2016 Chamonix Workshop Summary of the HL-LHC Session O. Brüning CERN, February 24, 2016

HL-LHC Sessions @ Chamonix Not a Status Report of all Work Packages: Rather: Discuss WPs where experience from the first year RunII oper. has an impact on the HL-LHC implementation and operation Discuss topics where decisions are pending Clarify the paths for implementing options and baseline choices Work Packages that are not covered are assumed to be on track 7 Presentations: 2 focusing on the path for HL-LHC hardware implementations 3 on LHC post LS2 operation with LIU parameters, 1 on required HL-LHC tests in the SPS, 1 on Civil Engineering aspects for constructing the HL-LHC infrastructure High light scope of the HL-LHC session: pending decisions, impact of 2015 operation on HL-LHC, revision and down selection of Options O. Brüning, Chamonix Summary session @ CERN, March 3rd

HL-LHC Sessions @ Chamonix Performance Limitations in the LHC after LIU upgrade: G. Arduini  e-cloud, UFOs, Z & instabilities, aperture, BI RF Upgrade Paths: E. Jensen  200MHz and 800MHz options, feedback Collimation Upgrade Path for the HL-LHC: S. Redaelli  quench tests, materials, radiation, DS collimation Crab Cavity Test Installation in the SPS: G. Vandoni  location, infrastructure requirements, schedule Coating Operation for the insertion magnets in IR2 & IR8: P. Costa Pinto  aC coating and laser surface treatment Vibration Studies and Tolerances for the Operation: J. Wenninger  test drills, shaker, Geotherm2020, earth quakes Ion Operation after LS2: J. Jowett  LIU prospects, L sharing options, 2015 MDs O. Brüning, Chamonix Summary session @ CERN, March 3rd

HL-LHC Sessions @ Chamonix Performance Limitations in the LHC after LIU upgrade: Different heat load in the LHC sectors  2 different classes  impact on scrubbing campaign E-cloud heat load ≈ constant as function of bunch intensity for SEY ≤ 1.3 and N > nominal  if we can condition the LHC up to nominal intensities the machine is good for HL-LHC Coating of IR2 & IR8 IR quadrupoles is mandatory! Luminosity limitation in IR1 & IR5 due to heat exchanger and Cryo Is important to push current in the LHC after LS2 up to HL-LHC values in order to identify potential current limitations before LS3 in order to discover and identify potential other bottlenecks! 2 categories for LHC cryo sections?! Conditioning to nominal intensity is sufficient for HL-LHC, interest in operating at HL-LHC intensities before LS3! O. Brüning, Chamonix Summary session @ CERN, March 3rd

Beam parameters after LIU (SPS ext.) Assuming measures for SPS long. Impedance reduction are implemented Parameter Before LIU (2016) After LIU Bunch population Nb [1011] 1.3 2.3 Max. number of bunches per SPS ext. 288 Normalized emittance en [mm] 2.7 2.0 eL [eVs] 0.66 r.m.s. bunch length [cm] 12 #bunches Bunch population [1011] Lev. time [h] Opt. Fill length Peak Lumi [1034 cm-2s-1] Int. Lumi for for opt. fill length [fb-1 /y] Pile-up density/Pile-up [ev./mm]/ [ev./xing] 2748 1.5 5.5 9.8 1.7 80 0.54/45 1800 2.0 11.5 14 1.25 70 0.6/50 Impressive progress in the understanding of the origin of longitudinal coupled bunch instabilities: Shielding of the MBA-QF flanges + damping of the TWC 200 MHz at 630 MHz should allow reaching HL-LHC parameters  will be included in the baseline. Need of enamelled flanges should be assessed. MKP shielding would solve the issues related to heating Corresponding reduction of the transverse impedance and TMCI thresholds should be evaluated in view of using Q22 or Q26 optics to provide additional longitudinal acceptance at flat top and possibly reduce peak dispersion (and losses) Need to determine rise-time for transverse coupled bunch instabilities due to impedance and study interplay with electron cloud for the coupled bunch instabilities observed in the horizontal plane G. Arduini - Performance Limitations in LHC after LIU Upgrade

HL-LHC Sessions @ Chamonix RF Upgrade Paths: Full detuning of the 400MHz RF system  ±15mm long. modulation (±50ps) of IP  Klystron power limited to 200kW Coupler lifetime (15y?), storage and consolidation for HL-LHC? 200MHz, 800MHz BL and 800MHz BS options  feasibility / prototype studies until LS2  need to decide when? RF noise for flattening bunches even in ‘bunch shortening mode’ ‘WBFB would be nice and studies should continue’  but no clear justification of need Why do we continue with 800MHz options; Brennan’s stateent that longer bunches in the SPS can make the LIU and HL-LHC parameters match! Klystron lifetime and need for matched Consolidation O. Brüning, Chamonix Summary session @ CERN, March 3rd

HL-LHC Sessions @ Chamonix Collimation Upgrade Path for the HL-LHC: 2015 operation experience:  up to 280MJ beam energy and no quench from beam losses  but machine configuration and beam parameters were not pushed Quench test: (Eb-max > 420MJ, LHCnom = 362MJ, HL-LHC = 630MJ)  difficult extrapolation for protons due to absence of quench  11T DS collimators in IR7 (2 Cryoassembly per beam  4 in total, 2 by LS2),  connection cryostat DS collimators in IR2 (2 units total)  mitigation in DS of IR1 & IR5 via orbit bumps Material tests:  encouraging result for MoGr (jaw survived 288b of 1.3x1011p)  Radiation test need to be redone due to damage with too high dose  coating studies for impedance reduction advancing well (2 jaws) Crystal collimation: successful channeling in MD!  option for Pb but NOT obvious for p (power on absorbers)! Hollow e-lens: interesting for Halo depletion  on path to Baseline Decision on 11T DS collimatros for IR7 only, alternative solutions for other IRs, progress with MoGr, Crystal collimation is NO solution for proton operation, Materials -> I would also emphasise that in 2015 we built to full-scale jaws that with a new design for HL. Important milestone. Eb-max > 420MJ, LHCnom = 362MJ, HL-LHC = 630MJ O. Brüning, Chamonix Summary session @ CERN, March 3rd

HL-LHC Sessions @ Chamonix Crab Cavity Test Installation in the SPS: Vital to gain feedback from operation with beam before launching of cavity production for HL-LHC  need results before LS2!!! Tight and ambitious schedule but doable!  Visualization and planning now Preparation in EYETS 16/17 Installation YETS 17/18  vital for project to be able to launch Carb cavity production by LS2!!! (international partners!!!) Cable and pipework length: ~150-200m 65m Cold-box +SPS fire safety CCCM 200m2 Ambitious and tight schedule but doable. Full support from the HL-LHC project. Only chance for getting experience with beam before production launch. O. Brüning, Chamonix Summary session @ CERN, March 3rd

HL-LHC Sessions @ Chamonix Coating Options for IR2 and IR8: Triplet magnets in IR2 and IR8 will not be changed for HL-LHC but they will see the same current as the new magnets in IR1/IR5 Need procedure to reduce SEY of the triplets beam screens! Two options: aC coating or Lase Engineered Surface Structures (LESS) Plan A - Baseline: a-C as in IR1 and IR5  can be done in-situ ✔ SPS tests: effect of radiation ✔; Impedance ✔; in-situ setup?  decreasing H2 desorption and increase deposition rate (B-field) Plan B - Option: LESS  proof of compatibility with HL-LHC 2017  Impedance, dust?  COLDEX  Both methods could be applied to all IPQ!!!! a-C LESS Low SEY based on the electronic properties of the material Low SEY is a morphological effect Two very interesting options! O. Brüning, Chamonix Summary session @ CERN, March 3rd

HL-LHC Sessions @ Chamonix Lessons from Civil Engineering Test Drills and Earth Quakes On Vibration Tolerances: Driven by worries about vibrations from the HL-LHC civil engineering GEOTHERM2020 a renewable energy production project by the Canton of Geneva GEOTHERM2020; O(100) amplification by triplet cryostat, worry about micrometer movements; hollow electron lens options O. Brüning, Chamonix Summary session @ CERN, March 3rd

HL-LHC Sessions @ Chamonix Lessons from Civil Engineering Test Drills and Earth Quakes On Vibration Tolerances: From Noise to Beam  O(100) amplification to cold-mass for certain modes (H0)  O(10-100) attenuation H1 and H2  order of micrometer tolerance for vibrations!  Schedule that allows CE construction during LS2!!  Hollow electron lens for halo depletion! In (ω) Out (ω) H1 (ω) H0 (ω) Beam stability H2 (ω) GEOTHERM2020; O(100) amplification by triplet cryostat, worry about micrometer movements; new schedule, CE contract, hollow electron lens options O. Brüning, Chamonix Summary session @ CERN, March 3rd

HL-LHC Sessions @ Chamonix Heavy Ion Operation after LS2: Experiments upgrade during LS2 (ALICE) LIU upgrades during LS2  Pb HL operation starts in Run3 Luminosity limitation from Bound Free Pair Production (BFPP)  Orbit bumps & Dispersion Suppressor collimators! Luminosity lifetime dominated by ‘burn-off’ Assume equal luminosity sharing: Projections of 1.7-2.1 nb-1 / Pb-Pb run (new LIU baseline + high efficiency) Requested running scenarios (LoI): 2021 - Pb-Pb  2.85 nb-1 2022 - Pb-Pb  2.85 nb-1 2023 - pp reference run 2024 - 2026 - LS3 2027 - Pb-Pb  2.85 nb-1 2028 ½ Pb-Pb 1.5 nb-1 + ½ p-Pb 50 nb-1 2029 - Pb-Pb  2.85 nb-1 2030   LS4 3 DS collimation solutions (bumps, collimators in empty cryostat and 11T DS); versatile program with request for flexibility, predictions are now within 40% of the experiments needs O. Brüning, Chamonix Summary session @ CERN, March 3rd