Princeton Instruments PI-MAX 3 System, Руководство пользователя, Страница: 59 / 150

Chapter 6 Gated Operation 59
Figure 23 illustrates the kinds of experiments that can be performed with a PI-MAX3
detector. Of the many gated measurements that can be performed with a PI-MAX3, most
will fall in one of the following categories:

Static Gate: This type of experiment may also be referred to as “Repetitive-
Continuous”. There is a repetitive trigger, and the Gate Width and Gate Delay are
fixed. Some variable in the experiment such as pressure, concentration, wavelength
or temperature is varied.

Swept Gate:
In this type of experiment, Gate Width, Gate Delay, or both may be
varied.
Repetitive-Sequential 1: The Trigger is repetitive, Gate Width is fixed, and Delay is
varied over the course of the measurement. The result of the experiment is a plot of
intensity vs. time, such as might be obtained with a sampling oscilloscope. This technique
is used to measure lifetime decays.
Repetitive-Sequential 2: The Trigger is repetitive and Gate Width and Delay are
varied over the course of the measurement. Gate Width and Delay can be
incremented in a linear fashion or in an exponential fashion. Increasing the Gate
Width is useful for trying to find fine detail in a weak decaying signal. If you choose
linear, you have to take a lot more points. Exponential lets you take data points closer
together where the signal is changing rapidly and further apart where the signal is
changing slowly.

Single Shot:
A single shot experiment is one where you have only one chance to catch
the data. Any experiment that can’t be repeated more often than once a minute, such as
high power lasers and explosives, is considered a single shot. You have to catch the
trigger when it comes. Prior to the event, the CCD runs in continuous cleans mode. You
don’t have the luxury of having the CCD just sitting there doing nothing because the
CCD will be accumulating dark current. When the trigger arrives, the intensifier gates,
the continuous cleans stop, and the array is read out with a minimum of dark current. Pre-
Trigger can be helpful if available.
The next section provides step-by-step instructions, along with diagrams and screen
shots, for setting up and performing a Swept Gate experiment with fixed Gate Width and
variable Gate Delay (type Repetitive-Sequential 1).
Procedure for Setting up and Performing a Swept Gate Experiment
(Fixed Width, Variable Delay)
This experiment is an attempt to time-resolve a Xenon light flash from a commercially
available strobe light. Since the strobe does not have a "pretrigger" out, an electrical
trigger is generated by using a photodiode. Output from the photodiode is connected to
the
Trigger In BNC of the PI-MAX3 (Figure 24). Then perform the steps that follow.