(57) Using Cloud Chambers to Study Alpha Particle Decay

Cloud chambers are particle detectors used to see the passage of ionizing radiation. As an alpha particle moves through an illuminated supersaturated vapor, it will make contact with the nearby atoms and cause the electrons... [ view full abstract ]

Cloud chambers are particle detectors used to see the passage of ionizing radiation. As an alpha particle moves through an illuminated supersaturated vapor, it will make contact with the nearby atoms and cause the electrons of these atoms to be attracted to the positive alpha particle.  Then over a short period of time, the vapor atoms will reattach with the electrons causing the vapor to condense onto the trail left by the alpha particle.  This will give a clear trail of the alpha particle for the period of time it takes for the condensed alpha particles to fall to the bottom of the chamber due to the force of gravity.  This was used to find the range of the alpha particle, which is defined as the distance that the alpha particle travels in the medium distributing its energy to the surroundings.  The range of these trails can be used to find the stopping power of the vapor using an integral of the “Bethe-Bloch” formula.  Using the model of alpha particles emitting from a radioactive nucleus, I found the expected values for the distance that an alpha particle will move through my medium of isopropanol vapor.  I then compared these results for an alpha particle emitted from my Pb-210 source to the observed values of my chamber to find the alcohol vapor to air ratio inside of the chamber.  This was done using the “Bethe-Bloch” formula which is the stopping power, or energy loss, of a particle moving through a material.