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Q:
What is a cable free ion chamber?
- Matt Stayduhar
Pittsburgh, PA, United States
A:
Hello Matt,
An ion chamber is a device used to measure radioactivity. It does
this with a volume of gas and has a high voltage applied from one end
of the chamber to the other. If a high-energy particle, such as an
electron, or more exotic particles from cosmic rays, passes through the
chamber, it will knock a few electrons free from the molecules of gas
within the chamber. The molecules missing some of their electrons are
positively charged ions. The electrons will drift through the gas in
the electric field (and the ions will drift in the opposite direction)
towards the charged plates or wires on the ends. If the voltage is high
enough, the electrons will pick up enough speed on their way to knock
more electrons off of more gas molecules, amplifying the signal in a
process known as an "avalanche." Sensitive electronic amplifiers read
out the signals on the plates or wires and counters count how many of
these signals are received in a particular amount of time. These count
rates indicate the level of radioactivity. I imagine a cable-free one
simply does not have an external connection for the required high
voltage. Many of the portable ones have their own internal high-voltage
generators.
These are used in radon surveys, maintaining airport search
equipment, and anywhere the detection of energetic particles is needed.
Tom
(published on 10/22/2007)
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