About Radiation Detectors – Advantages & Disadvantages

The term “Radiation Detector” can cover a large range of various detectors for different types of radiation. With the advent of the cell phone, the microwave, and advances in medical x-ray imaging and scanning technology to the applications of medical isotopes, it is important to determine the specific type of radiation you are trying to detect to get the right instrument for the job. The two major types of radiation are ionizing, such as gamma, beta, alpha, x-rays, and cosmic radiation, and non-ionizing, for example wireless radiation, microwaves, and radar.

Here at SEI, our specialty is ionizing radiation detection. Our instruments cover a wide range of application with our Geiger counters, Dosimeters, and Spectrum Analyzers. While the most widely used radiation detectors have typically been Geiger-Müller (GM) tubes for the last century, other types of detectors including scintillation detectors, semiconductor detectors, and ion chambers, have made great strides incorporating themselves into some detectors available today.  However, each detection method has its advantages and its disadvantages.

Geiger-Müller tubes are comprised of a charged Halogen quenched, gas-filled chamber. When radiation passes through the gas, it discharges the gas and is registered as a count or event, at which time the detector quickly recharges the gas in anticipation of the next count. Hence, the name “Counter”. This is a fair description of what they do, as they count the overall radiation present without identifying or qualifying the source of the radiation, such as our Radiation Alert® Ranger – Radiation Survey Meter. GM tubes really shine in the cost effectiveness and in situations where alpha and beta radiation are present with very little gamma radiation, which can have lasting health effects if ingested or with exposure to high quantities.

To identify potential sources of radiation, for example a specific isotope, A scintillation counter is necessary. Scintillation crystals utilize the light pulses resulting from the excitation effect of incident radiation on a scintillator material. The ability to measure both the intensity and the energy of incident radiation enables the identification of specific energies that are unique to various isotopes. They consist of a scintillator, the part that generates photons in response to incident radiation, a sensitive photo-multiplier tube (PMT), which converts the light to an electrical signal, and electronics to process and report on the signal. Though they have the advantage of being highly sensitive to gamma, they can also be fragile and will only detect alpha or beta via the detectable progeny.

Semiconductor detectors, which essentially act as diodes, take advantage of diamond, Cadmium Zinc Telluride (CZT), silicon, and germanium crystals and their sensitivity to ionizing radiation. Applications can range from radiation dosimetry to gamma spectroscopy. These detectors can be easily ruggedized, but are typically much more expensive when compared to the alternatives.

Ionization chambers, commonly used in the detection and measurement of X-rays, gamma rays and beta particles, are used exclusively to describe those detectors which collect all the charges within the gas through the application of an electric field created by direct ionization. It only uses the discrete charges created by each interaction between the incident radiation and the gas and does not involve the gas multiplication mechanisms used by radiation instruments, such as the Geiger-Müller counters commonly used to check for X-Ray chamber leakage and screening shields. Ion chambers generally have a uniform response to radiation over a wide range of energies, so they’ve become the preferred means of measuring X-ray beams and high levels of gamma radiation, as the lack of dead time will prevent pulses from being missed. However, moisture can have a varying effect on the accuracy of the ion chambers and the relative size of many models prevents them from being a field ready instrument.

In conclusion, though there are a wide array of technologies available in the realm of radiation detection, the Geiger-Müller tube will most likely remain the most common detector available due to its cost effectiveness, sensitivity, and tried and true history of dependability and versatility.

Check out the latest in our Radiation Alert®  line of nuclear radiation detectors, radiation dosimeters, radiation spectrum analyzers, and accessories.

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