Gamma Spectrometry Forum

Hello. One of my hobbies is collecting elements. I usually like safe transition metals but I have been branching out into rare earths, and so decided to put my Lutetium sample under the 2" CsI Scintillation detector. It clearly influences my PDS-100G monitor and in close proximity lifts the count from a normal background of around 10 to 20 cps up to 60.

My big scintillation detector will register a background count of 120cps here in London. Under my lead Shielding I get it down to under 7cps. The Lutetium gave me about 110 under shielding.

In no time the predicted peaks duly appeared and I have annotated them in the attachment when in no doubt. There was however a peak at about 510 to 520 KeV which the internet radiation commentariate describe as a 'sum' peak. I'm no expert. Here are the images. The Lutetium is placed upright along side a sample of iron to the right on a Scottish £5 note in order that you may get some sense of the relative hue and lustre of Lutetium.

Hi Photon (assumed not your real name),

Thanks for signing up to our forum and sharing your work in the Spectrum Forum.

As a general rule we ask new members to post using their real names and to give a brief intro in the Introductions forum, so please feel free to do that now. You can either change your login handle to your real name if it is available, or add a signature to your posts in the User Control Panel (UCP).

Cheers..

Steven

Hello,

I introduced myself on the 6th of August this year. I have updated my signature.

Matthew,

You did indeed, and I even replied, my apologies for not checking this first, and thanks for adding your signature.

Very nice chunk of Lutetium, and the sum peak is where the two pulses overlap so you get 201.82 + 308.88 = 510.76 keV

Steven

Nice Lutetium sample, Matthew. When two (or more) gamma-rays are emitted during the same decay event of the nucleus (seemingly instantaneously), the so called coincidence, the detector sees both of the gamma-ray energies as one larger energy and a summation photo peak is shown at the combined energy of the two gamma-rays (actually within 8% of this expected theoretical value for reasons I forgot). Except this "true coincidence", there is also "random coincidence", which results from gamma-rays from different decays registered simultaneously. I hope this explains a bit what is a sum peak.

Thank's Svilen. I think I'll have another try see if I can get some more resolution - this run was about 2h hours. I'll do some reading up on sum peaks too.

Nice Lu rod, must have been quite expensive. As I'm an elements collector too, I'm wondering where did you get it from. There are maybe 2-3 possible source of such rods that I'm aware of, my guess is Metallium Inc.?