Why Own a Geiger Counter?
Below, we will review important Geiger counter uses followed by a basic introduction into nuclear radiation. In addition, we will review the principle operation of the key element within a Geiger counter, the Geiger–Müller tube.
As Heard on National Radio:
“Mazur said he developed handheld Geiger counters so consumers and hobbyists could be aware of radiation levels in the things around them.
If you don’t have some sort of instrument… you’re completely a hundred percent certain that you have no idea what’s in your environment,”
he cautioned. Mazur shared a report about elevator buttons in France that were made from recycled metal containing nuclear waste, as well as a story about radioactive metal tissue boxes sold by a major home goods chain. A week spent near one of these ‘hot’ tissue boxes was equivalent to getting a chest x-ray, he revealed.”
Geiger Counter Uses Include:
- Check granite countertops, water filters, air filters, building materials and other items in your home for radioactive contamination.
- Test for radioactivity in antiques, watch and clock dials, antique pottery, smoke detector, lantern mantels, etc.
- Maintain informed awareness amidst a nuclear accident or emergency such as the once that occurred in the Fukushima prefecture of Japan in March of 2011.
- Detect radiation in food. Note: The extra sensitivity of the PRM-9000 is recommended.
- Test for radioactivity in metal objects in your home or office that could be made of recycled radioactive materials.
- Check for leaks or possible exposure if you work in or near an X-ray lab in a medical facility or medical office suite.
- Monitor environmental levels of radioactivity near a nuclear power facility.
- Test the soil and environment for dangerous levels of radioactivity, if located in close proximity to uranium mines
- Monitor personal levels of radiation due to radiation therapy, brachytherapy or other medical procedures that rely on radioactive substances
Examples of what Geiger counters do not detect:
- Neutron radiation
- Microwave radiation
- Cell phone and smart meter radio frequency (RF) electro-magnetic field (EMF) radiation
- Radon gas (Test kits available in home improvement stores)
- Laser energy
About Nuclear Radiation
Nuclear radiation is a normal part of our planet and the cosmos. It is also a by-product of man-made actions and activities. The unfortunate catastrophe in Japan has created a new sense of urgency for personal radiation measurement to an entirely new generation of post-Cold War individuals.
Against this backdrop we will provide a fundamental description of how a Geiger counter detects nuclear radiation. First a few words on radiation, and a particular type called ionizing radiation.
Radiation is all around us. The sun radiates energy, radio stations radiate electromagnetic waves and radiators in apartment buildings radiate heat to keep residents warm in cold weather. However, nuclear radiation is a different type of radiation known as ionizing radiation.
Ionizing Radiation – Four Primary Types
Ionizing radiation alters the structure and, by association, the electric charge of individual atoms by a process known as ionization. The substances that produce ionizing radiation are said to be radioactive.
There are four primary types of ionizing radiation – alpha, beta, gamma and x-radiation (x-rays).
Generally, an alpha particle can travel no more than one to three inches in the air before stopping, and can be stopped by a piece of paper. However, they can pass through a thin mica window on an alpha radiation detector. As we will see later, this property of mica is very important in radiation measurement.
Beta radiation can pass through a sheet of paper and some clothing, but not through thin metal or glass. Beta particles can damage skin, however, both alpha and beta radiation are most harmful when inhaled or ingested.
Gamma radiation occurs naturally in nature and is almost identical to x-rays. Generally, they can travel into and often times through anything. Gamma particles can be shielded with several feet of water or concrete, several inches of steel, or a smaller amount of lead.
X-radiation is man-made radiation with a number of valuable uses in medicine and dentistry. X-rays are electromagnetic radiation of the same nature as light and radio waves, but they are also ionizing. They can penetrate a variety of materials, including body tissue. The shielding techniques for x-rays are similar to those for gamma radiation. This is why the x-ray technician will wear a lead apron when taking x-rays.
The Geiger–Müller Tube
Having discussed the nature of radiation and the four primary types of ionizing radiation, we will now move to discussing how a Geiger counter operates. This tube is the key element that enables the Geiger counter uses discussed above. Please see the figure below for the following discussion.
The nuclear radiation detector within a Geiger counter is a Geiger tube that consists of two electrodes separated by a mixture of gases sealed within a tube that is typically made of metal. High voltage is applied to the electrodes which creates an electrical field within the chamber.
When radiation passes through the chamber and ionizes the gas, a pulse of electrical current is generated. This detection will typically result in a flashing of an LED and sounding of a “beep” on most Geiger counters. In addition, these pulses are electronically processed by the instrument and the radiation level measurement is displayed. The mica window on the tube (PRM-8000 and PRM-9000 only) allows alpha particles to pass so that they can be detected.
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