Minutes of the LIS Section meeting held on 22nd April 2013

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

 

General Information (Gianluigi)

Reminders:

The LIU Workshop (https://indico.cern.ch/conferenceDisplay.py?confId=23815) has taken place on 12/4: to be noted the impressive progress towards the HL-LHC beam brightness both for 25 and 50 ns beams thanks to the BCMS scheme.

The space charge workshop (http://indico.cern.ch/conferenceDisplay.py?confId=22144) has taken place from 16/4 to 19/4. Several good presentations have been given by LIS Gianluigi asked whether the tune scans in the PS Booster were performed in both planes. Vincenzo and Elena replied in the affirmative.

It seems that the micro-instability observed by F. Schmidt is a feature of the PIC solver but it seems that he effect on the evolution of the particle distribution is small. It is not clear why this is less marked in SYNERGIA but it seems that ORBIT-PTC and SYNERGIA simulations were run with different number of macroparticles. Gianluigi noted that the tracking part of SYNERGIA is not as well developed as in ORBIT-PTC (e.g. with respect to fringe fields).

Round Table (all)

SPS (Fanouria, Hannes, Yannis)

Hannes has presented at the MSWG the results of kick response analysis conducted in the SPS. Approximately 20 faulty BPMs and 24 BPMs with wrong calibration have been identified. Space charge studies will be presented at a forthcoming LIU-SPS Beam Dynamics working group meeting.

The analysis of the data taken during the 2013 SPS ion run seem to exclude Touschek as a possible source of the losses observed at low energy. It must be noted that these measurements have been taken with the fixed target beam which has a lower brightness than the LHC beam. The working point is different too in order to allow the slow-extraction of the beam.

 

PS (Alexander, Raymond, Simone, Letizia)

For the PS simulations with PIC codes and frozen space charge potential codes will be required. The first ones might represent well the behaviour close to the integer were fast blow-up might occur. Gianluigi speculated that fast blow-up might occur in the PS at injection as a result of the overlap of the space charge necktie with the integer. No losses or blow-up are observed as the emittance blow-up is very fast and affects only the beam core and not the tails. Gianluigi noted that the compensation of the skew sextupolar resonances is opening the way to operate the PS with higher tunes. Simone and Raymond pointed out that the compensation of the 0.25 resonance remains to be demonstrated. This seems to be induced by space charge as it is not visible at low brightness. Raymond is in touch with S. Machida to see possible schemes for the compensation of this space-charge-driven resonance. Simone noted that the present ORBIT-PTC simulations did not evidence any sign of this type of resonance so far.

Letizia is progressing in the benchmark of HEADTAIL (multi-bunch version) with the model developed by M. Migliorati to study longitudinal coupled bunch motion in the presence of impedance and longitudinal feedback.

LEIR (Michael)

The measurement of the chromaticity at low energy revealed that this is positive in the vertical plane. Gianluigi suggested Michael to verify whether there are signs of beam instabilities that could explain the losses at low energy.

Argon 11+ has been accelerated by LINAC3 with a transmission efficiency of approximately 50%. 55emA LINAC3 are obtained at the end of the linac. Michael will perform measurements of the beam parameters (in particular transverse emittances) at the output of the linac to understand what could be the LEIR performance with Argon ions.

Michael added that neutron radiation has been likely observed in the LINAC3 during the operation with Argon. The radiation protection team is taking data to confirm that. The implications for the operation of LEIR with light ions will have to be defined. 

ELENA (Christian, Tatiana)

More than 50 % of the contributions to the Technical Design Report have been collected. Aim to have all the contributions by the end of May.

Tatiana has made a first estimate of the resistive wall impedance. This should be higher at higher energy.

PSB (Elena, Meghan, Michel, Vincenzo) - slides from Michel

Meghan has been at FNAL for a few weeks to conduct some orbit response measurements at the FNAL Booster. A lot of data have been collected.

Simulations of the injection process have been performed and revealed some unexpected features in the evolution of the losses and transverse emittance. The multi-pole fields generated by the eddy currents on the Inconel vacuum chamber have been included.

LEIR for radiobiology (Adriano, Christian)

The design of the beam delivery is progressing. Two lines (one horizontal and one vertical) are being considered. There is no space to install and active scanning system for the vertical line. An optics with a large beta at the target is being considered. This implies to have a collimator to delimit the fraction of the beam with rather uniform distribution. This solution has the disadvantage that a large fraction of the beam is lost. The possibility of using non-linear lenses to flatten the beam profile and reduce the losses on the collimators is being investigated.

LAGUNA (Androula, Fanouria, Javier, Yannis)

The feedback from the magnet people on the design of the magnets for the High Power PS (HP-PS) is very slow. A contact person should be nominated by Luca Bottura.

Androula has started to look at a possible collimation system for the HP-PS. She is reviving the code used by Javier Barranco for the collimation studies for the PS2.

 

 

Monday, 6th May 2013 at 14:00 in room 6-R-012

Agenda:

General information (Gianluigi)

Simulations of the LINAC4 - PSB injection in the presence of space charge - issues and progress (Elena and or Vincenzo - tbc)

Round Table (all)

 

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