Blue enhanced photodiodes?

[Doug Coulter]

Awhile back, we were talking about compact portable scintillators. I recall Lutz was angling for a blue-enhanced photodiode to look at the deep blue (usually around 420 nm) output of most common scintillators, like the plastics or BGO. Well, I've found some, even Digikey has them, but they are far, far too pricey for the job I have in mind -- around $1k range.

Which makes me wonder - what sensitivity do we really need for a pocket scintillator? I also see a "mere" $54 PIN diode listed that shows a number that looks like low noise, and about half sensitivity up in the blue. Here's it's curve:

Data sheet here:

SD100-12-22-021-1.pdf

(101.53 KiB) Downloaded 664 times

OK, I'm no expert in the jargon of photonics. This thing is rated in amps/watt - but most things are done in lumens, candles etc -- all different units with different meanings; some are total power, some are power density, some are scaled to eyeball response - you name it. I get sick of doing the conversions, or even finding a decent explanation of each unit in this field, and magnetics. The specialized jargon might help the expert, but not me.

I know a phototube will handle most scints and return a decent signal I can get amplified to a useful level out of the noise from the typical hit on the scintillator. Those tend to be rated amps/lumen IIRC. Anyone willing to do the reverse conversion between a phototube output, the actual light it's seeing in use, then going the other way to see what kind of signal that would produce out of this (or anything you can find) diode? Being small, it can be tightly integrated into the preamp, and I'm pretty good at low noise preamps - you can assume that would be state of the art or very close.

The application is to improve over JoeJ's impressive keychain geiger, making it both smaller and more sensitive, with longer battery life.

[Jerry]

I see these Hamamatsu avalanche photo diode modules on ebay all the time. Maybe those will work:

http://www.ebay.com/itm/Hamamatsu-C5460 ... 4aafe30746