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STROMLO EVENT TIMING SYSTEM

CALIBRATION OF EOS/STROMLO TIMING CARD John Luck, Josh Vear and Chris Moore EOS Space Systems Pty. Ltd. STROMLO EVENT TIMING SYSTEM. Symmetricom XLi GPS Timing Receiver with high-stability ovenized crystal oscillator. Output: 1 p.p.s. and 10 MHz sine, etc.

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STROMLO EVENT TIMING SYSTEM

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  1. CALIBRATION OF EOS/STROMLO TIMING CARDJohn Luck, Josh Vear andChris MooreEOS Space Systems Pty. Ltd.

  2. STROMLO EVENT TIMING SYSTEM • Symmetricom XLi GPS Timing Receiver with high-stability ovenized crystal oscillator. Output: 1 p.p.s. and 10 MHz sine, etc. • “80 MHz Multiplier” producing 80 MPPS square waves (EOS – Josef Kolbl) • Buffer/Distribution Amplifier making 4 copies of 80 MPPS and of 1 p.p.s. (EOS) • Timing Card: Two Channels (for Start Diode and for CSPAD). Clock from 80 MPPS sync’d to GPS 1 p.p.s. at start of each pass or segment. Verniers based on capacitor discharge through constant-current circuit so voltage decay is linear (nominally) with time (EOS – Josh Vear) • Vernier Test Box (VTB) (EOS – Josh Vear) with LeCroy Wavemaster 8600 20 GS/sec Digital Oscilloscope • Delay Generator, producing laser & T/R commands, etc (EOS)

  3. EOS TIMING CARD with Scaler.Part of Vernier Test Box in background.

  4. EOS TIMING SYSTEM

  5. TIMING SEQUENCE

  6. VERNIER TEST BOX with 4 Delay Cables

  7. VERNIER TEST BOX Schematic

  8. AVAILABLE DELAYS IN VTBONLY NEED TO COVER 12.5 ns (1/80 MPPS)

  9. VTB DELAY CALIBRATION SETUP

  10. VTB CALIBRATION PROCEDURE • VERNIER 0 • Connect 1 GHz active FET probes at V0 and 80 MPPS inputs AT the Timing Card • For each delay cable combination take many readings of the input between 80 MPPS marks and VTB output on the Oscilloscope. Average. • Simultaneously read Timing Card results. Average. • Fit cubic curve to Oscilloscope vs. Timing Card. This constitutes its calibration curve. • Perform post-calibration “Confirmation Runs” per delay. • VERNIER 1 • Change one probe from V0 to V1 input, and repeat. Thus each channel is calibrated independently.

  11. FACTS AND FIGURES • Timing Card can handle 13,000 events/sec (but the computer operating system can not …..) • RMS JITTER from Confirmation Runs: 4.9 – 8.7 ps (~ 1mm) • Capacitor Leakage “droop” corresponds to about 2 ps It too will be calibrated and applied soon • 80 MPPS is the REFERENCE. Assumed on-time to GPS BUT: • Spec on 80 MHz Multiplier jitter not available • Jitter in Distribution Amplifier is Negligible (200 fs per ECL component) • Profusion of stiff cables in VTB to be replaced by Programmable Delay Lines (chip has been chosen)

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