Interference

My J305βγ tube is very light sensitive so I made a quick video demonstrating this. I shine daylight (on a miserable cloudy grey day) on the tube at first, then a 365nm UV flashlight and finish off with daylight again. The effects seem to work only at the anode end and not at the cathode end. Doing a little research I found that the light sensitivity of GM tubes only occurs in glass walled tubes that have an external cathode. The specifications show this about the tube wall: Tin oxide Cathode, Coaxial cylindrical thin shell structure (Wall density 50+-10cg/cm2). The cathode is on the exterior