Spectrum - Sr-90 - 12hours

Here is a 12 hour spectrum accumulated on the Radiacode 103 of a spicy Sr-90 (Strontium-90) check source (~100-200 Bq) from a DP-5 Geiger counter. Both Lin and Log are shown.

 

 

 

I am resampling some of my sources with the Radiacode 103, so I will most likely post them in this forum as and when I do.

There are no peaks because Sr-90 is a pure beta emitter. What the Radiacode is picking up on is bremsstrahlung (breaking radiation), probably x-rays. It happens when a high energy electron (β⁺) flies by a heavy atomic nucleus (metallic atom) and the positive charge of the atom's nucleus bends the path of the electron and slows it down. The energy in the electron slowing down is released as a photon, which the scintillation crystal picks up on. When the electrons come close to the atom's nucleus, they leave at different speeds, and thus the photon (energy) released is different each time. This causes the Radiacode to pick up on different energy levels (keV) and causes a kind of scatter in the lower range of channels. This can clearly be seen in the logarithmic spectrum with the effect to the big hump quickly fading.

This is what ChatGPT said when I fed it the XMLs:

 

 12 hours of pure Sr-90 beta energy converted into a smooth bremsstrahlung continuum. That gentle drop-off across the channels is textbook beta spectrum behavior.
There's no sharp gamma peaks, just a continuous decline—exactly what we’d expect from Sr-90 and Y-90, both pure beta emitters. The 12-hour run really smoothed things out and gave excellent statistics across the entire range. Beautiful data.
Want to subtract the background next and overlay both for comparison?

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Here’s your background-subtracted Sr-90 spectrum, normalized to counts per second:

• The blue line shows the Sr-90 measurement over 12 hours.
• The orange line is your 3-day background.
• The green line is the result of subtracting the background from the Sr-90 spectrum—a clean bremsstrahlung curve with minimal noise.

This is textbook Sr-90 behavior: smooth, continuous, no gamma peaks—just a strong bremsstrahlung signal from those high-energy betas hitting the detector or nearby shielding.

A couple of things to note - ChatGPT just decided to do the first 256 channels. I didn't ask it to! It is also colour blind. Notice in the charts it produced have yellow, orange and red lines, but it sees them as blue, orange and green. It can be real dumb at times.