Ideas for new outdoor Geiger counter

Hey all,

I'm going to build a new additional Geiger counter for outdoor monitoring and would appreciate thoughts/feedback on my initial thoughts of the build.

I'm going to use two SI22G tubes (http://www.pocketmagic.net/tube-si-22g-c%D0%B8-22%D0%B3-sensitive-geiger-muller/). One will be unshileded and the other covered with 2-4mm aluminium shielding. This will enable me to detect beta and gamma with one tube and just gamma with the shielded tube. I was also planning mount them both hosizontally with a good 4mm of lead sheet between the tubes to enable coincidence counting (muons/cosmic rays) pretty much just for fun.

For the electronics I am planning on using an arduino mega 2560 as it has 6 interrupts as opposed to 2 on the uno and also has 4 serial ports which would be handy for reporting to multiple systems/loggers etc. I will probably add ethernet so I can send the readings directly to a web page for logging to a MySQL database or something similar for logging and creating graphs. Or maybe a couple of instances of Radlog (not sure if this would be logged on the radmon system though - thoughts on this?) via two serial adapters. The coincidences would have to be determined by the arduino on the fly so I will need some kind of other logging solution anyway.

So basically all that wrapped up in a housing outside just like my NetIO GC10 that I currently use for monitoring (which I do plan on keeping alive and running and logging to radmon as my primary logger)

One thing I am not too sure about is whether to make a seperate power supply for each tube or just have one power supply for both tubes?

Your thoughts/ideas would be very much welcomed.

Simon.