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Half life determination 
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#1
Jul414, 08:54 AM

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Hello,
I have a gamma spectrum of one element (X). There are several gamma peak in the spectrum. For example, 800 keV peak, 1000 keV peak and 1200 keV. I have an information about the peak area changing with time. Namely, I know the peak area in different times. So I can calculate the half life of the element by using the area and time information. But I have a problem. I got 15 hours from 800 keV peak. 14 hours from 1000 keV. 16 hours from 1200 keV peak. Which halflife is correct. What should I do? Which is the most reliable? Should I get average value? Best wishes 


#2
Jul414, 11:03 AM

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P: 1,991

The widths of different peaks will be different.
Calculate the halflife, by measuring only the height of each peak. These should all decrease at the same rate. 


#3
Jul414, 02:43 PM

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P: 11,589

If the values are incompatible, it would be interesting to know more about the experiment. Do some lines come from decay products? That can give an activity that deviates from an exponential decay. 


#4
Jul614, 08:28 AM

P: 10

Half life determination
Thank you very much.
With the errors, 15 +0.3 14+0.1 16+ 0.5 The 1200 keV peak is more intense. The others are small peaks. Will I get an average of all them? Namely, (15+14+16)/3=15. Or, will I get the halflife as 16 due to the fact that 1200 keV is more intense. Or, will I get 14 for halflife due to the fact that this value is smallest error? Best wishes 


#6
Jul814, 12:52 PM

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14+0.1 and 16+ 0.5 are a bit far apart. It would be interesting to see the decay scheme. If there is a physical reason for them to have the same halflife, something went wrong, you were really unlucky (>3 standard deviations) or the uncertainties are nongaussian.



#7
Jul914, 02:38 AM

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#8
Jul914, 04:05 PM

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Did you identify the gamma energies in a decay scheme? 


#9
Jul1014, 01:37 AM

P: 10

Ga69 was bombarded by 10 MeV photon. A neutron was emiited from Ga69. The unstable Ga68 decayed to Zn68.



#10
Jul1014, 03:55 AM

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P: 16,166

None of those are near the half life of Ga68. Are you sure you are measuring what you think you are?



#11
Jul1014, 04:01 AM

P: 10

I was choosen the numbers randomly for an illustration. Actually the half lives that I measured are 65 min, 67 min and 66 min.



#12
Jul1014, 05:21 AM

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P: 16,166

I'm afraid by asking people to help you with made up, inconsistent numbers, you ended up wasting people's time. Perhaps it would be better to show us the real numbers.



#13
Jul1014, 05:35 AM

P: 10

My aim is to know the technique with a basic examples. It is not do an article all together. I have no realistic data. Again, I would like to know the technique. Because of someone, I made up an element, a realistic peaks and a realistic half life.
I do not have any of them. Just technique I wonder. A dream I had about this problem. So I ask to get an answer. Thats all. 


#14
Jul1014, 05:55 AM

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#15
Jul1014, 03:19 PM

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