74 PI-MAX/PI-MAX2 System Manual Version 5.F
shutter compensation time elapses, and the array is read out. If additional frames are
to be acquired, the photocathode will be gated on again and the ST-133 will wait for
an External Sync pulse.
PreOpen would be selected for experiments in which the event occurs before the
photocathode would have time to gate on (i.e., the time between the External Sync
pulse and the event is shorter than the propagation delay between the External Sync
pulse and the time it takes to bias the photocathode on).
Note: The main drawback to this shutter setting is that the CCD is exposed to any
ambient light while the photocathode is gated on between frames. To counteract
signal integration during this period, you could choose Continuous Cleans.
Timing Modes
External Sync w/Continuous Cleans
External Sync w/Continuous Cleans
Table 4. Timing Mode, Shutter Control, Ext. Trigger Input for Shutter Mode
The timing mode selection determines when signal integration will begin and end on the
CCD array and when the acquired signal will be read out. The following three timing
modes are available in Shutter Mode:
Free Run: One cycle follows another automatically at the fastest frame rate
possible. The intensifier is gated on for the set Exposure Time during each cycle,
gated off at the end of the exposure time, and then read out. Any External Sync
signals are ignored.
External Sync: A suitable signal from an external source must be applied to the
ST-133’s Ext. Sync input. When the External Sync pulse is detected, the intensifier
will be gated on and pass light to the CCD for the set Exposure Time, will be gated
off at the end of the exposure time, and CCD array readout will occur. The
Accumulations and Images parameters remain active; the proper number of pulses
need to be applied to finish the experiment. Note that when Continuous Cleans is
selected, there will be a delay between the time that the intensifier is gated on and the
start of the desired signal integration on the CCD array.
Internal Sync: (PTG only) This timing mode is only available if there is a PTG
installed in the ST-133. If Internal Sync is selected, the PTG will control the timing
of the camera as if the camera were in External Sync mode and the PTG was the
external trigger source. The PTG also has its own External Trigger In BNC that
accepts a wide variety of inputs, as opposed to the External Sync of the ST-133,
which only accepts TTL levels.
In order for the ST-133 to see signals from the PTG when Internal Sync is selected,
the following parameters should be set as indicated:
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