In the is shown the principle of conversion of X-ray quants to light quants.
Beside the thickness of the scintillator also the energy of the X-ray quants are a factor which indicates the efficiency of light conversion. To get an idea about the physics behind here is an example of the mostly used scintillator material (Gadolinium oxysulfide Gd2O2S).

The half value thickness is the thickness that converts 50% of the incoming X-ray quants to light quants; the dotation of the scintillator is about 45%. From the picture is could be seen that for X-ray quants with an energy of 160keV a Gadox scintillator screen has to have a thickness of 4mm to convert 50% of the energy to light quants (black line). This would result in a spatial resolution of about 4mm ... .
As this spatial resolution is not sufficient the most scintillation screens are thinner - in the range of 50 .. 350µm.


The efficiency with higher energies is quite low and the next graph shows some real existing Gadox screens with their efficiency:

To give an example: The scintillator DRZstandard - which is often used and about 150µm thick - has an efficiency at 120keV of about 10%; it decreases for 160keV down to 4% only.

Hello Klaus,
I wanted to ask if you could give any sources for the images or the data especially for the last one. I am currenctly working on my Bachelor Thesis in a NDT company. The topic is the filtration of the x-ray spectrum and to optimize it. To calculate the exposure time it would be quite helpful to know the efficiency of GADOX (as in the picture vs. keV). I'm using the x-ray simulation tool aRTist from BAM. There you can create digital detectors and can extract some data similar to your efficiency (sensitivity vs. keV). However the lower keV area seems odd to me. I don't know if I am allowed to post images from the programm due to copy right reasons.
Thanks in advance
Tim

Hello Tim,
yes, the sources are the .
I know the aRTist quite good .
You may ask UweZ, he should be also here with this user name, about the Copyright of results of aRTist. As far as I know the results are not protected by copyright - but in case of doubt you should ask him.

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Best Regards
Klaus