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2016 Chamonix Workshop

2016 Chamonix Workshop. Main outcomes from 2015 for LIU-SPS, and outlook. B . Goddard, E . Shaposhnikova , on behalf of the full LIU-SPS team. Outline. Scope Recall of target parameters, performance limitations and LIU baseline solutions Key 2015 progress Beam studies and simulation

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2016 Chamonix Workshop

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  1. 2016 Chamonix Workshop Main outcomes from 2015 for LIU-SPS, and outlook B. Goddard, E. Shaposhnikova, on behalf of the full LIU-SPS team

  2. Outline • Scope • Recall of target parameters, performance limitations and LIU baseline solutions • Key 2015 progress • Beam studies and simulation • Longitudinal impedance reduction • Systems progress (except RF & dampers – Heiko & Wolfgang) • Ions • Summary of 2015 decisions on scope or technical solutions • 2016 objectives • Conclusions

  3. SPS beam parameters: HL-LHC & LIU-SPS25 ns beam Above-nominal LHC beams (with 50 ns and 25 ns spacing ) were successfully delivered to the LHC during Run1 and in 2015, but twice higher intensity (even more for brightness) is needed in future for HL-LHC *bunch length limit with present LHC 400 MHz RF

  4. 2015 performance, with expected limits HL-LHC request

  5. SPS cycle for LHC beam • SPS budget for losses: 10% • at start of acceleration ~5% (nominal intensities) • Transverse scraping flat top ~3% • Other losses ~2 % • SPS emittance growth budget: 10% • → Need to preserve brightness along 11 s long flat bottom e-cloud longitudinal multi-bunch instability

  6. Known main SPS performance limitations: 25 ns beam (288 bunches) * Prototype in baseline in collaboration with US-LARP

  7. Other limits on beam intensity or brightness: 25 ns beam (288 bunches)

  8. Progress with beam studies for p+ • Extensive beam impedance measurements and simulation benchmarking of SPS impedance model • Longitudinal instability measurements and multi-bunch simulations for confirmation of impedance source and instability thresholds • Scrubbing tests to finalise ecloud mitigation decision • Quantification of beam losses with high intensity: transmission in cycle and location (high Dx) • Limits from MKP4 vacuum (impedance, degassing) • Max. 1.37e11 p+/b in 288b (one-off HiRadMat test)

  9. Beam studies & simulation: impedance & longitudinal stability • Simulations using latest model in reasonable agreement with impedance measurements – still some missing impedance? • Instability simulations benchmarked with measurements of single bunch instabilities in ramp • Multi-bunch simulations made with 24b, ongoing with 72b • In double RF effective voltage and phase uncertainty complicates situation: should be better after RF upgrades With assumptions on the 800MHz effective phase/voltage

  10. Longitudinal impedance identification & stability thresholds • 1.4 GHz QF flanges, 630 MHz HOMs and kickers main contributors Kickers

  11. Longitudinal impedance identification & stability thresholds • 1.4 GHz QF flanges, 630 MHz HOMs and MKP main contributors Unstable HL-LHC request LIU baseline Simulated threshold for current impedance model

  12. Longitudinal impedance identification & stability thresholds • Effect of QF vacuum flanges and 630 MHz HOMs Unstable Shield QF-SSS flanges and improve damping of 630 MHz cavity mode by a factor 3 baseline Simulated threshold for current impedance model

  13. Longitudinal impedance identification & stability thresholds • Effect of MKP injection kicker Unstable Shield QF-SSS flanges and improve damping of 630 MHz cavity mode by a factor 3 baseline Reduce MKP impedance by factor 2  option Simulated threshold for current impedance model

  14. Longitudinal impedance identification & stability thresholds • Additional mitigation – longer bunches at injection into LHC? ? Unstable Shield QF-SSS flanges and improve damping of 630 MHz cavity mode by a factor 3 baseline Reduce MKP impedance by factor 2  option Simulated threshold for current impedance model

  15. Longitudinal impedance identification & stability thresholds • Additional mitigation – longer bunches at injection into LHC? ? Unstable Shield QF-SSS flanges and improve damping of 630 MHz cavity mode by a factor 3 baseline Reduce MKP impedance by factor 2  option Could be crucial - need beam tests in 2016: including injection of long bunches into LHC in MD Simulated threshold for current impedance model

  16. Impedance improvement progress • Identified QF-SSS vacuum flanges as one of main impedance sources responsible for longitudinalcoupled bunch instability and emittance blow-up. • Decision:implement impedance reduction of QF-SSS flanges in LS2 • Prototyped shielded flange, started impedance measurements • 200 MHz HOMs and MKP impedance also contributing. Improvements under study. No “low-hanging fruit”…. Shielded QF flange design Prototype shielded QF vacuum flange Closure of remaining gap

  17. Impedance reduction – extraction kickers MKE • Scope: Improve serigraphy, reduce MKE kickers from 8 to 7 • No limitations with beam heating from the 8 serigraphed MKEs • In YETS, modified LSS4 kicker layout, removed one magnet • Swapped one kicker for magnet with improved serigraphy • Reconfigured ECA4 kicker PFN/switch zone Re-arranged PFNs and switches in ECA4 New MKE kicker layout in LSS4

  18. e-cloud mitigation • Scope: mitigate 25 ns ecloud effects to 2.5e11 p+/b by scrubbing, with partial in-situ aC coating • Scrubbing tests: losses with scrubbing could reach 20% (2x budget) • aC coating deployed in machine on 4-half cells: supresses e-cloud • aC coating proven on 2 MBB chambers in series, “in-situ” approach • External review: scrubbing baseline, aC coating partial deployment • EYETS : Pilot QF and SSS, some MBBs,10% of 159 mm chambers • LS2 : Remaining QF+SSS, 159 mm chambers, up to one arc MBBs eCloud current vs SEY in MBB chamber Horizontal coupled bunch instability when scrubbing Stability margin for different aC coating scenarios

  19. Improved arc vacuum sectorisation • Scope: Reduce max. sector length from ~400 to ~200 m, to halve pump-down time and preserve scrubbing / aC coating properties • Decided to re-use refurbished valves rather than new ones • Installation started in this YETS • Evaluation of impedance impact under way of the 12 additional valves (not equipped with RF shields) Location of a new sector valve in mid-arc Pumpdown time with new sectorisation

  20. New beam dump system in LSS5 • Scope: move dump system to LSS5, new subsystem designs • Single new block, shielding, solid state MKD generators, kicker layout, … • Layout and specifications finalised, for LSS5 and LSS1 • Relocation of other systems defined (BI, UA9, …) • Activation & personnel dose simulations: ~1 mSv/h next to dump shielding for 1 week cooling: >104times better than present LSS1 • Preparatory civil engineering and decabling started (YETS) Dump in ECX5 with shielding structure and transport volume Re-flooring of ECA5 New dump block

  21. Electrostatic septa ZS (slow extraction) • Scope: reduce impedance of Pumping Modules, improve 25 ns beam performance, mitigate ecloud • Built and tested one upgraded ZS tank (with embarked ion pumps and shielded transitions): for LSS2installation in present YETS • Prototyped and tested performance of new ion trap circuit • Tested solenoid winding to supress ecloud(deployed on test ZS) New design of shielded transitions and chamber Upgraded ZS ready for installation in LSS2

  22. Extraction protection (TPSG) and transfer line stoppers (TED and TBSE) • Scope: upgrade protection devices in LSS4, LSS6 and transfer lines • Analysed 2014 HiRadMat tests of existing TPSG design and MSE septum coil: no damage seen to MSE or TPSG • Finished thermomechanical studies for new TPSG absorbers • Approved new LSS6 concept and started mechanical design • Developed two LSS4 concepts (needs increased absorber length) • Still to finalise solution for access safety stoppers TBSE TPSG4 design option (with ½ MSE) New TPSG6 design

  23. TI 2/TI 8 transfer line collimators (TCDI) • Scope: upgrade 12 TCDI collimators for robustness and protection • Finished thermomechanical studies for new jaw • Finalised locations, integration, installation • Finalised optics and quadrupole powering • Finished 2.1 m TCDI collimator design, started procurement • Assembled HiRadMat test bench for materials tests for April 2016 HiRadMat jaw material test tank New horizontal TCDI collimator design TCDIM.29472 mask thermomechanical stress

  24. Beam instrumentation • Scope: upgrade BI systems: orbit, wirescanners, profile, headtail, fast loss monitors, fast beam current • Installed prototyperotational wirescanner • Upgraded headtailacquisition system • Commissioned fast loss monitors (diamonds) in extraction channels • Performance assessment of orbit electronics (low intensity resolution) • Delay with alternative transverse profile measurements (BGI, BSRT) Fast beam losses in LSS6 at SPS extraction MOPOS readout electronics

  25. 2015 progress with ions • 50% transmission: SPS is a large consumer of lead • Injection kicker MKP 150 ns rise time deployed  new baseline • 20% more bunches in LHC: reduces motivation for 100 ns MKP… • Damper deployed (with patch for fixed-frequency issues) • Dedicated beam studies performed: • Slip stacking: verified momentum aperture, beam behavior OK without phase loop, checked long. stability with small emittance • IBS, stability, detuning with amplitude, scans of working point, SPS transmission in ramp vs injected intensity MKP magnet rise time Measured on one magnet: 148 ns 2-98%

  26. Summary of 2015 decisions on scope/technical solutions • Deploy vacuum flange impedance reduction on QF SSS • Deploy partial aC coating by LS2: all QF SSS, standard 159 mm chambers and 1 arc MBBs/QDs. Retain option for MBBs in LS3 • Beam dump concept and layout defined • Solid-state main amplifiers chosen for 200 MHz power upgrade • Improve damping of 200 MHz HOMs at 630 MHz by at least x3 • Defined layout, optics and mechanical design for 2.1 m TCDIs • Reconfigured MKE4 (4 short-circuited magnets, 8 us rise time) • Solved space problem (Crab Cavity LSS6, COLDEX LSS4, dump LSS5) • No new 100 ns injection system for LS2 (ions), 150 ns baseline • RF low-level beam control concept defined for slip stacking (ions)

  27. Main 2016 objectives • Procurement and construction follow-up • EYETS and LS2: follow-up planning, co-activity and services • Longitudinal stability simulations/benchmarking with 72b • 200 MHz HOM damping: design adequate (x3) reduction • MKP impedance: feasibility of significant (x2) reduction? • Bunch length at LHC injection and SPS BQM: tests in MDs • 200 MHz fundamental power coupler: design & prototype • Beam stoppers: finalise interlocking for TED, solve TBSE • TPSG4 protection: finalise design • Wideband feedback: review prototype & deployment needs • Beam size instrumentation: review performance • Understand losses at highest intensities

  28. Post-LS2 limits: without SPS longitudinal impedance improvement HL-LHC request

  29. ….with improved SPS longitudinal impedance (and assuming no other limitations from protection devices, beam losses, heating, ecloud, …) HL-LHC request

  30. Conclusions • The major SPS work packages on track: RF 200 MHz, beam dump, TL collimators, orbit electronics (75% of budget) • 2016 objectives are procurement and construction • ecloud mitigation strategy is decided and being deployed • Longitudinal impedance improvement key to exceed LIU baseline of 2e11, to reach HL-LHC request of 2.3e11 p+/b • 2015: 24b multi-bunch simulation/understanding: 2016 72b • New QF vacuum flange shielding in progress • Challenging 200 MHz HOM damping and injection kicker impedance improvement under study • Additional mitigation of longer bunches to LHC to explore • 20% losses not sustainable in long-term (ring activation, larger emittance to LHC)

  31. The end

  32. Main 2016 objectives • Execution phase: procurement and construction follow-up for main systems • 200 MHz upgrade (series drivers, mains protos, coaxial lines, BAF3...) • LSS5: beam dump and shielding, kickers, generators and cables • TCDI collimators • MOPOS electronics: equip full sextant with new electronics, radiation tests (production 2017) • Vacuum flange impedance shielding (for EYETs installation) • In-situ 2xMBB aC coating bench • RF low level upgrade

  33. Main reviews in 2015 e-cloud: aCcoating or scrubbing RF 200 MHz main amplifier technology choice SPS beam instrumentation RF 200 MHz power and low-level Cost and schedule review Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

  34. RF 200 MHz power upgrade • Scope: increase available power from 3.6 to 7.4 MW • Two new 1.6 MW power plants, 2 new transmission lines, rearrangement of present cavities, new fundamental power couplers, new low-level, operation of existing 900 kW power plants at 1.05 MW pulsed • In 2015: • New building BAF3 completed, services being installed • New solid state main amplifier contract passed FC and signed • Prototyping of new driver amplifiers completed • LSS3 layout defined and SSR issued • Integration studies for coaxial transmission lines launched • Procurement strategy for power couplers, coaxial lines and hybrid combiners defined • Cooling water solution defined (SPS loop) and funded RF TALK (HD) New BAF3 building for 200 MHz RF

  35. RF 200 MHz low level upgrade • Scope: fully digital control, and reduce beam loading • New individual cavity controllers, new beam control, alignment of 200 and 800 MHz phase, batch-by-batch longitudinal blow-up, ppm settings, long. damper, fixed-frequency and fixed harmonic acceleration, fast phase, voltage and frequency modulation, amplitude modulation for average power reduction, reduction in RF noise • In 2015: • Specifications finalised, including requirements for slip stacking for ions • Architecture defined • Modeling and simulation started RF TALK (HD)

  36. Transverse damper • Scope: Upgrade existing transverse damper • New pickups,cabling, new electronics, digital control • In 2015: • Fully commissioned new system with FT and LHC beams (ions remaining) DAMPER TALK (WH)

  37. Wideband feedback prototype • Scope: Design and prototype vertical system • Stripline and slotline kickers, pickups, cabling, 4 MS/s acquisition and processing electronics, power amplifiers • In 2015: • Installed and tested stripline kickers, purchased new power amplifiers, finalised slotline kicker design and started production DAMPER TALK (WH)

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