Leginon

h1. Inspect the phase plate slot at low magnification

h2. Check for contaminant and recovery of irradiated spots

Phase plates conditions are not always consistent.  It is useful to monitor its global state once a month if used often to look for new contaminant and the recovery of irradiated spots. Here is the condition we use at NRAMM/SEMC.

1. Go to low enough magnification that most of the Volta phase plate slot is visible on the camera that will be used to capture the image.  We use 64x on Krios and take this image on Ceta camera.

2. Spread the beam to cover the camera and adjust spot size if needed and defocus to -100 mm if possible.  This allows good contrast to observe the phase plate.

3. Advance the phase plate patches or use aperture adjustment function to center the slot.

4. Take an image.

h2. Check for moving mechanism offset

Phase plate moving mechanism may slip over time.  It is useful to know whether it is centered in the slot.  Choose a patch position, usually 1 and move to that patch and record or memorize where it is.  It should clear the edge of the slot with good distance so that all diffracted beam can pass.  Request adjustment by a service engineer if off.