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Last LNO section meeting in 2023
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93/R-031 (CERN)
Last LNO section meeting in 2023
The last LNO section meeting in 2023
News.
Helmut reports that there has been an LHC Background Study working group meeting LBS#118 on the 27. November with as main subject the ALICE background observed during the Heavy Ion run. Further follow up is planned.
Highlights from JAP, Ewen Maclean, slides
Ewen presented a short summary of highlights of the recent Joint Accelerator Performance Workshop. The injectors and fixed target program profited from good availability and efforts to improve corrections and stability. Using non-linear correctors, there is potential to further reduce septum activation in slow extraction and good progress on the performance of the BGI (Beam Ionization monitors) to make these available as a standard operational tool in the coming years. The PS and in particular the transition crossing appears to be a main driver for halo generation ( from ~1 - 4 % ). Matteo Solfaro presented a summary of the LHC operation in 2023 that featured both periods of excellent production as well as several issues generating significant downtime.
The LHC 2024 - 2025 schedules were discussed. Short PbPb runs are planned for both years. A short oxygen run is planned for 2025.
MADX status, Riccardo de Maria, slides
A new minor version, MAD-X 5.09.01 is ready for pubic release. Changes are mostly related to PTC. The new version is already linked to cpymad.
MAD-X tapering, last updates, Guillaume Simon, slides
Guillaume presented updates on tapering that is important for rings with significant energy loss by synchrotron radiation like FCC-ee. Tapering scales the magnet strength to correct for the energy loss to preserve the horizontal orbit (correct the sawtooth). There are systematic discrepancies between the TWISS and TRACK methods that truncate at different (3rd, 2nd) order in map expansion. Guillaume compares the tune predictions by TWISS, EMIT and TRACK. Using transformation of coordinates, consistent results are now obtained from quadrupoles and sextupoles. Further work is ongoing for dipoles.
2023 studies of the octupolar RDTs in the LHC, Sasha Jade Horney, slides
Sasha presented studies of the octupolar Resonance Driving Terms (RDTs) based on measurements taken on the 8/4 and 14/6/2023 in the LHC at injection energy using the old and new optics (with/without phase knob) and both nominal and e-cloud tunes as well as different octupole settings. The phase knob introduced in the new optics did not have the expected effect to reduce the octupolar (f2002) RDT. The reason for this is presently not well understood (coupling, phase advance errors, MO magnet hysteresis, BPM calibrations, MO circuit imperfections). To be followed up with further measurements and more accurate models (as replicating measured coupling and phase advance) next year.
Skew Octupolar RDTs from MOs, slides, Updates on b5 model, slides, Mael Le Garrec
Mael presented studies based on the measurements as used for the previous presentation by Sasha, looking here for the diagonal resonance (coupling) peaks in the tune spectra using AC-dipole excitation in both transverse planes. Increasing the normal MOs (Landau octupole) positive strength increased the diagonal resonance terms indicating that the MOs are in fact a source of coupling which is not expected for ideal MOs.
Misalignment of the MOs as main source could be excluded by measurements with negative MO strength polarity.
As a second subject, Mael presented an update on decapole modeling (b5) based on Q’’’ measurements. The observed b5 appears to be a factor of two smaller than predicted by the WISE model. A possible reason could be a decay of b5 with time (initial decay times of order half an hour) not included in the model prediction.
Supervised Learning for Non Linear Corrections in the LHC, Alejandro Borjesson Carazo, slides
Using MADNG for the LHC collision optics to simulate RDT generation and correction, Alejandro shows that ML (Machine Learning) has the potential to correct multiple RDTs at once and that the performance is more robust and yields better results than obtained with the response matrix method. Correcting the f0220 RDT has been a challenge and may require additional observables. Alejandro plans to add realistic noise modeling to his simulations in preparation of applying these techniques to the real machine in commissioning.
Coupling Knobs: Where do they come from? - A python-implementation for xmask, Joschua Dilly, slides
Joschua describes his ongoing work on the re-implementation of FORTRAN based error and coupling corrections as described in the LHC Project Report 501 within python for xmask to improve flexibility (easier to de-select ATS-arcs) and system independence. MAD-X is now only used in the first step of the xmask workflow. The rest including corrector knob generation is all done in python. Stephane commented via email that there exist newer implementations of the coupling knob generation written in MADX and other implementations in e..g: https://cds.cern.ch/record/1422434/files/MD_Note.pdf
IR tuning knobs for the FCC-ee, Satya Sai Jagabathuni, slides
Sataya reminds that correcting field errors and alignment will be essential for the FCC-ee to achieve the ambitious high luminosity goals. Motivated by ideas presented by Leon in the 2023 optics and correction workshop, Sataya describes tuning studies performed with MADX for the current FCC-ee baseline z-lattice (45.56 GeV beam energy) using additional skew quadrupole (windings) and orbit correctors in the IP region and matching sections.
Update on HL-LHC optics studies, Yannis Angelis, slides
Yannis described his work done with Riccardo in rematching the HiLumi LHC IRs 1 and 5 to equalize the H/V maximum betas around the IPs, to increase betas at the crab cavities and minimize the chromatic W-functions.
Optics measurements in the SPS, Konstantinos Paraschou, slides
Kostas reminds that the SPS has a regular FODO lattice with single plane beam position monitors and that his study aims at correcting the 4Qy (f0040) resonance using individually powered octupoles to improve the lifetime of the LHC-type beams in the SPS. Some beta-beat measurements were peformed. Classic optics measurements from turn-by-turn data using “free kicks” were not good enough for f0040 correction. Improved measurements with driven oscillations and removing the current 2000 turn aquisition limitation should be possible next year.
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