A Spectrum to Ponder

[pietkuip]

Sm-147 has a half life of 1.06×10^11 years! Also it is just 15 % abundant. That is just very few alpha decays near the surface.

No gammas listed in http://nucleardata.nuclear.lu.se/toi/nu ... iZA=620147.
That means they cannot see any in all the background.

[brehwens]

I also tried to go through some list of the naturally occuring isotopes, and essentially only Lanthanum and Lutetium seem to be "hot" enough for any detection of gammas with our equipment (and some of the others do not emit any gammas)....

[iRad]

Hi Alfred, Alpha's need a very special setup to measure. The detector window must be thin enough to allow alpha particles to enter the detector, or the alpha source must be enclosed within the detector assembly (light tight of course). A very thin aluminized Mylar film (often referred to as Rad-Film) is used as the window material. Many gamma scintillators are not able to detect alpha, so usually an alpha sensitive substance, ZnS(Ag) is used for the alpha detection.
What you are detecting with your Am241 source is the week gammas, most notably the peak at 59.54, but with your nice Scionix probe, you should also be seeing a lesser peak at 26.34. Cheers, Tom