Choose timezone
Your profile timezone:
Discussion on LCF beam parameters
→
Europe/Zurich
6/2-008 (CERN)
Discussion on LCF beam parameters
Present: E. Adli, J. List, B. List, R. Tomas, L. Kennedy, A. Latina. Y. Papaphilippou, S. Stapnes, D. Schulte, A. Robson, A. Faus-Golfe, K. Yokoya
Purpose of meeting: discuss a way focused way forward for the design of BDS systems for the (SCRF) LCF, including considering DR parameters, and whether the CLIC BDS design, tuning methods and possibly footprint can be applied to the LCF.
Erik presented history of CLIC BDS:
2012: 3 TeV and 500 GeV for CLIC CDR
2016: Studies and adaptation of L* = 6 m (QD0 outside detector). The longer impact did not impact Lum. negatively, but lead to 200-300 m longer BDS
2019: Consolidated parameters for CLIC 380 GeV (CLIC PIP, EPPSU input)
2021: Dual BDS for CLIC
2025: Consolidated parameters with dual-BDS, and factor 3 improvement in lum. due to 100 Hz and improved tuning (CLIC RDR, EPPSU input)
2026: Updated (improved) lum. numbers for CLIC 1.5 TeV and 550 GeV. Using a CLIC-like BDS for LCF 550 GeV leads to lum. ~50% below design target. Can be recovered if hor. emitt. is reduced from 10 um to ~5 um. BDS length was assumed the same as for CLIC. GunieaPig was used to calculate the lum.
Benno presented an overview of the relevant ILC parameters and the lum. numbers for an LCF. LCF has fundamentally different parameters than CLIC.
Discussion on LCF DR: LCF DR is very different than CLIC DR due to long bunch train and larger bunch charge. A lower natural hor. emittance is possible. Yannis: an easy first step is to see the effect of increasing wigglers-B from 2.1T to ~2.5T.
Energy spectra and beamstrahlung: Kaoru: If considering to reduce hor. emitt. then beamstr must be considered; may be limited by beamstr Or, if keeping same spot size, a larger beta means tuning will be easier. Daniel: the disruption may be more important than beamstr, this will depend on the physics process. Ideally: select physics processes as benchmark. Daniel: The exact energy spectrum seems of less concern now than earlier.
Energy levels: Z-pole will be important, also for comparison LEP3. Rogelio: not yet studies, hunch is that BDS design and tuning for 91 GeV will be difficult. 380 GeV necessary (in practise requested by management). Also 550 GeV, at least for CLIC. And 250 GeV.
2-BDS: Power considerations allows 2-BDS from 91-550. Baseline should be 2-BDS for all these energies. Daniel: if, for some reason, the 2-BDS adds significant difficulties/cost, not strictly needed if FCC is not longer an option.
L* and X-angles: 6m L* star for all options as baseline. X-angles of ~15 mrad and ~25 mrad. Having 2-BDS opens for variation to this, but to be discussed.
Footprint: ideally same footprint as CLIC BDS, but larger footprint, and/or shorter L* etc can be considered to recover lumi.
Priorities: LCF 380 GeV and 91 GeV first priority because least studied so far. Update on LCF 250 GeV & 550 GeV (which remain the physics-driven priorities), CLIC 550 GeV and TeV upgradability next priority.
In parallel: investigate possibilities for lower hor. emitt. at LCF, out of the DR, and to the IP => the resulting (even preliminary, tentative…) beam parameters need to be communicated early to Physics&Detector for checking impact on luminosity spectrum and backgrounds.
Timescale: results by end-2027, including first input to costing by mid-2027. Some of the documentation may happen after.
Resources: necessary, and most urgent is to employ a new GRAD for focus on LCF BDS. New PhDs probably too slow to contribute. For DR, Yannis may look into the main parameters personally, including LCF DR natural emittance. Angeles: fast Bayesian optimisation of overall parameters is feasible.
New meeting in two weeks, please fill your availability here:
https://newdle.cern.ch/newdle/82W5hvff
There are minutes attached to this event.
Show them.