Minutes of the LIS Section meeting held on 1^st December 2008

Present: M. Aiba, G. Arduini, J. Barranco, E. Benedetto, O. Berrig, R. Calaga, A. Franchi, S. Gilardoni, M. Martini, E. Métral, Y. Papaphilippou, D. Quatraro, G. Rumolo, B. Salvant, C. Zannini

General Information (Gianluigi)

Gianluigi gave the list of the staff whose participation to PAC09 is approved:

For Elias final approval is pending according to the ABP travel budget 2009 which might be cut.

Students can participate provided they get external funding or a PAC09 grant.

An "Accelerator Complex Controls Renovation" Workshop will take place on 3/12. Supervisors are welcome to participate.

 Status of the collimation studies for PS (Javier) - slides

Following a question form Elias on the number of sigmas that are considered for the aperture (4.5 sigmas) it was felt that a larger value could be safer taken into account of the high intensity operation. This number is based on the PS values (assuming normalized emittances of 15 and 8 um.rad in the horizontal and vertical plane, respectively, which are the values measured for high intensity: ~3.2×10¹³ p/cycle) but it must be noted that the aperture of the PS was defined 50 years ago for operation to lower intensity. Given the expected lifetime of the PS2 it might be worth add some margin in particular in the horizontal plane where the impact on the cost of the magnets might be smaller.

Only betatronic collimation is being designed. Momentum collimation has not been considered yet. The maximum tolerable inefficiency is 33% assuming loss patterns similar to those observed in the PS and that the average energy deposition in the machine should remain below 1 W/m. Collimation for the injection and extraction is going to be studied separately. High intensity operation might require to review the reference value of ! W/m. For the Project X at Fermilab different limits are imposed according to the irradiated material.

The collimation system studied by Javier is not moving during the ramp to accomodate for the adiabatic reduction of the emittance during acceleration. The same approach has been followed at J-PARC. All the losses have been considered to occur at injection energy (4 GeV)

Javier has studied the dependence of the collimation efficiency according to the collimator length and material. Elias suggested to look also at the studies performed for the LHC collimation project (after the meeting he sent some references - see e-mail below):

As promised,

Please find the link to the talk I mentioned this morning: https://lhc-collimation-project.web.cern.ch/lhc-collimation-project/ph2_meeting_files/2nd_meeting_EnergyDep-FC.pdf.

The minutes of this meeting are the following: https://lhc-collimation-project.web.cern.ch/lhc-collimation-project/ph2_meeting_files/simp2_meeting2_minutes.pdf.

Cheers, Elias. 

The effect of beta beating and of orbit errors has been considered. Gianluigi asked whether several seeds have been considered in estimating closed orbit distortions. Javier replied in the negative: only the amplitude of the distortion has been varied. Gianluigi suggested to consider different seeds. Masamitsu suggested also to re-opimize the collimator position for any error scenario as the collimator position and opening can be varied. Gianluigi noted that the results obtained so-far could provide pessimistic information but valid if the considered errors occur dynamically.

It is planned to generate the halo by means of ORBIT and considering space charge effects.

 TMCI  far above the intensity threshold (Elias) - slides

Elias presented some studies he has conducted in order to estimate the growth rate dependence of TMCI far above the intensity threshold. This can happen close to transition where the intensity threshold is decreasing due to the reduction of he synchrotron frequency and it has been triggered by discussions with W. Fischer concerning the instability occurring at transition in RHIC. The formalism developed by Elias foresees a linear dependence of the growth rate on bunch intensity and it is confirmed by MOSES simulations. HEADTAIL Simulations could be performed to provide additional evidence.

Round table (all)

Yannis mentioned that an external review for the PS2 study might take place in spring 2009. Collective effects have not yet been considered. Gianluigi noted that this work should be performed by LARP (U. Wienands) with Giovanni as contact but for the moment nothing has happened.

Masamitsu is continuing the work on the optimization of the injection bump for LINAC4-PSB injection. Adequate choice of the pole face angles allow to reduce the beta beating to ~10 %.

Olav is finalizing the note on the estimate of the inital condition for the East extraction. He is trying to find papers describing the initial conditions for the FT61 line. Michel Martini will try to find additional documentation. Olav communicated that Lau is trying to re-match the FTN line for MERIT operation and he has some difficulties. As initial conditions for this extraction the LHC extraction optics conditions should be taken. Gianluigi suggested to Olav to arrange a meeting with Lau to understand the problems encountered by Lau.

Diego is working on the analysis of the instability data taken in the PSBooster. Gianluigi said that Michel Chanel seems to suspect some of the PSB kickers as the source of the impedance responsible of this instability. Gianluigi suggested to Diego to contact Michel to discuss with him. Elias asked whether the measured impedance of the kickers has been introduced in HEADTAIL to study the corresponding effect on the beam. Diego replied that this has not been done yet.

Rama is trying to analyze the data collected during the SPS MDs on impedance localization in preparation of the impedance meeting organized by Elias for 16/12. A vertical bump created locally at the position of the MKDV induces a small but visible variation of the measured detuning with intensity. Gianluigi asked whether a correspondingly larger phase advance per unit intensity is observed at the location of the bump. Rama will look into that in preparation of the impedance meeting.

Simone communicated that higher radiation levels have been measured in the PS as a result of the CNGS run. AS a result of that the list of magnets to be renovated had to be revised.

Gioavnni gave a brief overview of the Electron Cloud Mitigation Workshop ( http://indico.cern.ch/conferenceDisplay.py?confId=42645 ). Quite some progress has been done in the development of new coatings for reducing the secondary Emission Yield. This activity is based at CERN as well as the experimental activity in the accelerators. F. Caspers has also presented a new idea consisting in using magnetic substrates with magnetization patterns. This should reduce or suppress multipacting in a similar way in which grooves or porosities do that. Unfortunately it seems that this approach cannot be applied in regions with magnetic fields (e.g. in dipoles).

Benoit has looked in detail into the FFT routine used by B. Spataro to generate the impedance spectra from wake field data. The results fo this analysis and the conclusions have been documented in the minutes of the last impedance meeting ( http://sps-impedance.web.cern.ch/sps-impedance/SPSminutes_2008_11_19.htm )

Due to lack of time Elias kindly sent a summary by e-mail:

Dear Gianluigi,

Please find my slides attached.

In addition, what I wanted to say this morning (but it was late) is:

1) SPS BPM interlock system and MOPOS upgrade => Actions for Jorg and Elias:

- A complete list of all possible SPS beams & their parameters (foreseen for the mid-term future) is required before the design of the LogAmp cards can be finalised.

- MOPOS upgrade.

2) Discussion with Oliver Boine-Frankenheim at the CARE_HHH workshop => Possible future collaboration (Who is interested in the section? Subjects? 1-day workshop in February at GSI?)

3) Talk by me at the LCU meeting on 50 ns beam => Questions asked and follow-up to make: Check that the transverse emittances are within 10-20%. How can we do that? Other proposition from Helmut: Try and blow up the different bunches differently to have at the end the same emittances in all the bunches. How can we do that?

4) Meeting Phase 2 Collimator Prototype in SPS in 2009 => Possible installation of another collimator prototype in the SPS.

5) Elena Shaposhnikova informed us that we will coat 3 spare MBB magnets and plan their installation in the test area at following positions: 51490, 51530 and 51550.

Cheers, Elias.

Next meeting

Possibly on the ski slopes ==> Giovanni "volounteered" to organize it.

Agenda to be defined

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