On Tue, Oct 22, 2019 at 11:30 PM, Dude wrote:
My 50kV ?gun is limited to 50 kV due to the backscatter and the FDA shielding issues. The SSD drops off pretty quickly at about 60 keV for the photoelectric response unlike CdTe which can see the U Ka at 98 easily.? A Si Pin is similar to the SSD in range but much poorer in resolution. ?Both depend on the depletion depths and peaking time.? The problem is efficiency at the high energies. I can see Sm with a 50 kV xray but it¡¯s got to be in the percent range.? I have a Kevex 60 kV xray microfocus unit here but no detector other than some ?low energy ?HPGe¡¯s to use with it. I had been toying with the idea of picking up a Cd Te detector to play with.? A fast SSD would really help with resolution.
U and Th La¡¯s are easy to see.
?The problem with the HREE is you have to look at the La ?and Lb¡¯s which occur in the ?matrix of everything else and don¡¯t resolve well. Using the Ka, Kb¡¯s requires a 50kV tube up to Pm. Above that you want to be about 10 -20 keV above the binding energy. U and Th occupy a fairly open region above the mess below and are easily seen in the La and Lb range.
Rather than cooling down the HPGe detectors I look at the HREE with a homebrew LIBS system which see everything.
I¡¯ll be looking in to a CdTe detector but I¡¯m sure I¡¯d also be tempted to get a Fast SSD for the Kevex.
What are the specs on your SiPin? Window and SI thickness?? What do you have for the CdTe setup?
Dud
All AMPTEK stuff for Si-Pin and CdTe.?
0.001" Be windows.
The Si-PIN are essentially the 1-2-3 spectrometer package electronics, in a home brew housing. The CdTe is the PX-2CR power supply with a XR-100 CdTe head with preamp. No spectrum analyzer inside like the 1-2-3 setup, so have to use the external MCA.
Using @59.5 now for exciter, one to 8 points max. Much backscatter, working on the backshield and have a pretty good working arrangement now, mostly was interested in knocking down Np X-Rays, and it took a layered graded approach. Still have a little leakage of Cu X-Rays from? the brass I used to make the exciter rings. Next time will use a HDPE material? not brass I think ( will test first).
Got the angle of attach down pretty close to ideal already, so main thing is air attenuation. If in a vacuum or semi vacuum, that would clear up nicely. Propane purge helps, shows what can be expected with even partial vacuum.
Have a KEVEX tungsten target set with variable power supply, 10 to 50 kVp, adjustable from 10 to 200? uA.
same outfit as in 2013-14 in Las Vegas when used with the SDD 1-2-3, noted then 10 uA worked fine with 15? uA sometimes needed.
LIBS is a good idea.
You can use your best sensor and beta particles for exciting too. Also alpha particles. They used Plutonium on the Mars spacecraft rover. Maybe on those leased? Po-210 static bars??
With @59.5, about 10% comes from the alphas and of course only from the surface.
My first outfit used Fe-55, Cd-109 and Am-241 and a mercuric iodide probe It was licensed and too much hassle. Many of the XRF periodic tables still have reference to which isotope to use and which of it's X-Rays are used to excite the elements.
Geo
