How to use radiation detection devices?

Answer 1

When you are surveying for a source of radiation, it helps to know what kind of radiation it is emitting. Most unstable radionuclides emit gamma rays as well as particulate so we can begin with that.

Gamma rays are best spotted with a detector that has a high atomic number. A gamma scintillator like NaI is one of the most sensitive. The high atomic number means more of the gamma rays are stopped.

Geiger-Mueller counters are gas filled detectors and may also be used as long as you have a bit of metal tubing around them so the gamma strikes them first to create a shower of electrons in the detector.

You should take care to survey in a 360 degree arc to make sure that you are locating the direction of the radiation. Also survey not just at waist level. Some sources may be coming from above or below you.

To survey for an beta emitting source, you must use a thin window detector. Usually we use a Geiger-Mueller detector with a large thin window (a pancake probe). Here you must be close to the source because betas travel only a few feet in air and are easily shielded by water and dirt. Cloth wipes of surfaces can be taken and then held up to the detector to check for removable contamination.

Alpha radiation with no associated gamma is a very difficult problem. You must survey within an inch. The best survey instruments are usually alpha scintillators like ZnS. A big problem is that you can either contaminate or damage your probe while surveying for the radiation.

Some detectors useful on humans include gas-filled proportional counters that can see beta and alpha radiation. They have thin windows that can allow the alpha to penetrate. The problem they have, besides breaking the window, is that natural alpha from radon (a uranium daughter found in soil) confuses the counter into thinking there is contamination of a different source.

To search for very low energy betas, for example from tritium (hydrogen-3), liquid scintillation is used. Here the sample is usually water and a small bit of it is mixed with the actual detector fluid. The flash of light in the fluid corresponds to the amount of radiation in the sample. The light, as in all scintillation detectors, is picked up by photomultiplier tubes and relayed to a counter.

Hope this helps.

Answer 2

what is the definition of a radiation detecting device?
See, a radio detection and ranging device is more commonly known as a radar. [radio being part of the electromagnetic spectrum--it moves by radiation]
But, for measuring the emission of radioactive particles from something, a Geiger counter is used.
Motion sensors detect changes in either visible light or possibly IR (more parts of the electromagnetic spectrum)
And, a radiometer is something used to measure accumulated rads a person has been exposed to--usually worn by reactor workers to let them know when they have to leave a hot area.