Conversion from ionization chamber current to photon flux

Energy (keV): (must be between 1 and 100)

Input either current or counts:
Current (A) ( 1 micro ampere is 1E-6 A, 1 nano ampere is 1E-9 A)
Counts per sec (the counter is connected to a V/F converter)

Conversion from counts requires the followings:
V/F gain : MHz per volts
Current amplifier gain : 1.0E Volts/Ampere.

3.3cm (OKEN S-1329)
14cm (OKEN S-1194)
28cm (OKEN S-1196)
1cm (Teikoku Denki)

[Answer section]
calculated using mass attenuation coefficient:
Photon flux is photons/sec

calculated using mass-energy absorption coefficient:
Photon flux is photons/sec

Attenuation is %
Absorption is %

The ionization chamber is assumed to be filled with air (1atm, 295K).
Mass attenuation coefficents and energy-mass absorption coefficients were obtained from NIST for dry air near sea level (
The conversion is very inaccuate when the energy is high and the absorption by air is small.
There can be a large error due to re-combination of charges when the x-ray beam is small.
Probably, most people use the value based on the mass attenuation coefficient, especially with low energy x-rays.
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