|WikiProject Physics||(Rated B-class, Mid-importance)|
|WikiProject Electronics||(Rated Start-class, Mid-importance)|
There is a mistake in the photomultiplier schematic. It either should show one without a scintillator, or the label "Incident photon" should be "Incident particle" or "Incident ionizing radiation". 18.104.22.168 (talk) 00:49, 14 May 2010 (UTC)
there is a mistake in the drawing. It should say photocathode, not photocatode
I'm in the process of copy editing this article. There are several individuals mentioned in the article that do not have their first names given:
- History section
- Starke (History section)
- H.E. Iams
- B. Salzberg
- G.A. Morton
- L. Malter
- P. Gorlich
"Each dynode is held at a more positive voltage than the previous one" This is not necessarily true. Either polarity can be applied between the anode and the cathode, depending on the application. Maybe rewrite it in a sentence like: "There is a voltage difference between each dynode". —Preceding unsigned comment added by 22.214.171.124 (talk) 08:54, 23 January 2009 (UTC)
No! This is wrong. The anode MUST be more positive than the cathode and the dynodes must be arranged at voltages between and monotonically increasing. The cathode can be held at ground in which case the anode is at high positive voltage, or the anode can be held at ground in which case the cathode is at high negative voltage. —Preceding unsigned comment added by 126.96.36.199 (talk) 12:23, 26 January 2009 (UTC)
Although you could do it either way in theory, as a practical matter, as the article points out, the anode is near ground in all the applications I have seen. This is simply because it is much easier to measure the anode current in that configuration. The large negative voltage applied to the cathode is also applied to the magnetic shield, when it is used. --AJim (talk) 04:16, 2 September 2012 (UTC)
Who invented the photomultiplier tube?
It appears that a Wikipedia editor had altered the History section to state that the photomultiplier tube was invented not at RCA but by a Soviet Russian scientist, Leonid Kubetsky. The latter point of view is advocated by the Russian Academy of Sciences in a 2006 publication authored by one Academican Lubsandorzheiv (referred to in the main page). This publication also was presented as a talk in a conference taking place in Beaune the same year.
The Lubsandorzhiev paper asserts that "Kubetsky's Tube" has been denied the credit it deserves in the history of the invention of the photomultiplier, and implies that Kubetsky and his Moscow institute was deprived of his rightful place in history either purposely or because of poor communication between the West and Soviet Russian before WW II and during the Cold War. If true, it is quite an interesting comment.
I took it upon myself to investigate this claim as seemed quite provocative. Here is what I found:
If by "inventing" one refers to experimentally demonstrating the first functional prototype, in this case defined as a vacuum tube combining both the functions of photoemission of secondary electron gain, it seems clear that RCA invented the photomultiplier tube. It is true that the RCA Harrison prototype included only a single stage of secondary electron amplification, but this served to demonstrate the basic functionality of the photomultiplier tube especially in view of the fact that the multiple dynode chains for higher gain amplification were already known several years before according to the work at General Electric. The key demonstration was the integration of photoemission and secondary electron amplification.
Soviet Russian scientist Leonid Kubetsky, in his 1937 publication appearing in Proc. IRE claims to have realized a first prototype in June, 1934. However, the publication of Iams and Salzberg that appeared in Proc IRE in 1935 indicates that a PMT prototype was working in the RCA Harrison laboratories *before* June 1934. This is clear because the Iams/Salzberg manuscript was received by Proc IRE in June 1934 and it describes both a prototype having a gain of about 6 or 8, and an earlier prototype having a gain of about 3.
During this time, the RCA Camden laboratories were developing a multiple dynode photomultiplier tube described in Proc IRE in an October 1935 submission. The details published by RCA Camden on the multiple dynode photomultiplier, demonstrated earlier by the Soviet Russians in September 1934 (claimed to have been realized in the laboratory as early as June 1934 by Kubetsky), represent far more detail in terms of the comparison between expected and realized gain (for example) than the later publication by Kubetsky appearing in Proc IRE in 1937 (submitted in July 1936).
It is also known that RCA engineers and scientists were in the process of regularly visiting Soviet Russian during the late 1920s and early 1930s as part of a technology transfer of broadcast radio technology to, among other countries worldwide, Russia. The Soviets were quite keen to acquire broadcast technology, quite apparently among other reasons because it was an instrument of effective rapid communication from the centralized Soviet government to the far-flung proletariat whom it sought to control. The prominence of radio technology was represented by the fact that Leonid A. Kubetsky was transferred from Leningrad to Moscow where he could work under the newly established "All Union" institute for television. Older scientists who may have harbored political views less supportive of the regime had been purged and replaced by younger up-and-coming scientists who were evidently encouraged and supplied with adequate assistance to make rapid strides in demonstrating the potency of Soviet-regime technology of that era. Kubetsky's accomplishments were indeed outstanding, but they do not displace the primacy of the RCA juggernaut in radio and television technology as it is recorded in the record.
As for claims that Leonid Kubetsky's Soviet Patent filing in 1930 constituted invention of the photomultiplier, I don't find that convincing since he was not able to produce a prototype earlier than RCA. —Preceding unsigned comment added by 188.8.131.52 (talk) 18:43, 17 February 2009 (UTC)
Sorry I was not logged in
The recent edits on the photomultiplier page, some of which simply improve IMHO the style, and others which clarify priority issues between the RCA-Harrison team and the Leonid A. Kubetsky team in Soviet Russia, were mine. I apologize for not having had my password handy at the time. Jabeles (talk) 20:58, 19 February 2009 (UTC)
History section wandering off-topic?
A significant portion of the History section seems to be more concerned with the history of RCA and Burle than that of photomultipliers. IMHO, this has wandered off-topic, and should probably be copyedited down. Any thoughts before I do this? Oli Filth(talk|contribs) 20:22, 10 March 2009 (UTC)
- My thought is just that you are working too hard. I agree that there is a lot about RCA, but I think it does little harm, especially since they are out of business ;-). When I worked with high-end spectrometers and used pmts a lot, I found that customer pmt questions usually stopped when told that we only used Hamamatsu tubes. So, I never learned much about RCA, and I was interested to learn more. On the other hand, I think that there is a great deal more to say about using pmts and about their advantages, and I would encourage you to spend your time on expanding and clarifying that. For instance, I think the article could say more about what it means to be about as sensitive as the dark-adapted eye or how having a shot-noise limited detector changed the photometric game in a fundamental way. It would be useful to have direct performance comparisons to other detectors, too, to help people decide whether they should learn more. I guess the handbooks, being freely available, cover the details well enough. --AJim (talk) 01:03, 11 March 2009 (UTC)
There seems to be a conflict about how to express the gain of a pmt involving this statement: "...These detectors multiply the signal produced by incident light by as much as 100 million times (i.e., 80 dB),...". I think the statement is a little ambiguous in the use of "signal". However, if we are talking about gain in the sense of current amplification 108 seems about right to express "as much as". Insofar as current gain, that is Ianode/Icathode, is what is being discussed, then I think to convert it to decibels you have to convert to units of power, since that is what decibels are, power ratios. Since power is proportional to I2 the decibel formula has to use the ratio of current squared. Because we are working with logs we can factor out the squaring operation into multiplying the log of the power ratio by 2, so current decibels are conventionally calculated as 20 log (Ianode/Icathode), instead of 10 log (Panode/Pcathode). Therefore I think the correct result for 108 current gain would be 160 dB. --AJim (talk) 23:05, 6 May 2009 (UTC)