>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. -- http://www.piclist.com hint: To leave the PICList mailto:piclist-unsubscribe-request@mitvma.mit.edu