The question is derived from an experiment... "Red" tungsten TIG welding electrodes consists 2% of thorium-232. They are slightly radioactive... I have such electrodes, so I checked their radioactivity by an NR-750 Geiger counter (indeed they are radioactive).
I interpreted that particles, which are detected, are electrons from beta decay. But if I put electrodes behind a few mm steel shield, I still detect some events. Why? Does it mean that X-rays are also emitted? But why?
According to Thorium series, only alpha particles and beta particles are emitted.