WP #5195 

Dave Barker, Jim Batch

The 4310B Cesium Frequency Standard has been synchronized to the 1PPS output of the Symmetricom NTP server in the MSR. The 1PPS leading edge from the 4310B is now leading the 1PPS leading edge from the NTP server by 60 to 64nS, within the +/- 100nS specification of the 4310B.

The 4310B was then used to synchronize the Timing Solutions Time Distribution System (TDS).  The 10MHz output of the 4310B is connected to the 10MHz input of the TDS flywheel, the 1PPS output of the 4310B was connected to channel 1 input of an oscilloscope, and the 1PPS out of the TDS was connected to channel 2 of the oscilloscope.  The slew of the TDS was adjusted to provide 0 offset between the 4310B and the TDS 1PPS.

A second (older) 4310 was then synchronized to the 1PPS output of the Symmetricom NTP server in the MSR using the same procedure as the 4310B.  This 4310 is in a short equipment rack with a UPS and has been powered for over 1 month.  This setup is portable, used to synchronize the end stations.  The 1PPS leading edge of the portable 4310 lags the leading edge from the NTP server by 28-32nS, providing a difference of about 90nS between the two standards, where the TDS 1PPS leads the portable 4310.  Both the TDS 1PPS and portable 4310 1PPS were left connected to the timing comparator in the MSR overnight to monitor the stability, which was good.

Today, the portable 4310 was loaded into a van and taken to EY to compare with the 1PPS output of the time code translator (TCT) which is connected via fiber to the TDS in the MSR. The delay adjustment of the TCT was set to have the leading edge of the TCT be 90nS before the leading edge of the portable 4310, the 90nS being the time difference of the portable 4310 to the TDS.  The adjustment is to the nearest 10nS, and ended up at about 85nS.  The procedure was repeated at EX, and the adjustment ended up at 90nS.  This leaves the TCT units at the end station with 1PPS signals synchronized to the corner station TDS.  The 1PPS signals for each unit is connected to input 1 of the timing comparators at EX, EY, and the MSR, allowing the timing differences to be monitored as EPICS channels.

EX - H1:SYS-TIMING_X_FO_A_PORT_9 SLAVE_CFC_TIMEDIFF_1
EY - H1:SYS-TIMING_Y_FO_A_PORT_9 SLAVE_CFC_TIMEDIFF_1
MSR - H1:SYS-TIMING_C_MA_A_PORT_2 SLAVE_CFC_TIMEDIFF_1