Minutes of the LIS Section meeting held on 3^rd June 2013

Present: Androula Alekou, Fanouria Antoniou, Gianluigi Arduini, Hannes Bartosik, Elena Benedetto, Michael Bodendorfer, Christian Carli, Vincenzo Forte, Adriano Garonna, Cedric Hernalsteens, Alexander Huschauer, Michel Martini, Meghan McAteer, Bettina Mikulec, Tatiana Rijoff, Guido Sterbini, Letizia Ventura, Raymond Wasef

General Information (Gianluigi)

Gianluigi reminded the deadline for send him contributions for the annual report and for the slides that he will present at the Group Meeting. Delphine is looking for volunteers to help in the preparation of the barbecue on 19/6. Volunteers should contact Gianluigi.

The new Group structure will be implemented from the beginning of 2014.

Update on the space charge simulations for the LINAC4 to PSB injection (Vincenzo) - slides

The simulations results that have been presented so far referred to an LHC beam with an bunch population of 3.5x10¹² p (i.e. twice the population of the present LHC beam) and therefore they feature a huge tune spread (larger than 0.5 in the vertical plane). Gianluigi noted that in the future beam and simulation parameters should be clearly indicated on top of any plot presenting simulation results.

Vincenzo noted that there is a discrepancy between the dispersion calculated from the beam distribution and that used by ORBIT (calculated from the lattice/optics). The dispersion calculated from the beam distribution start to oscillate from ~turn 2000 and if this taken into account in the calculation of the horizontal emittance the observed oscillation in the emittance value disappears. Gianluigi asked what is happening at turn 2000. Vincenzo noted that there is no special gymnastic at that moment.

Even by recalculating the beam parameters and the dispersion the observed emittance jumps are visible if no cuts are applied in the longitudinal plane.

Gianluigi suggested to check the evolution of the longitudinal settings (RF voltage, magnetic field and its derivative, stable phase) to check whether any discontinuity is observable that could justify these oscillations.

Nevertheless it is not clear why these jumps are not visible if the aperture is not considered. Cedric and Raymond asked whether the aperture was introduced in ORBIT or in PTC/MAD-X. Vincenzo replied that the ORBIT aperture was used. Cedric and Raymond noted that this could result in a continuous re-adaptation of the grid.

Round Table (all)

ELENA (Christian, Tatiana)

The calculation of the impedance of the BPMs has started. There are issues in using Particle Studio to the low value of the relativistic beta. Gianluigi suggested to contact people from TSR for example to see whether they have experience with such calculations for non-relativistic beams.

Toshiba is going to provide another price estimate for the electron cooler. The possibility to build correction coils at CERN is being investigated

PS (Alexander, Cedric, Guido, Letizia, Raymond, Simone by e-mail)

Offers from companies for the shielding on top of the tunnel in the section 16 have been received. A proposal will go to the Finance Committee of Mid-June. The work on Goward road is progressing well. The earth for the shielding will be taken from the civil engineering work for the new nToF experimental work.

There is a problem related to the aperture for the installation of the skew sextupoles in Straight Section (SS) 58. Four large skew sextupoles are available but only one of them is operational (the other three present an earth fault) and this is installed in SS14.Dominique Bodart is investigating the reason of the earth fault. The skew sextupole in SS02 will go to SS10 whereas the one in SS72 was supposed to be installed in SS58.

The FLUKA team is studying the possibility of installing a shielding similar to that to be installed around the dummy septum. This is necessary to protect both the exit door giving to the EAST area and the electronics of the RF cavities used for the LHC beams.

Magnetic measurements: will take place on the PS main magnet reference unit in June with rotating coil. Survey support is required to measure the geometry of the main magnets. The measurements should be organized for September when the magnet will be refurbished and the Pole-FaceWindings (PFW) removed. This will be the only occasion to access the poles.

The Main Unit (MU) 98 will be removed to install a new vacuum chamber for two new electron cloud detectors, one optical for photons generated by the electrons when the impinge on the vacuum chamber and a pickup.

 Mauro Migliorati is going to take care of evaluating the impedance of the kickers. CST simulations are required.

Raymond is simulating the experiment conducted with Giuliano Franchetti in the PS. This is taking a very long time (300 turn/day). Raymond noted that simulations running with the version of MPI using shared memory are faster. He also noted that simulations are faster on the previously used cluster engpara. Gianluigi suggested to contact Frank Schmidt. He also suggested to ask Tatiana and Xavier whether we could profit of the EPFL computing experts on parallel computing.

 Alex has finished the analysis of the data concerning the instability observed at injection in the PS. No instability is observed at extraction in the PSBooster. The instability is observed right at injection in the PS. This could be due to the ripple in the extraction or re-combination kickers (it must be noted nevertheless that such instability is observed also for ring 3 that should not receive any kick from the recombination kicker) or by the PS injection kicker.

RF longitudinal damper is in construction. Shielding is required to protect the electronics is under discussion.

Letizia is progressing with simulations for the longitudinal coupled bunch instabilities.    

The specifications for the power converter for dipole installed in SS18 for orbit correction are being studied.

Cedric is finalizing the study of the trajectories at the dummy septum and the he is investigating the possible installation of sextupoles at large values of the vertical beta functions for chromaticity correction.

Guido is starting the campaign of simulations with the HEADTAIL code for the head-tail instability at injection and later to study coupled bunch instabilities in the presence of a feedback. An MD note will be written.

PSB (Bettina, Elena, Meghan, Vincenzo)

A preliminary analysis of the effect of the installation of an Inconel vacuum chamber (instead of a ceramic one with resistive coating) did not reveal any serious problem. The simulations were performed with a very high brightness LHC beam. Similar simulations should be conducted with LHC nominal beams and ISOLDE beams. Action: Elena.

Bettina mentioned that a realignment of the PS-Booster is planned. Alignment around a smooth curve calculated around the position of dipoles and quadrupoles is planned. The alignment will be done such to minimize the number of dipoles to be moved.  The measured tilts of the quadrupoles are consistent with those measured with beam based techniques. Recent radiation surveys have revealed that the BeamScope (expected to be the aperture bottleneck by construction) is no more the point with highest remanent radiation. This could be the results of the misalignments observed.

Bettina reported that the signals from the new BPM electronics for turn-by-turn data will be initially available in OASIS and only later will be available in digital form.

BIO-LEIR (Adriano, Christian)

The optimization of the slow extraction is being pursued

LEIR (Michael)

The quadrupolar scan for the measurement of the emittance of the Ar beam at LINAC3 extraction has been performed.

Neutrino activities (Androula, Fanouria)

The coupling observed on the extracted beam for the Short Baseline Neutrino experiment from LSS2 has been understood. The data previously provided were not difference trajectory measurements but the absolute position of the extracted beam. The observed coupling is consistent with that induced by the passage of the beam off-centre in the chromaticity sextupoles.

A LAGUNA-LBNO meeting will take place from Monday 17/6 to Wednesday 19/6 in the Keil Johnsen auditorium.

Monday, 24^th June 2013 at 14:00 in room 6-R-012

Agenda:

General information (Gianluigi)

Round Table (all)

Back to Minutes