Chapter 6
Timing Modes
49
Example 5
Laser (or other experimental equipment)
HV Gate Pulser
Controller
Freq out
Trigger out
Trigger out
Ext sync
Delay freq out
Trigger in
Inhibit
SHUTTER MONITOR (ST-130,
ST-133, ST-138, PentaMAX)
Most of the examples up to now required the laser light to be optically delayed to
compensate for the delay between the laser pulse and the gate pulse. It is possible to use
the internal frequency generator of the pulser to electronically delay the laser instead.
For experiments that require more than 7 µsec between the trigger and data collection,
the Frequency Out from the pulser can be used to trigger the laser, and the Delayed
Frequency Out from the pulser can be used to trigger itself. By adjusting the delay
between the two pulses, the detector can be gated at the proper time with respect to the
laser pulse.
For experiments where laser triggering is almost instantaneous, (< 7 µsec), the
Frequency Out and the Delayed Frequency Out outputs are reversed. Frequency Out
triggers the gate pulse, and the delayed output now triggers the laser. The delay option on
the pulser now allows the image intensifier to be gated before the laser is allowed to fire.
In either example, the controller can be operated in either Freerun or External Sync mode
(see dotted line above). Both modes use SHUTTER MONITOR to prevent the laser from
firing during CCD readout.
The value of 7 µsec is a typical limiting value. Consult the pulser manual for specific
minimum values.
Figure 15.
System
configuration
for experiment
where internal
frequency
generator
electronically
delays the
laser.
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