What would a muon (cosmic ray) peak look like?

[ColoRad-o]

Howdy all!

Scintillator + PMT detectors appear happy to detect muons or other cosmic rays. Marek Dolleiser distributed a very nice paper on systematic detection with a cosmic ray "telescope".
Only recently did I do a count long enough (40 million pulses: 5 stacked Th232 thorium mantle lanterns) to see a peculiar high-energy peak, with a GS-2020 NaI:Tl with a bias of 700 V.

(With all due respect to Impulse, I'm not yet familiar with it, so used PRA.)
I have nothing with which to calibrate beyond 2614 keV, so the energy may be substantially off. Has anyone seen such as peak before and identified it?
Thanks for any insight.
DMW

[Sesselmann]

DMW,

AFIK, muons can have a range of energies and I doubt you will see any peaks, what they do have in common is that most of them are very energetic and usually result in pulses way above 3MeV.

You can try turning the gain right down and calibrate with Thorium at 2614 at the end of your spectrum, and see what it looks like. The peak your are seeing in your spectrum might be an artefact caused by something else.

No offence taken for using PRA, it is still my recommended program for sound cards, but Impulse is getting better with every version and I am getting good feedback on the latest v2.2.6. The Impulse detection algorithm works in the same way as PRA so it should produce the same quality spectrum.

Steven

[Madmax]

It can be a summary peak.

[ColoRad-o]

I checked for "sum peaks" with InterSpec--no luck.

[Magnus7]

Hi D.M.Wood,

I tried to recreate your spectrum but I cannot see the high peak. A small peak at around 3500 keV is slightly visible but my calibration is also only valid to 2614 keV.
Otherwise, my spectrum looks very similar to your spectrum.
I also used 5 stacked lantern mantles.
GS-1530 NaI:Tl with a bias of 750 V
Around 70 million samples in total.

It would be interesting to bring the equipment onboard an airplane to see what the cosmic radiation would look like.

In an earlier thread I mentioned that my small scintillator (RadiaCode 103) at approximately 20 keV (no valid calibration) shows a high peak (several times the normal "noise peak") at altitudes above around 7000 meters where the cosmic radiation is higher. That peak is some kind of artefact that will not be reduced by lead shielding as expected. The peak has been found on 14 different flights so far. I tested copper tube and lead to rule out different kind of noise sources but it had just a very small effect (the normal "noise peak" was however reduced by the shielding). That peak puzzles me.

Magnus Linnér
Malmö, Sweden

[ColoRad-o]

Hello Magnus,
Sorry to have overlooked your post for so long! (I bought a RadiaCode 103G quite a while ago--DAMN is it convenient--well calibrated, and writes files I can import directly into InterSpec.) I attach another (uncalibrated) PRA spectrum from my 5x5cm NaI:Tl showing the same peak even within 2.3 cm of lead shielding in my basement; this is about 17.6 counts/second at 700V bias. I'll post more when I finish doing a fairly careful pulse analysis of the spectrum. Meanwhile, I'm curious about how you calibrate above 2614 keV?

[Magnus7]

Hi ColoRad-o,
My calibration ends at 2614 keV, above that it is just linear extrapolation so not exact at all.
Congratulations to the 103g!
I just got a RadiaCode 110 and brought it on my first flight.
It got the same peak at the very low end of the spectrum as I got with the 103. On my 103 I verified earlier that the source is high energy even if it shows up erroneously as low energy. I assumed high energy influence because by bringing lead and copper on a flight as shield, the result was almost not influenced.
On this premiere flight with the 110 I didn't bring any shield but I strongly assume that it is same artefact and mechanism as I have seen with the 103.
I had some short correspondence with the Physics department, Division of Particle and Nuclear Physics of Lund University and they gave muons a likely guess. They said that muons was a menace disturbing their normal ground-based measurements.
I assume that the low energy peak is from erroneous low intensity flashes in the CsI(Tl) crystal. It could of course also be some weird software error in the RadiaCode.
My main question is if there is anything related to cosmic particles that could be capable of giving tiny flashes in the crystal.
One thing that might interest you is channel 1023 of the RadiaCode. That channel is said to be a kind of overflow counter for hits above the maximum energy on the scale.
On my flights I always see a fairly high count number on channel 1023 at cruising altitude.

/Magnus

[ColoRad-o]

As I mentioned a couple weeks back, I find an unfamiliar peak in a PRA spectrum well above where I am able to calibrate. (This is from a 10-day count of some weakly radioactive soil, dominated by Th232 and K40.) The histogram of pulse lengths (to right of spectrum) is completely dominated by well-behaved pulses, with a mean of 52.4 microsec. (The advanced pulse filter reported a maximum pulse length of 521 microsec which caused me to investigate pulse length.) I have "localized" the relatively high end of the spectrum (roughly 115-160 au) as coming from pulses whose widths are only mildly higher (62-65 microsec) than the prominent peaks in the pulse length spectrum. Thus I can see nothing to cause me to discard the tall peak aound 149 or so au as an artifact. I have seached the scientific literature for a clear statement of what happens to the gamma spectrum at the high energy end, when the detector system ceases to respond properly, but found nothing. Can anyone point me in the right direction?

However, I AM mystified by the fact that the number of "filtered pulses" tracks exactly the number of total pulses for quite a while (in multiple counts I have done), and then stops increasing. Any ideas why? A bug?

[Rob Tayloe]

This topic and the mention of the Radiacode device caused me to do some further investigation. The main radiacode webpage is linked below. Of greater interest is the linked YouTube video explaining the Radiacode 103 (CsI version), including a destructive disassembly of the device. Such a device would be interesting using a CZT and SrI(Eu) detector.
https://www.radiacode.com/

https://www.youtube.com/watch?v=XjJky99_Gpk

[ColoRad-o]

Somehow I guessed right about muons.

I heard back from Marek Dolleiser, the author of PRA and who has lots of expertise with secondary cosmic rays. His reply:

"The peak at 150 au is so called muon bump. It is produced mainly by muon secondary cosmic rays. They are much higher energy than your detector can handle and simply goes through your crystal exciting all atoms along their path. This produce artificial peak as energy of the muons deposited in the detector is similar depending only on the size of the crystal. This peak is observed if you run data acquisition for long time. There is no way to filter cosmic rays with even thick layer of lead shielding. 2.6 MeV is highest gamma energy which I know, the peak around 130 au could be produced by 2 gammas detected at the same time (summation peak) or cosmic rays crossing detector at different than vertical direction (most likely).

The problem with counting filtered pulses could be limited "Duration time". Check that in "Data Acquisition and Analysis" dialogue box value at "Duration time" is longer or equal to "Acquisition time". If is not then set it at least equal to "Acquisition time" this can be done at any time after finishing or during data acquisition process. "Acquisition time" is period to acquire the data and "Duration time" together with "Beginning time" is defining period that you like to analyse."