profile picture

Technology In Use

The technology for radiation detection has come a long way from since the geiger counter. Geiger counters definitely have their place, but they are more suited to measuring than locating. As a result, the first device I use is a Scintillation Pager.

A scintillation counter is simply a device which can convert radiation into visible light flashes, and count the pulses. Radiation typically alpha, beta, neutrons, gamma or xrays can cause certain crystals or chemicals to emit a light pulse. When this happens a very sensitive photomultiplier tube or light sensitive diode can then be used count the light pulses, and electronic circuitry can convert it to measurable data. We use a PM1703M Pager Scintillator, which is designed specifically to find low levels of gamma and x-ray radiation from a great distance away to give us an idea if and where radioactive materials may be found. Scintillators are typically much more sensitive than geiger counters, but may have limitations such as only being able to detect gamma and x-ray radiation. This can be an issue if you scintillator is gamma - x-ray only, and you have an radioactive material such as polonium 210, since it is only an alpha emitter.

Geiger counters typically are more sensitive to three or more types of radiation. Our Dosimeter 3700 is sensitive to beta, gamma and x-ray radiation. Our Monitor 4 EC is sensitive to alpha, beta, gamma and x-ray radiation. It is also energy compensated, meaning it flattens out the response curve. In simple language, geiger counters tend to over respond to certain energies of gamma rays, meaning at some lower energies (gamma rays can be more or less energetic), higher counts will result with lower energies. A tin, copper, lead or beryllium shield can this out, reducing the lower energy over response, giving a more accurate reading in what is known as a Compensated Geiger Counter.  There are some hackers, who in efforts to make their geiger counters more sensitive (especially some Russian models).  Personally,  I feel that it is a poor idea, since sensitivity gains are marginal, and then one winds up with a geiger counter that may lack the ability to be accurately calibrated.

Ion chambers are yet another type of radiation detector. As radiation strikes a metal chamber, a charge is created, and electronic circuitry measures this charge and translates it to a meaningful reading.  Ion chamber devices are especially valuable to health physicists.  They work and give a true reading with pulsed radiation fields (like an Xray machine).  Also, they respond more accurately and give a truer dose reading as to what a human may be exposed to with gamma and xrays, depending on what they are exposed to.      

As for neutrons, rarely will they be found in common household radioactive materials. Typically they are only emitted from fissile (atomic bomb) radioactive materials. As a result I do not carry neutron detection equipment. However, even depleted uranium (DU, or Uranium 238, non fissile uranium) will emit some neutrons as a result of particle collisions and spontaneous fission (splitting of atoms).  Some  soil density gauges will also use an Americium 241 and Beryllium to emit neutrons (beryllium, when struck by energetic alpha particles, will emit a neutron).  Enrico Fermi used Radon gas and Beryllium in a test tube for his atomic fission experiments.  I may buy a neutron counter eventually, or make one, however they can be fairly expensive.

I typically provide a qualitative, not quantitative analysis. Simply stated, a qualitative analysis means either it is radioactive or not, is it a hazard or not. Referrals may be given to appropriate individuals who can help, or what measures you can take to limit exposure.

Have a Question about Radiation or Detectors?

Simply fill out the form below and we'll contact you with the answer. We guarantee your privacy.

My Form