Re: taking apart smoke detectors

[Thomas Walkiewicz <WALKIEWICZ@EDINBORO.EDU>]

Hi Ludwik - thanks for remembering.
you wrote:
> You can avoid this by using radioactivity (Rn and its daughters
> from air) collected from the screen of a common TV or computer
> screen. Details were discussed here about two years ago. The name
> of the thread was "radioactivity from air" or something like this.
>
> Perhaps Tom Walkiewicz will repost references to his good
> publications, especially the one in which a common balloon was
> used to collect ions. This source was much much stronger than
> 5 to 10 times the background (typical for what can be collected
> from a TV screen in my area).

Below are two previous posts that may be of interest, especially to new
subscribers.  Since I don't have an alpha detector, but can locally obtain
excellent dirt samples from the air, if anyone wants to collaborate, I
would be interested in trying to measure alpha spectra from dirt from air.
Po-214 decay (and possibly Po-218) in the uranium series and Po-212 decay
in the thorium series should be possible to observe.

Two more recent references (not mine) not listed below are:
1. Radioactive balloons: experiments on radon concentration in schools or
homes, Physics Education, 32, p.97-100 (1997)
2. Radioactive Balloon Measurements in Utah, The Physics Teacher 35,
p.478-479 (1997)

*********************

From: WALKIEWICZ@edinboro.edu (Thomas Walkiewicz)
Date: Wed, 10 May 1995 23:07:34 -0500

I have a paper scheduled to appear in The Physics Teacher (possibly September)
which may be of interest to the group.  The basic idea is to inflate a balloon,
rub it with fur to build up a static charge, and leave it suspended in air for
about 45 minutes (comparable to the effective/compound half life of Rn-222
decay products).  Deflate and squeeze as much of the balloon as close as
possible to a Geiger tube and count.  My record so far is 11,660 counts per
5 minutes above background (BG was 150 counts per 5 min)!

The TV/monitor screen wipe is "old" news (I was told of this in the late 60's)
but it is very interesting each time it is rediscovered.  This is also directly
connected to my paper - Radioactiveball in TPT, Vol. 30, pp. 16-17, Jan 1992 -
in which I, too, probably rediscovered how a handball or racquetball picks up
enough radon decay products to enable a decay study to be made with a G-M tube.
(Also, see my letter to the editor - Radioactivity as a Function of Speed in
TPT, Vol. 31, p. 260, May 1993 - for an interesting twist.)

It turns out that any negative-charged object (this statement can be subject
to investigation) can pick up enough radon decay products to be counted.  A
gamma-ray spectrum (NaI or GeLi) provides exact identification of these
products and you can even follow the half life of an individual gamma (alpha
spectra accomplish similar goals).

Although the balloon result can be spectacular, the standard method to extract
a radioactive dirt sample from the atmosphere by filtering air thru, eg., a
ShopVac (I use 8 layers of lens cleaner tissue because it is available to me),
can be more reliable and provides a much higher activity.  (See AJP, Vol. 30,
pp. 120-124, Feb 1962; AJP, Vol. 41, pp. 921-922, July 1973; and AAPT Announcer
Vol 7, p. 64 (4) 1975.)

Keep in mind that thoron (Rn-220 from the thorium series) decay products
deposited or filtered are governed by 10.64 h Pb-212 and the subsequent 60.55
m Bi-212 activities.  This means that an initially clean screen left for 1-2
hours before wiping will show mainly the activities of radon daughters, while
a screen left on overnight will have become saturated with this radon activity
and will only continue to build up the longer activities of thoron daughters.
This can be a complicating feature in simple decay measurements.

My RECORD of 11,660 cp5min was achieved in a room where I measured the radon
concentration to be only 0.3 pCi/l, comparable to the average U.S. outdoor
concentration.  See details in my forthcoming TPT paper.

PROPOSAL:  Please help me accumulate data by posting or e-mail to me directly
(Walkiewicz@Edinboro.EDU) your results and method for highest net activity
measured in 5 minutes via techniques described above (filtered dirt over 24 h
can become very hot).  I will post a summary of this info.  Include any useful
details, such as measured radon levels.  Try a variety of locations, especially
basement areas having exposed soil.

Thanks for your cooperation

Tom Walkiewicz                                  WALKIEWICZ@EDINBORO.EDU
Department of Physics & Technology              Office: (814)732-2468
Edinboro University
Edinboro, PA 16444


**********************************

Subj:   Hot Balloon
Date: Fri, 15 Sep 1995 14:35:27 -0500
From: Thomas Walkiewicz <WALKIEWICZ@edinboro.edu>

        Pages 344-345 of the current Sept. issue of The Physics Teacher
describes my experiment of charging an ordinary balloon, leaving it
suspended in air for about 45 minutes, then deflating it and counting the
radiation it emits with a thin-window GM tube.  My own record of 11,660
counts per 5 (five) minutes above background (30 counts per minute) was
obtained in a room with a low Radon level of 0.3 pCi/liter.  Another person
has obtained a higher reading of about 11,000 counts in one minute!
However, he was not able to measure the room Radon level.

        Please post or e-mail to me (Walkiewicz@Edinboro.EDU) your own
results if you try this experiment, and I will tabulate all information
and summarize what I can, especially what record values can be measured!

        Include any useful information, such as measured radon levels,
atmospheric conditions, especially relative humidity, location, etc.

        Have fun and thanks for your cooperation.

Tom Walkiewicz                                  Walkiewicz@Edinboro.EDU
Department of Physics & Technology              Office: (814)732-2468
Edinboro University
Edinboro, PA 16444