DIY Alpha Detector

I ran across this nifty little alpha detector, and decided to build one.  The concept behind the detector is simple - maintain a potential difference between the wires and the circular base plate and when an alpha crosses between the wires and the plate it will ionize the air, allowing for the dielectric breakdown of air resulting in a spark.

On the first iteration I couldn't find a current limiting HVPS (I didn't want to burn out a lab one), so I maintained the potential difference with an arc welder set for around 2 kV.  It worked, when I exposed the detector to an Am-241 source we got a few sparks, but we seemed to be burning the wires (too much current).

This could be a nice challenge problem for the undergraduate lab - build your own detector from scratch. You would get the base points for just working, with bonus points for detection efficiency (group with the highest detection efficiency receives 10 points, second highest 5, etc.) or spectra information.