Difference Between GM Counter and Scintillation Counter

The key difference between GM counter and scintillation counter is that GM counter detects ionizing radiation using the ionization effect produced in Geiger-Muller tube whereas scintillation counter measures ionizing radiation using the excitation effect of incident radiation on a scintillating material and detecting the resultant light pulses.

GM counter and scintillation counter are instruments useful in detecting and measuring ionizing radiation. The two instruments differ from each other according to the method of detection of the radiation.

1. Overview and Key Difference
2. What is GM Counter
3. What is Scintillation Counter
4. Side by Side Comparison – GM Counter vs Scintillation Counter in Tabular Form
5. Summary

What is GM Counter?

GM counter is the short name for the Geiger-Muller counter, which is useful in detecting ionizing radiation. This instrument has applications in dosimetry, radiological protection, experimental physics and nuclear industry. This instrument can detect alpha particles, beta particles, and gamma rays. It detects radiation using the ionizing effect produced in a Geiger-Muller tube. Thus, this leads to the name of the instrument.

Key Difference - GM Counter vs Scintillation Counter

Figure 01: GM Counter

The GM counter essentially contains a Giger-Muller tube, which is the sensing element that can detect the radiation. There is another important part of processing electronics which displays the result of the analysis. The Geiger-Muller tube in this instrument is filled with an inert gas; e.g. helium, neon, or argon gas at low pressure. A high voltage is applied to this gas. Geiger-Muller tube can briefly conduct electrical charge when a particle or photon of incident radiation makes the gas conductive by ionization.

However, ionization is significantly amplified within the tube via the Townsend discharge effect. This produces an easily measurable detection pulse. This pulse is then fed into the processing and display electronics. The large pulse produced in this method makes the GM counter relatively cheap to manufacture. There are two types of display methods in GM counter: detected radiation readouts and counts and radiation dose. The simplest readout is counts, which display the number of counts per time, e.g. counts per minute.

What is a Scintillation Counter?

The scintillation counter is an analytical instrument used to measure ionizing radiation using scintillating material. In this instrument, ionizing radiation can be measured using the excitation effect of incident radiation on a scintillating material and detecting the resultant light pulses.

Difference Between GM Counter and Scintillation Counter

Figure 02: Parts of the Scintillation Counter

The instrument contains a scintillator which can generate photons in response to incident radiation, a sensitive photodetector, which can convert the light to an electrical signal and electronics to process the signal. Mainly, scintillation counters are useful in radiation protection, assaying radioactive materials, and in physics research due to the inexpensive manufacturing process and good quantum efficiency. Moreover, we can measure both the intensity and the energy of incident radiation.

When considering the operation method of a scintillation counter, it involves the passing of ionizing particles into the scintillator material in which atoms are excited along a track. If these are charged particles, the track is the path of the particle itself. For uncharged particles such as gamma rays, their energy converts into an energetic electron via the photoelectric effect.

What is the Difference Between GM Counter and Scintillation Counter?

GM counter and scintillation counter are instruments useful in detecting and measuring ionizing radiation. The key difference between GM counter and scintillation counter is that GM counter detects ionizing radiation using the ionization effect produced in Geiger-Muller tube whereas scintillation counter measures the ionizing radiation using the excitation effect of incident radiation on a scintillating material and detecting the resultant light pulses.

Below infographic summarizes the differences between GM counter and scintillation counter.