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Identification of radiation source from gamma spectrum peaks.

  1. Mar 18, 2013 #1
    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.
     
  2. jcsd
  3. Mar 18, 2013 #2

    Astronuc

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    Staff: Mentor

    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 (Text):
    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
     
  4. Mar 19, 2013 #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.
     
    Last edited: Mar 19, 2013
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