Login

FCC-ee optics tuning WG meeting

→ Europe/Zurich
6/R-012 - conference room (CERN)

6/R-012 - conference room

CERN

40
Show room on map
FCC-ee optics tuning WG meeting
Zoom Meeting ID
65516078996
Host
Rogelio Tomas Garcia
Useful links
Join via phone
Zoom URL
Hide

News

We have the pleasure to announce that the Physics Briefing Book, which provides important input for the 2026 update of the European Strategy for Particle Physics, has been released by the Physics Preparatory Group* and is available via this link:   

https://cds.cern.ch/record/2944678

China delays CEPC timeline: 

https://cerncourier.com/a/cepc-matures-but-approval-is-on-hold/

WP2a summary report assessing the different collider projects:

 https://cds.cern.ch/record/2947131

We are proposing an IPAC26 paper on the tuning as done in previous years.

 

LCC high beta* optics matching, Marc

LCC IR is an achromatic telescope IP->Crab sextupole (phix,y=3, 2.75). The beta*x is proportional to betax at CS. The beta*y is proportional to 1/betay at CS.

Increasing beta* reduces W function which requires matching with sextupoles. This calculation is done with only the IR as a ring. This way only limited IP betas are reached. To increase them even further the tt IR strengths are loaded in the Z and constraints at the crab sextupoles are not respected. This achieves 1.5m in betax and 7mm in betay. The lattice behaves very well in terms of non-linear chromaticity and DA. 

This represents an optics for use during commissioning.Ballistic optics would still required to study the alignment of the IR region, but the ballistic optics might not be needed right away. Concerning the repository the files are now a bit scattered and some grouping will be applied. Reference parameters are also needed.

Pantaleo mentions that the scenario of a colliding commissioning optics is also needed with the crab sextupole condition (Marc achieved 50% larger betas). Which parameters would be adequate for first collisions (maybe beta*y~7mm), aiming at having also the detector taking data (scenario to be defined, betas, use or not of crab sextupole, etc.).

 

Injection optics study, Giulia

After injection beam is tracked to the doublet. GHC shows lower deformation in py than LCC. Heavy tails in the GHC and LCC are observed in the first 100 turns. This study shows a 69% injection efficiency for the GHC which is below the 80% previously assumed (collimators are not included in this study). The impact of the injection bump is very large, about 50%, this is stricking. Adding beam-beam further reduces efficiency to 13%.

The corresponding study for LCC shows lower efficiency, ~50%,  to be compared to the 70% of GHC (configuration is with beam-beam but no injection bump). Oscillations at the doublet should be further checked as they should not happen. 

The delta offset error like 0.1% can be tolerated as changes efficiency by few %.

 

Non-linear studies, Patrick

Patrick loaded a lattice from Satya reproducing Satya's results to reasonable numerical accuracy for linear optics.  Some larger differences seen in DA, but both results give below 10 sigma DA. 

Between baseline and error lattice large discrepancies are seen e.g. in the amplitude detuning. Spectra shows many more secondary spectral lines, specially skew resonances.

Studies to be extended to more seeds, possibly adding beam-beam and reviewing why different DA results were observed.

 

 

 

 

 

 

 

 

 

 

 

 

There are minutes attached to this event. Show them.