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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,

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SLIDE 1

What you get ? Transverse and Longitudinal distributions

Evian Workshop 2012

18-Dec-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) Many others ….

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SLIDE 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.

18-Dec-2012 1 F.Roncarolo - Evian Workshop

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

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SLIDE 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)

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

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SLIDE 4

Wire Scanners – Dumps due to losses

18-Dec-2012 F.Roncarolo - Evian Workshop

22-Aug 12-Oct 22-Nov System B1 H (aged wire, changed during intervention to fix bellow leak) B1 H (new wire) B1 V (new wire) Beam Intensity 4.29e12 No dump 4.18e12 Dump 3.54e12 Dump BLM signal [Gy/s] 0.0091 0.0218 0.0335 Losses / proton @ downstream BLM [Gy/p] 5.4e-19 2.7e-17 2.4e-17

  • Aged wire partially sublimated smaller diameter  lower losses

16 um aged wire 34 um new wire

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SLIDE 5

From beam profile to emittance

18-Dec-2012 F.Roncarolo - Evian Workshop

Beta from model Beta from beta beating Beta from K mod

  • 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

M.Khun G.Trad

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SLIDE 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

18-Dec-2012 F.Roncarolo - Evian Workshop 5

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SLIDE 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

18-Dec-2012 F.Roncarolo - Evian Workshop 6

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SLIDE 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

18-Dec-2012 F.Roncarolo - Evian Workshop

During p-p runs:

  • Calibration more difficult
  • Some evidence of

dependence on bunch length

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SLIDE 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?

18-Dec-2012 F.Roncarolo - Evian Workshop 8

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SLIDE 10

BSRT - Introduction

18-Dec-2012 F.Roncarolo - Evian Workshop

Gated camera (BSRTS) DC Camera

Abort Gap Monitor (AGM)

  • Long. Density Monitor

(LDM) Optical delay line Neutral filters Color filters Proton/Ion beam

90 % 10 % 60 % 40 % 40 % 60 % 9

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SLIDE 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

18-Dec-2012 F.Roncarolo - Evian Workshop 10

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SLIDE 12

BSRT – Calibration Example

18-Dec-2012 F.Roncarolo - Evian Workshop

  • 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

Scraping B1 Vertical Similar examples exist at 4 TeV 1.3 mm 1 mm 0.8 mm

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SLIDE 13

BSRT – Heating – Findings after B2 mirror removal

18-Dec-2012 F.Roncarolo - Evian Workshop

Mirror coating blistered Mirror clamps deformed

  • 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

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SLIDE 14

BSRT – RF simulations

18-Dec-2012 F.Roncarolo - Evian Workshop

  • Longit. wake impedance of BSRT

with and without Ferrite damping Measured LHC bunch power spectrum. A 650 MHz resonance is very dangerous.

LHC bunch power spectrum F = 650 MHz P_loss = 10-50W

Credits: T.Mastoridis, P.Baudrenghien/CERN

B-filed of the beam in Time Domain. Red = Hot (bigger current density) Blue = Cold

Mirror Back Mirror front

E-field of a dominant resonating mode at 650 MHz. (Q = 1263 / Rsh = 25841 Ohm)

From January: RF laboratory measurements on spare tank

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SLIDE 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 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 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?

18-Dec-2012 F.Roncarolo - Evian Workshop 14

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SLIDE 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

18-Dec-2012 F.Roncarolo - Evian Workshop

  • J. Wenninger – BI Day Dec.2012 15
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SLIDE 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

18-Dec-2012 F.Roncarolo - Evian Workshop

  • J. Wenninger – BI Day Dec.2012

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SLIDE 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

18-Dec-2012 F.Roncarolo - Evian Workshop

Energy Limit Reason 450 GeV 2.7e13p Wire damage 4 TeV 3.6e12 p BLM threshold 6.5 TeV ~1e12 p BLM threshold

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SLIDE 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

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

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SLIDE 20

Conclusions - Overview

  • 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, April 2013
  • Experts from GSI, DESY, FermiLab etc … presenting experience with BGI, Sync. Light etc …

18-Dec-2012 F.Roncarolo - Evian Workshop

Transverse 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) Transverse and longitudinal diagnostics allowed optimizing and safely running the LHC (WS as references, BSRT bunch-per-bunch, AGM)

Need high intensity run in Jan-Feb 2013 !!

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SLIDE 21

18-Dec-2012 F.Roncarolo - Evian Workshop

SPARES

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SLIDE 22

BSRT – Optical Line

18-Dec-2012 F.Roncarolo - Evian Workshop

Old Optics New Optics

Entrance (steering) mirror

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SLIDE 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

18-Dec-2012 F.Roncarolo - Evian Workshop

Energy Limit Reason 450 GeV 2.7e13p Wire damage 4 TeV 3.6e12 p BLM threshold 6.5 TeV ~1e12 p BLM threshold

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SLIDE 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

18-Dec-2012 F.Roncarolo - Evian Workshop 23

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SLIDE 25

BGI – Operational Specs

18-Dec-2012 F.Roncarolo - Evian Workshop

  • 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

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SLIDE 26

BGI – Results Example II

Typical p-p high intensity fill

18-Dec-2012 F.Roncarolo - Evian Workshop

  • 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) Measurement at injection, investigating bunch length influence on beam size seen by BGI.

Bunch length from 1.4 to 1 ns ns (NO RAMP) 25

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SLIDE 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

18-Dec-2012 F.Roncarolo - Evian Workshop 26

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SLIDE 28

BSRT Operational Specs

18-Dec-2012 F.Roncarolo - Evian Workshop

  • 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
  • ver all bunches at flat top
  • Ions: From ~30 bunches at injection to average over all bunches at flat

top

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SLIDE 29

BSRT – Heating vs bunch length

18-Dec-2012 F.Roncarolo - Evian Workshop 28

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SLIDE 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,
  • ptical 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)

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

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SLIDE 31

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

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SLIDE 32

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

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SLIDE 33

BSRT - Heating

  • B2 Temperatures end of August

18-Dec-2012 F.Roncarolo - Evian Workshop

Last two fills before putting mirror to OUT position and then removing it.

+ UFO activity ….

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SLIDE 34

BSRT – Heating – B2 Mirror 28-Aug-2012

18-Dec-2012 F.Roncarolo - Evian Workshop

1- Beam (spot not in the ‘right’ place vertically) 2- Beam dump 3- Close Vacuum sector and retract mirror to OUT 4-No beam, no motors movement, mirror moved

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SLIDE 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

18-Dec-2012 F.Roncarolo - Evian Workshop

M.Patecki, M.Sapinski

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SLIDE 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)

18-Dec-2012 F.Roncarolo - Evian Workshop

Energy Limit Reason 450 GeV 2.7e13p Wire damage 4 TeV 3.6e12 p BLM threshold 6.5 TeV ~1e12 p BLM threshold

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SLIDE 37

BSRT (and BGI) - Calibration

18-Dec-2012 F.Roncarolo - Evian Workshop

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

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SLIDE 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)

18-Dec-2012 F.Roncarolo - Evian Workshop

B1: new optics B2: old optics

Reflection on BSRT filter wheel, at a possible satellite location

Satellites 5ns from SPS 5 ns Different colors = different bunches

  • J. Wenninger – BI Day Dec.2012

After L

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