When I discovered that decent geiger tubes could be purchased on ebay for only $20 CAD, I knew I had to make a geiger detector. I researched some high-voltage power supply designs and built my own regulated supply. I experimented with a few different configurations to find the solution that consumed the least amount of power.
In the end I settled on a design that is mostly made with inexpensive, common parts. The current consumption is 29mA at 4.2V, approximately 130mW. This is very reasonable and allows the 18650 lithium battery to power the device for a few days.
The operation of the device is very basic. Each event detected by the geiger tube is indicated by a click of a speaker and a flash of an LED.