Ion Chamber Flux Calculator
X-ray attenuation/absorption data are from the NIST database (http://physics.nist.gov/PhysRefData/FFast/html/form.html).
and http://physics.nist.gov/cgi-bin/Xcom/xcom2-t
The average ionization enegies are obtained from the SLAC web site (http://www-ssrl.slac.stanford.edu/mes/xafs/flux.html)
Standard CHESS chamber lengths: short: 6 cm, long: 27 cm.
Input parameters:
Select gas                   Absorption mechanism              Ionization energy       Gas Density
            (eV)     (g/cm3)
Energy: (eV)   Chamber length: (cm)
Counts: (cts)     Counter range: (A/V)

Results:
Transmission:        aGas: (cm2/g) (cm-1)
         Current: (A)   Flux:  (ph/s)
        
A calculator program uses a simple model to calculate the X-ray flux from the ion chamber current data. The model includes single-ionization of the gas, and does not takes into account some of the seconary effects such as charge recombination, or space-charge effect.
The input parameters are:
* Selection of the gas; the choiches are: Nitrogen, Helium, Argon, Xenon or Krypton;
* Selection of absorption mechanism responsible for current production;
* Average ionazation energy in eV (default values from the literature are shown).
* The density of the selected gas.(default values shown for see level, at 25C)
* X-ray energy in eV;
* ion chamber current in Hz (counts/s)
* The ion chamber current amplifier gain on A/V; and,
* The length of the ion chamber in cm.

Example 1:
    At station A2 with multi-layer optics at 10keV.
    The 6cm N2 ion chamber count was 109400 at 1E-6 gain. The calculated flux: 9.6E11 ph/s.
Example 2:
    At station A2 with <111> optics at 50keV.
    The 6cm N2 ion chamber count was 722000 at 1E-10 gain. The calculated flux: 2.55E9 ph/s.

(©) Peter Revesz (pr20@cornell.edu), CHESS, (2007). last change: 11/12/2013