Chapter 7 WinX and Gated Operation 143
7.5.2 Single Shot Experiment
A single shot experiment offers only one chance to capture an event. As with any gated
experiment, the time budget of the experiment is critical. If there is no pre-trigger from
the experiment, a photodiode can be used to generate an electrical trigger from the
laser light. In this situation, light has to be delayed by optical means (e.g., fiber-optic
cable or mirror reflections,) to allow sufficient time for the electronics to be activated
after having received the trigger. Another important thing to note in single shot
experiments is that the CCD is operating in Continuous Cleans mode so that there is no
dark charge accumulation while it waits for the trigger.
This experiment is an attempt to capture a 60 ns fluorescence generated by a single
shot laser. The time budget of the experiment is detailed in Table 7-2. This information
is important in order to choose the correct length fiber optic cable.
In this experiment, cable lengths are kept to a minimum so that the length of the fiber
optic cable required may also be minimized.
Figure 7-25 provides a block diagram of the hardware setup for a single shot
experiment.
Figure 7-25: Block Diagram: Single Shot Experiment
Table 7-2: Single Shot Experiment Time Budget
Delay Source
Delay
(ns)
Total Delay
(ns)
Fiber Optic Cable
Length
Photodiode (light -> TTL pulse) 2 30 A minimum of 21 ft
of fiber optic cable is
required.
Photodiode -> PI-MAX4 (2 ft BNC cable) 3
PI-MAX4 25
PI-MAX4
Photodiode
Laser
Trigger In
Fiber Optic Cable
Beam Splitter
GigE
90-264
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