Date: Fri, 2 Mar 2012 12:00:06 -

Author: ---

Subject: Re: Franck-Hertz experiment- suggestions/feedback/advice

Post:

--f46d042c6c3f8499b404ba47306c
Content-Type: text/plain; charset=ISO-8859-1

Anna-

For the last decade or so, we have been using the mercury Franck Hertz
setup (Similar to the one seen at the top here
http://www.telatomic.com/tubes/franck_hertz.html), and it has done fairly
well for us. Earlier this year though, we had some extra funds leftover so
we purchased a tel-atomic neon frank hertz tube and stand (see further down
the webpage), and it has done very well this semester. We opted not to buy
the full system (not much funding was leftover), but the power supply (an
80V Texio power supply) and data acquisition setup (amplifiers and such
connected to an NI USB6069) we had used for our old mercury version
transferred over pretty well. The neon tube works very nicely up to about
60ish Volts, showing a few distinct peaks. it has been very nice to have
the two setup side-by-side for comparison and such.

The biggest problem we have had with the neon tube, however, is that the
mesh accelerating grid is connected by an electrode which travels down
inside the length of the tube, instead of exiting through the side as it
does in the mercury tube. At high accelerating voltages (60+V) the
electrons end up taking the shorter route to the side, which then ignores
any retarding voltage we apply between the mesh and the anode, and the
larger electric field (thanks to the shorter path) increases the current
off the cathode by a factor of ten or so. The problem is not as bad if the
voltage is ramped up fairly slowly, or if the filament is not as hot as
specified, but it is something to consider.

Now, the problem may be due to the fact that we are not using the power
supply that should come with the neon tube, but the design of the tube does
leave a little to be desired in my mind. It does work very well up until it
arcs to the side, which gives us the chance for a fair bit of data
collection. This new tube works quite nicely, but you may consider buying
the entire experiment in one go.

Kenn

On Fri, Mar 2, 2012 at 9:29 AM, Anna Kiefte wrote:

> Hi everyone,
>
> We are thinking about updating/replacing our Franck-Hertz experimental
> setup. Has anyone done this recently (within the last 10 years) and have
> any particular advice/information that would be useful to know?
>
> Thanks!
>
> Anna
>
>
> Anna Kiefte
> Department of Physics
> Acadia University
> Box 49
> Wolfville, NS
> B4P 2R6
>
> Phone: (902) 585-1274
> Fax: (902) 585-1816
>
>


--
*Kenneth Lonnquist
Assistant Coordinator, Introductory Physics Labs
KennLonnquist@gmail.com
970.491.2540
Physics Department
Colorado State University*

--f46d042c6c3f8499b404ba47306c
Content-Type: text/html; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable

Anna-For the last decade or so, =
we have been using the mercury Franck Hertz setup (Similar to the one seen at the top here http:/=
/www.telatomic.com/tubes/franck_hertz.html), and it has done fairly well for us. Earlier this yea=
r though, we had some extra funds leftover so we purchased a tel-atomic neo=
n frank hertz tube and stand (see further down the webpage), and it has don=
e very well this semester. We opted not to buy the full system (not much fu=
nding was leftover), but the power supply (an 80V Texio power supply) and d=
ata acquisition setup (amplifiers and such connected to an NI USB6069) we h=
ad used for our old mercury version transferred over pretty well. The neon =
tube works very nicely up to about 60ish Volts, showing a few distinct peak=
s. it has been very nice to have the two setup side-by-side for comparison =
and such.


The biggest problem we have had with the neon tube, however, is that th=
e mesh accelerating grid is connected by an electrode which travels down in=
side the length of the tube, instead of exiting through the side as it does in the mercury tube. At high accelerating voltages =
(60+V) the electrons end up taking the shorter route to the side, which the=
n ignores any retarding voltage we apply between the mesh and the anode, an=
d the larger electric field (thanks to the shorter path) increases the curr=
ent off the cathode by a factor of ten or so. The problem is not as bad if =
the voltage is ramped up fairly slowly, or if the filament is not as hot as=
specified, but it is something to consider.


Now, the problem may be due to the fact that we are not using the power=
supply that should come with the neon tube, but the design of the tube doe=
s leave a little to be desired in my mind. It does work very well up until =
it arcs to the side, which gives us the chance for a fair bit of data colle=
ction. This new tube works quite nicely, but you may consider buying the en=
tire experiment in one go.


KennOn Fri, Mar 2, 201=
2 at 9:29 AM, Anna Kiefte wrot=
e:


Hi everyone,

We are thinking about updating/replacing our Franck-Hertz experimental setu=
p. =A0Has anyone done this recently (within the last 10 years) and have any=
particular advice/information that would be useful to know?

Thanks!

Anna


Anna Kiefte
Department of Physics
Acadia University
Box 49
Wolfville, NS
B4P 2R6

Phone: (902) 585-1274
Fax: (902) 585-1816

-- Kenneth LonnquistAssistant Coordinator, Introductory Physics=
LabsKennL=
onnquist@gmail.com


970.4=
91.2540Physics DepartmentColorado State University

--f46d042c6c3f8499b404ba47306c--


Back