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-James Holton | -James Holton | ||
MAD Scientist | MAD Scientist | ||
</pre> | |||
and he posted two corrections, the first at Thu, 7 May 2020 09:06:29 -0700: | |||
<pre> | |||
Ah! I did that last formula wrong. Never do algebra in your head | |||
without checking. It should be: | |||
The equation then becomes: | |||
f = P/t/L/1.2e-5 | |||
Where 1.2e-5 = 0.2 cm^2/g * 1.2 g/cm^3 * 1e-4 cm/micron * 50%, f=flux | |||
and t=exposure (as above). | |||
For example, if you see an average pixel value of 20 photons on a | |||
Pilatus 6M, then that is P=12e6 photons. If that was a t=0.1 s exposure | |||
from a sample 100 microns thick, then the beamline flux was about 1e12 | |||
photons/s. Note that this is the flux after any attenuation, not before. | |||
Oh, and if you want a reference for that 2000 ph/um^2 = 1 Gy rule, it is | |||
here: | |||
https://doi.org/10.1107/S0909049509004361 | |||
And, of course, if you are lucky enough to have accurate flux, size and | |||
shape information for the beam and sample, plus chemical composition the | |||
most accurate dose you'll get from raddose-3D: https://www.raddo.se/ | |||
-James Holton | |||
MAD Scientist | |||
</pre> | |||
and at Thu, 7 May 2020 09:33:03 -0700 | |||
<pre> | |||
One more correction: | |||
For example, if you see an average pixel value of 20 photons on a | |||
Pilatus 6M, then that is P=120e6 photons. If that was a t=0.1 s | |||
exposure from a sample 100 microns thick, then the beamline flux was | |||
about 1e12 photons/s. Note that this is the flux after any attenuation, | |||
not before. | |||
</pre> | </pre> |