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15th HiLumi WP2 Task Leader Meeting
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Europe/Zurich
6/R-018 (CERN)
Minutes of the 15th WP2 Task Leader Meeting held on 03/09/2013
Present: G. Arduini, O. Brüning, R. De Maria, P. Fessia, M. Fitterer, M. Giovannozzi, R. Kersevan, G. Sabbi, A. Valishev, A. Wolski
Minutes of the last meeting and follow-up of actions
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The minutes have been approved without changes
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Gianluigi has contacted M. Guinchard concerning possible measurements of triplet movement as he had already conducted measurements in the frame of the hump searches in 2011. M. Guinchard has not yet replied. Action: Gianluigi
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Riccardo has contacted Luigi concerning the radiation to the crab cavities. Luigi is going to estimate the expected levels and discuss them with Rama et al.
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Gianluigi has contacted Francesco and Helmut. Helmut will follow up the possible design of a movable TAN.
Review of PIC Scenarios (Gianluigi)
Gianluigi presented a review of the RLIUP-PIC scenarios. He presented the LIU beam parameters proposed for all the RLIUP scenarios as proposed by the LIU team.
Few options for the filling scheme with BCMS were presented corresponding to different ratios of the colliding pairs in IP2 and 8 w.r.t. IP1/5. Oliver pointed out that the most conservative should be taken for the RLIUP estimates for IP1/5 and that the exact sharing of the colliding bunches should be in the hand of the physics coordinators. Riccardo noted that it might be worth considering also the standard PS production method as this gives approximately 10% more bunches and the larger emittance of these beams could lead to longer IBS lifetime. Action: Gianluigi to distribute the relevant information from the tables provided by G. Rumolo.
Gianluigi proposed to reduce the estimated luminosity by 2021 to 300 fb-1 because the values of 400 fb-1 cannot be achieved realistically in the considered period. Paolo observed that the radiation damage limit that justifies the PIC could be then further postponed.
Gianluigi reminded the proposed hardware changes for PIC and the expected performance with and without pile-up. It was agreed to rank the scenarios by the so-called “Machine availability for successful fills" i.e. the ratio between the target luminosity and the integrated luminosity of an ideal sequence of fills. This should be calculated both assuming a fill duration (=stable beams time) of 6 hours and for an optimum fill length maximizing the integrated luminosity provide that the fill length do not exceed 12 hours. The estimated minimum turn-around time is 3 hours. Using this definition the “Machine availability for successful fills” in 2012 was 50%.
Gianluigi concluded that the performance goal were meat if the pile-up limit was set to 140 events per crossing both for a round (30/30 cm) and flat (40/20 cm) optics. Note: after the meeting Gianluigi noted after the meeting that there was an error in the numbers reported in the table for the pile-up limit of 140 although the conclusions do not change. The slides have been corrected.
Review of US1 Scenarios (Oliver)
Oliver presented a selection of scenarios for US1. The luminosity goal for US1 can be reached (marginally) only for a flat optics (40/10 cm) that might require modifications of the matching section. However a much more comfortable scenarios is obtained by assuming that the SPS power upgrade would take place for US1 that would have the additional advantage of speeding up the scrubbing process). The PSB energy upgrade would not be required at that stage. In that case a solution with flat optics 40/20 cm could be also considered. All these cases assume that the beam-beam separation can be reduced to 10 sigma by operating the BBLR.
Optics and layout scenarios for PIC, US1 (Miriam, Riccardo).
Miriam and Riccardo presented the results of the validation of the optics scenarios proposed for PIC and US1. A new optics based on ATS and layout was built by taking the US2 triplet and D1 coupled with the present LHC layout.
After an optimization of the crossing scheme aperture margins were calculated using different methods. In conclusion TAN is the first aperture bottleneck followed by D2, Q4 and Q5. Flat optics are limited by the beta* in the non-crossing plane. 30cm are reachable without hardware changes, 20cm are reachable even without replacing the TAN, which is 4 sigma smaller than the surrounding elements, assuming that D2, Q4, Q5 could be protected by TCTs. Beta* reach could improve and reaching 10cm by replacing the TAN, re-orienting selected beam screens (if compatible at injection as well) and removing the optics limitation in IR6 (and possibly adding a sextupole in Q10) which limits the ATS squeeze. Action: Riccardo, Miriam, review injection optics and IR6 ATS optics limitations.
Gianluigi and Riccardo will summarize a limited number of possible scenarios for PIC/US1/US2 for the nest RLIUP preparation meeting on Wednesday 11/9. These will be then distributed to the WP2/5/10 members for further analysis concerning:
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Aperture
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Strength/correctability limitations
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Collimation settings
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Impedance
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Energy deposition
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Electron cloud effects
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Beam-beam aspects
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Cryogenics limits
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Action: Gianluigi, Riccardo
Reported by: Gianluigi and Riccardo
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