How many of you know that more expensive tungsten rods for arc welding
contain about 2% of thorium? A Geiger counter, when in contact with a
welding rod containing Th, ticks rapidly. The ion density near the
rod's tip is much higher that what is due to cosmic rays. The purpose
is to facilitate the initial arc formation, when the field E is
applied. Is it not true that -- for the same purpose -- tips of
lightning rods often contain very weak sources of ionizing radiation?
Ludwik Kowalski
Let the perfect not be the enemy of the good.