Minutes of the LIS Section meeting held on 7th September 2009
Present: G. Arduini, H. Bartosik, O. Berrig, M. Chanel, C. Carli, G. Lund, M. Martini, S. Maury, E. Métral, N. Mounet, D. Quatraro, E .Wildner, F. Zimmermann
General Information (Gianluigi)
An Extended directorate meeting has taken place to discuss the medium term plan and the manpower plan for this period.
LHC status: Sector 12 phase I commissioning went very well. Phase II powering in that sector should start in week 38 (HWC web page)
G. Lund is leaving CERN after finishing his training. Gianluigi thanked him for his work.
New results on impedances, wake fields and electromagnetic fields in an axi-symmetric beam pipe (Nicolas) - slides1 - slides2
Frank asked whether the formalism is valid for beams with any speed and not limited to beams travelling with the speed of light. Nicolas replied in the affirmative.
The results have been presented at the impedance meetings in a more extensive form (slides) and a paper is in publication.
A new matrix method has been proposed for the field matching determination of the constants involved in the field components. This allows much faster calculations by one, two order of magnitude as compared to present algorithms. Any number of layers can be dealt with the new algorithm.
Frank asked why the impedance of the copper collimators increases at high frequency (THz region). This is due to relaxation time of charges in the conductor.
The new algorithm has been benchmarked with existing formalisms covering only certain limited ranges: e.g. with Chao's formulas valid for ultra-relativistic beams and for the first frequency regime approximation. Furthermore the relative magnetic permeability m=1 is assumed in Chao's formalism
The Fourier transform algorithms used for the calculation of the wake fields starting from the impedance have been improved as well and are faster and more precise for smooth impedance functions transform as compared to the standard Fast Fourier Transform. The new algorithm becomes less effective in the case of narrow band impedances
Frank and Diego suggested to compare Nicolas and Elias' formalism with Frank's formula for the longitudinal plane also valid in the non-relativistic regime.
Nicolas will start now to work on the study of coupled bunch instabilities by simulations and experiments. Machine studies will be performed in week 38 and measurements will be compared with simulations. It is planned to extend HEADTAIL to deal with coupled bunch instabilities. At present a model with rigid bunches is implemented in HEADTAIL.
Gianluigi congratulated Nicolas for the excellent work and very clear presentation
Round Table
Elena Wildner and team presentations at NuFact. Discussions with FNAL people for issues related to the production ring. The two German BSc students finished their thesis and have presented their work to the group. N. Mokohov introduced in MARS the low energy part of scattering. FLUKA and MARS seem to give the same results.
Strategy for Future Neutrino Physics Workshop will take place at CERN on 1-3 October Elena will give a presentation.
A Neutrino coffee meeting is taking place every week to discuss the Neutrino Factory and Beta Beams activities.
It might necessary to go back to short bunches for the beta beam decay ring to reduce the background due to atmospheric neutrinos even with the higher energy to which new ions will be accelerated. The option of the capture in a barrier bucket might be therefore ruled out.
Hannes is conducting the study for the tunability of the PS2 lattice in its latest version with shorter straight sections allowing more space for dispersion suppressor. A new range of tunes is now being considered
Olav has tested and introduced in the optics DB the pre-squeeze in LHC IR8.
Michel Martini is continuing the simulation campaign for the LINAC4 injection into the PS Booster. 10% blow-up (in 10 ms) is still visible for the LHC ultimate beam although the observed blow-up is decreasing with increasing number of macro-particles. The simulations are still running on the oplapro cluster as there is an issue with lxclic related to afs. The afs token is lost after ~24 hours. A dedicated disk space might be needed. Christian is following that up. Action: Christian.
Diego suggested to study whether blow-up is observed even with a perfectly linear machine.
Michel Martini has also made some estimates for the IBS effects for SLHC for 1035 luminosity options. Some blow-up is seen also in the horizontal plane in spite of the synch radiation damping
The emittance growth rate is estimated to be 1% per hour. Longitudinal blow-up could cure that.
A bug has been found by Yannis in the calculation done by M. Korostelev for the CLIC damping ring and the emittance blow up is now smaller. The priority for this study is therefore decreased but A. Vivoli is going to conduct simulations for the damping ring with MOCAC. The programme is being modified to include the effect of synchrotron radiation. The evolution of the distribution will be included as well.
Matthias is conducting simulations with ORBIT to study the behaviour of the LHC ultimate beam in the PSB with LINAC4 for a working point above the half integer resonance.
Penny is running some simulations for a rough collimation scheme in the PSB. The very preliminary results seems to indicate that a single stage collimation system could be implemented.
Christian has worked on the LEIR to PS matching. Measurements in the ETL line profiles have been conducted and wrong settings have been found on a quadrupole.
The issue of the mismatch in the TT2-TT10-SPS transfer is not totally understood although the emittances measured in the SPS seem to be comparable with those measured in LEIR and are small. Christian and Michel Martini are following that up. The extraction settings in the PS are now the same as for the LHC proton beam. The LHC proton beam optics will be loaded and measurements will be taken. Action: Christian, Michel Martini
LEIR: the low work on the low level RF is now almost completed. Work on the nominal should now intensify. Action: Michel Chanel
Elias reported the progress on the work on impedance for the kickers (C. Zannini). Benoit is working on the update of the impedance model of the SPS and on the estimate of the instability thresholds with HEADTAIL. Elias has provided Carlo with the data for the 8C11 ferrite which is used for most of the SPS kickers.
L. Rivkin has proposed to Elias to set-up a collaboration with Novosibirsk. Nicolas would be involved. Gianluigi supports this idea.
Next meeting
Monday, 21th September 2009 at 14:00 in room 354-1-001
Agenda
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