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What you get ? Transverse and Longitudinal distributions

What you get ? Transverse and Longitudinal distributions. F.Roncarolo , W.Andreazza , S.Bart -Pedersen, A.Boccardi , E.Bravin , B.Dehning , J.Emery , J-J. Gras, A.Guerrero , M.Kuhn , T.Lefevre , A.Nosych , M.Sapinski , G.Schneider , G.Trad , R.Veness , M.Wendt Many thanks to:

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What you get ? Transverse and Longitudinal distributions

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  1. What you get ?Transverse and Longitudinal distributions F.Roncarolo, W.Andreazza, S.Bart-Pedersen, A.Boccardi, E.Bravin, B.Dehning, J.Emery, J-J. Gras, A.Guerrero, M.Kuhn, T.Lefevre, A.Nosych, M.Sapinski, G.Schneider, G.Trad, R.Veness, M.Wendt Many thanks to: R.Jones, L.Jensen OP teams (V.Kein, ….) A.Bertarelli, M.Garlasche & MME team F.Caspers, E.Metral, B.Salvant G.Lanza, G.Bregliozzi and Vacuum Team(s) Many others …. Evian Workshop 2012

  2. Scope / Contents SCOPE Focus on what did not work, what is missing, current limitations during the 2012 run.Present the changes to be made during LS1 and expected performance post LS1. CONTENTS • Wire scanners (WS) • Beam Gas Ionization monitor (BGI) • Synchrotron light detector (BSRT) • Abort Gap Monitor (AGM or BSRA) • Longitudinal Density Monitor (LDM) Will not cover: Matching monitor, proposal for a new VELO-Like detector, WCM F.Roncarolo - Evian Workshop

  3. Wire Scanners – 2012 issues • Vacuum leaks • Bellow designed for ~ 10’000 scans, in 2012 1 system failed at ~10200 scans • Wire breaking • No evidence of breaking due to beam during normal operation (RF or direct energy deposition). Evidence of ageing due to sublimation. • Wire damage can be traced back to power supply failure followed by server crash that left the wire in between IN and OUT position • Overall accuracy dependence on working point • PM voltage + filter settings on same beam give different beam sizes • Many studies in 2012 (see M.Khun’s talk) • SW, OP GUI • Judged as inefficient by OP (bunch selection, automatic scans, display) • Dumps due to BLM thresholds • Secondary shower amplitude depends on actual wire diameter, that changes with ageing (see next slide) F.Roncarolo - Evian Workshop

  4. Wire Scanners – Dumps due to losses • Aged wire partially sublimated smaller diameter  lower losses new wire aged wire 34 um 16 um F.Roncarolo - Evian Workshop

  5. From beam profile to emittance Beta from beta beating • WS measurements during a test fill, with a high emittance and a low emittance bunch • Beta values during the ramp from linear interpolation 450GeV – 4 TeV Beta from model Beta from K mod F.Roncarolo - Evian Workshop M.Khun G.Trad

  6. WS - Upgrades • TS#4 • Install 7 um wire on 1 system • tests before the end of the run for assessing robustness and signal/losses • Thinner wire more robust according to literature, but less material to sublimate before breaking • LS#1 • Possibly thinner wires on all systems • Slightly higher speed (~10% max) • New bellows (aim at gaining a factor 5 in lifetime) • Improve OP GUI (OP+BI) • More system redundancy (big investment, under discussion) • LS#2 (?) • New fast (20 m/s) devices, following SPS prototype after LS#1 • Possibly new detectors (e.g. diamonds) to replace scintillator + PM F.Roncarolo - Evian Workshop

  7. BGI – 2012 issues • Both beam 1 BGIs had MCP failures in early 2012 (MCPs were exchanged during winter TS). • Reasons of the failures are understood (Operational/Technical failure) • Protection measures in place (e.g. automatic HV shutdown). • Problem with remote camera gain control, important to provide repeatable beam size measurement. • Camera failures • intensifier reaching Mean Time To Failure • Difficult cross-calibration • no intensity overlap WS/BGI during p-p runs, BSRT B2 problem • Overall results interpretation still difficult F.Roncarolo - Evian Workshop

  8. BGI – Results example • WS vs BGI during p-Pb MD (R. Versteegen, see CERN-ATS-2012-094 MD) • 13 Pb bunches, 7e9 charges/bunch • could find good calibration w.r.t. to WS despite low BGI signal • During p-p runs: • Calibration more difficult • Some evidence of dependence on bunch length F.Roncarolo - Evian Workshop

  9. BGI - Upgrades • Will dismantle and re-surface the vacuum sealing surfaces to avoid leaks (some troubles in 2012 to have them leak-tight) • MCP refurbishment • Optical system upgrade • To cope with high brightness beams at 7 TeV • HV system upgrade • To ensure a more stable operation • Camera refurbishment • Low level SW re-design from scratch • What is the allowable gas budget during a year? Can we run continuously with gas injection? F.Roncarolo - Evian Workshop

  10. BSRT - Introduction Gated camera (BSRTS) Optical delay line Proton/Ion beam DC Camera 60 % 40 % Abort Gap Monitor (AGM) 10 % Neutral filters Color filters 90 % F.Roncarolo - Evian Workshop Long. Density Monitor (LDM) 60 % 40 %

  11. BSRT – 2012 Issues • Heating with high intensity beam • Mirror coating and mirror support failures • Absolute and relative calibration (even more difficult in 2012 , affected by heating) • Software • Fast scan on demand (expert GUI) working from early 2012 • Fast scan server (communicating with OP-GUI - V.Kain) tests started in October, to be validated during p-Pb run • Overall reliability – robustness affected by • Extraction mirror heating / failures • FESA server automatisms failures • Steering following heating and energy ramp • Camera gain adjustment following injections and energy ramp F.Roncarolo - Evian Workshop

  12. BSRT – Calibration Example • B1 with new optical line (focusing lenses instead of mirrors), 450 GeV during MD period • Excellent agreement BSRT – WS over a wide emittance range, after applying • Magnification within 10% w.r.t. nominal • PSF ~20% smaller than typical values with old optics B1 Vertical Scraping Similar examples exist at 4 TeV F.Roncarolo - Evian Workshop 1 mm 1.3 mm 0.8 mm

  13. BSRT – Heating – Findings after B2 mirror removal Mirror clamps deformed Mirror coating blistered • Later Removal of B1 mirror evidenced similar effects • Both mirrors were: silicon bulk + dielectric coating • TS#3: replaced both mirrors • B1: glass bulk + metallic coating – OK only at low beam intensities • B2: silicon bulk + polishing (no coating) – not usable for imaging F.Roncarolo - Evian Workshop

  14. BSRT – RF simulations From January: RF laboratory measurements on spare tank E-field of a dominant resonating mode at 650 MHz. (Q = 1263 / Rsh = 25841 Ohm) LHC bunch power spectrum F = 650 MHz P_loss = 10-50W Mirror front Credits: T.Mastoridis, P.Baudrenghien/CERN F.Roncarolo - Evian Workshop Mirror Back B-filed of the beam in Time Domain. Red = Hot (bigger current density) Blue = Cold Measured LHC bunch power spectrum. A 650 MHz resonance is very dangerous. Longit. wake impedance of BSRT with and without Ferrite damping

  15. BSRT – Upgrades TS#4 – Intervention on B2 only • Change mirror: dielectric bulk no coating  glass bulk + dielectric coating • 6 temperature probes in vacuum, to validate RF – Thermomechanical simulations BASELINE for after LS#1 • New optics • New light parasitic shielding • Extraction mirrors: likely glass bulk + dielectric coating • Need high intensity test to validate itbefore end of this run ! • Modified tank minimizing RF coupling • Operational fast scan server Studies during LS#1 • Expected performances (resolution/accuracy) at 6.5-7 TeV • Monitor lower wavelengths to reduce diffraction ? • Novel tank design, much less sensitive to RF coupling / heating • Reflective tapered pipe with view-port on the side instead of on the bottom? F.Roncarolo - Evian Workshop

  16. Abort Gap Monitor • The weakest point remains the steering of the BSRT: “no spot no AG monitor” • A signal presence check could be implemented in the sequencer, but this doesn’t eliminate the need to verify that the telescope is not completely out of steering • BI is preparing a list of self checks to be implemented if possible during LS1, but at the cost of dead times in the measure (less than 1% of availability loss) • Calibration was kept reasonably well updated • Re-calibration each time optical path changed (e.g. due to heating) • The new BSRT optics • Doesn’t use additional delay line to pass from Undulator to D3 imaging • eliminates the need to compensate for light loss at the moment of the delay line insertion F.Roncarolo - Evian Workshop After many discussions, we got in the end a rather reliable system – when the BSRT is ‘working’. J. Wenninger – BI Day Dec.2012

  17. Longitudinal Density Monitor (LDM) • The LDM remains an expert tool • The SW is still under development • Artefacts linked to the detector behaviour still need an expert to correct for in normal fills (no impact during VdM scans) • dead time and afterpulse seems to change with filling pattern, to be checked after LS1 • Some reflections can affect the measure and need to be recognized to avoid misinterpretation: particular care was placed in the new optic setup to solve this for B1 • It can measure satellites and ghosts up to 10^-4 but is not good to verify bunch shape at a fine level With 25 ns beams we have to go back to main-main collisions, the interest will then shift back to satellites at injection and luminosity calibration runs. F.Roncarolo - Evian Workshop J. Wenninger – BI Day Dec.2012 Noted …

  18. From 4 to 7 TeV • Smaller Beam Sizes • WS: less points per sigma, could need to apply multiple-scan or multiple bunches overlaps to increase resolution (as done @ SPS Flat Top) • BGI, BSRT: will adapt optical imaging to have ~mm/pix as @ 4 TeV • BSRT: higher contribution from diffraction • Can correct for it, after quantifying it precisely • Can think about going to lower wavelength detectors • Lower BLM thresholds • Limits WS scans to ~ 1e12 • AGM, LDM • More photons, will adjust optical filters if needed F.Roncarolo - Evian Workshop

  19. From 50 to 25 ns • WS cross-talk on electronics • ~ 10 % between 25ns slots (under study) • With a reduced wire diameter, can we scan 288b at injection? • BGI: • no evident impact • BSRT: 25ns would • Increase the time to loop over all bunches (currently ~7min for 1380 bunches) • AGM, LDM: • No evident impact F.Roncarolo - Evian Workshop

  20. Conclusions - Overview Transverse and longitudinal diagnostics allowed optimizing and safely running the LHC (WS as references, BSRT bunch-per-bunch, AGM) • need development for improving the overall performance and reliability after LS#1 • For each device we have a list of issues to study, improve, develop for 7 TeV and 25 ns • Fundamental checks before LS1 • BSRT heating • WS thresholds • SW/Control • We need to profit of LS1 for reviewing all instruments low and high level SW individually • Transverse Profile Workshop, CERN, April2013 • Experts from GSI, DESY, FermiLabetc … presenting experience with BGI, Sync. Light etc … Transverse Need high intensity run in Jan-Feb 2013 !! • Longitudinal • AGM reliability depends on BSRT optical line robustness. MP workshop will trigger again interlocking? • LDM needs some work to make it operational, efforts in LS#1, but will re-start likely as expert tool (need for development and relative resources) F.Roncarolo - Evian Workshop

  21. SPARES F.Roncarolo - Evian Workshop

  22. BSRT – Optical Line Old Optics Entrance (steering) mirror New Optics F.Roncarolo - Evian Workshop

  23. Wire Scanners – Present Performances • Integration • 40 MHz sampling of PM integrator allows bunch per bunch measurements • 50 ns ok • 25 ns cross-talk being studied • Repetition Rate • Ideally ~0.2 Hz, at cost of system lifetime (wire, bellows) • Dynamic range • From pilot bunch to ultimate intensity per bunch, but: • Limits on total beam intensity • Future: faster WS (20 m/s?) • can allow higher intensities at the cost of • multi-scans on a single bunch (go faster  few points/sigma)  need to overlap multi-scans with sampling position offsets • single scan, combine NN bunches to have enough points/sigma F.Roncarolo - Evian Workshop

  24. WS - Accuracy • Resolution • limited by minimum wire speed vs protons revolution frequency • 1 m/s  89 um between two consecutive wire position acq. ( profile points) • Can be improved overlapping multi-scans (or single scan combining NN bunches) with sampling position offset (as being tested now @ SPS) • Present wire position resolution limited by potentiometer noise (some 20um) • New WS: aiming for 2um resolution (independent of speed) • Accuracy • With proper PM and filter settings, absolute accuracy proved to be 1% for the SPS linear WS • Accuracy of LHC WS under study • theoretically equal to SPS linear WS • At the moment: evidence of dependence on working point (PM gain + filter settings SLIDE/PLOT ON THIS?) • Plan for different secondary shower detector (diamond), related to SPS prototype to be tested after LS1 • Improve dynamic range • Get rid of filters  avoid dependence on working point • PHD on electronics F.Roncarolo - Evian Workshop

  25. BGI – Operational Specs • Gating/Integration • Gated camera • Need to gate over multi-bunches to have enough signal (see dynamic range) • Repetition Rate • 50Hz, limited by image digitalization (BTV) • Dynamic range • With a “fresh” MCP: • 10 proton bunches with gas injection 10-8mbar • Single Pb ion bunch with gas injection 10-8mbar • A bit better at 4TeV due to denser beam • MCP aging rather quick F.Roncarolo - Evian Workshop

  26. BGI – Results Example II Typical p-p high intensity fill • emittance “decrease” at the beginning of the ramp (related to bunch length?) • variations of calibration parameters from fill to fill • emittance “decrease” right after the ramp… • signal amplitude decrease during the fill (more then expected from intensity) Bunch length from 1.4 to 1 ns ns (NO RAMP) F.Roncarolo - Evian Workshop Measurement at injection, investigating bunch length influence on beam size seen by BGI.

  27. BGI - Performances • Resolution • Present optics gives 0.115 mm/pixel • Accuracy • Optics magnification validated to 1% by • Beam orbit local bumps • Reference wire-grid calibration • Needs cross calibration w.r.t WS and BSRT • For the moment not better than 20%, degrading with MCP aging • Many studies on going to understand ultimate resolution/accuracy • LS1: • Replace MCPs • Second camera with better performances F.Roncarolo - Evian Workshop

  28. BSRT Operational Specs • Gating • Intensified camera gating down to 25ns with a 12.5ns gating resolution • Repetition rate • Max 200 Hz (limited by intensifier trigger rate) • Present image digitalization (BTV) 50 Hz • Present control + acquisition SW ~12 Hz • Can do bunch per bunch @ ~12Hz • Can do single bunch single turn but not on consecutive turns • Dynamic Range • Protons: From pilot at injection (single turn, every 220 turns) to average over all bunches at flat top • Ions: From ~30 bunches at injection to average over all bunches at flat top F.Roncarolo - Evian Workshop

  29. BSRT – Heating vs bunch length Clear evidence that heating is due to RF coupling with high intensity beams Temperature gradient changes at each bunch length step F.Roncarolo - Evian Workshop

  30. BSRT - Performances • Resolution • Present optics 0.1 mm/pix, next: 0.05 mm/pix • Relative bunch per bunch accuracy <= 5% • 5% on single shot, dominated by reproducibility affected by noise (airflow, optical elements vibration, fit accuracy, etc …) • 1% averaging on multi-shots • Absolute accuracy: • Optics magnification validated to <= 5% • Calibration target • Beam orbit local bumps • Ultimate accuracy dominated by aberration / diffraction • Need cross calibration w.r.t. WS •  calibration factors  accuracy <=10% after calibration • Calibration factors not stable • Possible drifts due to mirror coating aging (heating) F.Roncarolo - Evian Workshop

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  33. BSRT - Heating • B2 Temperatures end of August Last two fills before putting mirror to OUT position and then removing it. + UFO activity …. F.Roncarolo - Evian Workshop

  34. BSRT – Heating – B2 Mirror 28-Aug-2012 1- Beam (spot not in the ‘right’ place vertically) Access to remove mirror 2- Beam dump 4-No beam, no motors movement, mirror moved 3- Close Vacuum sector and retract mirror to OUT F.Roncarolo - Evian Workshop

  35. BGI - Introduction • Collect electrons from beam-gas ionization • Dipole B field to avoid drift from ionization location to MCP • MCP electron multiplication • Phosphor coupled to MCP output for electronphoton conversion • Imaging of phosphor output • Designed for heavy ions • Enough signal from protons by injecting local pressure bumps or high intensity • Can monitor average relative beam size variation during the ramp F.Roncarolo - Evian Workshop M.Patecki, M.Sapinski

  36. Wire Scanners - Introduction • Reference device for transverse profile measurements • 1 H + 1 V per beam (+ a spare for each) • 30 um Carbon wire flying at 1 m/s • Scan on-demand • Dynamic range controlled by PM gain and optical filters • Can be used up to a maximum intensity that depends on beam energy • Above such maximum intensity: wire damage and/or quench downstream magnets ( BLM thresholds to dump before reaching quench limit) F.Roncarolo - Evian Workshop

  37. BSRT (and BGI) - Calibration • sm [pixels] = Measured Sigma • M [mm/pixels] = System magnification (optical line + pixel size) • determined by optical line adjustment with energy (UND  D3) • reference target vs closed orbit bumps give up to 10% differences • spsf [pixels] = measurement error due to • aberration, diffraction • extraction mirror aging/deformation During 2012 heavily affected by extraction mirror heating (deformation + coating damages) Difficult to find a stable calibration w.r.t. WS F.Roncarolo - Evian Workshop

  38. Longitudinal Density Monitor (LDM) - Upgrades • After LS1: • new BSRT optics, new light shielding  less parasitic reflections • new detectors under investigation (e.g. fast PM) B1: new optics Reflection on BSRT filter wheel, at a possible satellite location B2: old optics Satellites 5ns from SPS Different colors = different bunches After L 5 ns With 25 ns beams we have to go back to main-main collisions, the interest will then shift back to satellites at injection and luminosity calibration runs. F.Roncarolo - Evian Workshop J. Wenninger – BI Day Dec.2012 Noted …

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