Date: Fri Feb 9 12:47:45 2007

Author: Dale Stille

Subject: Re: Discharge Electrometer w Alpha Source



The Beta ray deflection is in the Bib. 7D30.30......
If you are looking for references see my page although I can't remember if
either of those articles specifically addressed the deflection issue.


On Fri, 9 Feb 2007, Cliff Bettis wrote:

> Dale,
> Thanks for the explanation. I think the "See: ..." suggestion is worth
> considering.
> Another demonstration I would like to see listed in the Modern Physics
> section is the deflection of Beta rays with a magnet, but I haven't found a
> literature reference for that yet.
> Cliff
> ----- Original Message ----- From: "Dale Stille"
> To:
> Sent: Friday, February 09, 2007 9:18 AM
> Subject: Re: [tap-l] Discharge Electrometer w Alpha Source
>> Cliff,
>> We don't allow two listings of the same demo in the Bib. However, we do
>> allow a " See: 5D40.30 " type listing that could be put into the modern
>> section if the DCS committee agrees.
>> As to why it's in the E&M section.....In Phil Johnson's mind that was the
>> logical place for it. The reasoning being that you start by charging an
>> electroscope, capacitor, or electrometer, and then discharge it with
>> ionizing radiation. Much the same as discharging with ions from a candle
>> flame which is also in E&M.
>> Karl and Zig sat in on the original meeting about the order of the
>> Bib....maybe they have some first hand knowledge about the arguments used
>> when puting this in E&M.
>> Later,
>> Dale
>> On Thu, 8 Feb 2007, wrote:
>>> Dale,
>>> I don't think I have ever done that demonstration in the context of E&M;
>>> it's
>>> always been when I was talking about nuclear physics. Do we allow for
>>> crosslisting a demonstration to two major catagories or should it just be
>>> reclassified? Or maybe it's just me that wouldn't think of calling it an
>>> E&M
>>> demonstration.
>>> I have been thinking about your trying to use an electrometer, Jerry, and
>>> it
>>> seems like it would be tough. My electrometer with its Faraday cage has an
>>> input capacitance of 150 pF. My Braun electroscope has a capacitance of
>>> about
>>> 15 pF, and my leaf electroscope is quite a bit less than that. For a given
>>> potential, the capacitance tells you how much charge you need to remove we
>>> should be prportional to the rate of ionization of your source. I see a
>>> fairly
>>> large difference in the rates of discharge between the Braun and the leaf
>>> electroscope. It might take a long time to discharge the electrometer/cage
>>> combination. I'll try it tomorrow. When I first started doing this
>>> demonstration, I used a small Pb 210 source (0.2 uCi as I recall). The
>>> leaf
>>> electroscope took long enough to discharge that it was necessary to use
>>> another
>>> electroscope as a control just to be sure you weren't seeing charge bleed
>>> away
>>> because of humidity. I went to the stronger Po source and haven't had to
>>> do
>>> that as the discharge is immediate and obvious.
>>> The idea of using a blower to blow ionized air from a source at the
>>> electroscope is cute, too.
>>> Cliff
>>> Quoting Dale Stille :
>>>> Jerry and Cliff,
>>>> It's in the bib......just in the E&M section for some
>>>> reason....5D40.30.
>>>> Called "Ionization by Radioactivity:.
>>>> Dale