Radiation Sensors

Infrared and ultrasonic radiations are not the only type of radiation that is available in the atmosphere. Many other radiations like alpha rays and gamma rays can be found in the universe. These radiations can be used in many constructive ways. One of the major applications of radiation is the radiation sensor. The concept of radiation and radiation sensors are explained in the following article.


  1. What is radiation?
  2. What are the types of radiation?
  3. Properties of Radiation
  4. Radiation Sensors
  5. Working of a Radiation Sensor
  6. Types of Radiation Sensors
  7. Gas-Filled Detectors, Scintillators, and Solid State detectors.
  8. What is Radiation Sickness?

What is radiation?

Radiation is a form of energy that is emitted by a source object and travels at the speed of light. The visual representation of the radiation will be similar to a wave. Due to this property, radiation is also known as electromagnetic waves. The procedure by which radiation is generated either naturally or artificially is explained below.

  • Radiation is the release of energy from radioactive substances in the form of moving waves or streams of particles from a source object.
  • The source object would be certainly made out of atoms that contain a nucleus as the centre of an atom.
  • A nucleus is made up of two particles namely protons and neutrons with a tremendous amount of energy.
  • If the number of neutrons in the nucleus varies from the number of protons, then the nucleus becomes unstable and the instability leads to the source being radioactive.
  • The radioactive atoms release energy to get back to a stable state again using a process named radioactive decay.
  • The energy released during the radioactive decay is known as radiation and there are different types of radiation.

What are the types of radiation?

Generally, radiation is classified into four major types. The classification is shown in the figure below and explained elaborately.

Different Types of radiation
  • The alpha wave is mostly produced by natural radioactive materials such as uranium and thorium. The alpha is the heaviest radiation out of the four radiations.
  • The beta waves are produced by elements like tritium, carbon-14 etc. The beta particles of the carbon-14 are used to analyse the age of the fossil.
  • The third type is the neutron rays. This is produced by the fission or the fusion of particles inside the nucleus itself. Neutron radiation is used to generate nuclear energy.
  • The final and the most common type of radiation is gamma rays. This includes various other waves such as x-rays, UV rays, infrared rays etc.


Properties of Radiation

Electromagnetic radiation has a lot of properties that define its characteristics. Some of the main properties of radiation are listed below.

  • There are two major properties available to differentiate the type of radiation. They are the penetrating power and the ionizing power.
  • The penetrating power of the alpha rays is so low that they cannot penetrate through the paper while the ionization power of alpha is the highest among the three types.
  • The beta rays have a penetrating power higher than alpha and lower than gamma and ionizing power lesser than alpha and greater than alpha.
  • The gamma rays have the strongest penetrating power that they can penetrate through a concrete wall. But the ionization power of gamma rays is so low.
  • To stop the penetration of the gamma rays, a lead bar with a minimum thickness of 2-inches is required while the gamma rays can be shielded using an aluminium sheet.

Radiation Sensors

A radiation sensor is a device that is used to measure various kinds of radiation. Along with measuring radiation, the radiation sensors must also be capable of performing other tasks too. Some of them are explained below.

  • The sensor must measure all the different types of radiation like alpha, beta and gamma rays without being ionized or penetrated.
  • Though certain sensors like Geiger tubes consists of an inert gas like argon, neon or helium.
  • When the radiation is passed through the tube, some of the gas is ionized.
  • By analysing the amount of gas ionized, the intensity of the radiation can be calculated.
  • The intensity of radiation is then displayed as output using devices like an LCD screen or an OLED screen.

Working of a Radiation Sensor

Radiation sensors are of different types. Though the generalized working of all sensors will be of two types. They are the ionization technique and the excitation method. Both the methods and their working are as follows.

  • The ionization method is used for the radiation which has a high ionizing power such as alpha rays.
  • In this method, a glass tube is filled with any kind of inert gas like helium or argon or air.
  • When heavily ionizing radiation is passed through the tube, the gas gets ionized.
  • By measuring the ionized gas, the intensity and the ionization power of the radiation be analysed.
  • The excitation method uses the phenomenon that the atoms get energized when electromagnetic radiation is passed through them.
  • When electromagnetic radiation is passed through an atom that is in its ground state, it absorbs energy and moves to the excited state.
  • Due to the energy lost, the radiation is converted into light.
  • The light emitted is then measured and with the intensity of the light, the strength of the radiation can be calculated.

Types of Radiation Sensors

Based on the working mechanism of the radiation sensor, the radiation sensors are widely classified into three different types. They are gas-filled detectors, scintillators and solid-state detectors. The classification is briefly explained below.

  • Gas-filled radiation detectors are nothing but a simple sensor that uses ionization method to measure the intensity of the radiation.
  • The Geiger Muller counter is the best example of a gas-filled radiation detector.
  • A scintillator is a device that uses one of the properties of radiation i.e., the radiation is converted into light when some of its energy is used to excite an atom that is in its ground state.
  • A solid-state detector is a device that uses a semiconductor material to measure different types of radiation and their intensity.


Gas-Filled Detectors, Scintillators, and Solid State detectors.

All kinds of radiation sensors have something in common and differentiate from each other in some aspects. So the properties and working mechanisms of gas-filled detectors, scintillators and solid-state detectors are tabulated below.

Parameter Gas-Filled detectors Scintillators Solid-state detectors
Working Principle Uses the ionization effect of the radiation to measure the intensity of the radiation Uses the excitation effect of the radiation to measure the intensity. Uses a semiconducting material to measure the intensity of the radiation.
Processes involved Ionization is the only process taking place Excitation is the only process Both ionization and absorption occurs
Usage The most commonly used radiation detector Commonly used das detectors next to gas-filled detectors Rarely used radiation detector of all the other types
Example sensors Geiger Muller counter is the best example of a gas-filled radiation detector A magnetic spectrometer scintillator is an example of a scintillator. Photomultipliers using silicon crystal is the widely used variety of solid-state radiation detector.

What is Radiation Sickness?

Though most electromagnetic radiation can cause minimal damage to our skin and some weak tissues of the human body, radiations like gamma rays can cause permanent issues to the human body. This phenomenon is known as radiation sickness. The concept of radiation sickness is further explained below.

  • Radiation sickness can be caused due to two reasons.
  • One is the person should be exposed to harmful radiation for a long time in a smaller amount or the person may be exposed to a large amount of radiation during a medical analysis of something like that.
  • The major symptoms of radiation sickness are vomiting sensation and vomiting, dizziness, fever, nausea etc.
  • Radiation sickness can damage the thin tissues in the human body such as the intestines and blood vessels.
  • It can also damage some of the complicated body parts like the bone marrow.
  • Excessive exposure to radiation may lead to chronic radiation sickness and can even be fatal.

Key Points to Remember

Here are some key points we need to remember about “Radiation Sensors”

  • Radiation is a type of energy released from a radioactive substance.
  • Radiation is broadly classified into three types namely alpha rays, beta rays and gamma rays.
  • Ionization and penetration are the most important properties of electromagnetic radiation.
  • A radiation sensor is a device that is used to measure the intensity of radiation of different types.
  • Radiation sensors work on the principle of either ionization or excitation to measure the intensity.
  • Radiation sensors are widely classified into three types. They are the gas-filled detectors, scintillators and solid-state detectors.
  • Radiation sickness is a phenomenon that is caused due to exposure to radiation for a long time radiation exposure or exposure to intensive radiation all of a sudden.

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Manish Bhojasia - Founder & CTO at Sanfoundry
Manish Bhojasia, a technology veteran with 20+ years @ Cisco & Wipro, is Founder and CTO at Sanfoundry. He lives in Bangalore, and focuses on development of Linux Kernel, SAN Technologies, Advanced C, Data Structures & Alogrithms. Stay connected with him at LinkedIn.

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