The level of GIF camera chamber vacuum can be evaluated by comparing the current camera chamber vacuum reading to the good ones recorded historically. If the vacuum is poor, the following examination procedure needs to be performed to locate any leaks:
         i) Check if the location of photographic film in the camera chamber causes any leaks.
         ii) Observe the camera chamber vacuum when you move the TV rate camera in/out. It is normal if there is a slight increase in the vacuum reading when the o-rings are sliding. However, the vacuum should recover quickly once the movement has stopped.
         iii) Observe the vacuum of the camera chamber when you move the energy-selecting slit in/out. It is normal if there is a slight increase in the vacuum reading. However, it also should recover quickly one the movement has stopped. Otherwise, there may be a leak in the seals of the energy-selecting slit.
         iv) Locate the control lines for the gate valve. One should have a black label, the other one a red label. Normally when the TEM is fully pumped down, the black control line should be pressurized and the gate valve should be open. When the TEM is not fully pumped down, the gate valve may be closed so that the red control line should be pressurized. With the TEM fully pumped down, it will swap the gate valve control lines to close the gate valve.