What you get ? Transverse and Longitudinal distributions Evian - PowerPoint PPT Presentation

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 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) 18-Dec-2012  Synchrotron light detector (BSRT)  Abort Gap Monitor (AGM or BSRA)  Longitudinal Density Monitor (LDM) F.Roncarolo - Evian Workshop 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 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) - F.Roncarolo - Evian Workshop  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

Wire Scanners – Dumps due to losses 22-Aug 12-Oct 22-Nov System B1 H ( aged wire , B1 H ( new wire ) B1 V ( new wire ) changed during intervention to fix bellow leak) Beam Intensity 4.29e12 No dump 4.18e12 Dump 3.54e12 Dump BLM signal [Gy/s] 0.0091 0.0218 0.0335 18-Dec-2012 Losses / proton 5.4e-19 2.7e-17 2.4e-17 @ downstream BLM [Gy/p] new wire aged wire F.Roncarolo - Evian Workshop 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 450GeV – 4 TeV Beta from model Beta from K mod Beta from beta beating 18-Dec-2012 F.Roncarolo - Evian Workshop 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  LS#1 Possibly thinner wires on all systems 18-Dec-2012 - Slightly higher speed (~10% max) - New bellows (aim at gaining a factor 5 in lifetime) - Improve OP GUI (OP+BI) - F.Roncarolo - Evian Workshop 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). -  Problem with remote camera gain control, important to provide repeatable beam size measurement. 18-Dec-2012  Camera failures intensifier reaching Mean Time To Failure -  Difficult cross-calibration F.Roncarolo - Evian Workshop no intensity overlap WS/BGI during p-p runs, BSRT B2 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, 7e9 charges/bunch - - could find good calibration w.r.t. to WS despite low BGI signal 18-Dec-2012 F.Roncarolo - Evian Workshop 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 To cope with high brightness beams at 7 TeV -  HV system upgrade 18-Dec-2012 To ensure a more stable operation -  Camera refurbishment  Low level SW re-design from scratch F.Roncarolo - Evian Workshop  What is the allowable gas budget during a year? Can we run continuously with gas injection? 8

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

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 - 18-Dec-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 F.Roncarolo - Evian Workshop - FESA server automatisms failures - - Steering following heating and energy ramp - Camera gain adjustment following injections and energy ramp 10

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 18-Dec-2012 Scraping F.Roncarolo - Evian Workshop Similar examples exist at 4 TeV 1 mm 1.3 mm 0.8 mm 11

BSRT – Heating – Findings after B2 mirror removal Mirror clamps deformed Mirror coating blistered 18-Dec-2012  Later Removal of B1 mirror evidenced similar effects Both mirrors were: silicon bulk + dielectric coating - F.Roncarolo - Evian Workshop  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 - 12

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

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 18-Dec-2012 Need high intensity test to validate it before end of this run ! -  Modified tank minimizing RF coupling  Operational fast scan server F.Roncarolo - Evian Workshop 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? - 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 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) 18-Dec-2012  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 F.Roncarolo - Evian Workshop - - 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 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 18-Dec-2012 setup to solve this for B1  It can measure satellites and ghosts up to 10^-4 but is not F.Roncarolo - Evian Workshop good to verify bunch shape at a fine level J. Wenninger – BI Day Dec.2012 16