Princeton Instruments PI-MAX 3 System, Manual, Page: 37 / 150

Chapter 5 General Operation Factors 37
Cooling performance can be enhanced by circulating water with a temperature below
laboratory ambient but
this approach will increase the risk of condensation inside the
PI-MAX3 . This condensation can cause catastrophic failure of the camera electronics. Any
resulting damage would be considered to have resulted from improper operation and will not
be covered by the Warranty. Even ordinary tap water is too cold to be used without risk! For
safety, the water should be no colder than the laboratory ambient temperature. Closed
circulation systems that depend on ambient air-cooling of the circulating water will generally
give good results. If you feel that you must use water colder than the laboratory ambient
temperature, it is absolutely essential that the PI-MAX3 be operated where the humidity is
low enough to prevent internal condensation. If the coolant is below the freezing temperature
of water, we advise using a mixture of 50% water and 50% ethylene glycol as the coolant.
The easiest and most practical way to achieve the required low humidity is to put the
PI-MAX3 inside a closed container and to then purge the container with a continuous
flow of dry nitrogen. On completion of the experiment, be sure to continue the purge
until the PI-MAX3’s internal cold surfaces have had time to warm to the ambient
laboratory temperature. Contact the factory if you require additional information.
See "Making the Camera-Circulator Connections" , page 25 for CoolCUBE
II
setup
instructions.
Setting the Temperature
Regardless of the type of cooling, the CCD array temperature is set via the software
Detector Temperature dialog box, accessed by selecting Detector Temperature on
the Setup menu (WinView/32 or WinSpec/32). Temperature lock to a set temperature in
the operating range will typically occur within ten minutes. Another five minutes will be
required for maximum temperature stability to be achieved. To see when the array
temperature reaches and stabilizes at the target temperature, leave the
Detector
Temperature dialog box open. When the target temperature is reached, the dialog box
will report that the Current Temperature has Locked .
Note
: The Detector Temperature dialog box will not display temperature
information while you are acquiring data.
Exposure
Data acquisition has two parts: exposure and readout. Exposure refers to the integration
of a signal of interest on the CCD array and readout is the transfer of the integrated signal
from the array pixels to a shift register and from there to a preamplifier. During exposure,
each pixel in the two-dimensional grid of individual pixels senses the intensity of light
falling on its collection area and stores a proportional amount of charge in its associated
well. Once charge accumulates for the exposure time (via gating sequences defined in the
application software), the pixels are read out serially.
Because CCD arrays are always sensitive to light, light must not be allowed to fall on the
array during readout (with a few exceptions). Intensified cameras such as the PI-MAX3
rely on gating the intensifier off, to prevent light from reaching the array. During each
data acquisition, the intensifier is gated on and off (this may happen a number of times if
there are multiple gates per exposure) to allow the pixels to register light during the “on”
period. It is gated off for the readout period.
WARNING