[3dem] Dose meassurement in EFTEM mode.

[Christos Savva]

Hi

I am wondering how others equipped with a Tecnai (in our case an F20) and a Gatan imaging filter measure the electron dose on the specimen accurately. In TEM mode the FEI low-dose software allows us to measure the dose on the phosphorus screen based on the beam diameter and magnification. With the GIF we are dealing with a ~20X post magnification on the camera and in EFTEM mode the actual magnification on the phosphorus screen is 20 times less. However the low-dose software uses the EFTEM magnification for the calculation. Further more the beam must be focused to about 10-15mm to enter the CCD path.  If you have a similar setup could you let me know how you measure the dose?

Thank you

Christos Savva