Status%20of%20TTF%20HOM%20Project%20Aug%209,%202005

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Status of TTF HOM ProjectAug 9, 2005

• Project Scope Instrument both couplers for all
  SC cavities in the TTF2. (80 channels).
• System expected to operate as BPM system
• Expect ltfew micron resolution (train average)
• Expect lt30 micron resolution (bunch to bunch)
• Expect readout rate 1 Hz for all BPMs (5Hz May
  be possible)
• Want full integration into TTF2 control system.

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Hardware Status Downmix Chassis

• First Prototype board completed / stuffed Aug 5.
• Preliminary tests of Gain, Noise, linearity look
  good, should have numbers in a few days.
• Board designed for machine assembly
• Parts ordered
• In principal, just ship parts to vendor for
  assembly
• In practice, probably more involved that that,
  but no serious problems expected
• Chasses now simplified due to lower board power
  consumption (5 W / board).
• 5 Chasses spare, to be assembled at SLAC
• No problems anticipated

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Other Hardware

• VME crate / digitizers All commercial parts, but
  need to decide on control hardware.
• LO source Synthesizer, amplifier, Fan-out
  Straightforward.
• Calibration reference Must produce 1700 MHz
  tone, locked to harmonic of beam with 1
  picosecond stability
• Not designed yet (ideas only) technically
  challenging.
• Needs to use TTF triggers, timing signals to
  produce clean reference

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Timing

• The software / hardware must allow the HOM
  signals measurements to be correlated with
  specific conventional BPM measurement pulses.
• HOM system probably will not run at full 5Hz beam
  rate, so need method to identify which pulses are
  measured

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Software

• This probably represents gt3/4 of the entire
  project effort!!!
• Software architecture determines which VME
  hardware to purchase
• Architecture will depend on which group does
  which part of the work (software can have a steep
  learning curve).
• Need to make decisions soon!

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Software Components

• Data Download 10, 8 channel, 100Ms/s (12 or 14
  bit) VME digitizers.
• For 1 millisecond, get 8M samples / pulse, Can
  produce up to 80MByte/second data rate.
• Can run slower, but then this is limits bpm
  update rate
• Data Digital Downconversion, filtering to produce
  I,Q data for each bunch. Matrix multiply (small)
  to produce X,Y for each cavity.
• Very approximately 1 Gflop maximum processing
  required. 1Gbyte memory.
• DOOCS Server 1000 pulses, with X,Y, X, Y for
  40 cavities, at 5Hz beam rate.
• Total possible rate 800KWords / second.
• Calibration Software Same concept as existing
  HOM system but much more complex.
• Must move correctors, read conventional and HOM
  BPMs throughout machine.
• Use MIA, and model dependant analysis to
  determine cavity BPM calibration coefficients,
  download to DOOCS server.
• Does not need real time, but calculations can be
  complex.
• Probably have 1 computer as front-end, separate
  computer for calibration.

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Front End

• Data Download,Digital Down Conversion, DOOCS
  server.
• 2 Reasonable Options
• Standard DOOCS, VME crate controller (Force
  SPARC-56 CPU)
• Easy integration with TTF2
• Easy Support, (need new driver for digitizers)
• Low performance (250 specfp2k)
• SIS VME-PCI bridge
• Existing drivers for LINUX pc from SIS
• 80MB/sec transfer demonstrated by SIS
• 1600 specfp2k for PC.
• VME-2e
• Unique hardware difficult support

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Calibration Computer

• LINUX PC with Matlab probably the most reasonable
  solution.
• Interface with front end computer through DOOCS.
• Are large data transfers (1GB) in DOOCS OK?
• If we use a PC (PCI-VME bridge) for front end,
  can probably use same computer for calibration.