STS-6 CTC-6 Geiger Muller Tube

Hi! I’ve just received two STS-6 Geiger Muller tubes from Ukraine. They are HUGE! Their size is 199mm long X 22mm diameter. In this video that I’ve made you can see I’ve enclosed in into a thick walled Alluminium pipe so I can filter out all beta’s and count just gamma’s. This because without it, my pechblende sample count more than 14500 CPM at 2cm from the probe. Uranium decay emit alpha + a lot of beta BUT…some of his impurities (radium) decay with gamma. I’m interested in gamma emitting sources.

The Uranium decay

This is the video:

And some more info about the tube and pics:


  • Working Voltage 390 – 400V
  • Initial Voltage 285 – 335V
  • Plateau Length 80V Plateau Slope 0.125% / 1V
  • Inherent counter background (cps) 1.83 Pulses/s
  • Interelectrode Capacitance 10pF
  • Load Resistance 5 – 10 MOhms
  • Working Temperature Range -500 +700 С
  • Length 199 mm
  • Diameter 22 mm

The STS-6 tube with it’s original box and datasheet. The screwdriver is for size comparison

This tube is so BIG!