Update on impedance activities for HLLHC Benoit Salvant

Update on impedance activities for HL-LHC Benoit Salvant, Mike Barnes, Nicolo Biancacci, Branko Kosta Popovic, Adnan Kurtulus, Inigo Lamas Garcia, Elias Metral, Jamie Mitchell, Lorenzo Teofili, Vasileios Vlachodimitropoulos, Christine Vollinger, Carlo Zannini and the (Amorim, Antipov, Arsenyev)

Activities • [MKI already covered by Mike Barnes’s talk] • New collimators • • TCPPM TCSPM TCLD TDIS • Crab cavities • New IR • beam screens • New BPMs • Triplet deformable RF fingers • Y chambers • VELO and SMOG 2 • New requests for exotic installations for HL-LHC era • Forward physics in IR 5 • Fixed target experiments in ALICE (and apparently also LHCb) • Wire compensation outside of collimator

Vasileios Vlachodimitropoulos

Transverse impedance MKI: Dipolar X • 4 modes up to 50 MHz • Above 50 MHz their amplitude is significantly lower Vasileios Vlachodimitropoulos 05/02/2022 24 th IWG meeting 5

Transverse impedance MKI: Dipolar Y • 2 modes up to 50 MHz • Above 50 MHz their amplitude is significantly lower Vasileios Vlachodimitropoulos 05/02/2022 24 th IWG meeting 6

Transverse impedance MKI: Comparison with measurements • Good agreement in resonating frequencies – measurements predict a few MHz higher than simulations • Qualitative agreement in amplitude – discrepancies due to fitting, losses in materials, simulation inaccuracies Vasileios with the help of Fritz 05/02/2022 24 th IWG meeting 7

Activities • New collimators • • TCPPM TCSPM TCLD TDIS • Crab cavities • New IR • beam screens • New BPMs • Triplet deformable RF fingers • Y chambers • VELO and SMOG 2 • New requests for exotic installations for HL-LHC era • Forward physics in IR 5 • Fixed target experiments in ALICE (and apparently also LHCb) • Wire compensation outside of collimator

New collimators • Impedance aspects heavily addressed (obviously) at the HL collimation review. Elias et al • Discrepancy between expectations and measurements for current collimators are of the order of 20 to 60% for the IR 7 tune shift for all beams all planes. However discrepancy much larger for single collimators (up to factor 3). David et al • Coating on TCSPM (Adnan, Nicolo, Fritz et al). : Specifications for Mo Coated Mo. Gr blocks for TCSPMs to be installed in LS 2 were finalized DTI was validated for coating and their process turns out to give larger conductivity than CERN Blocks are being procured and first batch was validated Baseline is Mo coating on Mo. Gr for all TCSPMs, but new promising results of DTI Mo coating on graphite could change the picture? (Col. USM 22/03/2019). • Studies of impact of roughness and damage ongoing. • Following the homogeneity among blocks and between blocks and samples in the first batch, the IWG recommendation is to not measure any block in the next batch, unless measurements on samples are worrying (IWG#31). • • • TCLD and 11 T/connection cryostat were looked in a lot of detail and no harmful impedance contribution was identified (Lorenzo, IWG#31). • TDIS: recent request to put NEG coating instead of copper coating on TDIS transitions was approved at IWG#31.

Activities • New collimators • • TCPPM TCSPM TCLD TDIS • Crab cavities • New IR • beam screens • New BPMs • Triplet deformable RF fingers • Y chambers • VELO and SMOG 2 • New requests for exotic installations for HL-LHC era • Forward physics in IR 5 • Fixed target experiments in ALICE (and apparently also LHCb) • Wire compensation outside of collimator

Crab cavities • No particular news since last talk by Jamie and Sergey (https: //indico. cern. ch/event/788818/ ) • Very likely that remaining worrying horizontal modes for DQW are “driving/dipolar” modes, since longitudinal impedance is very small for those. f [MHz] Qe 1500. 18 1754. 364 1921. 985 Zv [Ohms/m] Zh [Ohms/m] Zl [Ohms] 28200. 36 3994. 96173 2008757 8788. 596 507. 6603013 750724. 1 58162. 86 12210. 03847 2504533 32 1 47

Activities • New collimators • • TCPPM TCSPM TCLD TDIS • Crab cavities • New IR • beam screens • New BPMs • Triplet deformable RF fingers • Y chambers • VELO and SMOG 2 • New requests for exotic installations for HL-LHC era • Forward physics in IR 5 • Fixed target experiments in ALICE (and apparently also LHCb) • Wire compensation outside of collimator

New IRs • Beam screen : • Request to increase horizontal aperture by 1. 5 mm on each side of the 120 mm full aperture beam screen. • Very recent request of EN-MME/TE-VSC to avoid randomization of pumping hole size and/or hole inter-distance to potentially reduce cost of manufacturing.

Request to increase H aperture of end of D 1 beam screen • 1. 5 mm increase in the horizontal plane out of 60 mm radius. • No cavity created as beam screen aperture continues to increase afterwards • For such a small step so far from the beam, taper does not seem justified, but IWG recommends rounding the inner edge

New IRs • Beam screen : • Request to increase horizontal aperture by 1. 5 mm on each side of the 120 mm full aperture beam screen. • Very recent request of EN-MME/TE-VSC to avoid randomization of pumping hole size and/or hole inter-distance to potentially reduce cost of manufacturing.

Model for traveling wave method Actual Q 1 beamscreen Little details almost impossible to simulate Model 8 mm-long holes spaced by 16 mm Period length = 24 mm 16

Non-randomization of pumping holes • Transverse impedance seems ok Sergey Arsenyev

Non-Randomization of pumping holes Z hole half hole no hole Z/n for 240 mm Z/n for 1 m Z/n for 232 m [Ohm] [m. Ohm] 0. 00052 3. 29 E-08 1. 37 E-07 0. 032 0. 00026 1. 64 E-08 6. 84 E-08 0. 016 2. 00 E-06 1. 26 E-10 5. 26 E-10 0. 000 (Assuming all apertures as Q 1) Longitudinal impedance seems also ok from these simulations Need to study impact of holes size and distance in more details to conclude

Activities • New collimators • • TCPPM TCSPM TCLD TDIS • Crab cavities • New IR • beam screens • New BPMs • Triplet deformable RF fingers • Y chambers • VELO and SMOG 2 • New requests for exotic installations for HL-LHC era • Forward physics in IR 5 • Fixed target experiments in ALICE (and apparently also LHCb) • Wire compensation outside of collimator

Triplet BPM Impedance (Adnan and Nicolo) • Accounts for analytical estimations only at the moment (K. Y. Ng formula). • 3 D models received and being simulated by Adnan. Budget/IP Zx~Zy: 56 k. Ohm/m Zl : 0. 039 m. Ohm Slight increase (20%) of impedance (closer striplines). Still acceptable: 100 k. Ohm/m in transverse (w. r. t total 20 MΩ/m), 0. 08 m. Ohm in longitudinal (w. r. t. total 93 m. Ohm). Refinement ongoing (CST models), and models anyway not fully final

Triplet deformable fingers • Measurements performed by Christine Vollinger et al last week • No mode measured below 2 GHz good news! • Analysis ongoing and will be reported soon.

Activities • New collimators • • TCPPM TCSPM TCLD TDIS • Crab cavities • New IR • beam screens • New BPMs • Triplet deformable RF fingers • Y chambers • VELO and SMOG 2 • New requests for exotic installations for HL-LHC era • Forward physics in IR 5 • Fixed target experiments in ALICE (and apparently also LHCb) • Wire compensation outside of collimator

Y chambers • Model for IR 2 simulated One mode below cut-off (due to the small radius increase before the Y chamber) Otherwise very close to the ideal case of a transition replacing the Y chamber in all contributions

Activities • New collimators • • TCPPM TCSPM TCLD TDIS • Crab cavities • New IR • beam screens • New BPMs • Triplet deformable RF fingers • Y chambers • VELO and SMOG 2 • New requests for exotic installations for HL-LHC era • Forward physics in IR 5 • Fixed target experiments in ALICE (and apparently also LHCb) • Wire compensation outside of collimator

VELO and SMOG 2 Branko, Christine et al • Heat load evaluated and localized to the SMOG 2 cell (see IWG#31) Courtesy B. Popovic et al 14 W for single beam to SMOG 2 Could be up to 14*4~50 W for 2 circulating beams It will be specified in the ECR that the SMOG 2 cell should withhold at least 50 W with appropriate margin

Activities • New collimators • • TCPPM TCSPM TCLD TDIS • Crab cavities • New IR • beam screens • New BPMs • Triplet deformable RF fingers • Y chambers • VELO and SMOG 2 • New requests for exotic installations for HL-LHC era • Forward physics in IR 5 • Fixed target experiments in ALICE (and apparently also LHCb) • Wire compensation outside of collimator

System studied in ALICE • Requires a crystal in the halo 72 m upstream of the IP… • … and a target at ~8 mm for the beam a couple of m from the IP Very invasive system from impedance point of view (even more for vacuum in fact) There are two beams at these locations not clear that it can be allowed with high intensity beams

• Apparently similar system planned in LHCb…

Next steps • Continue the validation of the Mo coated batches • lot of effort is devoted to compare all the LHC tune shift measurements with py. HEADTAIL simulations (David Amorim) • If needed by EN-MME, more simulations on the randomization of the holes • Complete the analysis of the BPM • Simulate current Y chamber in IR 8 • Include the MKI in the transverse impedance model for HL-LHC simulations (case cool and not cool) • Continue to follow up and guide the “exotic ideas” • New electron lens model is expected soon

Proposal to increase D 1 H aperture by 1. 5 mm

Update D 1 B. S. R. De Maria Thanks C. Garion, J. Hansen Integration meeting 15/2/2019

New D 1 B. S. C. Garion, 13/2/2019 Design criteria: All apertures should be in the shadow of the triplets by >0. 5 σ, ideally. Aperture [σ] Round Optics Flat optics Triplet 13. 1 12. 7 D 1 Magnet 13. 9 (+0. 8) 13. 0 (+0. 3) D 1 BS 81826 13. 5 (+0. 4) 12. 7 (0) New BS 82386 13. 8 (+0. 7) 12. 9 (+0. 2) D 1 BS 82386 13. 3 (+0. 2) 12. 5 (-0. 2) Increased aperture restores aperture hierarchy by ~0. 5 σ

• 1. 5 mm increase in the horizontal plane out of 60 mm radius. • No cavity created as beam screen continues to increase after that • Only question is whether a taper would be required • For such a small step so far from the beam, it does not seem justified

ECRs • TCLD/11 T/connection cryostat ok? See Lorenzo’s talk • SMOG 2 ok, with the potential 50 W to be highlighted there. • TDIS (suite à la modification des transitions) impact on impedance to remove copper and put NEG on transitions is considered acceptable.

Triplet BPMs A. Kurtulus, N. Biancacci, M. Krupa Acknowledgements: R. De Maria

IR 1/5 optics • HLLHCv 1. 5

Impedance • Accounts for analytical estimations only at the moment (K. Y. Ng formula). • 3 D models received and being simulated by Adnan. • Transverse impedance budget: only dipolar, accounts for rotation of 45 deg, Q’=0, 1. 2 ns bunch length, sinusoidal mode 0. • Longitudinal impedance budget: l=1, Gaussian profile. Budget/IP Zx~Zy: 56 k. Ohm/m Zl : 0. 039 m. Ohm

Old results • As in the HLLHC impedance report. • N. B. : bunch length 1. 08 ns, HLLHCv 1. 2 round • 20% lower impedance (no rotation, further stripline distance) Zx~Zy: 44 k. Ohm/m Zl : 0. 025 m. Ohm

Summary • Slight increase (20%) of impedance due to closer striplines. • Still acceptable: 100 k. Ohm/m in transverse (w. r. t total 20 MΩ/m), 0. 08 m. Ohm in longitudinal (w. r. t. total 93 m. Ohm). • Refinement ongoing (CST models)

CST models correspondence Round BPMQSTZA BPMQSTZB M. Kurpa

Total Losses • • Sum of all mode losses • Uniform Freq. Shift (1 KHz steps) Single mode losses • Shift to nearest beam spectrum line With no freq. offset (directly from Eigenmode results) → Negligible Heating (13. 73 W Total) 05/03/2019

VELO 05/03/2019