2 Background

Tecnai scope uses beam blanker all the time. When you change the magnification, the beam is blanked momentarily. In Tencai Low-Dose module, there even is a "blank" button for you to click. Usually, gun coils are used to perform this task. A large offsets to gun coil(s) will make beam disappear, so the beam gets "blanked".

In fact, when one starts a new account on Tecnai computer and the blanker in Low-Dose mode might not work at all. You still see beam or part of the beam on large screen. Gun coil gets a offset but not big enough. Fortunately, one can calibrate the blanker in Low-Dose mode so that the offset to gun coil can be sufficient to blank the beam completely. The calibration result will update into registry of computer so that next time you start TUI interface the blanker will simply work. This result can also be saved into a file separately.

The information used to blank beam in Low-Dose mode is stored in the registry, but it is not part of alignment file. Therefore, different user has to calibrate this again. Alternatively, they can load the saved beam blank calibration file. In any case, this information is only available for blanking purpose within Low-Dose mode.

SerialEM and other program that communicate with scope via scripting interface also need to blank beam from time to time. It uses the same gun coil, but the default amplitude for this gun coil change might not be correct, as it has never been touched before. This is the part that needs to be fixed.