IceCube Master Clock

Overview

The Master Clock subsystem of IceCube provides a timing reference for all elements of the IceCube array against which all non phase-locked clocks can be compared. The collection of 5000 optical modules, drifting randomly, and averaged, represent a highly reduncant, extremely stable reference.

The master clock in the counting house takes an even more stable and accurate frequency and time source, and distributes it throughout the counting house to all DOM Hubs, where it is fanned out to the individual DOR (line receiver) cards.

Available Time and Frequency Sources

The US Naval Observatory array of 20 atomic clocks keeps time to < 2x10-15.

GPS satellites synchronized to USNO clock.

GPS stability degraded to ~4x10-8 by
Radio Propagation Path variations
GPS Receiver Local Oscillator jitter.

GPS less stable than oscillators in the DOMs

Presentation

DOMHub Hardware Review and Workshop ppt Presentation

Comparing Products

The Loran-C frequency standard, the model FS700, has a phase comparator which allows it to be used to compare its internal standard to external sources.
Data File

PRS-10 Rubidium Oscillator modules

Settings
Tracking with default parameters (begins with power-on for one of units)

ET6000 Serial String Timing

The TrueTime XL series and the ET6000 series GPS clocks both deliver a similar time string data burst consisting of Julian day, Hour, Minute and Second, followed by a single 'quality' character. In the TrueTime clock, the time string data burst is contiguous to the <CR><LF> characters terminating the burst. The start bit of the <CR><LF> begins less than 1ms after the 1pps time tick in both the TrueTime XL clock, and ET6000 clock. For the ET6000, there is a gap between the time burst data and the <CR><LF>. See screen-snaps for more insight, and documentation of timing behavior.

First Year Fan-Out

Fanout for the Temporary Counting House, January 2005
10 MHz phase matching in Temporary Counting House, January 13, January 17 2005
Skew Study

Fanout Design Options

Fanout Trade Study

Work in Progress

Draft of Schematic