Recycler Dampers - Nathan Eddy

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					Recycler Transverse Damper System


      Pbars in Recycler Ring
     Stripline                    Split Plate
     Kickers                       Pickups
                             V1




                  Vertical    LPF     A-B
                   Digital
                  Damper
                              LPF               A-B


            Similar for Horizontal
                   V1 Digital Damper
•   Boards used for MI Damper
    systems                                 Implemented in one FPGA based damper
•   Standalone board with on board          board developed by B. Foster & A. Seminov
    cpu (Sharc) & ethernet –
    communicates with ACNET via
    OAC
•   Four boards are operational
     – 2 for MI dampers, 1 for Recycler
       Damper, 1 being used for Booster
       damper studies
     – A 5th board exists but was never
       made operational
     – At present, the Booster board can
       be considered spare hardware –
       work is needed to actually make it
       into a spare for any of the
       operational systems
•   Operational since fall 2005 with no
    major hardware/system issues
         V1 Damper Block Diagram
                                                                   Peak Detector & RMS
           4 Sample                                                Readback by ACNET
            Boxcar
             Filter
ADC                                                                                DAC
            Box        X      Delay   +               -     X       Delay
Input                                                                             Output
212MHz                Input                               Output
                      Gain                   1 Turn        Gain             Invert 212MHz
ADC                                                                                DAC
            Box        X      Delay          Delay                                Output
Input

                                          Notch Filter
   Peak Detectors
   Readback by ACNET


         • System Bandwidth is determined by analog LPF on inputs
         • Programmable delay is limited to 212MHz clock rate (1/4 RF bucket)
V1 Damper Amplitude and Phase
         Response




•   Phase has been inverted so that 0° is damping
•   The analog 30MHz LPF causes phase shift as it rolls off the gain
•   The system goes unstable at ~37Mhz once the Beam Density reaches about 2.5
                  V2 Digital Damper
•   Developed as next generation
    replacement for the “Foster” Board
•   VME format to take advantage of
    standard controls software
     – Interface implemented in FPGA
     – Remove Sharc processor
•   Same basic design with updated
    FPGA and Digital to Analog
    Converters
     – Applied lessons learned on V1 design
       to take better advantage of FPGA
       features
•   15 boards have been assembled
     – Used for Recycler RF Adaptive
       Correction
     – Used for Recylcer ACBEAM intensity
       Monitor
     – Used for MI Anti-proton Damper
     – Plan to replace MI Proton Dampers
     – 8 spares available
             V2 Recycler Damper
• Faster DACs and next generation
  FPGA allow us to double the         Use 2 VME boards
  system bandwidth and increase
  performance                           -1 per plane
• Standard Controls ACNET
  interface implemented in VME
  processor
• Use extra channels for Testing &
  Diagnostics
• Network analyzer can be hooked
  up to spare channels for transfer
  function measurements
   – Can make both open loop
     measurements without changing
     cables on operational system
   – Can also make closed loop
     measurements
         V2 Damper Block Diagram
                                                                Peak Detector & RMS
          8 Tap                                                 Readback by ACNET
           FIR
          Filter
ADC                                                                             DAC
          FIR       X      Delay   +               -     X       Delay
Input                                                                          Output
212MHz             Input                               Output
                   Gain                   1 Turn        Gain             Invert 636MHz
ADC                                                                             DAC
          FIR       X      Delay          Delay                                Output
Input

                                       Notch Filter
   Peak Detectors
   Readback by ACNET

    • System Bandwidth is controlled by FIR filter with constant phase
        the analog anti-alias filter is upped to 70MHz
    • Programmable delay possible at 636MHz clock rate (1/12 RF bucket)
    • This allows increased system bandwidth to improve performance
V2 Damper Amplitude and Phase
         Response




•   Phase has been inverted so that 0° is damping
•   The analog 70MHz Filter does not affect the phase until about 60MHz
•   System gain is controlled with programmable FIR filter
•   The system goes unstable >70MHz once the Beam Density is > 4
                       Brief V2 History
• First issue was with analog input circuit to the ADC
    – Modified circuit to improve signal termination
    – 1st modification was susceptible to a failure due to poor solder joint which
      caused 7.5MHz resonance
    – Has been fixed
• Remaining issues have all been caused by timing issues within the
  FPGA design
    – Fixed logic which handles ADC/DAC data
    – Found and eliminated temerature dependence in FPGA PLL clocks – was
      causing delay shifts in design
    – Latest issue appears due to rare (1 second/50 hours) timing glitch within
      the digital filter logic
        • Only present in Horz board whose FPGA runs hotter due to crate
             – Horizontal VME slots and poor air flow
        • This is a product of the most recent design – not observed before 12/07
    – Note that marginal timing issues are sensitive to temperature & power
           Installation on 3/18/08
• While preparing to switch that morning, Vertical board
  spontaneously performed a firmware reload from flash
  memory
   –   Made decision to abort the switch
   –   Never observed before
   –   FPGA lost design – power glitch?
   –   Glitch on VME_SysReset*?
   –   Has not happened again…
• Horizontal Board had PLL losing lock that afternoon
   – Clock input was swapped and moved to Z crate
   – Removed from MI60 and put in teststand – fine since…
         Installed on 4/23/08
• Found blown fuse on Reset Card
  – VME_SysReset* on backplane was 2V
• Updated Design to be less sensitive to
  glitches on VME_SysReset*
  – Require signal to be low for >200ns
• No further spontaneous resets observed
  for 3+ weeks of monitoring
• Made request to install
          Initial Results Good
• Attempted to induce
  instability with 80e10
   – Density reached ~3.5
                                                         RR damper closed loop measurements
                                        1.1                                                         30
                                                                  10/100/200/400 frot




   – No instability                     1.0                                                         20




• Measured closed loop


                            amplitude




                                                                                                           degrees
                                                          amplitude
                                        0.9                                                         10




  response during test                  0.8
                                                         phase
                                                                                                    0



   – Looked good                        0.7                                                          -10
                                           0.44   0.46    0.48        0.50        0.52    0.54   0.56
                                                                      f/frot
     Clock PLL Event on 5/1/08
• Vertical Damper Turned
  Off when it’s RF PLL lost
  lock
   – Got an immediate vertical
     instability
   – The Vertical Damper in the
     test crate also turned off
• Jim & I were both at MI60
  at the time looking into
  scope and network
  analyzer issues
                The Suspects
• Power
  – Hard to imagine this just hitting 1 of 2 boards in 2
    different crates
  – The crates are on completely separate circuits
• Temperature
  – Known temperature issues with FPGA and PLL
  – Found Fan on Operational Vertical board was
    stopped but Test Vertical was fine
• Noise/Problem with Clock
  – Could not see how only 2 of 4 boards would lose lock
              Temperature
• Installed Temperature
  monitors and new
  fanpacks
• Did not see any
  Events or
  temperature
  correlation
      Started Looking at Noise
• On 5/5 saw 4 glitches in 1 hour while poking
  around at MI60
• All recent glitches (last few months) occurred
  when someone was at MI60
• Discovered Cell phone activity at 800-900Mhz
  was coupling into clock circuit and causing PLL
  to lose lock
• Able to reproduce reliably in teststand
• Looking at circuit on NA showed high
  impedance from 700Mhz to 1GHz
        Clock Improvements
• Implemented filters and shielding to
  eliminate high frequency noise from the
  clock input circuit
• No longer see PLL glitches from cell
  phone or 1Watt RF antenna
• Also implemented state machine to
  provide best recovery scenario should the
  PLL briefly lose lock in the future
                   Summary
• Have identified cause for PLL to lose lock
  – Last few “glitches” now completely understood
  – Have a very plausible root cause for the timing issues
    which have plagued the system for the last 6 months
• The VME Dampers are now back in operation

				
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posted:4/23/2013
language:German
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