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					Beam Instrumentation Overview

Status for initial commissioning &
 recent results with BBQ & PLL

LHC Machine Advisory Committee
           7th December 2006


     Rhodri Jones (CERN – AB/BI)
                                Overview
 • What’s required & when

 • Status of BI Systems
       Orbit & trajectory measurement
       Beam loss measurement
       Synchrotron light monitor
       Other Systems

 • Recent Results with the BBQ & PLL system
       US-LARP Collaboration with BNL & FNAL
       Tune, chromaticity & coupling measurements
           • RHIC and SPS results


LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
        Instrumentation – the essentials
•   First turn
     Screens, BPMs, fast BCT, BLMs

• Circulating beams at 450 GeV
    BPMs, DC BCT & lifetime, BLMs
    Tune & chromaticity
    Emittance: wire scanners.

• Snapback and Ramp
    Continuous Tune, Coupling & Chromaticity
    Orbit (+ feedback)
    BLMs to beam interlock controller etc.
    Continuous emittance monitoring: synchrotron light

    LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
LHC BPM System - General Layout



                 24 Directional Couplers
                 52 Enlarged Button
                   8 Trigger Button ElectrodeBPMs -
                       Warm,Electrode Warm (24mm)
                54100ButtonBPMs for36BPMs Chromaticity,
                 &Special BPMs         Tune & BPMs
                 912 of 1186 BPMs for the LHC
                  Total
                 Interaction Regions & Button LEP
                                  34mm
                  TransverseRecuperated from Electrodes
                    Buttons Damper RF, Beam Dump
                                for the
                       and its Transfer Lines
                  Main Arcs & Dispersion Suppressors




LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
                    Delivery Status of BPM Hardware
• BPM components all delivered
      3750 standard and 500 enlarged buttons
      3724 pre-formed arc cables and 592 special configurations
      430 coupler feedthroughs
      1000 cryostat feedthroughs

• Warm BPM & stripline electrode production
    Manufactured by BINP
        •    initial delivery non conform
        •    delivery schedule was a worry in 2005 MAC presentation
    Extensive follow-up during 2006 by both AB/BI & AT/VAC
        •    Delivery of all components now complete (few non-conformities pending)

• Special BPMs for Tune Measurement & Dump
      Design only completed early 2006
      Production by TS/MME and CECOM (Italy)
      Delivery was “just in time” for LSS4 installation
      Awaiting final delivery of dump line BPMs
        LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
                               Installed BPMs
• Total of ~660 cold BPMs installed (~330 SSS)
• Warm BPMs in LSS 8, LSS 1L and LSS 4 all installed




Enlarged button BPMs                        Warm directional coupler
 installed in Point 4                         installed in Point 8
     LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
           Status of BPM Acquisition System
• Series Production of all components underway
    Wide Band Time Normaliser
     (40MHz position measurement)
      • 480 of 2400 front-end cards received
      • 200 of 2400 digitiser cards received
      • all delivery to be completed by March 2007
    Digital Acquisition Board
      (DAB64x - TRIUMF)
      • Standard for BPM, BLM, Fast BCT, Wire Scanners,
        Luminosity & Q measurement
      • 220 of 1200 BPM type modules received
      • 185 of 500 BLM type modules received
      • all delivery to be completed by March 2007

• Reception Testing
    2 automated test benches constructed and manned by external personnel
    Used for adjustment and calibration of all Wide Band Time Normaliser Cards
    Beam simulator allows position & intensity linearity measurement for all cards
    All data stored in MTF & linked to serial number chip located on each card
      LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
           Status of BPM Acquisition System
• Infrastructure
    Nearly all fibre-optic, coaxial cable and WorldFIP control links in place
       • LSS7 and LSS3 will be equipped with radiation hard fibres
       • Produced by Fujikura (Japan) – first batch in production
       • Tests by Fraunhofer Institute and mixed field test in the SPS has shown them to be
         an order of magnitude less susceptible than the standard CERN mono-mode fibre



• Installation
    Tunnel installation and hardware
     commissioning has started in 8L
       • 23 of 34 positions in place
         (92 channels)
                            BPM/BLM limit of 6dB


      LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
                The LHC Beam Loss System
   Role of the BLM system:
         1.    Protect the LHC from damage
         2.    Dump the beam to avoid magnet quenches
         3.    Diagnostic tool to improve the performance of the LHC

                                                                                     Time
Name          Type                     Number Area of use              Maskable
                                                                                     resolution
BLMQI         Ionisation Chamber         ~3100       Arcs                   yes      1 turn
BLMCI         Ionisation Chamber          ~150       Collimation
                                                                            no       1 turn
BLMCS         SEM                         ~150       regions
                                                     Critical
BLMEI         Ionisation Chamber          ~400       aperture
                                                                            no       1 turn
BLMES         SEM                         ~150       limits or
                                                     positions
                                                     Primary                         bunch-by-
BLM__         ACEM (phase II)              ~10                              yes
                                                     collimators                     bunch

        LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
                         Beam Loss Detectors
• Design criteria: Signal speed and reliability
• Dynamic range (> 109) limited by leakage current through insulator
  ceramics (lower) and saturation due to space charge (upper)

Secondary Emission Monitor               Ionization chamber:
(SEM):                                         N2 gas filling at 100 mbar
     Length 10 cm                              over-pressure
     P < 10-7 bar                             Length 50 cm
     ~ 30000 times smaller gain               Sensitive volume 1.5 l
                                               Ion collection time 85 s

                                         • Both monitors:
                                               Parallel electrodes (Al, SEM:
                                                Ti) separated by 0.5 cm
                                               Low pass filter at the HV input
                                               Voltage 1.5 kV


        LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
                                                      BLM production at IHEP
• After readjustment of the
  production schedule in March
  a constant rate has now been
  achieved
• SEM production to start after
  ionisation chamber production
  is complete
                                          Ionisation chamber production
   # of ionisation chambers




                              4500        schedule
                              4000        at CERN
                              3500
                                          needed for installation
                              3000
                              2500
                              2000
                              1500
                                                                                                  Sector 7 – 8
                              1000                                                                fully equipped with
                               500
                                0
                                                                                                  ionisation chambers
                               24/03/06    02/07/06   10/10/06   18/01/07   28/04/07   06/08/07

                                                                                       time

                                 LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
             BLM integration and installations
• Integration of monitors in layout of ARC, IR 1 and IR 8 finished
• Integration will continue for the remaining points following installation schedule
• IHEP installation team (1 team leader and 4 technician):
     test of monitors with radiation source, shrinking of insulation tube, mounting of
      monitors, cable tray/cable fixation and electrical test of system
     in case of accelerated interconnection closure an increase in the team is possible

                  ARC quadrupole with 3
                  monitors on either site           Triplet quadrupole magnets IR 8




       LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
First use of LHC chamber design at CERN
                                 • CNGS Secondary beam width measurements
                                 • Interleaved CERN produced and IHEP
                                   produced LHC type Ionisation Chambers
                                                           Give very similar response
                    270cm
                                                                                               comparison measurement-simulation, vertical pit1
                                                 0.4

                                                                                                                                                                                                  meas: nominal
                                                0.35                                                                                                                                              sim: nominal


                                                 0.3



                                                0.25
                                  charges/pot




                                                 0.2



                                                0.15



                                                 0.1



                                                0.05
                                                                                                                             3.20 m
                                                  0
                                                   -157.5 -146.3 -135 -123.8 -112.5 -101.3 -90 -78.75 -67.5 -56.25 -45 -33.75 -22.5 -11.25   0   11.25 22.5 33.75   45   56.25 67.5 78.75   90   101.2 112.5 123.7 135 146.2 157.5


                                                                                                                         simulation; P. Sala et al
                                                                                                                   Fluka cm                                                                        5           5         5




LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
             BLM Acquisition Electronics
                                             Implemented on BDI DAB64x




Threshold Comparator: Losses integrated and compared to
threshold table (12 time intervals and 32 energy ranges).
  LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
         BLM test measurements at the SPS dump
      • Validation of complete BLM readout electronics chain
            200MHz fixed target beam
            Use of SPS ionisation chamber located near the internal SPS dump

FULL beam
intensity on
dump
Remaining
beam
dumped at
end of slow
extraction

Injection &
acceleration
losses
                                             Remnant decay after full
                                             intensity dump



        LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
                    Measuring Beam Size
• Beam Profile Measurements in the LHC
   Workhorses
     •    Synchrotron light monitor
     •    Wire scanners for cross calibration

   For injection & matching
     •    OTR screens

   For ions
     •    Rest Gas Ionisation Monitor (BGI)
         – Also used as back-up for SR monitor


    LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
     Synchrotron Light Monitors (BSRx)




BSRT light source: 5T Superconducting undulators
• Latest news: both SC undulators in place, see next CERN bulletin!
     Congratulations to the AT/MAS team
  LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
             Synchrotron Light Monitors




• Dielectric coated silicon extraction mirror
     first of its type - replaces traditional beryllium mirror
•    Tons of shielding and support structure in place
    36over 98% reflectivity in visible/IR achieved by a small Scottish company
      (Helia) using similar techniques to coating silicon diodes
    LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
            Synchrotron Light Monitor (BSRT)
• LHC BSRT fast camera tested in the SPS, Nov 2006
    Image is single turn beam intensity seen by OTR screen
    Scale in pixels
    optical magnification gives 20x20mm frame.




• Able to capture and store raw images at the SPS revolution frequency
    Will have to optimise the trade off between transfer rate, data treatment &
     dead time between measurements
        LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
                    Abort Gap Monitor (BSRA)
• System based on gated photomultiplier
• Tested in the SPS with synchrotron light source on fixed target beam
        Observation of injection kicker gap while beam is debunched before extraction.


                                                                 • Worked extremely well
                                                                 • Gain of photomultiplier is
                                                                   not as high as advertised
                                                                        Requires 15x more light
                                                                 • For LHC a longer
                                                                   integration time is possible
                                                                   (every ms for SPS)
                                                                 • BUT BSRA will require
                                                                   more light than anticipated
                                                                   at expense of BSRT



        LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
                                 Other Systems
• Nearly all specialised BI equipment located in LSS4
    After LSS8 this was the second full LSS to be installed
    A big effort made by BI technicians and engineers during 2006 together
    with TS/MME and AT/VAC to get everything ready in time
      • We just about made it !!




  Dump and
   DCCT ionisation
 Rest gasline FBCT
Wire scanner tanks
    chambers and
  BTV tanks final
     awaiting
 and mechanisms
    compensation
awaiting final
      installation
      in placeplace
  installation
  magnets in




      LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
            Tune, Chromaticity & Coupling
• Clear three step approach:
  1) Day 1 with kicked beams and classical motion analysis
       • Q kicker for both planes & both beams located in Pt 4
       • Chirp excitation using the transverse damper
  2) Day N with PLL tune tracking (US-LARP)
       • Recent experience gives us the hope that N is small!
  3) Day N+ with PLL measurement & Feedback (US-LARP)
       • Tune, chromaticity & coupling


• Requirements for stable PLL operational:
      lowering the excitation level to an insignificant level
      coping with coupling
                                    Collaboration with BNL & FNAL via US-LARP
      coping with chromaticity
      achieving compatibility with resistive transverse damping


    LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
       Measuring with Little or No Excitation –
     The Base Band Q Measurement (BBQ) System
                                 Direct Diode Detection (3D)




LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
           Continuous FFT and PLL Implemented in FPGA
          CORDIC:
          polar  rectangular
          avoids large LUTs
          uses simple operations
          saves FPGA space !                                                                          Frequency   Sweep/Lock
                                                                                                      generator
                                         Correction
                                                        -
                                                            Phase reference
                                                            Delay compens.                                                       f
           Ph   PLL
                                 Ph  I
                                                 +                                    PID
                     cordic                                       cordic                     Ph                                       40Mhz
Ph  PLL        a                 x       LP
                                         Correction
                                                            x
                                                        Amp. reference
                                                                                  a              I

           A y                   A       IIR            -        y
                                                                                                                       Ampl FB Off
               PLL

                      a
                                     I
                                                 +                    a               PID                                        A
                                                                                                      Fixed
                                 y       LP                 y
                                                                                                      Amplitude
APLL                      x              IIR
                                           Sin/Cos                            x              A   I

                                           Excitation
                       A cos(wt)
                          PLL




                       A sin(wt)
                                                                     DAC
           A   BEAM
                           PLL




                                                                     ADC                         3D
                                                                                              Front-End


                                                                                      BEAM



    Uses Standard DAB64x Module
                          cordic                                                                          BBQ pickup                 KICKER
                                                a                         x       A cos(wt)
                                                                                      PLL
             LHC Machine Advisory CommitteeyDecember 2006 - Rhodri Jones (CERN - AB/BI)
   Setting-up the 25ns Beam in the SPS




                                            Low intensity beam
                                            Residual oscillation
                                            without additional
                                            excitation clearly
                                            visible



LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
                      PLL tracking in the SPS
               Resonantly Extracted 25ns Beam in the SPS
                        Real-time Tune Display




• Nominal Beam - PLL OFF                           • Nominal Beam – PLL ON
    tune hardly visible                                 tracking achieved throughout cycle

     LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
  PLL Measurement on SPS Fixed Target Cycle




Tracks tune change of ~0.1 units per second
 LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
      PLL Measurement during Collimator MD




     Resolution of 10-6 achieved with 1s integration


LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
       Beam Transfer Functions in the SPS




• When things go wrong – thought to be due
• Standard Beam Transfer Function to a coupled bunch instability!
    Stable phase shifts – PLL can no longer lock
    Multiple peaks appear in Beam Transfer Function
    LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
       Measurement of Coupling using a PLL
                 Tune Tracker
Start with decoupled machine            Only horizontal tune shows up in horizontal FFT
Gradually increase coupling             Vertical mode shows up & frequencies shift
Fully coupled machine: D = |C-|                                 FFT of Horizontal Acquisition Plane
                    Ver                                                   Set Tunes
                                                                         V        H




                                                    Amplitude
                                                                                       By looking at
                                                                              D        contribution
                                                                                       of vertical
                                                                                       PLL in
                                                                                       horizontal
                                                                                       plane &
                                              Hor                                      vice-versa
                                                                                       the degree of
                                                                                       coupling can
                                                                                       be calculated



                                                                                      Frequency
       LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
Tune & Coupling Feedback at RHIC (2006)




LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
       Continuous Chromaticity Measurements
• The focus of the development for 2007
     RHIC to attempt chromaticity feedback
     SPS used to qualify new techniques for the LHC
• RF modulation with PLL Tune Tracking
     Standard technique used at RHIC & Tevatron
     may not be compatible with nominal collimator settings in LHC
• Other techniques under test
     Fast RF phase modulation – tests at FNAL & SPS (RF power an issue for LHC)
     Additional side exciters within PLL to measure tune width (phase slope)
     Continuous head-tail measurement with PLL excitation
         • Constant phase shift proportional to chromaticity
         • Requires sensitive measurement of head & tail oscillations  diode detection!!




       LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)
                                      Summary
• Both large distributed systems (BPM/BLM) currently on schedule
     Production of ionisation chambers at Protvino is progressing smoothly
          • One of the major worries last year

• Support for AB/BI from TS
     Significant support for Design and from the main CERN workshops
     Regular meetings have allowed problems to be solved quickly and priorities to be
      juggled to fit with installation requirements

• Most Vacuum Hardware now in place in Point 4
     Attention can turn to completing and testing the final electronics
• Tune, Coupling and Chromaticity Measurement
     Combination of BBQ and PLL is proving very powerful
     RHIC demonstration of combined tune and coupling feedback is very encouraging
     All efforts in 2007 will be focused on adding chromaticity feedback to the list

• Outlook for LHC commissioning
     All necessary instrumentation for the start-up foreseen to be in place
     Functionality will evolve through the commissioning phases
      LHC Machine Advisory Committee December 2006 - Rhodri Jones (CERN - AB/BI)

				
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