BeamBeam wire compensator for Hi Lumi LHC operation

Beam-Beam wire compensator for Hi. Lumi LHC operation (BBLR) HS – 20 -3 -2014 BI-TB With slides from Ralph Steinhagen and Raymond Veness

Outline • The strict minimum on background information • 4 pillars: 1) Demonstrator project before LS 2 ( demonstrator installation in collimators, installation winter shutdown 2015 -2016 or 20162017) 2) Related beam instrumentation: lifetime, 2 D halo monitor, tune spectra 3) Optimization of parameters for Hi. Lumi 4) Preliminary integration studies, designs, integration studies, construction and commissioning of installations

Beam-Beam Interactions in a Nutshell Need crossing angle θ to avoid parasitic crossings → reduces bunch overlap LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 & luminosity long-range beam-beam interactions interaction region parasitic crossing reduced overlap q 3

LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 Beam-Beam Field long-range ~ 1/r head-on ~ r 4

LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 Beam-Beam Interactions – LHC Experiments I/II Courtesy W. Herr 5

What to do? 1) Presently the LHC works Ok in this respect. LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 2) For Hi. Lumi: Different beam parameters…most likely inacceptable long range beam-beam effects: 1) increase crossing angle? reduced luminosity compensate with crab cavities need more aperture in the triplets: we do not have 2) based on a proposal for J. P. Koutchouk and F. Zimmermann (years … 2001) install wires in the vacuum chamber (at the right phase advance to the IP), which are at about 6… 8 sigma distance from the LHC proton beam, and which produce a similar 1/r field (of opposite sign) than the LR beam-beam force (electrical current: 170 A) compensation of the LR BB effect needs to be done locally, i. e. at 4 (8) places close to IP 1 and IP 5. specifications presently far from being stable (alignment tolerances, pulsing of wires, two dimensional adjustments, tilt compensation…. ) 6

What to do? time line of whole project: LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 a) plan for winter shutdown 2015/2016 the installation of 2 wires in IP 5 into the jaws of the TCL collimators. Optionally create 2 vertical collimators in IP 1 with wires in addition. b) In parallel: Make theoretical predictions for the above configuration in terms of observables. Further develop the existing models. c) In parallel: Give a boost to related instrumentation: - reduced noise in bunch to bunch lifetime measurements - Halo monitor (in 2 D, 10 -4 … 10 -6) dynamic range, measurement time? - tune spectra with various excitations - tune meter for beam halo (i. e. probe the amplitude detuning of the machine): brainstorming: Wirescanner at fixed position in halo, measure spectra of beam losses…, higher order mode transverse cavity sensitive to halo particles and “no” signal from core (and no additional machine impedance) d) in parallel : First studies for the final implementation. - make experiments in the years 2016 and 2017; validate the concept and the modelization, make predictions for Hi. Lumi in 2013. 7

LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 Summary of LHC BBC Prototype Specifications Wire-in-jaw design: – Embedded (insulated) Cu wire inside W block 20 mm clearance – Possibility of 1+n wires (spare/redundancy)? – >100 um between wire and cleaning surface (RF screening) y – more compatible w. r. t. collimation and machine protection x W Cu Wire parameters: – Solid (round) wire radius of ~ 1 mm and e. g. 1 m length – sub-σ level of hor. /ver. position control (e. g. 0. 1 mm) – nom. scheme: I·lwire = Ipeak·√ 2π·σs·nparasitic·lwire = 72 … 350 Am (max. ) – DC compensation only – cooled via passive heat transfer (1 k. W) Initially two units: BBC-H. x. L 5. B 1 & BBC-V. x. R 1. B 1 – same location as present TCTP & planned TCL collimator Reuse as much of established infra-structure as possible (collimator type girders/motor control, LHC-type 600 A PC) 8

Working Principle of Thermocoax Wire-in-Jaw Option LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 Beam Jaws (tungsten) Electrical conductor Beam Jaws (Tungsten) Electric conductor (D=1 mm)) sheath Inox 316 L, thickness 0. 3 mm Insulator Mg. O, thickness 0. 5 mm Conductor (Copper), diameter 1 mm 9

Proof-of-principle testing for wire-in-jaw option 50 45 Temperature 35 30 Temperatures des sondes pos 1 (°C) 25 20 Temperatures des sondes pos 2(°C) 15 10 5 0 0 50 100 current (A) 150 200 7 magnetic field (m. T) LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 40 6 Champ magnetique à d= 7 mm (m. T) 5 Champ magnetique à d= 13. 5 mm (m. T) 4 3 Champ magnetique à d= 21. 5 mm (m. T) 2 Champ magnetique à d= 7 mm (m. T) TH 1 Champ magnetique à d= 13. 5 mm (m. T) TH 0 0 50 100 150 Current (A) 200 250 Champ magnetique à d= 21. 5 mm (m. T)TH In conclusion: It seems possible to make a wire with a diameter of 1 mm and to cool it, if embedded in the jaws. The main problem is to feed this current into the collimator. A larger cable section is needed, but 10 space limited.

LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 Design Proposal for Wire-in-Jaw proof of principle test in Phase I LHC Collimator (TCT) Glidcop Stainless Steel Design courtesy EN-MME 11

Working Principle of Thermocoax Wirein-Jaw Option Beam Jaws (tungsten) Electrical conductor Beam Jaws (Tungsten) Electric conductor (D=1 mm)) sheath Inox 316 L, thickness 0. 3 mm Insulator Mg. O, thickness 0. 5 mm Conductor (Copper), diameter 1 mm

Proof-of-principle testing for wire-in -jaw option 50 45 Temperature 40 35 30 Temperatures des sondes pos 1 (°C) 25 20 Temperatures des sondes pos 2(°C) 15 10 5 0 0 50 100 current (A) 150 200 magnetic field (m. T) 7 6 Champ magnetique à d= 7 mm (m. T) 5 Champ magnetique à d= 13. 5 mm (m. T) 4 3 Champ magnetique à d= 21. 5 mm (m. T) 2 Champ magnetique à d= 7 mm (m. T) TH 1 Champ magnetique à d= 13. 5 mm (m. T) TH 0 0 50 100 150 Current (A) 200 250 Champ magnetique à d= 21. 5 mm (m. T)TH In conclusion: It seems possible to make a wire with a diameter of 1 mm and to cool it, if embedded in the jaws. The main problem is to feed this current into the collimator. A larger cable section is needed, but space limited.

Design Proposal for Wire-in-Jaw proof of principle test in Phase I LHC Collimator (TCT) Glidcop Stainless Steel Design courtesy EN-MME

Two-Stage BBC Approach I/II – Initial Post-LS 1 proof-of-concept Primary aim: benchmark existing simulations and predictions prior to LS-2 Initial wire-in-TCTP-jaw design seems to be feasible LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 – Thermal, cleaning & impedance issues seem to be under control – Pending: worst-case beam impact scenario studies • i. e. asynchronous beam dump spraying 1 -15 nom. bunches onto jaw N. B. TCTP (W jaw) is known to fail “badly” but additional wire should not significantly deteriorate the situation further → A. Bertarelli's talk Allow to test the predictions but may not achieve the best-possible performance under nominal (HL-) LHC conditions – test require ε = 3. 5 - 3. 75 um vs. nominal ε ≈ 2. 0 um – larger phase-advance w. r. t. nominal BBC – limited min. wire-in-jaw-to-beam distance 15

Two-Stage BBC Approach II/II – Possible Nominal BBC Installation for HL-LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 Primary aim: improve luminosity via reduced crossing-angle & BBC mitigating long-range beam-beam interactions Several independent predictions, all consistent and quite promising w. r. t. potential to reduce the crossing angle, however Two inconvenient BBC constraints (from engineering/operation/MP point of view): a) needs to be close to the D 1 (i. e. in common beam pipe) b) Similar “wire”-to-beam distances as the targeted beam-beam separation Three (/more? ) nominal implementation options for HL-LHC: 1. Wire-in-jaw design → scale TCTP exp. and integrate between D 1 -TAN 2. For reference only: Simulate 'wire' effect through external fields 3. Simulate 'wire' field through e-beam running || to the p-beam → all three options are challenging w. r. t. design and integration … following slides give a glimpse on some of the issues 16

HL-LHC Option 1: Scaled Wire-in-Jaw Design placed between D 1 ↔ TAN neutron flux RP TCT D 1 s TAN 20 mm clearance s ~100 mm cooling water y x >160 mm cooling water y >160 mm LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 x 60 mm Non-neglible n-flux, impedance and TAN aspects need detailed simulations Major design and qualification effort → basically another collimator – materials choices: Cu, W, Carbon, Si. C, (CVD) Diamond, . . . Ideally targeting a 6 -7σ distance (from a physics point-of-view) → de-facto becoming a primary collimator next to the experiments (IMHO: “. . a very challenging scenario”) 17

HL-LHC Option 2 – more for reference purposes: Local 'wire'-like Gradient using External Magnetic Fields Long-range approximation with 8 -10 -pole off-centre multi-pole field LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 ± 6σ B 2 B 1 mu-metal / supercond. Septum-like design: mu-metal or superconductor to magnetically shield between B 1/B 2 aperture (n-flux may be limiting factor) Needs further investigation – numerically possible but may required magnetic peak-fields beyond what can be done with superconductors 18

HL-LHC Option 3: Local e-beam simulating 'wire'-like Field I/II LHC BBC brainstorming - Oxford, Ralph. Steinhagen@CERN. ch, 2013 -10 -15 E-beam has by-design perfect 'wire' field distribution x 2 (units are back-to-back) similar to existing e-cooler, (hollow-) e-lenses used at Tevatron & RHIC, however: offset e-beam! → much lower requirements on transverse e-beam parameters (i. e. beam size, profile distribution etc. ) Still need large solenoid field to stiffen e-beam rigidity no solid material close to beam → chance of being MP compatible @6 -7σ 19

Requirements and Technologies for HL-LHC Series Device • Magnetic field corresponding to ~170 Am of wire compensation, assuming 6~7 σ from beam • 8 devices (IR 1&5, 2 beams, L&R of IP) in D 1 -D 2 region Technology Pro- Con- Wire-in-jaw -”Proven” technology - Machine protection issues (at Optimal distance BBLR as close to the beam as primary collimator; other beam goes through device!) - Very high neutron flux in D 1 -D 2 zone - Can not pulse wire Multipole magnet -No material between beams -Required field shape complex -High peak fields -Compensation not complete - Shielding of 2 nd beam “funky” Electron beam - No material between beams - Based on e-cooler and hollow e- lens technology - Commercial e- sources can produce 10~30 A; - beam can be amplitude modulated - Integration problems High neutron flux Strong solenoids to keep beam parallel to proton beam Looks VERY expensive 20

Responsible People. . . (to be confirmed) • Demonstrator collimators : S. Raedelli & R. Losito et al. • Beam-beam simulations + Demonstrator experiments: Y. Papaphillipou, T. Pieloni • Beam instrumentation: - Halo monitor : E. Bravin et al. - Halo tune: ? - BCT (let’s see what needs to be done) - Tune spectra with various excitations: Marek? • Explorations for final solution: R. Veness + G. Tranquille 21

Slides for LHC Demonstrator design and HL-LHC Device Development Paolo Magagnin, Axel Ravni, Ralph Steinhagen, Ray Veness

Electron beam: Next Steps (2014 – 2017) Simulations from ABP to give e- beam requirements Specification/feasibilit y of e- source (10~30 A @ ~500 ke. V) Specification of solenoid Requirements for space, services, etc Preliminary integration into HLLHC layout Evaluation of neutron flux and damage Series cost evaluation 23

Summary • • Project just starting Names and teams get assembled, excel spreadsheets with names, budgets, planning «soon» Project will be in two phases: - collimator based demonstrators - final implementation for Hi. Lumi Both phases with interesting challenges for BI BBLR Project gets full (financial and moral) support from Hi. Lumi project BBLR project is part of the Hi. Lumi instrumentation WP (resp: Rhodri) Real specifications and description of demonstrator experiments not before 2015. BI should become proactive and start developments 24