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