About selecting energy range on the spectrometer

In summary: It is possible that the MCA has a coarse setting that is too big for this particular spectrum.2. The spectrum might be contaminated with background radiation.3. The spectrum might be contaminated with cosmic radiation.
  • #1
toex
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Hi everyone, I am doing an experiment about alpha spectrum. I am using Model P-2000/1 (don't know if this matters), a NaI(Tl) scintillation probe. I selected energy range 3-8 MeV at the front panel and waited for 3000 counts at the peak, it took ~800 seconds. But when I selected energy range 4-6 MeV and did the same measurement, it took me ~17000 seconds to have 3000 counts at the peak! Does anyone know why? Thanks a lot!
 
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  • #2
Was the peak fully contained within 4-6MeV?
Are you sure that the count was just the peak, not events in the whole range?
If it is not one of these things: No idea. Might be some strange effect from the setup.
 
  • #3
I'm not sure if I'm right but NaI(Tl) detector isn't good choice for alpha. IMHO its in endcap made by some metal maybe Al (hygroscopic material) so alpha particles cannot penetrate through this "cover". Alpha is mostly measured (spectrometry measurement) in vacuum chambers with some kind of semiconductor detectors. Are u sure u have NaI(Tl)? There are another scintilitor Zn(S)which is used for some kind of alpha spectroscopy. And regarding your question have to agree with mfb, u have narrower window so its possible that part of peak is out of your rang. BTW do u know what nuclide are u measuring?
 
  • #4
mfb said:
Was the peak fully contained within 4-6MeV?
Are you sure that the count was just the peak, not events in the whole range?
If it is not one of these things: No idea. Might be some strange effect from the setup.

1. Yes, the peak was fully contained in 4-6 MeV.
2. Yes, the count was just the peak.
3. Thanks for your reply :)

ramses22 said:
I'm not sure if I'm right but NaI(Tl) detector isn't good choice for alpha. IMHO its in endcap made by some metal maybe Al (hygroscopic material) so alpha particles cannot penetrate through this "cover". Alpha is mostly measured (spectrometry measurement) in vacuum chambers with some kind of semiconductor detectors. Are u sure u have NaI(Tl)? There are another scintilitor Zn(S)which is used for some kind of alpha spectroscopy. And regarding your question have to agree with mfb, u have narrower window so its possible that part of peak is out of your rang. BTW do u know what nuclide are u measuring?

Sorry, I mixed them up. I was not using NaI(Tl), I was using a charged silicon detector to measure Po-210 inside a vacuum chamber. Thank you for replying!
Another question, this time I was using a NaI(Tl) to measure the gamma spectrum of Cd-109. As it has two very nearby peaks(22.1 & 24.9 keV), I selected a very big COARSE value on the MCA so that the two peaks can be resolved. But when I chose the maximum COARSE value, the counting almost stop (I assume it is very long dead time?), what was happening? Also, when the Na(Tl) was measuring nothing, the spectrum showed two significant peaks and there were 10000 counts in 10 seconds! I don't think this comes from the background. Anyone know what was it?
 
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1. What is the purpose of selecting an energy range on the spectrometer?

Selecting an energy range on the spectrometer allows you to focus on a specific range of energies and wavelengths in your sample. This can help you isolate and analyze specific features or components of the sample.

2. How do I determine the appropriate energy range to select on the spectrometer?

The appropriate energy range will depend on the type of sample you are analyzing and the specific features or components you are interested in. You can consult previous research or use trial and error to find the best energy range for your experiment.

3. Can I change the energy range on the spectrometer during an experiment?

Yes, many spectrometers allow you to adjust the energy range during an experiment. However, this may affect the accuracy of your results, so it is important to carefully consider your energy range before beginning the experiment.

4. Are there any limitations to selecting an energy range on the spectrometer?

Yes, there may be limitations depending on the spectrometer you are using. Some may have a limited range of energies that they can detect, while others may have a limited range that can be selected by the user. It is important to familiarize yourself with the capabilities of your specific spectrometer.

5. How does selecting an energy range affect the data collected by the spectrometer?

Choosing a specific energy range will affect the data collected by the spectrometer, as it will only detect and measure energies within that range. This can help to eliminate unwanted noise or background signals, but it also means that any relevant information outside of the selected range may be missed.

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