4 Note about Shutter control

Currently, there is only one shutter control cable connecting from Gatan US1000 CCD FirstLight controller to CM12 electronics board. Therefore, there is no way to specify the offset between two shutters when taking a CCD shot, normally one is above specimen and one below. So, for plastic sections, it might cause problem of "drifting" due to charging.

Fortunately, the single cable is connecting to pre-specimnen shutter. To be more specific, it is using Gun-UX coil to shift beam away as a blanker. It is comforting to know at least cryo sample is protected, IF the camera is configured correctly.

The correct way to configure this is from DM → Camera → Configuration, to make sure the Shutter 1 is checked for "shutter idle status". The large screen of CM12 is now working as shutter switch - beam is there when screen is Down and beam goes away when large screen is Up.

One can easily check to see if the shutter is configured correctly by lifting the large screen handle slightly - the beam should go away. The value for current change related to large screen Up and Down should be noticeable on CM12 → Parameter → Display Current.

Interestingly, the beam blanker in Low-Dose mode uses the very same coil to shift beam away. It adds a large value on top of the value from camera shutter configuration.