Minutes of the LIS Section meeting held on 12^th August 2013

Present: Javier Alabau, Androula Alekou, Fanouria Antoniou, Gianluigi Arduini, Elena Benedetto, Michael Bodendorfer, Adriano Garonna, Cedric Hernalsteens, Alexander Huschauer, Meghan McAteer, Guido Sterbini, Raymond Wasef

General Information (Gianluigi)

Gianluigi reminded that all the Doctoral Thesis should be published in the CERN THESIS collection.

There has been a significant increase in the number of thefts. Gianluigi reminded to carry the necessary documentation to transport CERN equipment including laptops.

A new post is going to be published soon on CLIC/Injector Space charge studies.

The LHC splice consolidation is progressing on schedule so far. The larger fraction of non-conform splices observed so far will be repaired in the initially scheduled amount of time by increasing the required manpower.

Gianluigi will be absent from Thu 15/8 afternoon until Friday 23/8 included.

Status of HP-PS studies (Javier) - slides

The LINAC4 will operate at a maximum repetition rate of 2 Hz, while at present the PS Booster is operated at a repetition rate of less than 1 Hz. The unused LINAC4 pulses could be used to feed a synchrotron to deliver high power beams to the CN2PY target for neutrino physics.

The High Power Proton Synchrotron (HP-PS) has a lattice with three-fold symmetry. The proposed optics solution is similar to that developed for the PS2 with a negative momentum compaction factor. The tunability in the horizontal plane is guaranteed by the elements in the long straight sections as the optics in the arcs is constrained by the condition to get the negative momentum compaction.

Two solutions have been considered: one with an extraction energy of 50 GeV and a second with an extraction energy of 75 GeV both solutions are based on superferric magnets but while the dipole magnets needed for the lower energy have characteristics similar to those conceived for PS2 the magnets for the 75 GeV solution are extremely challenging because of the specified ramp rate.

The emittance of the beam has been defined by considering a maximum space charge tune spread of 0.2 calculated in the conservative case of a Gaussian distribution. Transverse painting and longitudinally flat bunches could be considered to reduce the space charge tune spread. The physical aperture of the magnets has been derived accordingly.

A first estimate of the dynamic aperture for realistic errors (similar to those estimated for the PS2) has been provided and it appears to be well beyond the mechanical aperture of the magnets and well beyond the aperture defined by the collimation system which, in its preliminary design, should limit the aperture down to 2.5 sigmas.

Preliminary estimates seem to indicate that the TMCI threshold might be limit at high energy. Gianluigi suggested to review the longitudinal parameters both in terms of longitudinal emittance and RF voltage. Longitudinal emittance blow-up and RF voltage increase (to increase the synchrotron frequency at flat top) could help in increasing the TMCI threshold at high energy. Otherwise the absolute value of the transition energy might have to be reduced.

Round table (all):

Neutrino activities (Androula, Fanouria)

Androula  is discussing with Javier Barranco for the use of the post-processing of the SIXTRACK data for determining the loss distribution and optimize the collimation system.

Fanouria is performing a Frequency Map Analysis to determine possible harmful resonances.

PS (Alexander, Cedric, Guido, Raymond)

Cedric is presently finalizing a paper on MTE he should then continue his work on the dummy septum with FLUKA simulations taking over the work from Sanja on the radiation expected in the area.

Alexander is analyzing the frequency of the transverse motion of different longitudinal slices of the TOF beam which is getting unstable at injection. The fit of the motion of the first few tens of turns (to be compared with the synchrotron period of 500 turns) indicate a different frequency of oscillation of the central slice as compared to the tails. A different behaviour is observed for the LHC beam.

Raymond is studying the possibility of compensating the 4th order resonance excited by space charge with octupoles. Possible settings have been found and the effect on dynamic aperture is being considered.

Guido has conducted some measurements on the response of the transverse damper amplifier in collaboration with A.Blas with the aim of characterizing the amplifier before replacing it with an upgraded one. The measurements confirm that the amplifier cannot be used in saturation (as expected) and the input signal is clamped digitally at the level of the ADC.

BIO-LEIR (Adriano)

Adriano has defined a set of realistic parameters for the maximum expected closed orbit distortion and momentum offset at top energy in collaboration with Christian and Michael based on the presence LEIR performance.

The Hardt condition at extraction imposes running with positive chromaticity. This could lead to instabilities and the threshold for those should be determined.

Adriano is converging towards a solution for the BIO-LEIR extraction based on an electrostatic septum (the old LEIR electrostatic septum used for antiproton extraction) and two magnetic septa (a spare LEIR injection septum and a new magnetic septum to be build). This would allow the extraction of beams up to the highest LEIR energy.

PSB (Meghan)

Meghan has determined the minimum excitation kicks required to measure resonant driving terms in the PS Booster. She will discuss with the equipment experts to see whether this can be achieved with the available equipment.

LEIR (Michael)

The replacement of the LEIR electron cooler collector is ongoing

Michael cannot yet launch ORBIT-PTC simulations as he has not yet the rights. Elena suggested to contact Andrea Latina

Monday, 26^th August 2013 at 14:00 in room 6-R-012

Agenda:

General information (Gianluigi)

 Summary of the wire scanner studies in the PS (Guido)

Round Table (all)

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