A middle of the road solution for moderate sensitivity is to use a PMT in a
Peltier cooled housing, easy to get down around 0 degress without the hassle
of LN2 (Also easy to do the temp control with a PIC!)  This is also much
more feasible for a field installed monitoring application.

The solutions proposed cover a huge range of sensitivities and wavelengths,
you really need to do some rough calcs on the sensitivities before you can
choose a path.

I would recommend getting hold of a set of catalogs from Hamamatsu, they
make a huge range of photonic devices, CCD's, photodiodes, PMT's and lots of
useful info in their catalogs.

Kirk

> -----Original Message-----
> From: Alan B. Pearce [mailto:A.B.Pearce@RL.AC.UK]
> Sent: Wednesday, January 16, 2002 8:37 AM
> To: PICLIST@MITVMA.MIT.EDU
> Subject: Re: [ee]: photodetectors ( tag changed from OT)
>
>
> >If you need extreem sensitivity and can't afford cryogenics, look at
> >photomultiplier tubes.  They can be pretty cheap on the
> surplus market
> >(there are several under US$10 at the moment on Ebay).
>
> This may not be much use either, as the "snow" that you see
> in the image is
> thermal noise, which will drop as the temperature is lowered.
>
> In terms of dealing with cryogenics it may be enough to
> enclose the detector
> in a thermal housing and then pour liquid nitrogen through
> some pipes by
> gravity feed from a thermos. LN is very cheap and gets you a
> significant
> amount below 0C.
>
> If you do try this do be very careful in handling it because
> it is all too
> easy to end up with skin burns.
>
> --
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>
>

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