Jones-CAS2003_instrumentation_handout by wuzhengqin

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									Beam Instrumentation
         &
 Beam Diagnostics

          CAS 2003

Rhodri Jones [Hermann Schmickler]
              (CERN)
         Write-up and Hand-Outs
• The two lectures on beam instrumentation and
  diagnostics contain a lot of visual information
  (movies etc) which are not easy to reproduce in hand-
  outs.

• On the internet a similar lecture from CAS2002 can
  be downloaded from the url:
  http://sl-div.web.cern.ch/sl-div-bi/CAS%20/lecture/

• In about 2 weeks the lectures of 2003 will be
  available from the same url.

              CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
                               A Starter

A Beam Diagnostics and Instrumentation activity shall design,
build, maintain and improve the diagnostic instruments that allow
the observation of particle beams with the precision required to
diagnose, tune, operate and improve the accelerators and associated
transfer lines.

This means that Beam Instrumentation combines the disciplines of
accelerator physics, mechanical engineering, electronic engineering
and software engineering.

 In Short: One of the most fascinating fields of work I can imagine



                    CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
                    Starter Example:
             Setup for Head-tail observations
            SPS Tunnel                         Fast (2GS/s per channel)
                                                 Digital Oscilloscope
                                        Sum
Straight                   Hybrid
Stripline
Coupler
                                        Difference


                                                   Bunch Synchronous
 Beam       Beam Pipe                                   Trigger

                                                        VME
                                                     Acquisition
                   UNIX
                                                      via GPIB GPIB link
                User Interface
                   CAS 2003 Rhodri Jones (CERN - AB/BDI)          Beam Instrumentation
          …snapshot of movies to follow...

I ∆x
       Simulated betatron
       oscillation of bunch


                                                                       time


                                                          2 cursors marking time of
                                                          head- and tail sample



                   Time evolution of
                   head-tail phase-shift


                              CAS 2003 Rhodri Jones (CERN - AB/BDI)              Beam Instrumentation
The Head-Tail Principle




  CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
The Head-Tail Principle




  CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
  Deducible Beam Parameter: Chromaticity
(…more of this tomorrow in the diagnostics part)




                      Qs-1 = 230 turns




            CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
         Outline for Today
• Focus on “What and How we Measure”
      & the technologies involved
• Introduction
   → What do we mean by “Beam Instrumentation”
   → What instruments are involved

• Beam Instrumentation Selection
   →   Beam Position Measurement
   →   Beam Loss Measurement
   →   Beam Intensity Measurement
   →   Luminosity Measurement


            CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
                             Introduction
• What do we mean by beam instrumentation?
   → The “eyes” of the machine operators
     • i.e the instruments that observe beam behaviour

• What beam parameters do we measure?
   → Beam Position
      • Horizontal and vertical all around the ring
      • Corrected using orbit corrector magnets (dipoles)
   → Beam Loss all around the ring
      • Especially important for superconducting machines
   → Beam Intensity (& lifetime measurement for a collider)
      • Circulating current and bunch-by-bunch charge
   → Beam size
      • Transverse and longitudinal distribution
   → Collision rate / Luminosity (for colliders)


                      CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
                            More Measurements
      • Machine Tunes
                    QD       QF           QD
                                                    QF
            QF
                                                                Characteristic Frequency
                                                                 of the Magnet Lattice
                   SD       SF       SD                        Produced by the strength of the
            SF                                 SF
                                                                   Quadrupole magnets


      • Machine Chromaticities
Optics Analogy:                                              Spread in the Machine Tune
Achromatic incident light                                    due to Particle Energy Spread
                                                              Controlled by Sextupole magnets

                                                 Focal length is
                                                energy dependent
                         Lens
                                 CAS 2003 Rhodri Jones (CERN - AB/BDI)             Beam Instrumentation
      The Typical Instruments
• Beam Position
   → electrostatic or electromagnetic pick-ups and related electronics
• Beam Loss
   → ionisation chambers or pin diodes
• Beam Intensity
   → beam current transformers
• Beam Size (transverse)
    in diagnostics section of tomorrow
• Beam Size (longitudinal)
   → RF pick-ups or synchrotron light
• Luminosity
   → ionisation chambers or semiconductors
• Machine Tunes and Chromacitities
    in diagnostics section of tomorrow

            CAS 2003 Rhodri Jones (CERN - AB/BDI)         Beam Instrumentation
   LHC BPM System - General Layout
   ~ 24 Special BPMs for
  Transverse Damper, Tune
& Chromaticity Measurements                                                            44 Warm BPMs -
                                                                                    24mm Button Electrodes




                               Total of 1158 BPMs for the LHC
                                    and its Transfer Lines            24 Directional Couplers
                                                                      & 44 Enlarged Button
             100 Warm, Button Electrode BPMs                          BPMs for the
               Buttons Recuperated from LEP                           Interaction Regions




922 Button Electrode BPMs (24mm)
              for the
Main Arcs & Dispersion Suppressors
                              CAS 2003 Rhodri Jones (CERN - AB/BDI)                       Beam Instrumentation
The Arc BPM - SSS Layout




     CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
LHC Arc Type BPM (String 2)




     CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
              Interaction Region BPMs
                                        Liquid Helium
                                          Capillaries




                                                              Stripline
                  Q2 Coupler
                                                              Electrode

• Directional stripline couplers
   → Outputs signals only from the upstream port
   → Can distinguish between counter-rotating beams


                   CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
         Electromagnetic (Directional) coupler
• Is a transmission line (strip line) which couples to
  the transverse electromagnetic (TEM) beam field
                                                                                 a
       Zt ∞= 60 ln[(r+h)/r] ≡ Z0*[a/2π(r+h)]
      • Z0 is the characteristic impedance                               h            r
      • a, r, h, l are the mechanical dimensions
      • t = l/c is the propagation time in the coupler

   Downstream               Upstream

                                           • Two termination ports
                                                → Upstream: usually used to acquire signal.
                                                  • Same signal seen whether Downstream port is
                                                    open, shorted or terminated on Z0
                                                → Downstream: 3 cases
                             Beam                 • Upstream terminated on Z0 ⇒ no signal
                                                  • Downstream open            ⇒ delayed signal
                                                  • Upstream short circuit ⇒ delayed & reversed signal

                                 CAS 2003 Rhodri Jones (CERN - AB/BDI)                    Beam Instrumentation
              Coupler frequency & time response
 0                                                          300
 dB 0         1000       2000      3000     MHz      4000    mU                    Pulse width = 1.6 ns / I = 1e9p/b
 -5                                                         200                            30 cm
                                                                                           50 cm
                                                                                           75 cm
-10                                                         100


                                                              0
-15
                                                                   0   2       4              6              8    ns 10
                                                            -100
-20

                                                            -200
-25
                                                            -300
-30
                                                            80
-35                                                         mU                 Pulse width = 4.8 ns / I = 1e9p/b
                                                            60
                                Coupler 15 cm long

-40                                                         40
                                                                                            15 cm
                                                                                            30 cm
                                                            20                              50 cm

      → Sinusodal amplitude response
                                                             0
        •Maximum signal for f = 1/4*t                       -20
                                                                  0        5          10                15       ns    20


        •Zero signal for    f = 1/2*t                       -40

      → Time domain:                                        -60


        •Bipolar pulse                                      -80

                                CAS 2003 Rhodri Jones (CERN - AB/BDI)                              Beam Instrumentation
             Electrostatic PU (Button)

• Variant of electrostatic PU
                                                                    d
• Low cost ⇒ most popular                                  r
                                               Reference
                                               orbit


      Zt∞ ≡ d / 2πrCe

  Low frequency cut-off
  T = RlCe (few hundreds MHz)                                                 Ce
                                                                    V to V

                                                      Ib       Zt                    Rl




                   CAS 2003 Rhodri Jones (CERN - AB/BDI)                     Beam Instrumentation
          Button Frequency & Time Response
 0                                                         80
dB 10                    100                    MHz 1000
                                                           mU         Button; Ce = 8 pF / Zt = 1.1 Ω / Q = 1e9p/b
 -5                                                        60

-10                                                        40
                                                                                            W = 5.0 ns
                                                                                            W = 2.0 ns
                                                                                            W = 1.0 ns
-15
                                N = 1:1
                                                           20
                                N = 2:1
                                N = 4:1
-20                                                         0
                                                                 0              5                    10             ns
                                                                                                                     15
-25                                                        -20
              Button; Ce = 8 pF / Rl = 50 Ohm
-30                                                        -40


-35                                                        -60


      • Frequency domain:                                        • Time domain:
        → Impedance transformers                                     → Differentiated pulse
          improve the low frequency                                  → Amplitude is exponentially
          levels at the expense of the                                 bunch length dependent
          high frequency
                                CAS 2003 Rhodri Jones (CERN - AB/BDI)                              Beam Instrumentation
What does a real (LHC) electrostatic
    button monitor look like?




        CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
                  Processing system families
                                                         AGC
                                                         on Σ
                                          Heterodyne             Synchronous
                           MPX                                                   POS = (A-B)
                                                                  Detection



                          Hybrid                                 Homodyne
                                          Heterodyne                             POS = ∆ / Σ
                           ∆/Σ                                   Detection


          Electrodes                                            Sample,Track,
                                          Switch. gain                           POS = ∆ / Σ or
             A, B                                               Integr. & Hold       = (A-B)/(A+B)
                                           Amplifier

                         Individual       Logarithm.            Differential     POS = [log(A/B)]
Legend:                  Treatment         Amplifiers            Amplifier        = [log(A)-log(B)]

   / Single channel
                          Passive          Amplitude             Limiter,
     Wide Band           Normaliz.          to Time             ∆t to Ampl.      POS = [A/B]


    Narrow band
                                           Amplitude               Limiter,
                                                                      .
                                                                  φ to Ampl.     POS = [ATN(A/B)]
                                           to Phase
       Normalizer
       Processor


           Active
          Circuitry
                       From G.Vismara: BIW 2000; highly recommended
                            CAS 2003 Rhodri Jones (CERN - AB/BDI)                    Beam Instrumentation
  Criteria for Electronics Choice
 so called “Processor Electronics”
• Accuracy: mechanical and electromagnetic
  errors, electronic components
• Resolution
• Stability over time
• Sensitivity and Dynamic Range
• Acquisition (Measurement) Time
• Linearity (over aperture & intensity)
• Radiation tolerance


           CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
      LINEARITY Comparison
                                   1
                          Transfer Function


                                0.5
     ∆/ Σ
     Atn(a/b)                                                   Normalized
     loga-logb                                                  Position (U)
                                  0
-1           -0.5                      0                  0.5                  1


                               -0.5

                                            Computed
                                           Position (U)
                                  -1

                 CAS 2003 Rhodri Jones (CERN - AB/BDI)                  Beam Instrumentation
          Simple Example:
Sampling of Individual Detector Signals

                                        Dynamic range!

        LP
      Filter
                     S&H               ADC               A
A
                                                          Position
                                                             =
        LP                                             (A-B) / (A+B)
B     Filter

                     S&H               ADC               B


               CAS 2003 Rhodri Jones (CERN - AB/BDI)         Beam Instrumentation
                     A Real System:
LHC Amplitude to Time Normaliser Schematics




         A                      T1 = 1.5 ns                 A

        INPUT                   T1 = 1.5 ns             OUTPUT

         B                                                  B




                CAS 2003 Rhodri Jones (CERN - AB/BDI)            Beam Instrumentation
                     The Wide Band Time Normaliser
              1.5                                                                       3.0
                     A + (B + 1.5ns)
              1.0                                                  A            B       2.5
Amplitude A




                                                                         Beam
              0.5    A                                                                  2.0

              0.0                                                                       1.5

              -0.5                                                                      1.0




                                                                                               Amplitude B
              -1.0                                                                      0.5
                     B
              -1.5                                                                      0.0
                     B + 1.5ns          1.5ns
              -2.0                                                                      -0.5

              -2.5                                                                      -1.0
                                                 Time [ns]

                                 CAS 2003 Rhodri Jones (CERN - AB/BDI)          Beam Instrumentation
                     The Wide Band Time Normaliser
              1.5                                                                    3.0
                     A + (B + 1.5ns)
              1.0                                                  A         B       2.5
Amplitude A




              0.5    A                                                               2.0

              0.0                                                                    1.5
                     A + 1.5ns         1.5ns
              -0.5                                                                   1.0




                                                                                            Amplitude B
              -1.0   B                                                               0.5

              -1.5                                                                   0.0
                     B + (A + 1.5ns)
              -2.0                                  ∆t depends on position           -0.5

              -2.5                                                                   -1.0
                                                 Time [ns]

                                 CAS 2003 Rhodri Jones (CERN - AB/BDI)       Beam Instrumentation
                     The Wide Band Time Normaliser
              1.5                                                                3.0

              1.0                                                A       B       2.5
Amplitude A




              0.5                                                                2.0

              0.0                                                                1.5
                     A+(B+1.5ns)
              -0.5                                                               1.0




                                                                                        Amplitude B
              -1.0   B+(A+1.5ns)+10ns                                            0.5

              -1.5                                                               0.0

              -2.0
                                                 Interval = 10 ± 1.5ns           -0.5
                     System output
              -2.5                                                               -1.0
                                               Time [ns]

                               CAS 2003 Rhodri Jones (CERN - AB/BDI)     Beam Instrumentation
    Amplitude to Time Normaliser Evaluation
     Advantages                                   Limitations
• Reduced number of
  channels (x2)                             • Mainly reserved for
• No need for gain selection                  bunched beams
• Input dynamic > 50 dB                     • Tight time adjustment
• Signal dynamic independent                • Propagation delay
  on the number of bunches
                                              stability and switching
• ~10 dB compression of the
  position dynamic                            time uncertainty are the
  (recombination)                             limiting performance
• Auto-trigger                                factors
• Reduced N° of bits at
  equivalent resolution                     • No Intensity information
  (Normalisation)
                 CAS 2003 Rhodri Jones (CERN - AB/BDI)       Beam Instrumentation
    LHC Beam Position System Layout



                                                        Σ
           50 Ω                                     Intensity
                CALIBRATOR
          CABLE                                   Measurement
                                    LOW
                                    PASS
                                   FILTER



                  CAL. and TEST
PICK-UP                                 Trigger   NORMALISER                    INTEGRATOR             ADC        DAB
                   GENERATOR
                                                                     OPTICAL
                                                                      LINK

                                    LOW                                                       Auto
                                    PASS                                                     Trigger
                                   FILTER
           50 Ω    CALIBRATOR
          CABLE


                                                            TUNNEL             SURFACE




                                  CAS 2003 Rhodri Jones (CERN - AB/BDI)                                Beam Instrumentation
                                                    WBTN - Linearity v Intensity
                                                                                   For LHC Arc BPMs 1% ~ 130µm
                                          5%
Percentage Error w.r.t. Half Radius [%]




                                          4%
                                          3%
                                                                               Pilot                     Nominal Ultimate
                                          2%
                                          1%
                                          0%
                                          -1%
                                          -2%       Linearity - High Sensitivity
                                                    Linearity - Low Sensitivity
                                          -3%
                                                    Noise - High Sensitivity
                                          -4%       Noise - Low sensitivity
                                          -5%
                                            1E+08              1E+09                   1E+10               1E+11               1E+12
                                                                       Number of Charges per Bunch

                                                                 CAS 2003 Rhodri Jones (CERN - AB/BDI)                 Beam Instrumentation
                                                     WBTN - Linearity v Position
                                          8%                             For LHC Arc BPMs 1% ~ 130µm
Percentage Error w.r.t. Half Radius [%]




                                          6%

                                          4%

                                          2%

                                          0%

                                          -2%
                                                                                                 Calibration Point
                                          -4%                                                    Measured Value

                                          -6%                                                    Calibrated Value
                                                                                                 Linearised Value
                                          -8%
                                                -1        -0.5                 0                    0.5                  1
                                                                     Normalised Position

                                                         CAS 2003 Rhodri Jones (CERN - AB/BDI)                  Beam Instrumentation
           WBTN - Radiation Issues
• The Front-end Electronics for the Arc BPMs will be
  located under the main quadrupoles
   → can expect to see a dose of some 12Gy/year


• Tests in the SPS-TCC2 area during 2000 showed that
  use of DIGITAL components in the tunnel should be
  avoided
   → Most memories and FPGA’s too easily corrupted
   → Qualification of components long & difficult




                CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
             WBTN - Radiation Issues

• In 2001 : Fibre-Optic Link added to LHC BPM system
   → only the minimum of analogue electronics kept in tunnel
   → all sensitive digital electronics located on the surface
   → allows easy access to most of the acquisition system


• Cost of large scale fibre-optic installation compensated by
   → elimination of 13km of expensive low loss coaxial cable
   → reduction in number of acquisition crates
   → no bunch synchronous timing required in the tunnel




                   CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
             WBTN - Radiation Test Results
                                               2001 Test results of the
                                             very front-end WBTN card
                                                with Fibre-Optic Link
                                                    Initial performance
            6ps rms jitter




                                                             6.5ps rms
                                                                jitter

After 650Gy no significant
deterioration in the performance
is visible
                     CAS 2003 Rhodri Jones (CERN - AB/BDI)          Beam Instrumentation
The LHC BPM Acquisition System
                                Very Front-End WBTN Card
                                70MHz Low Pass Filters
                                Supplied by TRIUMF (Canada)
                                1310nm Diode Laser Transmitter
                                                     Tunnel
                                Single-Mode Fibre-Optic Link
                                               Surface
                                        VME based
                                 Digital Acquisition Board
                                    TRIUMF (Canada)
                                       (2 x 12bit 40MHz Acq)
                                    WBTN Mezzanine Card
                                     (10bit digitisation at 40MHz)
       CAS 2003 Rhodri Jones (CERN - AB/BDI)              Beam Instrumentation
      Operational Prototype Results in 2001
System extensively used in SPS for electron cloud & instability studies.




                     CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
      The Typical Instruments
• Beam Position
   → electrostatic or electromagnetic pick-ups and related electronics
• Beam Loss
   → ionisation chambers or pin diodes
• Beam Intensity
   → beam current transformers
• Beam Size (transverse)
    in diagnostics section of tomorrow
• Beam Size (longitudinal)
   → RF pick-ups or synchrotron light
• Luminosity
   → ionisation chambers or semiconductors
• Machine Tunes and Chromacitities
    in diagnostics section of tomorrow

            CAS 2003 Rhodri Jones (CERN - AB/BDI)         Beam Instrumentation
          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

• Acquisition requirements:
   → Calculation of quench level equivalent chamber signal
            – Electric currents from 600 pA to 300 µA
   → A dump should be requested at 50% of the quench level
            – i.e. from 300 pA to 150 µA
   → Extend dynamic range for sufficient sensitivity at low losses
            – Measuring current from 60 pA to 300 µA
   → Arc BLM acquisition rate not faster than one turn (89 µs)
            – Fastest total loss is ~ 6 turns & will be detected by special BLMs.

                      CAS 2003 Rhodri Jones (CERN - AB/BDI)              Beam Instrumentation
      Structure of the BLM Readout Chain
• Ionisation Chamber
   → transforms particle losses into an electric current
   → 6 per quadrupole (3 for each LHC ring) ⇒ ~3000 monitors
• Analogue Front-End
   → measures current and transmits data from Tunnel ⇒ Surface
• Dump Controller
   → processes data and interfaces to the beam interlock system

       Ionization                                       Tunnel     Surface
        Chamber
                                                                        Dump
                                   Analog                              Controller
                    max. 400 m    Front end         max. 2 km




                Analog Signals
                                                 Digital Signals


                       CAS 2003 Rhodri Jones (CERN - AB/BDI)                 Beam Instrumentation
                                       Quench Level Equivalent
                                          Chamber Current
                      1.E-03
                                                                             300 µA            450 GeV max
                      1.E-04                                                                   450 GeV min
                                                                                               7 TeV max
                      1.E-05
                                                                                               7 TeV min
Chamber current [A]




                      1.E-06

                      1.E-07

                      1.E-08

                      1.E-09
                                                                        600 pA
                      1.E-10                 One turn          60 pA
                      1.E-11
                           1.E-05   1.E-04     1.E-03    1.E-02    1.E-01    1.E+00   1.E+01   1.E+02      1.E+03
                                                              loss duration [s]


                                              CAS 2003 Rhodri Jones (CERN - AB/BDI)               Beam Instrumentation
                      Charge-Balanced Converter

                   Integrator                         v(t)
                                                             iin(t) + Iref               iin(t)
                       C
iin (t)                                 Treshold
                                        comparator
                                                                        va(t)
                                                                                                     ∆va
                                 Vtr
    Iref
                                       One-shot                                                       VTr
                                         DT
                                                                                                       t
                                                                                ∆T
                                                                                     T
               Reference
               current source           fout

          V-                                                                    iin
                                                                        f =
                                                                            I ref ∆T

                                CAS 2003 Rhodri Jones (CERN - AB/BDI)                    Beam Instrumentation
                          Current-Frequency Characteristics
                                              Frequency versus input current with linear error (with 400 m)

                        1.E+07                                                                                                     1%

                                                                                                                                   0%
                        1.E+06
                                                                                                                                   -1%
                        1.E+05
                                                                                                                                   -2%
                        1.E+04
output frequency [Hz]




                                                                                                                                   -3%

                        1.E+03                                                                                                     -4%

                        1.E+02                                                                                                     -5%

                                                                                                                                   -6%
                        1.E+01
                                                                                                                                   -7%
                        1.E+00
                                                                                                              Frequency [Hz]       -8%
                        1.E-01                                                                                flin_corr [Hz]
                                                                                                                                   -9%
                                                                                                              Lin Error [%]
                        1.E-02                                                                                                      -10%
                            1.E-11   1.E-10       1.E-09      1.E-08       1.E-07          1.E-06   1.E-05      1.E-04         1.E-03
                                                                       input current [A]




                                                 CAS 2003 Rhodri Jones (CERN - AB/BDI)                                    Beam Instrumentation
      The Typical Instruments
• Beam Position
   → electrostatic or electromagnetic pick-ups and related electronics
• Beam Loss
   → ionisation chambers or pin diodes
• Beam Intensity
   → beam current transformers
• Beam Size (transverse)
    in diagnostics section of tomorrow
• Beam Size (longitudinal)
   → RF pick-ups or synchrotron light
• Luminosity
   → ionisation chambers or semiconductors
• Machine Tunes and Chromacitities
    in diagnostics section of tomorrow

            CAS 2003 Rhodri Jones (CERN - AB/BDI)         Beam Instrumentation
Fast Beam Current Transformer




• Installed in the SPS and LHC transfer lines
• LHC fast BCT will be a scaled version
• Capable of 40MHz bunch by bunch measurement
• Dynamic range to cover 5×109 to 1.7 × 1011 cpb
          CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
      Fast Beam Current Transformer
      Image                                              1:40 Passive
      Current                                            Transformer
                                     Ceramic
                                      Gap



                                                        BEAM


                                                         80nm Ti Coating
                                                        ⇒20Ω to damp any
Calibration winding                                     cavity resonances

                 • 500MHz Bandwidth
                 • Low droop (< 0.2%/µs)
                CAS 2003 Rhodri Jones (CERN - AB/BDI)            Beam Instrumentation
             Acquisition Electronics
• Analogue Acquisition based on a fast integrator chip
   → Designed by the Laboratoire de Physique Corpusculaire, Clermont-
     Ferrand for use in the LHCb Preshower Detector.

   → Uses interleaved, 20MHz integrators and sample & hold circuitry to
     give 40MHz data.

• Digital Acquisition
   → PMC size Mezzanine card developed by CERN & contains
      • Fast integrator chip
      • 12bit, 40MHz ADC
      • Timing provided by the TTCbi module, part of the Timing,
        Trigger & Control system developed for the LHC experiments

        Mezzanine sits on the same VME 40MHz Data Acquisition
        Board developed for the LHC Beam Position System (TRIUMF,
        Canada)
                  CAS 2003 Rhodri Jones (CERN - AB/BDI)       Beam Instrumentation
                  Acquisition Electronics
                                                                       To VME
               Fast Integrator Chip                                     Digital
                                               Track                  Acquisition
                                               & Hold                   Board
Differential                                                         12-bit
Input from                                                     MUX
                                                                     ADC
 Fast BCT
                                              Track
                                              & Hold

                    20MHz Clock Creation

                       40MHz TTC Input from TTCbi

                       CAS 2003 Rhodri Jones (CERN - AB/BDI)         Beam Instrumentation
       Acquisition Electronics

              Integrator Output




                  25ns



             FBCT Signal after 200m of Cable




Data taken on LHC type beams at the CERN-SPS (2002)
           CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
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                                                                                                        Results from the CERN-SPS (2002)




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                                         Bad RF Capture of a single SPS LHC Batch (72 bunches)
Beam Instrumentation
      The Typical Instruments
• Beam Position
   → electrostatic or electromagnetic pick-ups and related electronics
• Beam Loss
   → ionisation chambers or pin diodes
• Beam Intensity
   → beam current transformers
• Beam Size (transverse)
    in diagnostics section of tomorrow
• Beam Size (longitudinal)
   → RF pick-ups or synchrotron light
• Luminosity
   → ionisation chambers or semiconductors
• Machine Tunes and Chromacitities
    in diagnostics section of tomorrow

            CAS 2003 Rhodri Jones (CERN - AB/BDI)         Beam Instrumentation
  Luminosity & Beam-Beam Tune Shift
                                                     MN 2
                                         L = f rev
• Luminosity                                         4πσ*
                                                        2


                                               σ*
                                                2

• Normalized emittance                  εN = γ
                                               β*
                                                Nrp
• Beam-beam tune shift               ∆ν bb =           ≤ 0.006 ( LHC)
                                               4πε N


                                 MNγ∆ν bb
               ∴       L = f rev
                                   β*
• To maximize L and minimize the stored energy,
  increase N to the tune shift limit, choose large M
  and small β*
               CAS 2003 Rhodri Jones (CERN - AB/BDI)               Beam Instrumentation
      Nominal locations of the front quadrupole
        (TAS) and neutral (TAN) absorbers




• The TAS absorbs forward collision products that have escaped the beam
  tube in front of Q1 (mostly charged pions and photons)

• The TAN absorbs forward neutral collision products (mostly neutrons and
  photons) and is placed in front of the outer beam separation dipole D2



                  CAS 2003 Rhodri Jones (CERN - AB/BDI)       Beam Instrumentation
        TAN Power Deposition (W/kgm)




• Peak power density of 1-10 W.kg-1.m-1 (location of ionization chamber)
• A 3m radiation hard cable will allow electronics to be located in a region with
  power density < 10-5 W.kg-1.m-1 (100 Gy/year for nominal operation)

                       CAS 2003 Rhodri Jones (CERN - AB/BDI)         Beam Instrumentation
        LHC Luminosity Measurement
Requirements:
• Capable of 40MHz acquisition
• Has to withstand high radiation dose: ~108 Gy/year
    → estimated 1018 Neutrons/cm2 over its lifetime (20yrs LHC operation)
    → estimated 1016 Protons/cm2 over its lifetime (20yrs LHC operation)
• No maintenance

Candidates:
• Ionisation Chambers
   → developed by LBL
          – Good radiation hardness
          – Difficult to get working at 40MHz
• CdTe detectors
   → developed by CERN in collaboration with LETI (Grenoble)
          – Fulfills 40MHz requirement
          – Not yet proven for the highest levels of radiation
                     CAS 2003 Rhodri Jones (CERN - AB/BDI)       Beam Instrumentation
    Polycrystalline CdTe Detectors
• Experience at CERN with CdTe X-RAY detector
  → running in LEP for beam emittance measurement
  → was used up to the end with total dose 1014 Gray
• Advantages
  → large number of e- created per MIP (~5 × Diamond)
  → very fast response time
  → simple construction




               CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation
            CdTe Detectors – Test Set-up
                                          B ia s V o lt a g e

         D e te c to r
 Sr90                                                            Digital
Source                                                           Oscilloscope

                                             A= 80
                  5 0 o h m c a b le

                                                                 Amplifier Output

                                               ~10ns
                                                                   Averaged
                                                                 Amplifier Output



                                                                 Output Histogram


                         CAS 2003 Rhodri Jones (CERN - AB/BDI)               Beam Instrumentation
                                  Polycrystalline CdTe Detectors

                                       Comparison of charge collection
                                                       (normalized for a thickness of 470 microns)
                               70000
                                           det 253 / 2 GhZ linear Amplifier
(e- per detected Sr90 decay)




                               60000       det172 / integrating amplifier
      Charge collected




                               50000
                               40000
                               30000
                               20000
                               10000
                                   0
                                       0        100          200           300       400             500   600        700
                                                                           Bias voltage



                                                  CAS 2003 Rhodri Jones (CERN - AB/BDI)                    Beam Instrumentation
                                  Irradiation Test Results
• CERN-SPS (2001)
                → Irradiation test up to 1015 neutrons/cm2

                                            T ime response of CdT e samples
                                              b e fo re ir ra dia tion : sa m ple 1 7 2R E F
                                       a fte r irr ad ia tio n s am p le 17 2 N (10 ^ 15 n /c m 2 )


                       -1
 Output signal (A.U)




                       -3
                                                                                            17 2R E F
                       -5                                                                   17 2N

                       -7

                       -9
                            -10   -5         0       5       10      15      20       25      30         35      40
                                                                    ns
                                           CAS 2003 Rhodri Jones (CERN - AB/BDI)                        Beam Instrumentation
                                            Irradiation Test Results
• Triga type reactor (Ljubljana,Slovenia - 2002)
   → Irradiation steps
      • 1013 neutrons/cm2
      • 1015 neutrons/cm2
      • 1016 neutrons/cm2 activation of all set-up
                                         – next step 1018 neutrons/cm2 (2003)

                                                     Carrier lifetime measurement
                                             CdT e detector n:417 (326 microns /400 Volts)

                                                  0.00
                                   -10       -5           0     5        10           15           20   25    30
   Amplitude of the signal (A.U)
           linear scale




                                                                              After 10^16 n/cm2
                                                  -0.50                       before irradiation




                                                  -1.00
                                                              Time in nanosecond

                                                  CAS 2003 Rhodri Jones (CERN - AB/BDI)                      Beam Instrumentation
  We have seen a wide variety of
   technologies and applications

Tomorrow we will see how to use the
  instruments to run and optimize
           accelerators
                =
     Accelerator Diagnostics

 http://sl-div.web.cern.ch/sl-div-bi/CAS%20/lecture/

         CAS 2003 Rhodri Jones (CERN - AB/BDI)   Beam Instrumentation

								
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