Minutes of the LIS Section meeting held on 28 January 2013

Present:  Javier Alabau, Androula Alekou, Gianluigi Arduini, Hannes Bartosik, Elena Benedetto, Michael Bodendorfer, Christian Carli, Vincenzo Forte, Adriano Garonna, Yannis Papaphilippou, Tatiana Rijoff, Guido Sterbini, Adrian Ulsroed, Raymond Wasef.

General Information (Gianluigi)

Gianluigi has attended the IPAC13 SPC for the definition of the contributed oral presentations. Japan is still pushing for linear collider to be constructed as Higgs factory. New Japanese government has confirmed that this is one of the priorities and ready to provide additional money on top of existing research funds so to cover 50% of the total cost.

A joint LIU/HL-LHC workshop will take place in May or June to identify the possible upgrade steps and corresponding performance for the LHC starting from expected performance after LS1.

ICFA mini-workshop on "Beam-Beam Effects in Hadron Colliders" will be held at CERN from March 18th to 22nd 2013.

ICFA Mini-Workshop on Space Charge (SPACE CHARGE 2013) at CERN rom 15th to 19th April 2013. This has not been discussed yet in the Space Charge WG meetings. Gianluigi will mention that to Elias.

Christian Carli has taken over the ELENA Project Leadership from Stephan Maury from the beginning of the year. Congratulations and all the best for the new challenge.

A new pilot fellowship scheme is being put in place for Technicians.

Round table (all)

PS (Raymond, Guido)

Work is ongoing to tests the possibility of compensating resonances 3Qy=19  and 2Qx+Qy=19 with skew sextupoles installed during the Christmas stop. First results are encouraging indicating a reduction of the losses when injecting close to one of these two resonances. The strength of the compensation has been calculated from the existing PS magnetic model based on the magnetic errors provided by the magnet team.

An optics with large beating and dispersion functions obtained by exciting the gamma jump quadrupole triplets (after injection) has been tested  to verify the possibility of reducing the space charge tune spread by increasing the beam size. The wire scanner beam size measurements conducted so far are not completely consistent with the expectations. Larger than expected beam sizes are observed. This could be due to an incorrect estimation of the momentum spread. This could be done so far with single bunch beams. Losses are observed when the triplets are excited with 50 ns LHC beams. For the single bunch beams no emittance blow-up is observed by comparing the emittance measured before the triplet excitation and after the triplet excitation.

Beam based measurements are being performed with the transverse feedback pick-ups 98 and 02 to compare them with measurements performed during the winter stop with a network analyzer. For the vertical plane there is a mismatch between the measurement without beam and with beam. During next week measurements of the damping time as a function of the chromaticity settings will be performed after correction of the coupling.

ELENA (Christian, Tatiana)

The first cost estimate for the electron cooler made by Toshiba is higher than initially estimated. This should come as an in-kind contribution from Tokio University and they might have difficulty to cover the extra cost. Denmark Institutes got less money than expected for the construction of the main magnets (Danish in-kind contribution). Christian mentioned that RIKEN might be able to cover the extra costs of the magnets. Some preparation work for the transfer line between AD and ELENA should start during LS1 but the study of the line is not yet advanced enough.

Tatiana is working on the estimate of the beam stability. Resistive wall impedance is being considered at present. The Re-wall programme written by Nicolas Mounet is being used for the calculations of the resistive wall impedance. Tatiana is also looking at the thesis work of Diego Quatraro that was considering non-relativistic beams for the estimation of the instability growth rates.

LEIR for Radiobiology (Adriano)

Adriano is still experiencing difficulties with PTC. He is in touch with Massimo Giovannozzi, Cedric during the meeting it was suggested that Adriano should discuss with Hannes and Yannis who went through similar simulations for the PS2.

An alternative is to move back to the solution using the Sextupoles in section 40 for the slow extraction. This was giving straight separatrices. Adriano and Christian noted that the Hardt condition could be relaxed if extraction techniques different not using a variation of the momentum distribution of the beam (betatron core excitation or RF noise) are used.

LEIR (Michael)

The capture process has been optimized and the longitudinal emittance at extraction has been reduced from 11-12 eV.s to 8 eV.s. Larger longitudinal emittances were required in the nominal design because splitting was supposed to take place in the PS. The splitting is not applied at present and therefore lower emittances are preferred. No significant reduction of the losses at low energy has been observed.

Gianluigi asked whether additional measurements of the emittance at injection have been performed reminding the suggestion of Yannis to measure the emittance in the measurement line. Michael replied that these have not been performed yet. Measurements of the extracted beam emittance and Twiss parameters in the ETL line have been tried but this will require steering the line. The measurement of the emittance and Twiss parameters of the beam at injection in LEIR in the ETL line are not yet possible. This should be followed up.

Michael is trying to measure the chromaticity at injection but he had problems to get decent tune and orbit measurements. Gianluigi and Christian suggested to contact the responsible persons in BI (Sob and Jackson). Gianluigi offered to contact Rhodri Jones if the problem persisted (solved after the meeting)

PSB (Elena, Vincenzo)

Machine studies on the effect of the integer resonance are continuing. The losses observed when crossing the Qy=4 resonance seem to be related to the orbit distortion in the vertical plane. It is not yet understood why the orbit distortion in the horizontal plane is smaller when approaching the integer resonance Qx=4. The distribution of the correctors required to correct the orbit distortion should be checked as this could give a hint on the magnetic/alignment error distribution.

Neutrino Studies (Androula, Yannis)

The coupling observed at extraction in the SPS when kicking the beam in the horizontal plane needs to be understood. Simulations with MADX are ongoing.

Yannis is contributing to the preparation of the LAGUNA meeting to be held at DESY at the end of February.

Fanouria is preparing a specification table for the magnets team to start working to a possible model of superconducting magnet for the high energy option for the high power/high energy synchrotron.

SPS (Adrian, Fanouria, Hannes, Yannis)

 Betatronic mismatch at injection in the SPS could not be measured yet as one of the OTR screen in the TT2 line was saturated. The OTR screens in TT10 were not used. It is very important to get another measurement possibly including the TT10 line and the SPS. In the past single bunches with no bunch rotation at PS extraction. If no additional data can be collected the saturated profile could be used by additional post-processing.

Measurements are ongoing with the ion beam at injection in the SPS on the fixed target cycle. No emittance blow-up is observed. The effect of the RF noise is being studied in collaboration with T. Bohl. The Q26 optics is used for the fixed target cycle and the fractional horizontal tune is in that case larger than 0.5 to allow the slow extraction.

Hannes has been working to the preparation of the beam for the LHC Van der Meer scans. Most of the tails observed on this beam are due to the finite rise time of the injection kicker resulting in a large kick imparted to some of the bunches. The oscillations are not damped as the transverse feedback has not been switched on for this cycle. For the time being 50% more intensity is provided by PSB-PS and aggressive scraping applied.

SPS closed orbit review: a reference orbit will be saved and the orbit corrected towards the reference in particular in the extraction region by using the LSS4 and LSS6 extraction bumpers.

SPS scraping review. The present system with a graphite scraper in LSS1 seems to be satisfactory. A resistance test will be done at the end of the run by hitting the scraper blade with a nominal LHC beam. After the test the scraper will be inspected during the shut-down to assess potential damage.

Yannis was teaching at JUAS last week (linear and non-linear imperfections). Guido has given a course on MADX in the week starting 14/1.

From Cedric (by  e-mail): Good progress with the new extraction bump scheme. The extracted beam has been sent to the SPS and it is planned to send it to the LHC. Restarted the work on the "hybrid" MTE extraction scheme which should continue until the end of the run. 

 

Next meeting

Monday, 11th February 2013 at 14:00 in room 6-R-012

Agenda:

to be defined

 

 

 

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