Minutes of the LIS Section meeting held on 6^th September 2010

Present: G. Arduini, H. Bartosik, C. Carli, S. Gilardoni, P. Jackson, A. Lachaize, M. Newman, Y. Papaphilippou

General Information (Gianluigi) 

The Medium Term Plan has been presented to the SPC and to the Finance Committee at the end of August and it has been positively received by the delegations

The accelerator-related projects are being re-organized. The various accelerator-related projects would be grouped into four: high-luminosity LHC (HL-LHC); injector chain upgrade (including the current Linac4, PSB and SPS upgrade projects); injector complex consolidation (including the existing consolidation efforts), and linear collider. The first three would be hosted in the A&T Departments (one each). At the same time, the current Projects’ Office would become a Project-support Office.

The number of bunches has been increased from 25 to 50 and luminosities larger than 10³¹ cm^-2s^-1 have been achieved. Efforts are now directed to set-up the machine with a fast ramp (10 A/s) and for operation with bunch trains with 150 ns spacing.

PS2 MTE (Antoine) - slides

Christian asked why the option of re-matching the whole machine when changing the tune has not been considered. Antoine replied that this was driven by simplicity considerations. Yannis noted that re-matching of the machine is not difficult and Simone added that the it is desirable to keep optical parameters under control (e.g. dispersion) even more taking into account that non-linear elements are excited.

Simone asked whether different initial distributions for the beam have been considered. Antoine replied that only a Gaussian distribution has been considered. Simone suggested to include a study for different distributions to optimize the capture efficiency.

The compatibility of the MTE with the PS2 aperture should be checked as well as the number and characteristics of the bumpers to be used for the extraction bump.

Myriam said that she is looking into aperture issues for CT and MTE for the PS implementing it in A. Franchi's code. It could be interesting to conduct a similar study also for the PS2 MTE.

Yannis and Simone suggested to evaluate and correct non-linear chromaticity and non-linear coupling due to octupoles. Antoine said that the non-linear coupling is already corrected with a second family of octupoles.

Gianluigi suggested to include the study of the effect of the synchrotron energy.

Round Table

Yannis:

• A first experiment to test an new optics with low gamma transition has been done in the SPS in collaboration with Hannes and OP. Only a very first exploration has been possible. A new user is being defined by OP based on the optics provided by Hannes and Yannis. Matching of the injection line should be added. The lower gamma transition might imply larger capture voltages for the LHC beam in the SPS but also it might imply  larger voltages at extraction in the SPS to obtain short enough bunches before transfer to the LHC.
• A meeting took place to define the PS2 RF maximum voltage. It has been decided to fix it at 1.5 MV. According to E. Shaposhnikova this is twice higher than what probably required.

Hannes:

Working on the evaluation of the dynamic aperture of the PS2 for given magnetic errors (taken from J-PARC and FNAL. Only rough estimates have been given by the magnet team.). A large impact on the dynamic aperture has been observed when these errors are included. The dynamic aperture is shrinking down to 6 sigmas in the H plane. The results are presently being checked. Gianluigi suggested to determine limits for the magnetic errors to have an aperture larger than the physical aperture.

Yannis said that he was aiming to have a dynamic aperture a factor two larger  than the physical aperture.

There is a problem with the release of the last version or MADX/PTC. The previous version contained a bug not allowing a proper definition of the magnetic errors.

MADX PTC should be the right tool to low energy machines. Gianluigi will discuss about that with Massimo.

Christian suggested to compare the PTC results with SIXTRACK as it seems that the dynamic aperture reduction is not due to fringe fields. Yannis said that for the moment they are comparing results of simplified models with analytical formulas

Christian

• LEIR: Machine working well. The nominal beam has been delivered but the emittance cannot be measured due to a problem with the electronics of one of the SEM grids in the extraction line. This has not been fixed during the technical stop by BI although requested by Christian.
• A student from the UK is working with Christian on the possible uses of LEIR ion beams in radiobiology. Christian is presently explaining what are the possibilities in terms of beams and to understand what are the requirements. The source and LINAC3 experts will be involved.
• The information on the requirements for the ions beam intensities for the SPS fixed target experiments is still missing.
• PS Booster. Christian agreed with Klaus that they will have a discussion with PO to understand what are the present limitations on the power converter side for the PSB energy upgrade.

Myriam:

She is studying of the effect of different parameters on capture efficiency and losses

Simone:

Calculations on possible operation of MTE with the electrostatic septum 31 in parallel to CT are ongoing. This will require the polarity reversal of KFA 21. It will be proposed to implement this inversion in the last 2 weeks of the run and to run like that for 2 weeks.

Fluctuations of the losses are still visible but settings have been found that allow to operate the machine at an AVERAGE capture efficiency of 20 %. It has been seen that the frequency pattern of the losses is not equal to that for the of the fluctuations of capture efficiency

UA9 crystal collimation experiment: channeling has been studied with all the crystals installed and the suppression of the nuclear interaction when in channeling has been studied. 8 hours were lost due to LHC set-up. Thanks to the installation of scintillators in the dispersion suppressor the suppression of the nuclear interactions when the crystal is aligned for channeling can be observed. Simone has proposed to conduct an MD with ions during the LHC ion running.

Measuring the suppression of nuclear interactions of the ions channeled in a crystal is very important.

There are still problems with the instrumentation in the PS: wire scanner, orbit are not working. The calibration of the ring DCCTs has been performed by BI in the PSB and PS. Additional BLMs have been installed in the PS in critical areas where losses are observed. Both SLAC BLMS (scintillator with phototube) and LHC SEM have been installed.

Outcome of the meeting on PS Complex BLMs: more tests are required and help from BI is required to analyze the data. Test BLMs will be installed in the PS-Booster. Due to their size the LHC BLMs are not adapted to the PSB as thy would not allow disentangling losses in the different rings. Christian noted that this requirement is very important although he thinks that turn-by-turn resolution is not strictly necessary.

Next meeting

Monday, 20^th September 2010 at 14:00 in room 354-1-001

Tentative agenda

• General information (Gianluigi)
• Round table (all)

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