Help Identify Radon Detector Module

[fuzzoli]

I just purchased a "Corentium Home Radon Detector by Airthings" to collect radon readings at various locations throughout the house.  It's a nice little unit, but of course, I had to take it apart. 

It's powered by a TI M430F4152 mixed signal microcontroller.  I'd love to tap off the point where the uC starts counting and maybe add in a wireless module so I can graph the data over time.

In the attached photo, the shielded parts above the uC must be the signal conditioning for the radon detector.  Does anyone one recognize which type of detector is being used?  It's the round silver thing on the right side of the case.  Once I find the specs on the module, reverse engineering the signal conditioner-to-uC connection should be straightforward.

Thanks!

** Edited to stop all the electrons from falling out. **

[jmelson]

Its an ionization chamber.  it is filled with some gas at low pressure, and a voltage is applied between (presumably) an interior plate and the case.
Gamma rays go through the case and ionize the gas, and then there's a cascading avalance discharge inside.  A small capacitance provides some current to keep the discharge going for some microseconds, when the capacitor charge runs out, the avalance quenches and the circuit recovers to the steady state.  A coupling capacitor passes the pulse along to an amplifier.

Jon

[jmelson]

Ah, there's a string of replicated components along the bottom of the shielded area.  That is a Cockroft-Walton multiplier stack to boost the
voltage for the detector.

Jon

[fuzzoli]

Thanks, Jon!  Any clues on a model number for the ionization chamber?

[LaserSteve]

Um, Their web site implies that it looks at Alpha and is an avalanche photodiode.

Steve