Master%20Clock%20for%20IceCube:%20First%20Year%20Implementation

1
Master Clock for IceCubeFirst Year
Implementation

• Gerald Przybylski
• October 5, 2004
• Lawrence Berkeley National Laboratory

2
The Big Picture
GPS Clock
Passive Fanout
DOM Hub
DOM Hub
DOM Hub
DOM Hub
DOM Hub
DOM Hub
DOM Hub
DOM Hub
DOM Hub

• Temporary Counting House
• 1 GPS Clock
• 1 Passive Fanout
• 9 DOM Hubs

8 Tuned Fanout cables for phase matching 18
Identical 32ns Fanout cables 1 serial daisy chain
cable
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Goal

• Strong requirement
• 10 MHz Clock Delivered, in-phase, to all DOR
  cards, within fraction of a ns
• Time-tick arrival to satisfy DOR FPGA firmware
  set-up and hold requirements
• Weak requirement
• Timely arrival of serial string, within 1ms

4
GPS Technology

• TrueTime absorbed by Symmetricom
• Symmetricom part of Datum Inc.
• Performance Similar to other units at pole
• OCXO Option for better Allan Variance
• 10 MHz, 1Hz (or 1pps) and Serial Time string

5
Pulse and Timing Signals

• Multiple RF/Pulse Outputs- Internal jumpers -
  MUX outputs (control by front panel, or serial
  port)- Specialized (option) outputs
• IceCubes needs- Three 10 MHz outputs (sine)
  Fixed outputs J3e, J3f, J7- Five 1 Pulse per
  Second (or 1 Hz) Mux selected outputs J4,
  J5, J6, J8, J9
• Phasing required Tuned Cables for all outputs

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Passive Fanout

• 12 and 13 Resistive Matching Networks
• Simple, but effective
• Economical
• Trouble-free

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Time String

• Similar (standard?) time string format
• 1-second Burst format from printer port
• Content options - Like TrueTime string
  dddhhmmssq - Optional data suppressed by
  mode control
• ltcrgtltlfgt lt1ms after 1pps (1Hz) rising edge
• Firmware soon Kalle, and John Jacobsen
• Daisy-Chain fan-out cable required

8
Status

• GPS clocks Procured and Tested
• Passive Fan-out Fabricated and Tested
• Tuned BNC cables Fabricated and Tested
• Identical LEMO Cables On Order
• Shipment to Wisconsin Imminent