I have always used 4.8uS peak time.
Can you show why
you think you are resolving individual peaks down to less than 1.5 keV?
Charles
Thanks for that report Charles. Of the two, can you say what is the lowest peak that can be resolved and is there a difference between them?? My just finished overnight run using the Si-PIN on a weakly radioactive sample for Gamma Spec (not excited XRF) is resolving individual peaks down to less than 1.5 keV. In the Peaking Time topic thread I'll post that test @19.2us PT along with a nearly similar test done last February at 4.8us. The main difference between those seems to be both in the clarity and narrowness of the big peaks, and better performance at the lowest end going to the 19.2.
Today I'll try even longer peaking times, up to 32us just for the historical record.? I think you've been using 32us and I can't fault your scans, that's for sure.
Geo
----- Original Message ----- From: Charles David Young < charlesdavidyoung@...> To: XRF < [email protected]> Sent: Fri, 30 Oct 2020 08:26:25 -0400 (EDT) Subject: Re: FW: [XRF] 59.5keV spectrum cleanup
I did 2 runs on a brannerite specimen.? One like normal (red) and the other with a paper adhesive label covering the buttons.? The proportions of the peaks pretty much look the same to me.
Charles
On Wed, Oct 28, 2020 at 11:30 AM Dude < dfemer@...> wrote: Charles, My
mistake, I now see the problem you¡¯re using a log energy axis. That should always
be linear, counts can be log, lin or sqr as appropriate. Dud ? ? Charles, Looking
at the png you sent there is something seriously wrong on the low energy below
4 keV. Send the mca file for a look as it may just be a Theremino problem. For
these low energies you¡¯ll want to keep the Np in there, but to pull these
elements out you really need a high flux rate which the Am source isn¡¯t doing.
Even with a tube the efficiencies are very poor and the counts are low making
it hard to quantify. However, the Al Si, P, S, Ca and K ?are absolutely
essential to determining the basic mineralogy types and every effort should be
made to verify their presence. To
get the count times up readjust the gain to look only at the low energy range
say from 10 on down and see ff that helps pull them out. Using a tight focused
beam and close up to the target will also help concentrate the flux. Dud
? From:[email protected]
[mailto:[email protected]] On Behalf Of Charles David Young
Sent: Wednesday, October 28, 2020 8:12 AM
To: XRF
Subject: Re: FW: [XRF] 59.5keV spectrum cleanup ? I agree and I did not mean to dis this exercise, even if it
turns out to be primarily academic. When I get a chance I'll try the paper filter with a mineral
like Brannerite (UTi2O6) to see how it affects the Ti peak at 4.5keV.?
That is typically the lowest element that is essential to my application.?
Other peaks like P, K, Ca would be nice but I have learned to live without
them.? If we could somehow dig those out by an adjustment it would be
great. ? "The filter comes at a cost.? Am I reading it
correctly that it reduced the input count to %25 of the non-filtered?? Do
we need to wait 4x longer for equal counts when this is used as an exciter?
" All that is to be determined Charles. It well may be much
worse than that, if the low energies in the beam are what's helping to dig out
the low energy XRF signals we are looking for. I agree about our perspective points of view too.? You system is as ideal as can be for your main task, and
your display program is an advancement in the area of display and
identification, especially for the audience of that group. Now the photography
meets the same standard too. No one has added all those dimensions in one place
to the amateur mineral group before.? All for science' sake, and I applaud
that. For you and others I would recommend trying a paper filter
over the exciter source, just to see. The rest is for the X-Ray Physics and X-Ray Optics crowd. We
now have an inexpensive but powerful tool in our toolbox that wasn't there 2
days ago. ----- Original Message -----
From: Charles David Young <charlesdavidyoung@...>
To: XRF <[email protected]>
Sent: Wed, 28 Oct 2020 08:33:01 -0400 (EDT)
Subject: Re: FW: [XRF] 59.5keV spectrum cleanup The filter comes at a cost.? Am I reading it correctly
that it reduced the input count to %25 of the non-filtered?? Do we need to
wait 4x longer for equal counts when this is used as an exciter?? Was all
that low energy activity that is filtered out detrimental or beneficial when
the button is used to stimulate XRF in the target? I come at this from a different perspective.? I use the
Si-PIN with an Am241 exciter to identify minerals.? In my experience the
XRF coming from the target is much stronger than the noise introduced by the
Am241, which is mounted on a shield and facing away from the detector.?
Attached is a scan of xenotime, which shows a large Y component as well as some
U and Pb.? I turned on the Am241 reference lines to show that the Np and
Au peaks are very small in comparison.? One quickly learns to recognize
and ignore them when identifying the important peaks that emanate from the
target: Ti, Mn, Fe, Ta, Th, U, Y, Zr, Nb, REEs. After trying many slight thickness variations of Source
Filter components, the best result is show in the second picture.
First up is the spectra coming out of the Am exciter source with just a paper
alpha blocking filter. That alone made significant improvements at the low end
vs no alpha filter. The goal of this project is to apply a filter to the source
that will effectively remove most of the low energy component that is caused by
Np- daughter and self-XRF of elements in the button, such as Au, Ag, Fe.
Error! Filename not specified.
Now a filter applied to the source and another Gamma Spectrum ran.
Error! Filename not specified.
Thanks to member Dudley Emer for the design of the filter elements and thicknesses,
based on selective filtering using the K-edge X-Ray absorption effect.
Geo ? ?
|
