Re: [Phys-l] Geiger counter

[Bernard Cleyet <bernardcleyet@redshift.com>]

On 2011, Mar 28, , at 09:52, brian whatcott wrote:

> Pre-Fukushima radiation:
> 14 counts/minute 12 midnight sat March 19th. (That's relatively quiet.)
> 11 counts/minute march 20,
> 12 cpm March 21 at 6:04pm
> 12.7 cpm at 10 pm tues 22nd march
> 11.1 cpm at 9:20 pm wednesday March 23
>  11.1 cpm at 11:30pm (125 min average) saturday march 26th
> 12.0 cpm sunday 9 pm march 27th.
> 13.8 cpm monday 11:48 am March 28th.
>
> Brian W
> ______


These are rather low rates, so did you count for a considerable time, so the total number was in the 10k counts range?

Which results in a sigma (IIRC) of one percent.  Of course not practical,  as this takes about twelve hours.  By then the earth will have turned giving another rate from "external" sources.


Not incidentally, all your readings are approximately w/in the +/- given by the Poisson theory, i.e.  +/- square root (N).   Assuming they are the total counts.

bc long time ago

p.s. I finally read!   125 min average, therefore, total counts ~  1.4k  or 11.1 +/- 0.30        If all were that, perhaps possible to detect a diurnal variation?

p.p.s.  I've found the Vernier G-M counter convenient for half life of Pa (decay from U using solvent separation), also, using their Logger Pro to collect data to show the exponential relationship of Poisson intervals.