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event. The 3377 measures the time of the event relative to the 100 kHz
clock. The correct absolute time is calculated by using the 100 kHz
counter value as a coarse clock. The dead time is 5 microseconds (worst
case for 16 bits equal to 1) plus the time for the event data. Sixteen input
channels are available or the event data. The data block is 17 words
(average) plus the event data. Another method is simply to read out the
counter data as part of each event, either by CAMAC or the ECL port. A
31 word FIFO can easily be programmed into the 2366 to match the
event FIFO in the 3377.
The 16 bit counter allows 655 milliseconds of recording before rollover. A
null event can be provided to record the rollover, allowing an unlimited
time range. More than 31 events can be recorded if the ECL port is used
to move the data to a external buffer. With the 4302 memory as above,
as many as 1000 events may be recorded.
Both of these methods can use one of the 2277/EXP modules, to provide
improved double hit resolution and more hits per channel (for fewer
channels). When using two 3377s in a ping pong mode, the EXP mod-
ules can drive a double termination to provide the identical signals to the
TDC modules. The EXP module drives the center of a short cable (the
cable has 3 connectors), the two ends connect to the two 3377s. This will
only work for short cables, since the differential ECL signal is reduced in
amplitude by 40%. Note that the lower connector on the 2277/EXP
module is inverted.
The internal clock in the 3377 provides 0.5 nanosecond accuracy for
intervals less than the 32 microsecond full scale. The accuracy of the
extended time range depends on the clock used in the 2366 universal
logic module. For accurate results with the extended time range, the
external clock input must be used, not the internal crystal time base. A
readily available time standard is based on Loran-C reception, and can
provide 0.5 nanosecond accuracy for intervals up to one minute.
LABVIEW™ SUPPORT
You can download a driver for LabView 4.x from our website at
http://www.lecroy.com/lrs/support.htm.
LabView™ is a registered trademark of National Instruments Corporation.
