Ionization Chamber Explained
An ionization chamber is a device used for two main purposes:
detecting airborne particles (such as a smoke detector) and the detection or
measurement of ionizing radiation.
An ionization chamber is an instrument constructed to measure the number of
ions within a vessel full of gas between two conductive metal plates (or two
parallel electrodes flat or cylindrical coaxial) separated by a gap, can
be a wall of the container itself. A voltage is applied (called current
calibration) between both plates, which cleans electrons so that the device
is not saturated. When the gas between the electrodes ionizes for some reason, for example
X-rays or radioactive emissions, ions move towards the electrodes sign
opposite, thus creating a ionization current which can be measured by a
galvanometer or electrometer. As in the ionization smoke detector.
Ionization chambers are widely used in the nuclear industry, for
They provide proportional to the dose received value and have a shelf life greater than
standard Geiger tubes. Ionization chambers used in nuclear medicine
determine the exact activity of the therapeutic radiation treatments (calling
such devices “radioisotope dose calibrators’).
A Geiger-Muller tube (used in Geiger counter) is another type of camera
ionization. In it one of the plates is rolled into a cylinder. The other
replaced by a cable located in the axis of the front. This type of tube is usually sealed
and filling an inert gas, so that no current flowing in the two electrodes
if they kept at different potentials.
If a particle of ionizing radiation entering the tube (an alpha particle, beta or
a gamma) beam creates a trace of ions in the gas. These ions allow for a
instant that forms a conductive path between the electrodes, triggering a brief
current pulse. If this output is connected to a speaker, you can hear the familiar
click of a Geiger counter.
Many different types of detectors and radiation counters are based
on similar devices to Geiger-Muller tube. Some contain different gases
fillings, others use liquids and others are open to the air. different are possible
measures depending on the type of device window (no glass window
alpha particles will pass, while mica window yes) or difference
potential between the electrodes.
A smoke detector in the gap between the plates is left exposed. The
chamber contains a small amount of americium-241, which is a particle emitter
alpha. These particles carry a considerable amount of energy, and when
collide with the gas in the ionization chamber (mainly nitrogen and oxygen)
the moment transferred can ionize molecules, ie, molecules uncharged
gas will lose one or more electrons and become charged.
Because the plates are different voltage (in a typical smoke detector,
the voltage difference is a few hundred volts) ions and electrons will
attracted to them. This small flow of ions between the plates represents a current
electrical measurable. If smoke enters the detector, interrupts this current. ions
hit and smoke particles are neutralized. This current drop triggers