Minutes of the LIS Section meeting held on 17th September 2012

Present: Androula Alekou, Gianluigi Arduini, Michael Bodendorfer, Christian Carli, Adriano Garonna, Michel Martini, Meghan McAteer, Yannis Papaphilippou, Guido Sterbini, Adrian Ulsroed, Raymond Wasef, Cedric Hernalsteens

General Information (Gianluigi)

The next specialized CERN Accelerator School “Superconductivity for Accelerators” will be held in Erice, Italy, from 24 April - 4 May, 2013. Interested candidates should contact Gianluigi by tomorrow Tue 18/9 morning. It must be noted that the Advanced Course in Accelerator Physics will take place in fall and the it will not be possible to attend both courses.

 

Haixin Huang, group leader of the Brookhaven National Laboratory Booster is going to visit CERN from 15 to 26/10. He will give a seminar on high intensity operation of the PS Booster and AGS on 18/10 afternoon. He will also be ready to discuss issues related to H- injection.

 

LHC: almost 15 pb-1 have been accumulated in proton-proton physics. Proton-Lead collisions have been achieved successfully. High beta star optics (1 km) has been set-up.

 

The Evian meeting will take place from 17 to 20/12. This will include the following sessions:

 

Round Table (all)

Q20 optics (Yannis)

The last SPS MD was dedicated to revisit 50ns with Q20 optics and to have a first look to the 25 ns beam with this optics. Unfortunately a lot of time lost due to LHC frequent filling and to various HW problems. The initial plan to deliver the 50 ns LHC beams with Q20 optics on Thursday was delayed by 2 days due to a vacuum leak on a LHC wire scanner. Extraction and transfer lines were not yet properly tuned and the steering could not be completed. We will restart with the Q20 optics after the technical stop.

Tests of the 100 GeV fast extraction to the north area in the SPS are taking place today.

Plan to revisit extraction and transfer for Q20 in the SPS doing the week and try to get beam to the end of the TI2/8 lines. No longitudinal blow-up will be applied in the SPS as the beam is longitudinally stable in the SPS up to the intensities of 1.5-1.6x1011 p/bunch.

The next SPS MD block will feature Q20 tests with 25 ns beams in preparation of the scrubbing run.

Neutrino - LAGUNA (Yannis, Androula)

Yannis has contributed to the paper of R. Steerenberg to be presented at HB2012. Yannis is going to organize a meeting on the High Power Proton Synchrotron for LAGUNA every second week.

Tests have been made in the SPS to test the possibility to extract protons in LSS2 with the fast extraction kicker in point 6. amplitude and phase dependence on kick strength and bunch intensity have been measured in the range 2.5x1010 p/b to 1011 p/b. No significant dependence has been observed. Gianluigi reminded that detuning is also observed with total intensity and can affect the phase advance between the kicker and the extraction septum.

TT2-TT10 transfer line (Adrian, Cedric)

A new extraction bump from the PS is going to be tested (not using the corrector in 15 that will have to be removed for the installation of the dummy septum in 16). Injection matching and tails will have to be compared with the present scheme and the new scheme. The extraction bump has been rematched to get same amplitude and same angle as the present bump at the extraction point by using 4 independent power supplies that are available. A new application is available for the tuning of the extraction bump.

LEIR (Michael)

The transmission efficiency in the cycle is rather low and losses occur from time to time in the flat-bottom in addition to the losses at the beginning of the ramp. Michael mentioned that an optimization of the electron cooling might be required including the orbit at the electron cooling location. Christian asked what was the value of the transmission efficiency. Michael will look into that. Tune scans have been tried but no significant improvement was observed. The issue with the emit module in MADX(calculation of the gamma transition) has been solved thanks to the help of Cedric. There are sill issues with the space charge simulations with ions, Sasha is aware. Christian mentioned that it should be possible to run these simulation by using proton equivalent parameters opportunely calculated

LEIR for medical applications (Adriano)

Slow extraction has been modelled. For both optics configurations considered for LEIR (antiproton and ion optics) the required strengths of the sextupoles for correcting the chromaticity and exciting the third resonance are exceeding the maximum current level. Christian suggested to investigate the possibility of using pole face windings in addition. These correction circuits are installed in low dispersion areas and could be used for resonance excitation. The present values of the magnetic septum thickness and of the electrostatic septum electric field are 10 mm and 7 MV/m. Gianluigi noted that for the SPS slow extraction the electrostatic septa are operated at fields of ~10 MV/m.

ELENA (Christian)

The inner aperture of the vacuum chamber for the ELENA decelerator has been chosen to be 64 mm. Christian noted that this leaves some margin to account for tolerances (orbit control, alignment, etc.) but not a lot.

PS (Guido)

The transverse feedback has been tested on the TOF and LHC cycle as well as on a MD cycle used for space charge studies by Raymond. The feedback is in operation for the TOF cycle allowing to reduce the sensitivity to cycle composition (in terms of losses). For the LHC beam the damper has been tested at high energy as well in a dedicated cycle with a long 26 GeV plateau to study the effectiveness in damping the horizontal instability observed when the bunches are kept bunched by the 40 MHz system. It has been shown that it is possible to delay the start of the instability and reduce the emittance blow-up at the end of the flat-top. It must be noted that the damper is not yet designed to operate at full power (3 kW) for more than 2 ms and this can explain why the instability is delayed and the emittance blow-up at the end of the plateau cannot be suppressed. Measurements of the emittance should be done earlier on the cycle when the damper is still active at full power. No optimization of the gain has been attempted yet.

The study conducted in the PS to determine the optimum operating range for the wire scanners has been applied to the PS Booster and the resulting guidelines are applied in operation.

PSB Space Charge studies (Michel)

Michel is running simulations of the injection for the LHC beam with orbit PTC after solving some problems with the definition of the RF phase (likely related to the use of the second harmonic cavity). So far the aperture limitations have not been added as well as no errors. The stripping foil module is not tested yet. Michel mentioned that there are feature which are not fully understood leading to unexplained and non-reproducible crashes of the PTC-ORBIT programme.

PS space charge studies (Raymond)

Raymond is going to study space charge effects by enhancing space charge tune effects by bunch compression

MTE (Cedric and Antoine)

Trapping has been re-established while the preparation for the hybrid extraction are ongoing with the tune and chromaticity compensation during the slow extraction bump rise. Hybrid extraction will be put in stand-by soon to give priority to the capture studies and nominal MTE extraction. Hybrid extraction studies will be resumed at low intensity at the beginning of 2013.

FLUKA simulations have demonstrated a reduction of the losses by a factor 5 on the septum 16 thanks to the dummy septum. A meeting with BI is going to take place to discuss how to overcome the effect of the saturation of the pick-ups in the orbit measurements. A tool has been provided to flag orbit data that are affected by the saturation of the pick-up.

PSB optics characterization (Meghan)

Meghan has started first optics measurements by kick response analysis. During the technical stop 16 orbit correctors will be wired to perform LOCO-type analysis and 3 beam position monitors will be equipped with electronics for turn-by-turn acquisition of the beam position. This should allow starting resonant driving term measurements. Gianluigi suggested Meghan to discuss with Cedric, Antoine and Simone to get their experience with the PS turn-by-turn beam position measurement system as the electronics installed in the PS Booster is the same as that installed in the PS.    

Next meeting

Monday, 8th October 2012 at 14:00 in room 6-R-012

Agenda:

To be defined

 

 

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