Radiation Detector

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What is a Radiation Detector?

Those people who work with or around radiation, one of the most important factors is an awareness of the levels of radiation around them. This is primarily accomplished through the use of radiation detectors of varying types. 


How do you define the terminology radiation detector? Simply, a Radiation detector or a particular detector is a device used to detect, track, or identify ionizing particles, such as those produced by cosmic radiation, nuclear decay, or reactions in a particle accelerator. Radiation detectors can measure the particle energy and other attributes such as momentum, spin, charge, particle type, in addition to merely registering the presence of the particle.


Evolution of Radiation Detector

In the early days, photographic plates were used to identify tracks left by nuclear interactions. A photographic plate would be placed in the path or vicinity of a radioactive beam or material. When the plate was developed, it would have fogged or spotted from the exposure to the radiation. Then the sub-nuclear particles were discovered using cloud chambers, which needed photographic recordings and a tedious, complicated measurement of tracks from the photography.


Another commonly used radioactive detector in the early days was the electroscope. These used a pair of gold leaves that would become charged by the ionization caused by radiation and repel each other. This process provided a means of measuring radiation with a better sensitivity level than was reliably possible using photographic plates. Depending on the arrangement of the device, they could be configured to measure alpha or beta particles and were a valuable tool for early experiments involving radioactivity.


Another interesting early device, invented out of a desire to measure the actual individual particles or rays being emitted by a radioactive substance, as opposed to a more gross measurement of a dangerous field, was the spinthariscope.


Developed by William Crookes, who had also invented the Crookes Tube used by Wilhelm Roentgen to discover X-Rays, it used a zinc sulfide screen at the end of a tube and a lens at the other end, with a small amount of a radioactive substance near the zinc sulfide screen. The zinc sulfide would react with the alpha particles emitted, and each interaction would result in a tiny flash of light.


This was one of the first means of counting a rate of decay, albeit a very tedious one, as it meant scientists had to work in shifts watching and literally counting the flashes of light. The spinthariscope was not very practical as a long term Radiation detection, though it did undergo a revival later in the 20th century as an educational tool.  The tendency of certain materials to give off light when exposed to radiation would also prove valuable in future radiation detection technologies.


Electronic detectors were developed with the invention of the transistor. Modern detectors use calorimeters to measure the energy of the detected radiation. They may also be used to measure other attributes of the particles.


These early used devices, and many others, such as cloud chambers, played a valuable role in understanding the basic principles of radiation and conducting important experiments that set later scope development. This included the development of new types of radiation detectors, many of which are still in use today, such as ion chambers, G-M Tubes, and Scintillators. 


Types of Detectors

There are various types of detectors that are in use. Some of them are:

Scintillation

One of the significant types of detectors utilized in radiation detection instruments is Scintillation Detectors. Scintillation is the act of giving off light. For radiation detection, some material can scintillate when exposed to radiation that makes them useful as detectors. Each of the photon radiation that interacts with the scintillator material will result in a distinct flash of light, meaning that in addition to being highly sensitive, scintillation detectors capture some specific spectroscopic profiles for the measured radioactive materials.


When a scintillator is coupled to an electronic light sensor such as a photodiode, photomultiplier tube (PMY), or silicon photomultiplier, a scintillator detector, scintillator-type detectors use a vacuum and first convert light into electrical pulses.


Gaseous Ionization Detectors

A radiation detection device which is used to detect the presence of ionizing particles, and in applications which are radiation protected to measure ionizing radiation is called Gaseous ionization detectors.


There are other types of gas-filled detectors such as proportional counters, and Geiger-Mueller (G-M) tubes. The major differentiating factor between these different types is the applied voltage across the detector, which determines the kind of response that the detector will register from an ionization event.


Geiger Counter

Geiger counter is an instrument that measures or detects ionizing radiation. It is also known as Geiger -Muller counter. It detects ionizing radiation such as alpha particles, beta particles, and gamma rays.

FAQ (Frequently Asked Questions)

Q1. What are the Types of Radiation?

The types of radiations are-

  • Alpha radiation- Alpha radiation is the stream of doubly ionized helium nuclei. The doubly ionized helium nuclei are the fast-moving helium atoms; they have high energy ranging in MeV. They have low penetration depth, typically few cms of air or skin due to their large mass.

  • Beta Radiation-Beta radiation is the stream of electrons, which are fast-moving electrons. Their energy ranges from hundreds of KeV to several MeV. They have better penetration depth due to their comparatively lighter mass.

  • Gamma radiation- They are the stream of photons. They have comparatively very low mass. Thus, they possess good penetration depth. Typically a few inches of lead.

Q2. What are the Detectors for Radiation Protection?

The different types of particle detectors which are widely used for radiation protection, commercially produced in large quantities are given below:

  • Dosimeter

  • Electroscope (when used as a portable dosimeter)

Gaseous ionization detector -

  • Geiger–Müller tube

  • Ionization chamber

  • Proportional counter

  • Scintillation counter

Commonly used detectors for particle and nuclear physics-

  •  Gaseous ionization detector

  • Ionization chamber

  • Proportional counter

  • Multiwire proportional chamber

  • Drift chamber

  • Time projection chamber

  • Geiger–Müller tube

Solid-state deducted-

  • Semiconductor detector and variants including CCDs

  • Silicon Vertex Detector

  • Solid-state nuclear track detector and Cherenkov detector