of halo with cavities…

December 6 2006 Ground Motion Group 9

Other Actuators

• In Bunch Compressor and early LINAC, exploring the possibility of tilting either cryo-modules or individual cavities. – Not Baseline ( = Not to be investigated. (?))– Beam Based Alignments Algorithm for back-

tilting do exist, just the right variant of DFS. – Coded in CHEF, running, need to document

performance.

December 6 2006 Ground Motion Group 10

Dynamical DFS

• In CHEF, DFS was re-implemented keeping in mind the need to establish steering while the machine, burping, ( not belching?), creaking and moaning. – Iteration and convergence criteria.– Rudimentary controls

• ( beam permit dropping when x mm excursion at BPM • Pause while we change DFS section.

– Crude visualization, analysis code..

• ATL Ground Motion integrated. • Ready to Crank at bit more jobs.

December 6 2006 Ground Motion Group 11

ILC Main Linac Lattice.

• In CHEF, – Using corrected sBend/rBend code, got a

matched bunch through the LINAC, with fraction of emittance growth.

• But the Dispersion at injection is close to 0. ? • Am I really bending? • Need checking.

• If checks, start DFS steering into it. – Few days of work to check if CHEF/DFS

implementation good enough..

December 6 2006 Ground Motion Group 12

Plans, Short term

Finishing documenting DFS steering, cavity tilt relevance.

Prepare talk for Daresbury meeting.

Keep running dynamical steering

Dynamical Steering with ILC-ML Lattice, after tuning static tuning.