[3dem] Current measurement with viewing screen

[Fred Sigworth]

To calibrate our CCD camera we have been using the viewing screen to measure the beam current in our Tecnai F20.  Of course this measurement is in error due to backscattering, secondary electrons, etc. and the right way is to use a Faraday cup.  But, has anyone compared the value from a Faraday cup with the screen current?  If the conversion factor is known, even approximately, that would help us a lot.

Fred Sigworth

Fred J. Sigworth
Department of Cellular and Molecular Physiology
Department of Biomedical Engineering
Yale University
New Haven, CT  06520
tel.  203 785 5773
fax 203 785 4951
fred.sigworth at yale.edu