Present: Alexandre Lasheen, Andy Butterworth, Anthony Rey, Antonio Grande Mallavia, Arthur Spierer, Brennan Goddard, Carlo Zannini, Chiara Pasquino, Christine Vollinger, Christos Zamantzas, Danilo Quartullo, David Mcfarlane, David Nisbet, Elena Chapochnikova, Eric Montesinos, Kiki Veyrunes, Etienne Carlier, Fabio Follin, Francesco Maria Velotti, Francois-Xavier Nuiry, Frank Gerigk, Gerd Kotzian, Giovanni Rumolo, Giulia Papotti, Gregoire Hagmann, Hannes Bartosik, Heiko Damerau, Ivan Karpov, Ivan Romera Ramirez , James Ridewood, Johan Dalla-Costa, Johannes Bernhard, Julie Coupard, Kevin Shing Bruce Li, Leandro Intelisano, Loic De Oliveira, Lotta Mether, Luciana Kolbeck, Maciej Suminski, Marine Gourber-Pace, Michael Schenk, Nico Madysa, Nicolas Magnin, Paul Cruikshank, Philippe Baudrenghien, Reyes Alemany Fernandez, Simon Albright, Stephane Cettour Cave, Tom Levens, Verena Kain, Wolfgang Hofle, Yannick Le Borgne, Zisou Charilaos

Actions and matters arising

Ripple measurements (Hannes Bartosik)

• Shifted to next week

Kicker balancing for batch spacing minimisation (Francesco Maria Velotti)

• Voltage balancing was not in place - reason for limitation of MKP kicker, now again protecting magnet 7
• Needed to re-steer line to golden - question whether we should instead establish a new golden in TL (ACTION: decide whether to establish new goldens in TT10)
• Fine delays was set up using new capacitive pickups - beam base synchronization not yet done; batch spacing now educed to 250 ns;
• After delay se5tting up and batch spacing no effects on the beam were seen;
• When can we close further? Limitation given by what? Will first need to do beam based fine synchronization - this will need about a few hours, will be done automatically; can be done with 2 batches with low intensity;
• Our golden works so we steer back to the golden;
• Hannes: we have observations that with the same settings we don't get the same orbit; we see that the present golden is not the best golden; schedule a new golden after the scrubbing run; location 109, 135 have strange characteristics;
• Francesco: was this quality reduction mainly on orbit or also on; try scheduling for next week during scrubbing ACTION;
• Hannes: plots were with not ideal voltage seting with WS, more precise measurements still show a few remnants but much better than in the past;

Scrubbing update (Lotta Mether)

• Scrubbing status over last week - did well with 4 batches at flat bottom; no obvious limitation at flat bottom;
• First ramp started, reach flat top with 72 bunches at low intensity and pushing gradually (4e10 - 9e10 ppb);
• Longitudinal instability for intensities above 5e10 ppb;
• MKDH gave vacuum spikes at flat top; perhaps linked to long. instability? ACTION
• Transmission still switching from time to time - source not identified;
• Q' had to be increased more than expected...? Where are the stripes?
• Why is 3 batches worse than 4 batches???
• Verena: commented orbit had moved to very much inside so this fits with scraping at aperture limitations; there are two items that are strange, both mean and rms!
• Francesco: what is the source? Hannes: the correction suggests 200, 220; needs study! Follow-up!
• MD5 cycle sometimes had good transmission, sometime has a bad transmission; not clear yet; as mentioned above already;
• Effect of intensity on e-cloud shown;
• ZS? small sparks; not more than on fixed target; essentially quiet;
• Scrubbing at flat bottom is tapering off and is now mostly done; MKDV pressure is settling just below interlock value; K: what is the intensity at the moment; H: it is 1.45e11 PS is working on their longitudinal feedbacks,
• Verena: MKDV, can we somehow further scrub with shorter bunch length? What if this saturated level is the final one? Is this a problem? Etienne: during acceleration we see lots of change accumulation which is removed when we pulse at high enery; we need to understand this better whether or not this is a problem;  Verena: what about adding solenoids or something the like; Etienne will take this into account;

RF status update (Philippe Baudrenghien)

• Team in access working on cavity 6

Voltage calibration measurements (Danilo Quartullo)

• Idea is to perform beam base voltage measurement using tomography;
• Explanation of set up; ideally all loops are off and beam is far from stationary for measurements;
• Using waterfall plots, estimate synchroneous phase; two fundamental parameters are total voltage and synchronous phase; solution of problem are  pair of voltage and phase that minimize discrepancy to measurement; what is the quality function you use here?
• Can be done as brute-force scan or can use optimizer (Nelder-Mead); problem seems to be convex with single minimum; to be sure, we reconstruct phase space using resulting values and check how well this coincides with measured profile;
• Procedure done for both individual cavities as well as for "total voltage" and phases;
• How long does the analysis take? Does this need to be done offline, or could one imagine to have this only;
• Similar measurements were done for AWAKE bunch at flat top; large errors seem to be present - deviation by 22%;
• Proof-of-principle done - we can use voltage calibration using tomography in the SPS; different ways to excite oscillations can be done;
• Could potentially be done online; Simon is aiming at online tomography;
• Kevin: It is a bit surprising that we see such large discrepancy between set and reconstructed voltages, would we expect this? Danilo: it is somewhat normal, we measure this in all other machines as well; Elena: is it normal because it is a systematic error in the measurement or is it normal that we have a difference between HW settings and what is actually physically present in terms of voltage; Ivan commented that the plan is to try this reconstruction method also on simulated data to identify the systematic error of the procedure itself in order to answer this question;
• Francesco: what optimization algorithm are you using; D: using Nelder-Mead; F: could try others, e.g., COBYLA which may be faster
• in PS -> depends on the type of cavities, main accelerating cavities were between 0-5% (in 2018, to be refreshed), high frequency cavities for bunch rotation between 10-20%
• final comment: the method is as accurate as your knowledge of your parameters for longitudinal beam dynamics is, all this rely on good knowledge of the synchrotron motion, rf voltage is assumed to be the most uncertain here

Status of 800 MHz for operational cycles (Gregorie Hagmann)

• Team in access working on cavity 6