Minutes of the LIS Section meeting held on 5th October 2009

Present: S. Aumon, G. Arduini, E. Benedetto, C. Carli, M. Chanel, S. Gilardoni, M. Martini,  S. Maury, E. Métral, D. Quatraro, G. Rumolo, E .Wildner.

General Information (Gianluigi) 

Three new LD posts should be opened in ABP in 2010 for: LINAC4/PSBooster, CLIC and PS2

Gianluigi has submitted the following list of participants to IPAC10 Oliver. There will be certainly limitations due to budget constraints: Gianluigi Arduini (IPAC10 Organizing Committee), Elena Benedetto, Yannis Papaphilippou (could be combined with a visit to J-PARC related to  PS2 studies, we can try to get some funding from PS2), Christian Carli (could be combined with a visit to J-PARC related to LINAC4-PSB, we can try to get some funding from LINAC4), Sandra Aumon (if she gets a grant or if paid by EPFL), Diego Quatraro (if he gets a grant or paid by University), Nicolas Mounet (if paid by EPFL)

Gianluigi reminded that any car accident at CERN should be declared.

LHC: Commissioning of the nQPS ongoing in Sector 12. The nQPS system is now connected to the interlock loop.

Sector 78: splice measurement for the bends completed with ramp up to 2 kA with nQPS in monitoring mode. Still to be done for quadrupoles. During the week-end it was detected that the dump resistor of the main quadrupoles was not connected. No damage has occurred as verified with additional electrical quality assurance tests

Sector 56: preparation to go in Phase 2.

Sector 23 phase 1 powering ongoing and sector 45 due to start.

More information can be found in the HWC web page and in the minutes of this morning HWC meeting

Electron cloud studies at CESR-TA and SPS (Giovanni) - slides

Giovanni has described the set-up of the CESR-TA experiment for the qualification of a carbon coated vacuum chamber with respect to a reference aluminum vacuum chamber. The coated vacuum chamber was equipped with and electron cloud monitor, a solenoid, a residual gas analyzer and a dipole magnet magnet was installed downstream of it to avoid electrons to flow longitudinally in the test area. The magnetic field in the dipole was 100 G. No "electron clearing" dipole magnet was installed upstream of the coated chamber.

During the experiments it was not possible to go to 4 ns spacing because of a problem with the transverse feedback system. The aluminum vacuum chamber had exactly the same geometry and diagnostics and was installed in another position.

No solenoid and clearing dipole magnets were installed around the reference chamber.

The electron cloud monitor data show a central stripe. This could be due to the different transmission efficiency for the electrons as a function of the radial position as the holes in the chamber are vertical and not perpendicular to the vacuum pipe surface.

The reference chamber sees a lower flux of synch light for electrons as compared to carbon coated chambers. Factor 6 lower flux of electrons for the carbon coated chamber.

Several observations:

seem to indicate that the main source of electrons is photo-emission and not multi-pacting

The photo emission yield has not been measured.

Elias asked whether the test has been done as well with a single bunch. Giovanni replied in the negative.

It is also suspected that the carbon coated vacuum chamber has been contaminated during the bake-out process because of the presence of a kapton tape in the electron cloud monitor. The sample of the chamber that was sent back to CERN was showing in fact a SEY of 1.5 while the SEY of the same sample measured at CERN before shipping was 0.98.

Gianluigi noted that it would be important to conduct measurements comparing the resistive wall impedance of the coated and uncoated vacuum chamber.

Giovanni continued showing the results of the simulations he has done to understand the dependence of the electron cloud flux measured in the SPS in the test bench in LSS5 as a function of the magnetic field. The observed dependence can, to a large extent, be explained by variation of the transmission efficiency of the e-cloud monitor as a function of the magnetic field.

Elias asked what are the options for the coating of the dipole magnets vacuum chamber. Giovanni replied that the central part (along the axis) of the vacuum chamber of the magnets should be coated because the electron density at the centre of the chamber is larger for larger magnetic field. The extent of the central stripe need to be estimated. The question whether we need to coat quadrupoles needs to be clarified as well.

Round Table 

Elias reported that a campaign of tests of the SPS wire scanners has been done. The wire scanners 416H and V, 519 A and V, 521 H and V and 414 V are working. Gianluigi noted that it is important to have the linear wire scanner 517 working in order to measure precisely the emittance of the pilot beam in view of LHC operation.

Discussion on possible schemes with proton beams with spacing larger than 100 ns is ongoing. This scheme is now supported by the LMC and experiments should be performed.

The analysis of the correction of the 5 beamlets trajectories for the MTE with the DFAs is ongoing (Elena Benedetto). The measurement of the optics of the line is not yet complete.

The teams involved on Neutrino Factory and Beta Beams studies have partecipated to the workshop on the European Strategy for Future Neutrino Physics (1st to 3rd October). Michaela Schaumann and Elena Benedetto have presented information about work done on production ring for Beta Beams and on proton driver for Neutrino Factory.

Simone mentioned that there are still problems with the radial position control at injection and at top energy. This seems to be related to a problem with the phase loop (possible offset). Gianluigi asked whether the phase offset can be adjusted remotely. Simone replied in the negative.

Ions in LEIR: Christian and Michel Chanel mentioned that work is still ongoing on the RF low level controls (cavity voltage controls and double harmonic). Losses are still visible at low energy for the nominal ion beam. Furthermore the intensity delivered by the LINAC3 is still pretty low (~20 microA). A cycle with a longer flat bottom is being prepared in order to increase the number of injections and the total intensity to compensate for the lower intensity delivered by the LINAC3.There are still some issues in the generation of the cycle in LSA.

Michel Martini mentioned that the IBS code based on the MOCAC algorithm (SIRE) by Alessandro Vivoli is now complete and it includes radiation damping and quantum excitation. Simulations are being  performed for the CLIC damping rings.

Next meeting

Monday, 19th October 2009 at 14:00 in room 354-1-001

Agenda

 

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