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9th HiLumi WP2 Task Leader Meeting
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Europe/Zurich
6/R-018 (CERN)
Minutes of the 9th WP2 Task Leader Meeting held on 06/06/2013
Present: G. Arduini, R. De Maria, M. Giovannozzi, R. Kersevan, E. Métral, T. Pieloni, A. Valishev, A. Wolski
Minutes of the previous meeting and follow-up of actions
Presentation on beam screen impedance by the end of June (Action: N. Mounet 25/6 or 2/7). Questions to be answered:
Gianluigi has discussed with Ezio. For the fringe field estimations the triplet quadrupole magnets can be considered independent as assumed so far. There is no interference among the quadrupoles.
Alexander asked whether Gianluigi got the information on the RF multipoles from Maria Navarro Tapia. Gianluigi replied in the negative and will reiterate the request. Action: Gianluigi.
The non-linear effects of fringe fields needs to be assessed in simulations as well as the effect of crab-cavities. Massimo commented that first results are expected by September.
Alexander Valishev asked for clarifications on the status of the Weak-Strong simulations and 6D lens benchmarking. Tatiana pointed out that most of the previous simulations have been done with the flag for 6D lens not active and she noted that very preliminary simulations seem to indicate that differences are observed between 4D and 6D lens simulations at b*=10 cm. At 15 cm there is a small difference but not as evident as at 15 cm. Gianluigi asked Tatiana and/or Alexander to give a presentation on the status of the weak-strong simulations by the end of the month or beginning of July. Tentatively scheduled for 2/7. Action: Alexander, Tatiana. The presentation should cover:
Andy Wolski asked what are the observables against which specifications for the accuracy, reproducibility, stability and resolution of the power converters for the new elements should be reviewed. Massimo and Gianluigi replied: tune reproducibility and tune ripple amplitude and frequencies.
Report from meetings (Gianluigi)
WP4 High Harmonic RF meeting (indico: http://indico.cern.ch/conferenceDisplay.py?confId=254151)
Operation at high intensity will imply a modulation in the RF cavity phase due to the power limits. This implies that Crab Cavities and High Harmonic RF (HHRF) system phases will have to follow this (deterministic) modulation. The present location of the HHRF system is at the position of the 200 MHz capture system. Need to keep contact with WP4 to make sure that aperture and location are consistent with optics model.
While it is expected that HHRF (operated in bunch lengthening mode) will have a positive impact on longitudinal beam stability and the effect on beam induced RF heating has been evaluated by B. Slavant (https://espace.cern.ch/lhc-machine-committee/Presentations/1/lmc_152/lmc_152c.pdf ) it is not yet clear whether this is the case for transverse stability. It is important to answer this question before going much further in the design of this RF system. Action: E. Métral to assess transverse stability in the presence of an HHRF system.
JointWP2-WP3 meeting (https://espace.cern.ch/HiLumi/WP3/SitePages/Minutes%20and%20Presentations.aspx )
Estimates of the radiation produced by the collision debris indicate that the D1 aperture can be reduced from 160 to 150 mm at constant beam screen size. Agreed by WP2 provided that there is not a deterioration of the radiation levels downstream (crab-cavities, Q4, D2).
It is important to evaluate the means of increasing the effective aperture at Q2, Q3 by:
Gianluigi asked what were the considerations for the definition of the position and number of the BPMs in the triplet area. Action: Massimo and Tatiana to follow-up on that
Roberto mentioned that there was a suggestion (S. Fartoukh) to reduce the beam screen thickness possibly avoiding the co-lamination with copper. This will be addressed in the presentation of N. Mounet.
HL-LHC v1.0 optics (Riccardo)
The following additional features since the talk in November at the Frascati workshop were presented.
Apertures: a plot quantifying and clarify the position of bottlenecks in sigma and physical size is required (e.g. to get an idea of the margin in the reduction of the aperture at Q1). Action: Riccardo.
Present: G. Arduini, R. De Maria, M. Giovannozzi, R. Kersevan, E. Métral, T. Pieloni, A. Valishev, A. Wolski
Minutes of the previous meeting and follow-up of actions
Presentation on beam screen impedance by the end of June (Action: N. Mounet 25/6 or 2/7). Questions to be answered:
- Contribution to impedance and heat load for the beam screens in the triplets
- Specification for the tapering between sections of different cross-sections: is 15 degrees reasonable?
- Can we reduce the beam screen thickness and avoid co-laminating stainless steel and copper.
- Impact of a-C coating on impedance
Gianluigi has discussed with Ezio. For the fringe field estimations the triplet quadrupole magnets can be considered independent as assumed so far. There is no interference among the quadrupoles.
Alexander asked whether Gianluigi got the information on the RF multipoles from Maria Navarro Tapia. Gianluigi replied in the negative and will reiterate the request. Action: Gianluigi.
The non-linear effects of fringe fields needs to be assessed in simulations as well as the effect of crab-cavities. Massimo commented that first results are expected by September.
Alexander Valishev asked for clarifications on the status of the Weak-Strong simulations and 6D lens benchmarking. Tatiana pointed out that most of the previous simulations have been done with the flag for 6D lens not active and she noted that very preliminary simulations seem to indicate that differences are observed between 4D and 6D lens simulations at b*=10 cm. At 15 cm there is a small difference but not as evident as at 15 cm. Gianluigi asked Tatiana and/or Alexander to give a presentation on the status of the weak-strong simulations by the end of the month or beginning of July. Tentatively scheduled for 2/7. Action: Alexander, Tatiana. The presentation should cover:
- Status of the benchmarking Lifetrack-SixTrack
- 6D lens: status of the verification of the model
- Summary of the results
- Next steps
- Required input
Andy Wolski asked what are the observables against which specifications for the accuracy, reproducibility, stability and resolution of the power converters for the new elements should be reviewed. Massimo and Gianluigi replied: tune reproducibility and tune ripple amplitude and frequencies.
Report from meetings (Gianluigi)
WP4 High Harmonic RF meeting (indico: http://indico.cern.ch/conferenceDisplay.py?confId=254151)
Operation at high intensity will imply a modulation in the RF cavity phase due to the power limits. This implies that Crab Cavities and High Harmonic RF (HHRF) system phases will have to follow this (deterministic) modulation. The present location of the HHRF system is at the position of the 200 MHz capture system. Need to keep contact with WP4 to make sure that aperture and location are consistent with optics model.
While it is expected that HHRF (operated in bunch lengthening mode) will have a positive impact on longitudinal beam stability and the effect on beam induced RF heating has been evaluated by B. Slavant (https://espace.cern.ch/lhc-machine-committee/Presentations/1/lmc_152/lmc_152c.pdf ) it is not yet clear whether this is the case for transverse stability. It is important to answer this question before going much further in the design of this RF system. Action: E. Métral to assess transverse stability in the presence of an HHRF system.
JointWP2-WP3 meeting (https://espace.cern.ch/HiLumi/WP3/SitePages/Minutes%20and%20Presentations.aspx )
Estimates of the radiation produced by the collision debris indicate that the D1 aperture can be reduced from 160 to 150 mm at constant beam screen size. Agreed by WP2 provided that there is not a deterioration of the radiation levels downstream (crab-cavities, Q4, D2).
It is important to evaluate the means of increasing the effective aperture at Q2, Q3 by:
- Reducing nominal sizes and tolerance control of the beam-screen/shielding/cold-bore package. R. Kersevan to provide a Table of the various components (nominal dimensions and tolerances). Action: Roberto.
- Optimizing the shielding size. Can this be done without exceeding the 20 MGy/3000 fb-1 limit? Can we increase further the shielding thickness at Q1 if this has a positive effect on the radiation downstream such that the shielding at Q2 and Q3 could be reduced? Action: Riccardo.
Gianluigi asked what were the considerations for the definition of the position and number of the BPMs in the triplet area. Action: Massimo and Tatiana to follow-up on that
Roberto mentioned that there was a suggestion (S. Fartoukh) to reduce the beam screen thickness possibly avoiding the co-lamination with copper. This will be addressed in the presentation of N. Mounet.
HL-LHC v1.0 optics (Riccardo)
The following additional features since the talk in November at the Frascati workshop were presented.
- A new 3m injection optics. This should be kept as a back-up solution. Effort should now be put in the validation of the baseline optics and its transitions from injection to collision at 15 cm.
- The integration of the fringe field (linear effect) can be plugged in as an additional component (provide) but it is not included in the baseline optics.
- Tracking tools for the evaluation of the beam-beam long range footprints in thick optics are going to be provided in MADX, in parallel with thin lens models will be provided for SixTrack simulations.
Apertures: a plot quantifying and clarify the position of bottlenecks in sigma and physical size is required (e.g. to get an idea of the margin in the reduction of the aperture at Q1). Action: Riccardo.
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