Electron Dose Reading from CCD Camera

The electron dose measurement can be done with CCD image since the illumination on each CCD pixel is proportional to the dose of elctrons hitting on the corresponding scintillator screen. Under proper calibration with Faraday cage, the electron dose can be coverted from the counts on each CCD pixel. Total 35 samples are taken under different aperures, spotsizes and CCD exposure times. The results shows that each electron produces 10.5 (+/- 0.1) counts on CCD camera. The raw data is listed in the following table, where:

Sum - Total CCD counts when all the beam spot is within the CCD image.
Max - The maximum counts on a CCD pixel.
Sum/S - Total CCD counts (Sum) normalized to one second exposure.
Electron - Total electrons collected by the Faraday cage in a second. (the beam is focused within the Faraday cage aperture).
Counts/Electron - CCD counts generated by an electron.
1nA = 1/1.602x10^-10 electrons/sec

Average counts per electron: 10.50443
Absolute deviation from mean: 0.107175

Faraday Current from Exposure Meter Reading

The Faraday current can be calculated from the exposure meter reading by an empirical equation:

Faraday Current (nA) = 2.2 x Emulsion / Expo.

That is the Faraday current in nanoampere equals 2.2 times the emulsion setting for the camera and divided by the exposure meter reading from the main screen. The raw data is listed in the following table, where:

IFaraday - Faraday current measured with Faraday cage.
Expo - Exposure meter reading from the main screen in second.
Iexpo - Beam current calculated from the above empirical equation.