Skip to main content

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


Comments

Popular posts from this blog

Cool Math Tricks: Deriving the Divergence, (Del or Nabla) into New (Cylindrical) Coordinate Systems

The following is a pretty lengthy procedure, but converting the divergence, (nabla, del) operator between coordinate systems comes up pretty often. While there are tables for converting between common coordinate systems, there seem to be fewer explanations of the procedure for deriving the conversion, so here goes!

What do we actually want?

To convert the Cartesian nabla



to the nabla for another coordinate system, say… cylindrical coordinates.



What we’ll need:

1. The Cartesian Nabla:



2. A set of equations relating the Cartesian coordinates to cylindrical coordinates:



3. A set of equations relating the Cartesian basis vectors to the basis vectors of the new coordinate system:



How to do it:

Use the chain rule for differentiation to convert the derivatives with respect to the Cartesian variables to derivatives with respect to the cylindrical variables.

The chain rule can be used to convert a differential operator in terms of one variable into a series of differential operators in terms of othe…

Lost Phone

We were incredibly lucky to have both been in university settings when our kids were born.  When No. 1 arrived, we were both still grad students.  Not long after No. 2 arrived, (about 10 days to be exact), mom-person defended her dissertation and gained the appellation prependage Dr. 

While there are lots of perks attendant to grad school, not the least of them phenomenal health insurance, that’s not the one that’s come to mind for me just now.  The one I’m most grateful for at the moment with respect to our kids was the opportunities for sheer independence.  Most days, we’d meet for lunch on the quad of whatever university we were hanging out at at the time, (physics research requires a bit of travel), to eat lunch.  During those lunches, the kids could crawl, toddle, or jog off into the distance.  There were no roads, and therefore no cars.  And, I realize now with a certain wistful bliss I had no knowledge of at the time, there were also very few people at hand that new what a baby…

Lab Book 2014_07_10 More NaI Characterization

Summary: Much more plunking around with the NaI detector and sources today.  A Pb shield was built to eliminate cosmic ray muons as well as potassium 40 radiation from the concreted building.  The spectra are much cleaner, but still don't have the count rates or distinctive peaks that are expected.
New to the experiment?  Scroll to the bottom to see background and get caught up.
Lab Book Threshold for the QVT is currently set at -1.49 volts.  Remember to divide this by 100 to get the actual threshold voltage. A new spectrum recording the lines of all three sources, Cs 137, Co 60, and Sr 90, was started at approximately 10:55. Took data for about an hour.
Started the Cs 137 only spectrum at about 11:55 AM

Here’s the no-source background from yesterday
In comparison, here’s the 3 source spectrum from this morning.

The three source spectrum shows peak structure not exhibited by the background alone. I forgot to take scope pictures of the Cs137 run. I do however, have the printout, and…