Here are some initial thoughts, from a starting point of true ignorance in radiation metrology. Please beat it up as necessary, and I will morph the block diagram.
1) In the 90's, all electronic instrumentation became a computer peripheral. Now more so, except connected by wi-fi or bluetooth to either a computer, tablet or smart phone; modules to do so are commonly available. The 'Altoid can' (actually a plastic box so the RF link would not be shielded) would contain this module, a uP, lithium battery, battery charge controller, probe HV PSU, preamp PSU.
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2) Make the sensor/preamp remote on a cable, so that it is pluggable into the head unit. Different probes for evaluating different environments can then be used, and the cable length helps isolate the preamp from the HV PSU. If the interface between the 'Altoid can' and the probe includes ID lines (say 3 inputs with pullup into the uP that are selectively grounded by the probe), the uP can tailor the HV and preamp power to one of up to 8 probe types automatically.
3) I agree with Doug on not modding a CCF PSU -- I think they are designed for much more amps out than we need. I have had good results getting +5V--> +100V with a 470uH coil (CDRH74NP-471MC from DigiKey). It is about as small as they get:
http://parts.digikey.com/1/parts/642131 ... 471mc.html.
4) As a team, come up with a specification and feature list. I favor putting a hardware platform in place that can accomodate more analysis features (like spectroscopy) than just a count further on. It seems like the Russian-made (
http://www.google.com/search?q=Soeks+Radiation+Detector) is setting the price/performance bar right now in handheld devices, largely due to its software.
5) As a team, determine who is going to be the Czar of what project aspect, and stick with it.
Doug, I don't know anything about sensors, so I will let you guys fight that one out. I would like to focus on what is necessary to allow a head unit to accept any kind of probe, ranging from a gallon jug on a table at the end of a cable, to a little GM tube that plugs so seamlessly into the head unit that it looks like part of the same box. Re battery life with wi-fi: how long does an iTouch last? Can wi-fi only be enabled during a [short] data burst? Power the head unit by USB from the analysis platform for long term measurements? These are questions I think bear resolving.