Gamma Spectrometry Forum

Hello,

I buy 2 units of 313CC tubes, they should have some Kr85 gas, but the spectrum that I have looks like Ra 226 ...

Does anyone here has this tubes ? what results do you get ?

I will post a picture tomorow, I will leave the system overnight to make a smooth spectrum.

not in the modd for waiting to long

https://i.ibb.co/dsj7YD5Z/2025-02-27-00 ... -3600s.png

3600 s

dont bother with the keV values for the peaks, it´s only calibrated for low energies, Am241 are on the corret places, my plan was to use the 514 keV from Kr85 to calibrate for medium energy and K40 for higher energy, but th spectrum that I get looks Ra 226.

What are your opinions ?

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In my opinion, it is radium 226 and your spectrum is out of calibration. I see Goldilocks and the three bears characteristic peak group.

Jim K

my problem with this result is that in the datasheet for the tubes we can see Kr85.

maybe some models from a diferente manufactuer have Ra 226 ?

http://www.r-type.org/pdfs/313cc.pdf
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I would go also say Ra-226. I have a copy of an unofficial source of vacuum tubes with radioactive isotopes ("Cliffs Radioactive Tube List") and there the 313CC / CB are both listed as Kr-85 and Ra-226. Its common that vacuum tubes use different isotopes, for example there are 0A2WA tubes in Co-60, Ra-226, Ni-63 and U-238 Variants around.

Do you have a date code for the tube? Mine has a date code 1966, and since it should have had around ~0.5uCi of Kr-85 then, it would have decayed to around 0.012, that's 470bq, with a branching rate of 0.004 this would add up to ~2 events per second, so very hard to measure with a standard detector..

See also attached a HPGE-Spectrum comparing a Ra-226 (green) to a Kr-85 (black) spectrum

No date code, only 313cc and the brand Hytron.

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