Absorption of Gamma Radiation

[M. next]

After performing this experiment, we will get different peaks on the computer screen, where on x-axis lies thickness of the absorber and on the y-axis the nb of channels. What do these represent exactly? Why do we have a high peak and a medium sized one?
What are the significances of each?

Thanks.

 

[ZapperZ]

After performing this experiment, we will get different peaks on the computer screen, where on x-axis lies thickness of the absorber and on the y-axis the nb of channels. What do these represent exactly? Why do we have a high peak and a medium sized one?
What are the significances of each?

Thanks.

Don't you think that it will be significantly clearer if you describe in detail the experiment (i.e. what material were you looking at), and actually show the graph of the data you are referring to?

Zz.

 

[M. next]

I didn't because I thought it is a known experiment.
So here's the graph, see attachment please.
And this is experiment aims as its title says absorption of gamma radiation by some absorber (lead for example) in order to measure its attenuation.
What we're changing through the experiment is the thickness of the absorber.

What I don't get is the peaks? Why do we have different peaks?

 

[jtbell]

What is your gamma source (which isotope)?

What kind of detector are you using? I'm guessing a sodium-iodide scintillator, because it's cheap and easy to use in an undergraduate lab.

 

[M. next]

For all isotopes, similar graphs occur with different peaks. Am just asking why do different peaks appear? Am asking a theoretical question.

 

[Vanadium 50]

You were asked nicely - twice - to describe what you are doing. Making us guess is neither efficient nor polite.

 

[jtbell]

I was referring to the particular picture that you attached.

 

[jtbell]

If I guessed correctly that you are using a sodium iodide scintillator, then this might be useful:

http://en.wikipedia.org/wiki/Gamma_spectroscopy#Sodium_iodide-based_detectors

 

[M. next]

Thank you jtbell.

 

[jtbell]

So I guessed correctly, then?

 

[M. next]

Thank you but my question was not related to what of scintillator to be used. I was asking about the meaning of the peaks. What do they represent in general. That's why I said I was asking theoretical question and materials used didn't have to do with answer I thought. But thank you for your reply, jtbell.

 

[Vanadium 50]

Since you refuse to provide necessary details, this thread is closed.

 

[Astronuc]

After performing this experiment, we will get different peaks on the computer screen, where on x-axis lies thickness of the absorber and on the y-axis the nb of channels. What do these represent exactly? Why do we have a high peak and a medium sized one?
What are the significances of each?

Thanks.

It appears one is performing gamma spectroscopy. I doubt the x-axis is absorber thickness, but rather is related to the energy of the gamma. The y-axis should be the counts (gammas detected) in the corresponding channel (gamma energy bin) on the x-axis. So already, it seems one is misinterpreting the data presented.

The type of detector (NaI, GeLi or other) affects the resolution of the peaks.

When one mentions absorber, it is not clear if one is referring to the detector material, or some attenuator.

Some gamma emitters, e.g., Co-60, have two gamma peaks. The spectum in one's attachment appears to that of Co-60. Other radionuclides, e.g., Cs-137, emit one predominant gamma ray.

The detector will also respond to lower energy gammas from internal conversion, Compton effect, and pair production.

 

[jtbell]

I didn't [give details] because I thought it is a known experiment.

It is dangerous to do this, because people may guess the missing details incorrectly. This causes people to give answers which may not be appropriate for your situation, wasting both your time and theirs.

We have seen it happen many times, that someone makes an incorrect guess about the questioner's situation, and then the questioner has to say "no, this is what it really was..." So we're not simply nit-picking.