LaBr3 intrinsic activity at 32keV ?
Posted: 16 Aug 2023, 21:46
Hello folks,
Long time I didn't do any spectro, so this summer (north side ;) ) I managed to get some time to do some again with my LaBr3:Ce detector GS-1010 and tried several times to calibrate from Cs137, Am241 and Lu176 and had a hard time figuring out why the 30-40keV range appeared to be not-linear-at-all even with polynomials calibration, stable temperature and even long power-on period before starting measures.
Indeed, I firstly calibrated from the intrinsic LaBr3 cristal activity which should give also 32keV and ~1440keVs peak and then tried to make another spectroscopy of Am241. The last one was not correctly aligned with expected calibrated bins and finally I went comparing the background spectra with a Cs137 one and noticed something I didn't before: the Cs137's 32keV peak seems to appear on the left peak of the ..32keV's LaBr3 ??
Taking this new 32keV (from Cs137 and not LaBr3) peak as reference, all the calibration went perfectly fine and very precise on almost the entire 0-3MeV.
With this setup, I measured the background crystal La138 peak (?) being at ~37keV.
I tried looking for more resources on the web but I can't find anything different from specifying LaBr3 giving actually a nice 32keV peak on the lower energies.
I thought maybe interaction from La138's Alpha particules with crystal aluminium enclosure may give this but didn't find any relation.
Is there something I forgot at some point ?
Please find in attachment the spectrum of Cs137 with that LaBr3:Ce crystal (red line is background) :
-> first file is zoomed on the low energies portion : notice the peak that appears on the left of the La138 one (compared to background and, yes, it's not that obvious as it's almost merged into the huge one).
-> second file is the full spectra on log scale
Thanks !
Yvan.
Long time I didn't do any spectro, so this summer (north side ;) ) I managed to get some time to do some again with my LaBr3:Ce detector GS-1010 and tried several times to calibrate from Cs137, Am241 and Lu176 and had a hard time figuring out why the 30-40keV range appeared to be not-linear-at-all even with polynomials calibration, stable temperature and even long power-on period before starting measures.
Indeed, I firstly calibrated from the intrinsic LaBr3 cristal activity which should give also 32keV and ~1440keVs peak and then tried to make another spectroscopy of Am241. The last one was not correctly aligned with expected calibrated bins and finally I went comparing the background spectra with a Cs137 one and noticed something I didn't before: the Cs137's 32keV peak seems to appear on the left peak of the ..32keV's LaBr3 ??
Taking this new 32keV (from Cs137 and not LaBr3) peak as reference, all the calibration went perfectly fine and very precise on almost the entire 0-3MeV.
With this setup, I measured the background crystal La138 peak (?) being at ~37keV.
I tried looking for more resources on the web but I can't find anything different from specifying LaBr3 giving actually a nice 32keV peak on the lower energies.
I thought maybe interaction from La138's Alpha particules with crystal aluminium enclosure may give this but didn't find any relation.
Is there something I forgot at some point ?
Please find in attachment the spectrum of Cs137 with that LaBr3:Ce crystal (red line is background) :
-> first file is zoomed on the low energies portion : notice the peak that appears on the left of the La138 one (compared to background and, yes, it's not that obvious as it's almost merged into the huge one).
-> second file is the full spectra on log scale
Thanks !
- Zoomed Cs137 view, linear
- zommed_Cs137.png (93.31 KiB) Viewed 4219 times
- Full Cs137 view, log