241Am is naturally radioactive. It decays by emitting alpha particles of about 5 MeV energy. It also emits some low energy beta particles and gamma rays in the keV range, which can also be detected by Monitor 4. The alpha particles interact with your aluminum foil and produce the isotope 30P and a neutron. 30P has a half life of about 2.5 minutes and decays to the stable isotope 30Si by positron emission. The positron will annihilate with an electron producing two 0.511 MeV gamma rays that are easily detectable. Note the decay of 30P to 30Si will not necessarily be to the ground state of the nucleus, but to one of the several excited states of 30Si, which will quickly decay by gamma emission. The more probable of these gamma rays have energies between 1.2 MeV to 2.2 MEV. These are also detectable with your detector. Last but not least, is the neutron which was emitted from the interaction alphas with the aluminum. Addition of paraffin disk, since it contains lots of hydrogen atoms, will slow down the neutrons. Slow neutrons can be captured by nuclei in paraffin, mica window and the body of the detector itself. The results are several other isotopes that can decay by emitting gamma and other radiation.
This is how you have increased the radiation from your 241Am source.
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I HAVE A MONITOR 4 RADIATION SURVEY METER WITH .36" DIAMETER MICA END WINDOW GM TUBE. PLACED 241AM SMOKE DETECTOR BUTTON IN WRAP OF ALUMINUM FOIL, THEN 1/8" PARAFFIN DISK ATOP THE WRAPPED BUTTON. ARE 4X ABOVE BACKGROUND READINGS FROM PROTON EMISSION OR SOME OTHER PARTICLE RADIATION?