Conversion Efficiency of Cameras at Brandeis

Chen Xu

$BrandeisEM: ~emdoc-xml/en_US.ISO8859-1/articles/CountsPerEpectron-Faraday/article.xml 1 2013-07-11 07:58:28 xuchen Exp$

The conversion efficiency values listed in this doc have been calibrated using Faraday cage. This is neccesasy because the screen current from FEI interface might not be accurate for whatever reason. The Faraday cage instrument used in this calibration includes a Gatan double tilt holder with Faraday cup built in and a picometer. It is borrowed from Anchi Cheng at Scripps.

Based on the calibration, it is found that on F20, the screen current is accurately agreed with what Faraday cage measurement, under 200 and 120kV. However, under 80kV the screen current displayed is about 6% less than Faraday cage measurement. On F30, screen current is about 10% more than Faraday cage measurement, at both 300 and 200kV.

You can also get pdf version of this document here.

Table of Contents
1 Counts Per Electron table

1 Counts Per Electron table

Camera 300kV 200kV 120kV 100kV 80kV
US1000 (on CM12)     31.7 33.7 33.3
K2 (Linear, on F30) 30.5 45.28      
Orius SC1000 (with K2 on F30) 2.55 3.67      
GIF 795 (on F30) 5.37 6.83      
Falcon (1st gen. on F20)   189.7 313   388
Falcon II (backthinned)   203      
Orius SC200 (with Falcon on F20)   19.7 25.5   20.1
US4000 (on F20)   22.13 33.81   42.6