What you get Transverse and Longitudinal distributions Evian

What you get ? Transverse and Longitudinal distributions Evian Workshop 2012 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) 18 -Dec-2012 Many others ….

Scope / Contents F. Roncarolo - Evian Workshop 18 -Dec-2012 SCOPE Focus on what did not work, what is missing, current limitations during the 2012 run. Present the changes to be made during LS 1 and expected performance post LS 1. 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 1

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 F. Roncarolo - Evian Workshop 18 -Dec-2012 - § 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) 2

F. Roncarolo - Evian Workshop 18 -Dec-2012 Wire Scanners – Dumps due to losses 22 -Aug 12 -Oct 22 -Nov System B 1 H (aged wire, changed during intervention to fix bellow leak) B 1 H (new wire) B 1 V (new wire) Beam Intensity 4. 29 e 12 No dump 4. 18 e 12 Dump 3. 54 e 12 Dump BLM signal [Gy/s] 0. 0091 0. 0218 0. 0335 Losses / proton @ downstream BLM [Gy/p] 5. 4 e-19 2. 7 e-17 2. 4 e-17 new wire aged wire 16 um 34 um § Aged wire partially sublimated smaller diameter lower losses 3

From beam profile to emittance § WS measurements during a test fill, with a high emittance and a low emittance bunch § Beta values during the ramp from linear interpolation 450 Ge. V – 4 Te. V F. Roncarolo - Evian Workshop 18 -Dec-2012 Beta beating Beta from model K mod M. Khun G. Trad 4

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 18 -Dec-2012 § LS#1 - F. Roncarolo - Evian Workshop - 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 - 5

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). F. Roncarolo - Evian Workshop 18 -Dec-2012 - § 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 B 2 problem § Overall results interpretation still difficult 6

BGI – Results example § WS vs BGI during p-Pb MD (R. Versteegen, see CERN-ATS-2012 -094 MD) 13 Pb bunches, 7 e 9 charges/bunch - could find good calibration w. r. t. to WS despite low BGI signal F. Roncarolo - Evian Workshop 18 -Dec-2012 - During p-p runs: § Calibration more difficult § Some evidence of dependence on bunch length 7

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 F. Roncarolo - Evian Workshop 18 -Dec-2012 - To cope with high brightness beams at 7 Te. V § 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? 8

BSRT - Introduction Gated camera (BSRTS) F. Roncarolo - Evian Workshop 18 -Dec-2012 Proton/Ion beam Optical delay line Abort Gap Monitor (AGM) 60 % 10 % DC Camera 40 % Neutral filters Color filters 90 % Long. Density Monitor (LDM) 60 % 40 % 9

BSRT – 2012 Issues § Heating with high intensity beam - Mirror coating and mirror support failures F. Roncarolo - Evian Workshop 18 -Dec-2012 § 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 - 10

BSRT – Calibration Example F. Roncarolo - Evian Workshop 18 -Dec-2012 § B 1 with new optical line (focusing lenses instead of mirrors), 450 Ge. V 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 B 1 Vertical Scraping Similar examples exist at 4 Te. V 1 mm 1. 3 mm 0. 8 mm 11

BSRT – Heating – Findings after B 2 mirror removal Mirror clamps deformed 18 -Dec-2012 Mirror coating blistered § Later Removal of B 1 mirror evidenced similar effects F. Roncarolo - Evian Workshop - Both mirrors were: silicon bulk + dielectric coating § TS#3: replaced both mirrors B 1: glass bulk + metallic coating – OK only at low beam intensities - B 2: silicon bulk + polishing (no coating) – not usable for imaging - 12

BSRT – RF simulations LHC bunch power spectrum F = 650 MHz P_loss = 10 -50 W From January: RF laboratory measurements on spare tank F. Roncarolo - Evian Workshop 18 -Dec-2012 Credits: T. Mastoridis, P. Baudrenghien/CERN Longit. wake impedance of BSRT with and without Ferrite damping Measured LHC bunch power spectrum. A 650 MHz resonance is very dangerous. Mirror front Mirror Back B-filed of the beam in Time Domain. Red = Hot (bigger current density) Blue = Cold E-field of a dominant resonating mode at 650 MHz. (Q = 1263 / Rsh = 25841 Ohm) 13

BSRT – Upgrades F. Roncarolo - Evian Workshop 18 -Dec-2012 TS#4 – Intervention on B 2 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 it before 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 Te. V - 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? 14

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 F. Roncarolo - Evian Workshop 18 -Dec-2012 - BI is preparing a list of self checks to be implemented if possible during LS 1, 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 D 3 imaging - eliminates the need to compensate for light loss at the moment of the delay line insertion J. Wenninger – BI Day Dec. 2012 15

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 Vd. M scans) - dead time and afterpulse seems to change with filling pattern, to be checked after LS 1 - 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 B 1 F. Roncarolo - Evian Workshop 18 -Dec-2012 - § It can measure satellites and ghosts up to 10^-4 but is not good to verify bunch shape at a fine level J. Wenninger – BI Day Dec. 2012 Noted … 16

From 4 to 7 Te. V § 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 Te. V - BSRT: higher contribution from diffraction - Can correct for it, after quantifying it precisely - Can think about going to lower wavelength detectors F. Roncarolo - Evian Workshop 18 -Dec-2012 - § Lower BLM thresholds - Limits WS scans to ~ 1 e 12 Energy Limit Reason 450 Ge. V 2. 7 e 13 p Wire damage 4 Te. V 3. 6 e 12 p BLM threshold 6. 5 Te. V ~1 e 12 p BLM threshold § AGM, LDM - More photons, will adjust optical filters if needed 17

From 50 to 25 ns § WS cross-talk on electronics ~ 10 % between 25 ns slots (under study) - With a reduced wire diameter, can we scan 288 b at injection? - § BGI: F. Roncarolo - Evian Workshop 18 -Dec-2012 - no evident impact § BSRT: 25 ns would Increase the time to loop over all bunches (currently ~7 min for 1380 bunches) - § AGM, LDM: - No evident impact 18

Conclusions - Overview Transverse and longitudinal diagnostics allowed optimizing and safely running the LHC (WS as references, BSRT bunch-per-bunch, AGM) Transverse § 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 Te. V and 25 ns § Fundamental checks before LS 1 F. Roncarolo - Evian Workshop 18 -Dec-2012 - BSRT heating WS thresholds Need high intensity run in Jan-Feb 2013 !! § SW/Control - We need to profit of LS 1 for reviewing all instruments low and high level SW individually § Transverse Profile Workshop, CERN, April 2013 - Experts from GSI, DESY, Fermi. Lab etc … presenting experience with BGI, Sync. Light etc … 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) 19

F. Roncarolo - Evian Workshop 18 -Dec-2012 SPARES 20

BSRT – Optical Line Old Optics F. Roncarolo - Evian Workshop 18 -Dec-2012 Entrance (steering) mirror New Optics 21

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 F. Roncarolo - Evian Workshop 18 -Dec-2012 - From pilot bunch to ultimate intensity per bunch, but: - Limits on total beam intensity Energy Limit Reason 450 Ge. V 2. 7 e 13 p Wire damage 4 Te. V 3. 6 e 12 p BLM threshold 6. 5 Te. V ~1 e 12 p BLM threshold § 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 22

F. Roncarolo - Evian Workshop 18 -Dec-2012 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 20 um) - New WS: aiming for 2 um 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 LS 1 - Improve dynamic range - Get rid of filters avoid dependence on working point - PHD on electronics 23

BGI – Operational Specs § Gating/Integration Gated camera - Need to gate over multi-bunches to have enough signal (see dynamic range) - § Repetition Rate F. Roncarolo - Evian Workshop 18 -Dec-2012 - 50 Hz, limited by image digitalization (BTV) § Dynamic range With a “fresh” MCP: - 10 proton bunches with gas injection 10 -8 mbar - Single Pb ion bunch with gas injection 10 -8 mbar - A bit better at 4 Te. V due to denser beam - MCP aging rather quick - 24

BGI – Results Example II F. Roncarolo - Evian Workshop 18 -Dec-2012 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) Measurement at injection, investigating bunch length influence on beam size seen by BGI. 25

BGI - Performances § Resolution - Present optics gives 0. 115 mm/pixel F. Roncarolo - Evian Workshop 18 -Dec-2012 § 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 § LS 1: - Replace MCPs - Second camera with better performances 26

BSRT Operational Specs § Gating - Intensified camera gating down to 25 ns with a 12. 5 ns 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 @ ~12 Hz Can do single bunch single turn but not on consecutive turns F. Roncarolo - Evian Workshop 18 -Dec-2012 - § 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 - 27

BSRT – Heating vs bunch length F. Roncarolo - Evian Workshop 18 -Dec-2012 Clear evidence that heating is due to RF coupling with high intensity beams Temperature gradient changes at each bunch length step 28

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 - F. Roncarolo - Evian Workshop 18 -Dec-2012 § 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) - 29

F. Roncarolo - Evian Workshop 30 18 -Dec-2012

F. Roncarolo - Evian Workshop 31 18 -Dec-2012

BSRT - Heating § B 2 Temperatures end of August F. Roncarolo - Evian Workshop 18 -Dec-2012 Last two fills before putting mirror to OUT position and then removing it. + UFO activity …. 32

BSRT – Heating – B 2 Mirror 28 -Aug-2012 1 - Beam (spot not in the ‘right’ place vertically) e v o m e r r o r r i m F. Roncarolo - Evian Workshop 18 -Dec-2012 2 - Beam dump o t s s e c Ac 3 - Close Vacuum sector and retract mirror to OUT 4 -No beam, no motors movement, mirror moved 33

F. Roncarolo - Evian Workshop 18 -Dec-2012 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 M. Patecki, M. Sapinski 34

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 F. Roncarolo - Evian Workshop 18 -Dec-2012 - § 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) Energy Limit Reason 450 Ge. V 2. 7 e 13 p Wire damage 4 Te. V 3. 6 e 12 p BLM threshold 6. 5 Te. V ~1 e 12 p BLM threshold 35

BSRT (and BGI) - Calibration F. Roncarolo - Evian Workshop 18 -Dec-2012 sm [pixels] During 2012 heavily affected by extraction mirror heating (deformation + coating damages) Difficult to find a stable calibration w. r. t. WS = Measured Sigma M [mm/pixels] = System magnification (optical line + pixel size) • determined by optical line adjustment with energy (UND D 3) • reference target vs closed orbit bumps give up to 10% differences spsf [pixels] = measurement error due to • aberration, diffraction • extraction mirror aging/deformation 36

Longitudinal Density Monitor (LDM) - Upgrades § After LS 1: new BSRT optics, new light shielding less parasitic reflections - new detectors under investigation (e. g. fast PM) - B 1: new optics F. Roncarolo - Evian Workshop 18 -Dec-2012 Satellites 5 ns from SPS B 2: old optics Reflection on BSRT filter wheel, at a possible satellite location Different colors = different bunches After L 5 ns J. Wenninger – BI Day Dec. 2012 Noted … 37