Bending Beta Particles with Magnets

By George Dowell

There are many different types of atomic and nuclear radiation.

"Atomic" refers to the atom as a whole, but the commonly accepted definition of atomic reactions are those that

originate in the electron shell area of the atom. "Nuclear" on the other hand is specific to the nucleus of an atom.

Some radiation cosists of particles of matter, betas and alphas are the two main ones. Another kind of

radiation is pure energy, in the form of photons. If those photon originate from the nucleus of an atom, we call it a Gamma Ray.

If the photon happens to originate from the electron shell area of an atom, we call it an X-Ray. Gammas and X-Rays are identical in every way except their origin.

 

In this lab demonstration we are concerning ourselves with beta particles. These are nearly massless particles, identical to an elecron in every way, but they come from a nucleus, therefore they are a nuclear particle. Negatively charged beta particles are identical to an ordinary electron in every way, and are called negatrons. Positively charges beta particles which we call  positrons are considered to be anit-matter, while negatrons are ordinary mater. as with all anti-matter particles, a positron will, under the right conditions, annihilate itself and be replaced with a pure energy photon. During annihilation, a positron combines with a negatron, and they both dissaper, replaced with a pair of 511 keV photons, which are 180 degrees opposed.

 

Fig 1

Materials List

The detector is a beta-sensitive pancake Gm type, hooked to a SPECTECH scaler-ratemeter

Model ST-350. This instrument provides the high voltage needed to run the detector and also

totalizes the counts oroduced by the detector, over a timed test period of 1 minute. Results are expressed

in CPM (Counts Per Minute). Some of the beta and mixed beta-gamma sources we are to test are also shown.

The analysis magnet is a General Tools 16 ounch horseshoe "Power Magnet".

Fig 2:

Source holder jig setup. Since we are separaing the betas from any other particles or rays that may be coming from the source, we can use mixed-sources, that is one that has multiple types of radiation present. The Cs-137 source is an excellent school lab source, as it has both beta particles and gamma rays.

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