Saturday, May 24, 2014

Photomultiplier Tube History and the Bell Laboratories Record

In our experimental search for H-Rays, we're using a NaI crystal attached to a photomultiplier tube, (PMT),  to detect the predicted x-ray radiation.  While studying up on photomultiplier tubes[1] this week, I came across quite a few interesting historical points.  Among these are:
1.  PMTs were first invented for use in movie theatre projectors to provide the sound tracks.
2.  Equipotential lines were important for design, but computers for the necessary didn't exist yet.  The lines were mapped by stretching thin rubber sheets over wood block models of the electrodes and rolling small balls along the sheets to predict how electrons would move between dynodes in the actual tube.[2]  The picture, (picture 1), below shows one of the models being used



3  PMTs were used as radar jammers in world war II.  When fully illuminated,they produce a very natural white noise that can't be distinguished from natural radio static.  The noise was amplified and broadcast to swamp enemy radar.

The article mentioned above is contained in the Bell Laboratories Record. If you're ever looking for an issue, or just want to do some old time tech reading, I found a repository of the back issues[3].

In addition to writing about PMTs, Pierce also wrote an interesting piece on the large balloon satellites that were used for microwave communications testing.  It included a rather spectacular picture of one of the balloons.


G+er's, +Jonah Miller and +Patrick D. Garvey pointed out that the satellites were instrumental in radio astronomy and the discovery of cosmic background radiation.[4]  One of the great things about writing about science on G+ is the incredible audience that frequently adds more information and interesting perspectives!





References:
1.  The Photomultiplier Tube Handbook
http://psec.uchicago.edu/links/Photomultiplier_Handbook.pdf

2.  The article on equipotential analog computers
http://www.americanradiohistory.com/Archive-Bell-Laboratories-Record/30s/Bell-Laboratories-Record-1938-05.pdf

3.  Bell Laboratory Record
http://www.americanradiohistory.com/Bell_Laboratories_Record_Issue_Key.htm

4.  Post with cosmic background comments
https://plus.google.com/108242372478733707643/posts/XTeaDbTNKaP


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