Identification of radiation source from gamma spectrum peaks.

In summary, the conversation is about identifying an unidentified radiation source using a NaI(Tl) detector and multichannel analyzer. The data collected showed peaks at energies of 86.3, 123.7, and 369.6 keV, but the source could not be identified using Kaeri. Suggestions were given to try integrating counts and checking the calibration, as well as looking for isotopes with similar intensities and half-lives.
  • #1
wsomma
4
0
I have an unidentified radiation source. I used a NaI(Tl) detector and multichannel analyzer to collect data and plotted the spectrum. I found peaks at energies of 86.3, 123.7, and 369.6 keV. From this data I am attempting to identify the source, but I am having a difficult time. I tried using kaeri but I can't find anything that matches this data. Could anyone help me out.
 
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  • #2
wsomma said:
I have an unidentified radiation source. I used a NaI(Tl) detector and multichannel analyzer to collect data and plotted the spectrum. I found peaks at energies of 86.3, 123.7, and 369.6 keV. From this data I am attempting to identify the source, but I am having a difficult time. I tried using kaeri but I can't find anything that matches this data. Could anyone help me out.
Did one do more than one set of counts. In addition to measuring the energy of the peaks, one can integrate the counts in each peak over some period of time, then wait and repeat in order to determine the half-life.

Ostensibly one has some idea of the material one is counting. For example, if one is doing an activation analysis, normally one would know that the specimen is a metal/alloy or mineral or some chemical compound, and it's state, e.g., solid, liquid, gas.

From Kaeri - http://atom.kaeri.re.kr/gamrays.html (just put in appropriate range)

Putting in 123 to 124 keV with > 0.0001 days
Code:
E(keV) Intensity Nuclide 
123.07( 3)   30.303 Tb-154 (EC 9.4 H) 
123.07( 3)   22.226 Tb-154 (EC 21.5 H) 
123.071( 1)  40.557 Eu-154 (B- 8.593 Y) 
123.2( 2)     1.08  Ir-172 (A 4.4 S) 
123.27( 3)  100.    Lu-164 (EC 3.14 M) 
123.3( 1)   135.    Re-172 (EC 55 S) 
123.5( 6)    69.    Ba-123 (EC 2.7 M) 
123.675(15)  83.516 Hf-173 (EC 23.6 H) 
123.805( 3)  28.983 Ba-131 (EC 11.50 D) 
123.9( 2)     8.781 Ta-168 (EC 2.0 M)

and 369.5( 2) 7.405 Hf-169 (EC 3.24 M)

However, Hf has stable isotopes 174, 176-180, so with activation, one would expect isotopes of A>180 from Hf.

86.3, 123.7 keV are down in the X-ray (K) range, but the closest to 86.3 keV is 86,834 ev X-ray of Bi Kβ3 or 86,100 of Fr Kα1, but neither seem satisfactory.

See - http://xdb.lbl.gov/Section1/Table_1-2.pdf
 
  • #3
I assume this is for a lab course?

Which peak is the dominate peak? Which is the 2nd? and which the 3rd?
What are their relative sizes?

The dominate peak is going to be the most accurate. You should start your search using this peak. Also, the calibration you did in class probably isn't to accurate so give yourself a 5 to 10 keV margin of error to begin with. As you go for through the list, try to find isotopes that not only have right energies but also the same ratio of intensities.

If you can't calculate the half lives don't sweet it too much. But if you can, do so. Peaks with similar half lives are usually from the same isotope.

Also I'd double check you calibration. Your gamma energies seem low. Typically there are a few peaks in the MeV range.
 
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1. How can gamma spectrum peaks be used to identify radiation sources?

Gamma spectrum peaks are unique signatures that can be used to identify the type of radiation source. Each element or isotope has a specific energy level at which it emits gamma rays, and these energies appear as distinct peaks on a gamma spectrum. By comparing the peaks on the spectrum to known energy levels for different elements and isotopes, scientists can determine the source of the radiation.

2. What is the process for analyzing a gamma spectrum to identify the source of radiation?

The first step in analyzing a gamma spectrum is to calibrate the equipment to ensure accurate energy measurements. Next, the spectrum is examined for distinct peaks, and the energies of these peaks are compared to a database of known energy levels for different elements and isotopes. By matching the peaks on the spectrum to those in the database, the source of the radiation can be identified.

3. Can gamma spectrum peaks be used to determine the level of radiation exposure?

While gamma spectrum peaks can help identify the source of radiation, they cannot be used to determine the level of exposure. This is because the intensity of the peaks on a spectrum is influenced by factors such as distance from the source, shielding, and type of detector used. To determine the level of radiation exposure, a different type of measurement called a dose rate measurement is needed.

4. Are there any limitations to using gamma spectrum peaks for identifying radiation sources?

While gamma spectrum peaks can be a useful tool in identifying radiation sources, there are some limitations to this method. For example, if the radiation source is shielded or if there are multiple sources present, the peaks on the spectrum may be distorted or overlap, making it more difficult to determine the source. Additionally, the accuracy of the identification depends on the quality of the equipment and the expertise of the analyst.

5. Can gamma spectrum analysis be used to identify all types of radiation sources?

Gamma spectrum analysis is most effective for identifying gamma radiation sources, as this type of radiation produces distinct energy levels that appear as peaks on the spectrum. However, it can also be used to identify beta radiation sources by examining the low-energy end of the spectrum. Other types of radiation, such as alpha particles, do not produce distinct peaks and therefore cannot be identified using gamma spectrum analysis alone.

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