[R-390] Radioactivity and meters

[rbethman]

2002tii wrote:
> Roger wrote:
>   
>> I though all the R390 meters would make a counter tick even the
>> phosphorescent (non-radioactive) replacement meters in a 390A.
>>     
>
> It takes ionizing radiation to trigger a Geiger-Muller (GM) 
> tube.  Phosphorescence produces only non-ionizing photons (the E and 
> H fields resulting from the photon emission are the wave properties 
> of the photon itself).  As a check, I just now waved my counter at a 
> number of phosphorescent clock faces and got no elevated readings.
>   
My use of GM equipment has been almost exclusively the Eberline series.

There is a window on the bottom that the aluminum slide over and opens 
the mica window.

Every so often this thread comes up.  Do you remember the "glow in the 
dark" watches everyone wore during the '50s and into the '60s?  The very 
same material was painted on the dial faces!  How many have had issues?

Yes, alpha particles decay into other particles.  However, alpha 
particles cause the most damage if inhaled or ingested.  The other 
particles do far less damage to tissues due to far less mass.

What no one discusses, and what really matters, is what is the 
disintegrations per minute?  This allows one to then determine the 
actual activity.  A GM will not do this.  It is going to take a lab 
counter with a lead pig, and time.

Since the amount of material applied to the meter face is small, the 
overall activity should be pretty small.

I've yet to hear of radio intercept operators having suffered ill 
effects over numerous years of operating these radios, AND the material 
being at a higher level of activity.

The level of activity decreases over time.

I believe that if someone had access to a lab with the appropriate 
equipment, we could get some "real" data that could shed light on the 
subject.

Otherwise people are getting concerned over something that isn't at a 
level to be worried about.  You'll get more radiation on a transoceanic 
or transcontinental flight.

Bob - N0DGN


> In response to some former posts in this thread:  Glass-window GM 
> tubes will not detect most alpha particles, but mica-window tubes 
> will.  Better counters have mica windows and generally come with one 
> or more caps to filter the incoming particles and allow the user to 
> determine what kind of particles are being detected.  Note that the 
> alpha sources used in luminous paint do not typically decay to a 
> stable state -- they decay to other radioactive isotopes, some of 
> which emit gamma radiation when they, in turn, decay -- so most 
> luminous paints are capable of penetrating the skin with ionizing 
> radiation, notwithstanding that the primary radiation consists of 
> alpha particles.
>
> Best regards,
>
> Don
>
>
>
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