Re: [Phys-L] geiger counter

[bernard cleyet <bernard@cleyet.org>]

> On Mar 9, 2023, at 00:58, Mark Sylvester <wk76msyl@uwcad.it> wrote:
>
> I don't see mention of my favourite source: filter air through a cotton pad
> using a vacuum cleaner for about 5 minutes. 


The method I've read from several sources (Phys-l is one) is to charge an inflated  “rubber” balloon — (careful some don’t work) at the beginning of the class; near the end deflate scrunch up and count.  I verified at home and then performed during a workshop I gave, pre-covid, at a NorCal/NV AAPT meeting.  Also using  the ion-exchange resin kit for Cs/Ba and beta and gamma absorption; Alpha with a sheet of paper absorption.  

The best maybe the correct mask, as some are zapped with high joltage (similar to an electret) to better trap aerosols.   (more like a Cottrell filter)

After a week or so, I’ve collected the coarse dust captured on a HEPA prefilter.   IIRC (during height of covid) both a short and rather long half lives.   

I have an Air things wave. It includes an ionization chamber to measure Radon.  Background in sit. room currently is 60 Bq m^3.   I just put the wave and claimed 2µCi Th-232 in a box.  The Th is about 25 cc of crystals.  This is from a device that with a squeeze bulb the emanation from the crystals is brought into a chamber with a conducting rod into another chamber with a thin Al (not Au) electrometer. and attached microscope.  The electroscope is charged from an above banana jack.  Very crude as the filar is 0, 1, 2, 3, 4.  I suppose one is to calibrate with known charging  EMFs.  Three point graph?  Well one can estimate the halves.  (8 points?).  

The wave has a very slow response.  So maybe I can report before I bed.