Geiger Counter Vs. Dosimeter

Geiger counter and dosimeter are both used for measuring or detecting certain kinds of radiations (ionizing radiation). However, both the devices are meant to perform different tasks and are very different from each other in terms of features and their applications.

A Geiger counter (Geiger-Mueller counter) is not a dosimeter, but rather an ionizing radiation detector that counts the number of ionizing radiation hits on the tube. If you are well informed on the nature of the radiation that you detect, you can create a preliminary estimate of the likely dose to yourself.

On the other hand, a dosimeter monitors the dose or the amount of energy deposited in the body (or something else) by ionizing radiation. Again, you must be aware of the radiation levels recorded. If you don’t know the nature of the radiation, you’ll need a complex gear that comprises spectrometers and detectors that can detect charged particles, electromagnetic waves – photons, and neutrons. With this equipment, you can determine the source of the radiation and then interpret the measurement in terms of hazard to living beings or objects.

That is the main difference between the Geiger counter and dosimeter. There are also the other things that make them different. So let’s compare them both, analyze their workings, study their designs and see if either of the two can be used in the place of the other.

1. How They Work

Geiger Counter

A Geiger counter also known as Geiger Muller tube is an instrument used to detect or measure alpha, beta, and gamma radiations.

This instrument has two main parts: the tube and the counter. The tube has two electrodes inside, surrounded by an inert gas. The most commonly used gas is Argon.

When any kind of radiation enters the tube, the particles ionize the gas, and an electric charge is produced between the electrodes.

During the ionization phase, an electron is kicked out from the atom, making the atom positively charged.

The electron that was pushed out of the atom is attracted towards the positive electrode while the ion produced is attracted towards the negative electrode. These two attraction produces a pulse.

A scalar is used to count the number of pulses produced when a particle enters the tube.

Therefore, a Geiger counter measures in CPM (count per minute) or CPS (counts per second).

Dosimeter

Using a dosimeter to measure the radiation dose
Using a dosimeter to measure the radiation dose

Dosimeters are scientific equipment or sensory detectors that aid in the detection of radiation exposure because exposure to any form of radiation is hazardous and unavoidable. These devices are often worn by workers working in a dangerous environment to notify them and protect them from potential harm.

When dosimeters were first developed, films were put in the badges to gather the quantity of radiation it was exposed to, and the badges were then sent to be examined.

However, as technology has advanced, the technique of measuring radiation has changed as well. Exposure is instantly calculated on smartphones, computers, or mobile devices as these are clipped on garments (clothes). Most importantly, the exposure measurement does not require the burden of carrying badges that must be sent in for examination.

Technically, the digital ones work in the following way:

They basically capture the ionizing radiation caused by radioactive particles of any kind. This capture leads to the loss of electrons.

The electrons are thus captured by phosphor crystals like those that encapsulate dosimeters.

Electron captured by phosphor crystal causes it to heat up and release electrons in the form of light.

The light is then used to detect the exact amount of radiation subjected to.

If a Geiger counter measures in CPM or CPS, a dosimeter measures in µS/hr (microSievert per hour) or mR/hr.

2. Types and Their Design

Types of Geiger Counter

Although there are numerous designs available, the following are the most common types of generalizations:

  • End Window: In this form of Geiger counter, at the end of the tube is a tiny window that aids in ionizing the particles.
  • Windowless: This form of Geiger counter, on the other hand, lacks a window and is typically employed to detect penetrating radiations. This model requires a thin wall so that the gamma rays can penetrate the wall. The thickness of the wall ranges from one to two millimeters.

Types of Dosimeters

In general, you need to know that there are two basic types of dosimeters, which are further subdivided into many types:

  • Active Dosimeters: To detect the real-time value of the exposed radiations, an electronic personal dosimeter is commonly used. In general, signals induced by exposure to radiation are thus produced to display real-time dose values.
  • Passive Dosimeters: In this situation, signals induced by the radiations are stored in the device and subsequently processed to check the output. Thermo-Luminescent dosimeters and the film badge are the common types of passive dosimeters.

These basic primary categories are frequently employed in ways that are compatible to complement one another. Subdivision of these includes the following types:

  • Film Badge Dosimeters: These essentially consist of a badge with a film embedded in it that detects ionizing radiations emitted by particles when exposed to them. The badges are then sent out to be processed and analyzed in order to determine the outcome of the radiation exposure.
  • TLD- Thermos Luminescent Dosimeters: This particular detector basically detects the amount of radiation that was exposed through the intensity of visible light that was emitted after the heating up of sensitive crystals present in the detector.
  • EDP- Electronic Personal Dosimeter: A modern type of dosimeter that displays a direct measurement of the detected dose in cumulative form and frequently alerts the person who is wearing it when the reading exceeds the given limit.
  • Self-reading Dosimeter: These are unpowered devices that are worn to measure the accumulated doses. They do not require a battery. This type is further subdivided into Quartz Fiber dosimeter and self-developing photochemical cards. Quartz Fiber dosimeter is pen-type dosimeters used to read readings throughout a single work period. While self-developing photochemical cards are used for radiological medical treatment and to alleviate any panic and worry.
  • Radioisotope Identification Device: These are frequently employed in emergency situations or when the level of radiations detected is too low to identify. They are configured to produce estimations of the values detected.

Conclusion

Both the instruments are unique in their own ways and provide features that differentiate them from each other.

  • A Dosimeter measure the dose of ionization, while a Geiger counter counts the ionization particles
  • If a Geiger counter measures in CPM (counts per minute) or CPS (count per second), a dosimeter measures in µS/hr (microSievert per hour) or mR/hr.
  • A Dosimeter can be worn and is compact, while some Geiger counters are compact they are usually bulky.

Though the Geiger counter and dosimeter are different, it’s easy to find devices that measure in µS/hr (dose rate) but they are marketed as Geiger counter. In this case, you have to be more diligent to check the product description.

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