About Cloud Chambers
|Since introducing the Lecture
Hall Chamber in 1990, Supersaturated Environments has satisfied many customers
at educational institutions worldwide. We currently manufacture several
oversized diffusion cloud chamber models for classroom, lecture hall, and
museum use. Our chambers are crafted from quality materials using a proven
design which provides maximum track visibilty and reliable demonstrations.
These products help educators share the discoveries of modern physics by
direct visual observation.
The diffusion cloud chamber creates a volume of supersaturated alcohol vapor that condenses on ions left in the wake of charged particles. This is accomplished by establishing a steep vertical temperature gradient with dry ice, liquid nitrogen, or mechanical refrigeration. Alcohol evaporates from the warm top side and diffuses toward the cold bottom. The gravitationally stable temperature distribution permits a layer of supersaturation near the chamber bottom. Charged particles passing through the supersaturated air at close to the speed of light leave behind numerous ions along each centimeter traversed. Since each ion becomes a nucleation site for droplet condensation, tracks of alcohol droplets form in this region, indicating trajectories of the charged particles. The fine, threadlike tracks fall to the chamber bottom, leaving room for other tracks to appear in the next moment. This continuous process yields uninterrupted sensitivity to airborne ionizing events, and provides an enthralling window on the subatomic world.
The “oversized” feature of our cloud chambers aids in revealing the random ionizing radiation that perpetually surrounds us. The sensitive volume of our Lecture Hall Chamber, for example, is about 900 times that of the common “petri dish” cloud chamber. The vast majority of background radiation is not the result of human activity, but caused by natural processes that have been present throughout the existence of life on earth. This ionization can be caused by cosmic rays or environmental radionuclide decay. The cloud chamber will sometimes enable differentiation between these two sources.
Secondary cosmic rays present at ground level include muons and Compton scattered electrons. These cosmic rays result in droplet trails passing across the chamber’s entire sensitive area. Muons are often observed as long, straight, and dense condensation trails. Cosmic ray showers are occasionally recorded as simultaneous parallel tracks.
Natural radioisotopes present in the earth’s crust produce another component of background radiation. Radon-222 is a chemically inert gas emanating from the soil and stone; it diffuses through the air and decays with the emission of an alpha particle. This particle appears in the cloud chamber as a dense, straight track several centimeters long, with no connecting track on either end. Radon concentration can be measured by recording the frequency of such events.
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