Hello from Massachusetts

[Phouly]

Hello everyone, I'm Patrick, I just got into this rabbit hole about a month ago, So far I've Cast my own lead bricks. Constructed a copper - leadfree pewter lined lead castle and used it to lower my background radiation from ~113cps to 1.9cps , I've tested my spectrometer on some Thorium Lantern Mantles, Radium Watch hands, and an Americium Source. for Equipment I've got a GS-Pro V5 and a Scionix Holland 1.5" NaI Scintillation detector. I have no formal background in Radiation or Nuclear engineering aside from a Short stint in Physics -201 at a Local University, Most of my knowledge is self taught or Learned from the experience and guidance of others, So I'm hoping this forum will help me a lot, and that I can do my own share of Contributing.

I currently have a Mystery Spectrum that I am having trouble Identifying Identify as I am quite new to this. that I'll be posting about shortly.

I Live in a Small town here in South eastern Mass, and am eager to learn more about Gamma spectroscopy.

[Sesselmann]

Patrick,

Just noticed your post had no replies, so welcome to the forum and good luck with your experiments. Feel free to post your mystery spectrum here and for sure we will demystify it for you.

Steven

[Phouly]

Thanks!, I'm going to try and give my full backstory here so about 7 months ago I won an auction on a ton of "Junk" from a place called Stewart Radiance Labs here in Massachusetts, They did a lot of Optics work with MWIR LWIR, for the local airforce base. a lot of the stuff I got is very old before 1990. I was grabbing random items and placing them infront of my detector until my cps went up by even just 1 or 2 and let it run for a full 24 hours. This item in question is from what I can tell a Helium Spectral Lamp.



From what I could Tell, Only SB-125 and Th234 Match up, but from what I looked up SB-125 isn't something I would just find as a constituent material. and from what I could find If I am Looking at Thorium 234 Then I should see Other Decay Daughters.
any help would be greatly appreciated, Also I dont know if its common or I'm just confused but I think my scintillator has a non linear response sort of. where it will over estimate energy levels on the lower end of the higher end is calibrated and under estimate the higher end if the lower end is calibrated. that being said. in the attached chart the lower end is calibrated to a 59.6kev americium source just before I started testing. that is why my K40 peak is appearing at 1350kev. Also If a non linear response is unheard of, then please let me know what I messed up.

Also, The Peak After my K40 Peak appears on all of my Spectrums, Is this actually a radio Isotope or is my Volume set too high, or pulseshape malformed. It is more Triangular than the other Nodes.

[Sesselmann]

Patrick,

It's difficult for me to diagnose anything in Theremino because there are no reference points. In PRA or Impulse you have arbitrary units wihich allow you to set your gain so your spectrum fits in the 0-100 arb.u range. Then whatever exceeds 100 arb.u is just overshoot and can be ignored. I suspect that triangular peak on the right is overshoot, but can't confirm it.

Not sure what the isotope in your tube might be, so I shall leave it up to others to comment.

Steven

[Phouly]

I have Fixed my Pulse width, it was spanning from 50% to 90% of the Audio input Panel During pulse shape acquisition, now it is closer to 50%-70% on the x axis and lowered the volume so that my arbitrary units should get me up to 2.4mev on PRA, I will be Re running a Scan tonight and will post an update in PRA tomorrow after my spectrum develops.

[Sesselmann]

Patrick,

Unless you are specifically looking at x-ray spectra, a good rule of thumb is to set your gain to a level where the K40 peak at 1460 lands around 50 arb.u (middle of the spectrum). This will give you a range of around 3000 keV. Most of us don't see gamma rays above 3MeV.

Typically you may find that smaller detectors will have some compression towards the higher energies, you can calibrate quite well with a second order polynomial function. Larger detectors tend to show better linearity for reasons I have still not fully understood.

Fitting the whole pulse within the pulse shape window doesn't seem to be critical, I did quite a few tests with Impulse and had good results at high sample rates where only the tail ends of the pulse were outside the window.

PRA will plot the overshoot counts above 100 arb.u, but these counts do not correctly indicate pulse height, so in Impulse I decided not to show these. If you are looking for high energy gamma rays above 3 MeV you should lower the gain so they falls within the dynamic range of the input.

Steven

[Phouly]

Okay I've, rerun the spectrum, and Adjusted my Volume so that K40 is around 60 Arb units, I still have the spike behind my K40 so it doesn't seem to have been overshoot, It must be something in my lead shielding, besides that, I've got 4 prominent peaks at ~35kev ~71kev ~105kev and ~198kev, this Scan detected 450,000 Pulses in 86,400 Seconds so almost 2/3rds of all the pulses are from the sample.
Ive attached 2 Pictures, 1 is in arb units and one is still linearly calibrated. I'm Starting to lean toward some sort of Depleted uranium as the Main spikes seem to be Th-234 But compared to other spectrums on this forum such as fiestaware they seem to have a lot higher 185kev spike

[Phouly]

After some searching, I found a post on here of Uranium Glass, which seems to have, for some reason or the other, the Th234 peaks a lot closer in intensity, compared to a UO2 sample or depleted uranium, I will shine a blacklight on it once I get out of work To see if there is any Fluorescence. maybe uranium glass was used for its optical properties in the Helium Spectral Lamp.

[Phouly]

Ive gotton to the Bottom of this,

"Uranium glass is used as one of several intermediate glasses in what is known to scientific glass blowers as a 'graded seal'. This is typically used in glass-to-metal seals such as tungsten and molybdenum or nickel based alloys such as Kovar, as an intermediary glass between the metal sealing glass and lower expansion borosilicate glass." - Wikipedia


Although I Still wonder What causes uranium glass to have such a higher spike on the 63kev ray from TH-234, I wonder if it is a good/bad geometry issue when comparing it to depleted uranium or uranium ore. where half of the 63kev rays, just hit the surrounding rock and get absorbed and that doesn't happen in Glass where it is spread apart and in lighter element structures.

[Sesselmann]

Patrick,

Nice work, great to see you are going deep, I'm out of my depth here, but following your work with interest 😊

Steven