I have read somewhere that it's possible to dope low Z materials such as PVC and polyethylene to alter their electron cloud structure. It was claimed that this change make these low Z materials behave like heavy materials and hence they attenuate x or gamma radiation like metals.
Dear Smj Mortazavi,
I cannot see any mechanism to significantly change the hard photon interaction probability of any material.
A hand-waving argument: Due to momentum conservation a free electron is not able to absord the full photon energy. Only a bound elctron can do. If you increase the photon energy the weakly bound valence electrons can be regarded as quasi-free (binding energy much lower than photon energy). As consequence, for high photon energies the photoionization cross section scales with the principle quantum number n^-3. This tells you that about 80% of the absorbed photons will be due to K-shell ionization. Roughly another 10% is associated with the L-shell.
However, this strongly bound electrons of the inner shells dont care too much about the chemical environment which is important for the valence electrons. So, hard x-rays are in general not sensitive to details of the chemical structure of materials.
Dear Gunter
Thank you vry much for your response. The claim I wrote about is discussed as a citation in a Chinese journal. I checked the reference but it seems that it is not a correct reference. I am enclosing the paper. Please see the highlighted text:
"However, the USA Radiation Shielding Technology Company (RST) (2001) modified the tantalum doped PVC and PE to make their electron cloud structure similar to heavy metal elements, thus it can be used to absorb radiation energy by the electron resonance effect and it is more efficient than the traditional radiation shielding
materials.[10]"
Again thank you.
Dear Smj Mortazavi,
the attached paper is interesting. However, I think one should put a big question mark behind the presented data. Looks like the authors simply ignored the uncertainty due to counting statistics in the analysis of their measurement. But anyway the reported increase in the photon attentuation coefficient is very small.
You can find the cited US patent here: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=6281515.PN.&OS=PN/6281515&RS=PN/6281515
However, I have no idea what these guys really achieved/claimed with this patent. I doubt that they turned PVC to lead (from the radiation shielding point of view).
Best greetings
Günter
- Badges
- Science topic
- Similar topics
- Instrumentation Engineering
- Instruments