Diode Flux Calculator
X-ray attenuation/absorption data are from the NIST database (http://physics.nist.gov/PhysRefData/FFast/html/form.html).
Absorption calculations using:
Photoelectric + Compton
Mass-energy absorption coefficient
Mass photoabsorption coefficient
Total mass attenuation coefficient
Depletion:
(microns)
Diff-length:
(microns)
Energy:
(eV)
Counts:
(cts)
Counter range:
(A/V)
Results:
Current:
(A)
Flux:
(ph/s)
aSi:
(cm-1)
Responsivity:
(A/W)
A calculator program uses a simple model to calculate the X-ray flux from the diode current data. It includes an accepted model for electron-hole pair creation by X-rays in Silicon requiring 3.66eV energy per charge-pair. The model does not takes into account some of the seconary effects such as charge recombination and multiplication. The calculations are based on the one-dimensional model of the p-n junction working in photovoltaic mode (no-bias) taking into account photo-current generation originating from the depletion region and minority minority carrier diffusion from the space-charge-neutral region.
The input parameters are:
* Selection of absorption mechanism responsible for current production;
* The depletion layer thickness in microns.
* The minority carrier diffusion length in microns.
* X-ray energy in eV;
* Counter for diode current in Hz (counts/s)
* The diode current amplifier gain in A/V;
Example 1:
At station B2 with Ge <111> optics at 12keV.
The depletion layer was 53 microns, diffusion length: 0, count was 163909 cts at 1E-6 gain. The calculated flux: 1.47E10 ph/s.
(©) Peter Revesz,(pr20@cornell.edu), CHESS, (2007). last change: 4/6/2011