[R-390] meters arrived

[2002tii]

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.

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