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ABP-HSS Section meeting
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Starting with a presentation:
Issue with SixTrack - SixDB Post-Processing, Frederik Van Der Veken, slides
Frederik reports on studies done with Massimo, Malte and Riccardo. A combination of two issues was found, where quickly-lost particles are not stored. In the presence of disconnected stable resonance islands, this can lead to an over-estimation of the dynamic aperture (DA).
Riccardo implemented a quick fix available in the latest SixDB version on GitHub. The fix consists on defining DA as the last stable particle instead of the first unstable. It will be pushed soon to SixDesk.
The impact on average DA determinations for the LHC appears to be small and more significant for HL-LHC.
News and round table, slides
Rogelio shows the list of new and recent papers by HSS-members.
There has been an increase of sexual harassment cases at CERN. Management wants this to be known and improved. In case of problems the CERN Ombud's can be a good first anonymous consultation.
Helmut reports from the LPC Meeting https://indico.cern.ch/event/957040/ on Monday and the upcoming LHC run planning with wishes and feedback from experiments. He presented possible high-beta* options and got the feedback that the 3/6 km option looks particularly interesting. These optics will require a new de-squeeze and a special very tight collimation hierarchy. A presentation of the new optics along with aperture, etc, should be foreseen in HSS.
Collimation, Stefano:
This week has the 10-th HL-LHC annual collaboration, where Stefano will present this afternoon. Work for RUN3 continues and will have to adapt to the 11T magnet planning and crystal collimation as possible plan B.
Injectors, Alex
The PS alignment campaign is done. The optics repository includes now knobs for the Booster and PS.
Discussion took place on MD priorities for '21. IPP meeting tomorrow Thursday to discuss the BPM turn-by-turn data acquisition application which is common across the accelerator complex.
OMC, Tobias
The meeting last week had presentations and discussions on subjects including improving algorithms for beta and amplitude oscillations and natural tune dependence.
Followed by two presentation:
First experience using MAD-NG with the PS lattice, Alexander Huschauer, slides
The PS MAD-X files use sub-sequences. The MAD-ND sequence parser had to be adapted to cope with theses needs.
PTC is much used for the PS, typically using model 2, method 6 and the time=false option to take the relativistic Lorentz-beta into account.
Alex observed significant differences in betas and tune between PTC and MAD-NG, depending also on the MAD-NG method choice.
MAD-NG has new type boolean in the twiss header, that is not yet supported by the TFS-pandas package.
Experience translating MADX scripts into MAD-NG, Laurent Deniau, slides
Laurent illustrates differences between the MAD-X and MAD-NG input syntax, starting from a simple MAD-X FODO example.
He then shows what was needed to adapt PS, CLIC and LHC lattices and jobs for MAD-ND and the time it took (minutes to hours). He concludes that the effort of translating MAD-X scripts into MAD-NG is comparable and in some cases easier than translating MAD-X scripts into MADX-PTC, and the importance of writing and updating the manual of MAD-NG in parallel to the translation of the studies.
The issue concerning the discrepancy in tunes observed for the PS should be understood in the coming days to continue sending the recently converted MAD-NG files of CLIC BDS, and LHC to the users.
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