Minutes of the LIS Section meeting held on 29^th July 2013

Present: Androula Alekou, Gianluigi Arduini, Michael Bodendorfer, Vincenzo Forte, Adriano Garonna, Simone Gilardoni, Cedric Hernalsteens, Alexander Huschauer, Yannis Papaphilippou, Guido Sterbini, Letizia Ventura, Raymond Wasef

General Information (Gianluigi)

Following the proposal of Simone for the PS (see the following directory: \\cern.ch\dfs\Departments\BE\Projects\PSUpgrade\MDs\Planning_after_LS1) Gianluigi suggested that it would be good to prepare a prioritized list of proposals for Machine Development studies for the PSB (Elena), SPS (Yannis), LEIR (Michael) to be presented together with that for the PS by the end of the year during the LIS meetings.

Gianluigi reminded the section members to fill the EDH leave requests for any official travel (e.g. Norway CAS)

LSS2 fast extraction measurements and analysis (Androula) - slides

A non-local fast extraction from LSS2 by kicking the beam with the injection kicker (MKP) in LSS1 of the SPS has been proposed as a mean to extract the beam from the SPS for the CENF facility.

Simone asked whether the observed coupling could be due to a tilt of the MKP kicker. Christian noted that the ration between the vertical and horizontal trajectories were a factor 0.1 which would imply a huge tilt.

Androula noted that there are some BPMs that are appearing in MADX but not in YASP. Gianluigi noted that a few BPMs might be installed but not connected and some of them might be used for other purposes. It should be possible to make a distinction between instruments and beam position monitors. The class INSRUMENT might be used for that.

The measured orbit was reproduced in MADX by calculating the strength of the correctors required to fit it. MADX was returning an error when  more than 97 orbit correctors were used. This is likely due to the excessive number of correctors with respect to the number of constraints. The effect of the MKP kick was then added on top.

A clear disagreement between estimated kicked trajectory and measured one (supposed to be the difference trajectory according to the people performing the experiment) was particularly evident in the vertical plane. The measured vertical trajectory could be explained only by huge unphysical misalignment

It turned out that the provided data were absolute trajectory data and not difference data between trajectories with kicker on and off. When this is taken into account then it was found that the coupling in the machine is very small and this is due to the vertical orbit displacement at the lattice sextupoles

A bug with MADX has been observed when using the CORRECT command. The introduction of markers changes visibly the twiss .parameters. This problem has been communicated to MADX support team.

Round Table (all)

SPS (Yannis)

A review of the SPS High Bandwidth Feedback is planned for Tuesday 30/7 (from LIS Hannes is going to give a presentation on the aperture requirements and Gianluigi is going to participate as a reviewer. Giovanni Rumolo, Giovanni Iadarola and Kevin Li from ICE are going to make presentations too). A review of the proposal of installing a new kicker with reduced rise time for ions is going to take place on 4/10/2013.

The 3rd Low emittance ring workshop took place at Oxford on 8-10 July with more than 80 participants. Eirini Koukovini Platia (supervised by Giovanni Rumolo) got a prize for her poster. This is the second prize she received in 2013 (the other one at ICAP)

A lot of effort is ongoing in the synchrotron light sources to reduce the emittance of the beam below the diffraction limit i.e. to reduce the beam size below the diffraction limit corresponding to the wavelength of the synchrotron light emitted.

LEIR (Michael)

Vacuum sector 1 of LEIR will be opened at the beginning of August. The Multi-Channel Plates (MCP) of the Ionization Profile Monitor (IPM) will be inspected to check their status

Michael has started simulation work with MADX PTC for LEIR.

ELENA (Christian, Tatiana)

The date of the review has to be defined. The information on beam instrumentation and electron cooling for the Technical Design Report is still missing. Review: date to be defined

Impedance simulations for the Beam Position Monitors: Tatiana is simplifying the structure to allow CST simulations for beta <<1. She has verified that the simplified structure provide the same results as the detailed one for beta=1.

PS (Alexander, Guido, Letizia, Raymond, Simone)

Raymond reported crashes of  PTC-ORBIT when simulating a large number of turns (~30000). H. Renshall is working on that but no solution has been identified yet. For the moment simulations implying a large number of turns are split in more runs with a smaller number of turns. The EPFL cluster appears to be the fastest for space charge simulations. Raymond will contact Tatiana to join the potential computing requests.

Work to compare PTC-ORBIT simulations with the space charge frozen model of Giuliano is starting. Some issues have been found in the definition of the sequence as used by Giuliano.

Letizia has verified whether there could be other sources of impedance producing the longitudinal Coupled Bunch instability observed in the PS. 40 and 80 MHz cavities have been considered by their effect is negligible. The 10 MHz cavities are the main responsible. The new Finemet cavity for the longitudinal damper has been considered as well but the contribution to the impedance is negligible. Leitizia has started to write her diploma thesis.

Guido is completing the analysis of the machine studies for the PS Wire Scanners. The precision of the beam size measurements is of the order of few percents. Gianluigi suggested to include the results of the beta-beating measurements as part of the uncertainties might come from beta beating.

Tail measurements are not yet consistent among wire scanners, even in the vertical plane. According to Ana Guerrero this could be still due to the calibration. This could be improved with a more extensive calibration campaign that now should be possible thanks to the modified bellows that should stand a much larger number of scans without failure.

Laboratory measurements of the impedance of the dummy septum are planned. Installation is planned for December.

Alexander is analyzing the data taken to characterize the instability observed at injection in the PS for the high intensity beams.

BIO-LEIR (Adriano, Christian)

Adriano is introducing a realistic model of the aperture and of the expected orbit and momentum offset tolerances to estimated the extraction efficiency.

PSB (Vincenzo)

An issue has been identified in the transfer of the time varying parameters like the energy between PTC and ORBIT. This might introduce and error in the calculation of the space charge kicks. Further issues are suspected in the calculation of the stable phase in PTC. Gianluigi said that we should invest time to look into the code and understand the origin of the above problems as a long term investment. Action: Elena, Vincenzo.

Monday, 12^th August 2013 at 14:00 in room 6-R-012

Agenda:

General information (Gianluigi)

Status of HP-PS studies (Fanouria, Androula, Javier)

Round Table (all)

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