Beam-beam and Luminosity Studies Meeting

Friday 15 May 2020, 16:00 → 17:40 Europe/Zurich

6/R-012 - conference room (CERN)

Guido Sterbini (CERN), Yannis Papaphilippou (CERN)

Preparation for the HL-LHC Collaboration Meeting

Zoom meeting link 

https://cern.zoom.us/j/98897351714

 

Present (remote connection): Guido, Axel, Georges, Adriana, Hannes, Ilias, Yannis, Kostas, Kyriacos, Lily, Matteo, Natalia, Sofia, Stefania

---

Guido presented the pythonic function to compute the luminosity. This will be used for the leveling module of cpymad. 

Georges asked if the longitudinal profile (now Gaussian) could be generelaized (e.g., parabolic). Guido answered positively, explain that the longitudinal profile are always numerically integrated (differently from the transverse ones that are analytically integrated).

Georges  asked if this formula could be used during the emittance scan to compute the bunch-by-bunch luminosity. Guido and Yannis  answered that it is possible to take into account the linear beta-beating introduced by the beam-beam effect. The level of complexity increases significantly if we consider higher order effects.

Ilias commented that in some case,  during the use of  cpymad, he observed an erratic behavior of the code, possibly connected to memory problem. Guido suggested sharing the specific case to have an informed discussion on the topic.

---

Axel presented the status and the progress of the feed-forward for the wire compensators to be used in Run3.

The analysis for B1 is completed, The one of the B2 is still missing but is expected to be very similar to the one of B1. 

Guido commented that it would be interesting to show the maximum betat beating for different tele-indexes.

 

16:30 → 17:00 Luminosity leveling in python/cpymad

Presently the luminosity leveling in (HL-)LHC mask is performed using the BB macros of MAD-X. Typically, the leveling is adopted only in IP8 and consists in a separation leveling.

After a review of the luminosity formula, we show how, with a pythonic approach, we can generalize this workflow.

Speaker: Guido Sterbini (CERN)

Example

Luminosity Computation

luminosity.py

Slides

17:00 → 17:30 Wires knobs in the Run3 Optics

The status of the wire Q-feed-forward knobs for Run3 will be presented. After reviewing the dipole-quadrupole effects (in open loop, i.e., no feed-forward) at injection (B1+B2), we analyze it at top energy (e.g., ATS at $\beta^*=30$ cm). Then we show the impact of the proposed 4 knobs (2 knobs for each beam) on the Q, beta-beating, chromaticity, dispersion (etc...) as function of the ATS tele-index as function of the TCT opening and the wire current.

Speaker: Axel Poyet (Universite Grenoble-Alpes (FR))

lhcmask_doc

Slides

17:30 → 17:40 AOB