Tevatron Software Digital Receiver Beam Line Tuner

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Tevatron Software Digital Receiver Beam Line Tuner

• Vic Scarpine
• Instrumentation
• Instrumentation Meeting
• July 13, 2005

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Introduction

• Primary function of a Beam Line Tuner (BLT) is to
  measure turn-by-turn transverse beam positions
  for all bunches during transfers from one
  accelerator ring to another
• Can measure betatron oscillations, fractional
  tune, coupling, time-of-arrival, synchrotron
  oscillations, emittance growth, etc
• Focus has been on betatron measurements for
  improved closing
• Feed-forward correction system correct magnets
  for next transfer
• BLT is a key component for reducing transverse
  emittances and increase luminosity

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Tevatron BLT

• Measure all proton and pbar transfers from Main
  Injector to Tevatron
• Requirements
• Measure initial injection oscillations for every
  proton and pbar bunch
• Measure tunes, emittance growth, synchrotron
  frequency
• Measure bunch time-of-arrival relative to RF
• Beam formats
• Pbar
• Four 53 MHz bunches separated by 392 ns at 150
  GeV
• Protons
• Single 53 MHz bunch at 150 GeV

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Basic BLT System
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Analog Signals - Striplines and Fanout

• TeV Stripline Parameters
• 30 dB directionality
• 1 meter long (lt 1/4 l)
• D 83 mm
• 0.65 dB/mm Sensitivity
• Located at near F0
• Optimally separated proton and pbars
• Fanout Box
• M/A-Com H-9 Junction Hybrid generates AB and A-B

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Tevatron Scope BLT

• Use Tektronix TDS7104 as fast waveform digitizer
• 2.5 GSample/sec/channel
• Segmented memory
• Embedded PC/Windows
• Samples pbar bunches each transfer
• Signal processing analysis of waveform in Scope
  PC
• Decimate data to single position per bunch
• Pbars 64 turns
• Too slow for protons
• Only used for closing pbars

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Tevatron Software Digital Receiver BLT

• Software Digital Receiver system for pbars
  (similar for protons)
• 30 MHz LP to ring single 53 MHz bunch
• Digitize bunches at 2RF
• Transfer digital data to PC
• Down convert at 30 MHz
• Correlate with window function
• Correlation max gives A and B
• Generate position and time-of-arrival for 1000
  turns

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Tev BLT Trigger

• UCD VXI trigger module
• Use TCLK and BSCLK to trigger pattern generator
  turn-by-turn at injection
• Use pattern generator to gate Struck digitizing
  card for injected proton or pbar bunches

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Tev BLT Digitizer

• Struck SIS3300 Digitizing card
• 8 ADC channels per board
• 12 bit ADCs
• Digitizing clock at 106 MHz (2RF)
• 128K samples per channel
• 128 sample per turn for 1024 turns
• 4 x 32 sample per pbar bunch ( 320 ns window for
  each pbar bunch)
• 30 MHz signal damps out in 150 ns

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Analog Signals

• 53 MHz signal too short for 106 MHz digitizer
• Stretch signal using 30 MHz low-pass filter

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Down Conversion
Down convert digitized signal
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Windows for Convolution
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Convolution
Use peak of each convolution bump for A and B
values
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Store 4175 Proton Vertical Oscillations
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Store 4175 Proton Horizontal Oscillations
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Store 4175 Injections Oscillations
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Store 4210 Pbar Injections
Why is 4th bunch different closed orbit than
first three bunches? (Of course it cant be!)
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Proton Contamination on Pbars

• Two effects
• Proton reflection 600 ns later falls on pbar
  bunch (except for last pbar)
• Proton signal generates some sort of structured
  reflection in pbar signal
• Fix Add 10 db attenuators at stripline on proton
  signal cables

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Pbar Oscillations after Attenuators
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Pbar Fractional Tunes
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Pbar Time of Arrival Relative to RF

• Use real and imaginary portions of convolution to
  determine phase of bunch relative to RF
• T 1/(2pf)atan(Imag/Real)

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Summary

• Tevatron software Digital Receiver BLT measuring
  turn-by-turn transverse positions for all proton
  and pbar bunches for each shot for 1000 turns
• Position information being used for emittance
  growth estimates
• BLT also determining bunch time-of-arrival
  relative to RF
• Presently system only used for time-of-arrival
  information
• Want to use system to close on protons (and
  possible close on pbars)

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