Gatan UltraScan 894, Руководство пользователя

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General Precautions
UltraScan Use r ’s Guide Reference Series Rev 1.0 5-2
If the flow rate of the cooling water deviates significantly from the value
originally set, make sure the lines are not obstructed and adjust the pressure
regulator to bring the flow back to the original level. Remember, if the water
flow stops while the Peltier cooler is on, an over-temperature condition will be
detected and the automatic protection will shut down the cooler.
•
The Peltier cooler should not be left on when the TEM cooling water is
turned off or fails.
The Peltier cooler is cooled by water from the TEM chiller. If the Chiller is
turned off or fails for a long period, an over-temperature condition will be
detected and the automatic protection will shut down the cooler. Be aware that
for some mic roscopes the cooling system turns off in the Stand By mode. Be
sure the cooler of the camera is also turned off in that situation.
•
Turn off the Peltier cooler if the microscope viewing chamber is to
remain at air pressure for a long period (more than 30 minutes to an
hour).
When isolated by the gate valve, the CCD vacuum is good for about half an
hour, after which some frosting on the CCD may occur if the CCD is kept cold.
A small amount of ice will sublimate away once high vacuum is restored in the
viewing chamber and the CCD gate valve opens. Removing large amounts of
condensation will require the electronics to be switched off for about 30
minutes after the vacuum in the viewing chamber is restored, so that the CCD
warms up while it is in a good vacuum.
5.1.2 Scintillator maintenance and precautions
•
Minimize exposing the scintillator to the electron beam when the
camera is not in use.
It is particularly important to protect the camera from being unnecessarily
exposed to an intense unscattered beam. As a general rule, if you avoid
conditions which would saturate any part of the sensor area in less than 0.1 sec
(about 10
2
cm nA
at the sensor), the scintillator lifetime will probably exceed
the lifetime of the rest of the system. On the other hand, each time any CCD
pixels are intensely saturated, the scintillator efficiency may be permanently
impaired for those pixe ls, resulting in a variation of the scintillator efficiency
across the image field. If you are not using the camera, keep the viewing screen
down or retract the camera to protect the scintillator from beam damage. Also, a
retracted camera will not collect debris or abrasive particles that may fall down
from the TEM’s film-transport mechanism.
•
Minimize exposing the scintillator/CCD to high beam intensity when
acquiring diffraction patterns.
There is no defined cutoff where the scintillator will be damaged. Rather,
damage can result from prolonged exposure of the scintillator to a very high