Re: Franck-Hertz experiment

(1) In the book of Melissinos and related application notes of Keithley on
the Franck-Hertz experiment, one is supposed to use an oven to heat the
tube. If you want to do this in the home and don't want to buy the Keithley
oven, what is it ok to use to heat the tube? The recommended temperature
is about 200 C, which one get even get in a toaster oven.
(2) Also, Melissinos tells you to use a copper-constantan thermocouple to
monitor the temperature of the tube. I don't have any experience doing
that on my own. I don't know where to buy one or how much it costs. I
don't know any simple experiments to do with just the thermocouple to
get practice using it.
(3) The RCA tube manual lists several tubes as being gas filled tubes but
doesn't say which ones are mercury vapor tubes. Which tubes, other than
the specially built Leybold tubes, are mercury vapor tetrodes that one
can still purchase from modern suppliers? I've located some vendors of
tubes but they don't have a list of mercury vapor tubes.
(4) Assuming one deciphers out Figures 1.5 and 1.7 of Melissinos on how to set
up the Franck-Hertz tube, Melissinos says the tube will produce nanoamps,
which one then has to measure. I don't know how to justify the assertion
about nanoamps based on any books I have about tubes. Also, I don't
presently have equipment to measure nanoamps; I don't even have a scope.
Probably, buying the Keithley 600A electrometer is an expensive way to do
it. I'm told that National Semiconductor has an op amp that can even
amplify femtoamps, the LMC6001. I haven't found a supplier for it yet and
don't know what it costs or what might be hard about using it. I've
downloaded the spec *** and will try to make sense of it.

On the positive side, I'm getting better at writing assembly language
programs for the PC and expect that by the time I am able to do the
other things I described above, I'll also be able to interface the
experimental apparatus to the PC for control and data acquisition. But
I do need help with the other things.

Usually, when people do the FH experiment, someone has already solved all
the logistical problems related to it. Doing it in the home makes it necessary
to solve them myself and I'll need all the help I can get. In fact, I once
did the Franck-Hertz experiment in a university laboratory in a lab course
but that experience doesn't help me acquire the materials I need to set it
up on my own. Yes, I know Leybold sells the whole kit and kaboodle, but it
is expensive. There should be a dirt cheap way to do it.
--
Ignorantly,
Allan Adler <ara@xxxxxxxxxxxxxxxxxxxx>
* Disclaimer: I am a guest and *not* a member of the MIT CSAIL. My actions and
* comments do not reflect in any way on MIT. Also, I am nowhere near Boston.
.

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