Minutes of the LIS Section meeting held on 04 June  2012

Present: G. Arduini, H. Bartosik, M. Bodendorfer, C. Carli, A. Garonna, S. Gilardoni, C. Hernalsteens, A. Lachaize, Y. Papaphilippou, M. Pivi, G. Sterbini, A. Ulsroed, R. Wasef, C. Yu

General Information (Gianluigi)

The ABP group meeting will take place on 18/6 in the PS Auditorium and it will be followed by a barbecue in the Prevessin area.

Gianluigi thanked the members of the section for their contributions for the annual report.

Future meetings: LEP3 (18/6 - unfortunately colliding with the Group Meeting) and LHeC (14-15/6)

LHC status:

Good production with ~0.9 fb-1 accumulated in 1 week. Some instabilities have been observed during the squeeze or when going in collision. The origin of these instabilities is not yet known.

Gianluigi will be absent (training) from Tuesday 12/6 to Thu 14/6 included.

Status of the wide band feedback for the SPS (Mauro) - slides - Movies: Dipole excitation - Quadrupole excitation - Spectrum with variable excitation frequency

The main experimental effort so far has been focussed on the characterization of the beam observation part of the feedback and on beam transfer function measurements. An exponential pick-up has been used for the measurements. This type of pick-up has a frequency response with no nodes which are typical of a standard stripline. This pick-up was designed by Trevor Linnecar.

A rather realistic model of the wide-band feedback has been introduced in CMAD and HEADTAIL. Benchmarking between these two codes has been performed and seem to show good agreement between them.

A small reduction of the emittance is visible and this could be the result of the number of macroparticles, in that case a sort of stochastic cooling is simulated but given the number of particles it is highly unlikely that a reduction of the emittance can be observed. For that reason the power requirements might be underestimated.

Round table (all)

Adrian, Hannes, Yannis

Measurements of the initial conditions for the TT2-TT10 line are being performed both for:

Dispersion measurements have been performed. Measurements of the betatronic mismatch should be performed with OTRs. Gianluigi suggested to use single bunches with small momentum spread for the measurements, to minimize errors in the profile resulting from bunch-to-bunch trajectory differences.

The dispersion on the Q20 optics is not yet totally under control and some beating with respect to expectations is still observed at flat-top

Yannis has presented the results of the studies on the LHC ion beam performance with the low gamma transition optics at the MSWG. The Q20 optics gives a reduction of the space charge tune spread by ~15% with respect to the nominal optics. The transverse emittance growth times due to IBS increase by 50% for the Q20 optics with respect to the nominal optics. Experiments seem to indicate that for the moment the RF noise is the main responsible for the observed losses along the injection plateau.

Christian

 ELENA: review of the parameters and estimation of the IBS growth rates. These are larger than initially estimated.  IBS simulation during the ramp down will be performed (M. Martini). Needed to define the required machine acceptance.

Michael

Michael has discussed with Richard about the operation of the ECR ion source at 18 GHz.

 Antoine, Cedric, Simone

Measurements for he reproducibility of the trajectories of the MTE beamlets to be analyzed

The measurements of the orbit at high energy with the corrections scheme using either DHZ3 or DHZ15 show difference in the extraction conditions of approximately 1 mm in position and 1 mrad in angle at the extraction point. This could originate different initial conditions for the dispersion and Twiss parameters at the beginning of the TT2-TT10 line.

Hybrid MTE. Measurements and correction of tune and chromaticity progressing. Non-linear chromaticity might be more tricky.

MDs for electron cloud instability at the PS: (Giovanni’s, Simone, Mauro) evidenced once more instability developing when the nominal LHC beam (25 ns) is kept for some time at flat-top. Electron cloud signal observed. Need to determine whether this is an electron cloud instability (this was the understanding so far but needs to be confirmed).

Adriano

Trying to match the optics to satisfy the Hardt condition at LEIR extraction. Gianluigi suggested to look also at the SPS solution with low dispersion for which satisfaction of the Hardt condition should not be necessary.

 

Next meeting

Date and time to be defined

 

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