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96) Another negative result.

Ludwik Kowalski (August 13, 2003)
Department of Mathematical Sciences
Montclair State University, Upper Montclair, NJ, 07043

It is easy to generate a negative result; postulate something that nobody expects to happen and conduct an experiment showing that this does not happen. In unit 31 I already described a negative attempt to observe excess heat. Here I will describe a negative attempt to observe induced gamma radioactivity. But first a little start. About a week ago a colleague, Robert Dorner, told me about a modern “plasma metal cutting tool” he purchased. A highly controlled electric arc is established (in air) between the nozzle of the device and a metallic plate. The unit operates at 220 volts and the current of about 20A. An electric arc in air reminded me off the experiments of Hal Fox, from Salt Lake City, except that the medium is air instead of water. It also reminded be of Karabut’s experiment, in Russia, except that the medium is air instead of deuterium gas. Is it possible that gamma radioactive isotopes are produced when metals are cut by the arc? Our conversation resulted in an experiment we performed this afternoon in Bob’s garage. No induced gamma radioactivity was observed with a simple Geiger counter.

What follows is a description of what we did. The metal cutting tool used was “Plasma 30,” from Harbor Freight ( It has a nozzle from which hot compressed air is forced to flow along the electric field lines (between the wire in the nuzzle and the plate). The exposed areas melted and ejected metallic pieces were collected in a stainless steel dish. These pieces were then placed in front of a Geiger tube whose thin window was protected with two layers of a common office paper. Here are the results;

1) For our counter the center of the plateau curve was near 1300 volts.
   That voltage was used in all subsequent measurements.
2) Background before the experiments --> 226 counts in 5 minutes
3) Aluminum sample --> 232 counts in 5 minutes
4) Copper sample --> 245 counts in 5 minutes
5) Steel sample --> 233 counts in 5 minutes
6) Bismuth sample --> 220 counts in 5 minutes
6) Carbon brush sample -->  458 counts in 10 minutes
7) Background after the experiment --> 218 counts in 5 minutes
I know that it is silly to report such results. I am posting this description to show what one can do in a student-oriented project.

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