Radiation Detection and Survey Devices

Key Radiation Detection Device Monographs and Articles

top of page

If you want to learn more, please visit our website introduction to radiation detectors.

Introduction and Basic Information

top of page

Review of Radiation Dosimeters Types for Dose Monitoring, Worker Safety, and Environmental Monitoring

top of page

Selection of Radiation Detection Devices by Radiation Incident Response Zone

Table 2. Comparison of Radiation Devices by Preferred Response Zone

Source: Radiation Dosimeters for Response And Recovery, Market Survey Report (PDF - 1.87 MB) (DHS/OSTP/NUSTL, June , page 9)

• This graphic shows that no one device is appropriate for every situation.
• The x-axis on the bottom of the table above is exposure rate (R/h)
• The x-axis on the top corresponds to Response Zones (Cold, Hot, Dangerous-Radiation) and denotes where each dosimeter type might be most useful. Definition of response zones is shown on the graphic, but various groups have defined the zones differently.
• The y-axis on the left of the graphic lists types of dosimeters that are appropriate for the assigned rose rate work area
• In the source document for this table, the many categories of dosimeters are mentioned with many individual products listed for each type.

top of page

More about Selected Examples of Detection Devices

Geiger Mueller (GM) Detectors with Pancake Probes

• What is a Geiger counter? (The Vega Science Trust Videos)
  • Detects and measures radiation in the environment in real time
• How to survey for external contamination
• How to Use Hand-held Radiation Survey Equipment (Part 1) (YouTube - 19:02 minutes) (HHS/CDC)
• G-M Detectors Job Aid - Use a Geiger-Muller survey meter to check for contamination. One page pamphlet. (PDF - 429 KB) (HHS/CDC)
• What is a "count" of radiation? A 'count' is not a unit of radiation but rather a defined (unitized) response capacity of a device to an energy domain and dose rate. The count rate is affected by attenuating material between the dectector and the source and the source energy spectrum.

  
  

  • Radiation energy detected by some devices is registered as a "count."
  • Devices detect only a percent of the total energy (radioactive decays or disintegrations) released by radioactive material. This is the solid angle of the source point to the detector vs 4π spherical domain from the point source.
    • Efficiency: the percentage of the total radiation energy released that is detected by a device
  • Appropriate "efficiency" conversion factors can be used to
    • Determine the actual number of disintegrations per second or minute (DPS or DPM); requires a standard reference source
    • Actual disintegrations per unit of time are measured in units of curies or becquerels
  • Example
    • [CPM] divided by [efficiency] equals DPM
    • Example: 100 CPM at 20% efficiency = 100/0.2 = 500 DPM
• See Selected References section below.

top of page

Alpha Radiation Survey Meter

• Radiation survey meter with probe appropriate for detecting alpha radiation.
• Alpha Scintillation Detectors (Part 3) (YouTube - 3:54 minutes) (HHS/CDC)

top of page

Dose Rate Meter

• This survey meter measures environmental levels of penetrating, ionizing radiation
  • May be used to determine whether it is safe to enter an area and, if so, for how long
  • Provide readings in units of roentgens per unit time (e.g., mR/hr)

top of page

Personal Dosimeters

• What is a personal dosimeter?
  • A small radiation monitoring device worn by persons entering environments that may contain radiation
  • See historical collection of personal dosimeters (ORISE)
• Who should wear a personal dosimeter?
  • Healthcare or laboratory workers in non-emergency environments that may contain protected (contained/or open) radiation sources (lead 'pig') or open source exposure fields (Cs-137 and Co-60) sources, for example.
    • Examples: radiology, nuclear medicine, and radiation oncology department staff
  • Workers in emergency environments that may contain radiation
    • Examples: first responders and first receivers
  • Workers in industrial environments where radiation is used
    • Examples: nuclear power plant workers or employees at radiation sterilizing facilities, nuclear medicine facilities, etc.
• Where are personal dosimeters usually worn?
  • Flat badges are usually worn on the torso, at the collar or chest level, but can be worn on the belt, or forearm
  • Ring shaped badges can be worn on the finger when dose to the finger may exceed dose to the badge worn elsewhere on the body, i.e. material handling and source operations or transfers.
  • First responders and first receivers
    • Wear water-resistant personal dosimeters on the outer layer of personal protective equipment (PPE).
    • Should be able to easily see and hear a dosimeter alarm while wearing PPE
    • May wear a personal dosimeter underneath waterproof outerwear
• CAVEATS:
  • Radiation exposure in the environment may not be uniform.
    • Dose registered by a badge worn on the torso may not be the same as dose received elsewhere on the body.
    • When working close to radiation sources (e.g., removing radioactive shrapnel), the hands/fingers may receive a higher dose than the torso, and should be monitored by a personal dosimeter on the finger.
  • Real time readings from personal dosimeters are not available from all devices.
  • Emergency responders may require self-reading devices that provide dose information in real time.
• Types of personal dosimeters
  • See REMM table which reviews many types of personal dosimeters
  • Non-self reading dosimeters: real time dose information not available
    • Film badges
      • Contain filters and film which identify and quantify the type of radiation (e.g., x-rays, gamma, beta, neutron)
      • Least accurate personal dosimeter for recording very low exposure (e.g., below about 10 mR)
      • Sensitive to temperature and humidity, which may limit use by emergency responders
      • Available for use on torso and finger
      • See historical collection of personal dosimeters (ORISE)
    • Thermoluminescent dosimeters (TLDs)
      • More sensitive than film badges
      • Some can measure readings lower (more sensitive) than film badges. Film badges can saturate to no longer respond to added doses; films reach maxima asymptotically ' use the most linear response domain to limit the dose maxima
      • Use lithium fluoride crystals to record radiation exposure
      • Not sensitive to heat and humidity
      • Available for use on torso and finger
      
      
      
      
    • Optically stimulated luminescence (OSL) dosimeter
      • More recent device of choice for occupational exposure monitoring
      • More sensitive than film badge or TLD
      • Use aluminum oxide to record radiation
      • Results can be read up to a year following exposure
      • Available for use on torso and finger
      
      
      
      
      
  • Self-reading dosimeters (aka. direct-reading dosimeters, self-reading pocket dosimeters, pocket electroscopes): provide real time dose information
    • Older types: See historical collection of personal dosimeters (ORISE)
      • Dose is determined by looking through the eyepiece on one end of the dosimeter, pointing the other end towards a light source, and noting the position of the fiber on a scale

      
      

    • Newer types
      • Electronic
      • Some can measure and display dose rate and total dose
      • Some can alert wearer that pre-set dose rate and/or total dose limits have been exceeded by both visual and vibrating alarms
      • Dose rate and total dose readings can be downloaded in real time to a computer
      • Some are designed for use in extreme environments by emergency responders wearing bunker gear or higher-level PPE (See examples below)
      
      
      
      
      
      
      
      

top of page

Portal Monitors

top of page

Multimedia Training about Radiation Detection Devices

top of page

Selected References

Disclaimer:
Reference on this page to any specific commercial product, process, service, manufacturer, or company does not constitute its endorsement or recommendation by the U.S. government or the U.S. Department of Health and Human Services or any of its agencies. Products are displayed as examples only. HHS is not responsible for the contents of any "off-site" Web page referenced on this site.

top of page

Introduction To Radiation Detectors: What Are They And How Do They Work?

Since we can't physically detect radiation on our own, knowing what kind of radiation and how much of it is around you is paramount to your personal safety. Thus, radiation detectors are an extremely important part of your kit when you're traveling through or working around radiation.

Different kinds of radiation detectors detect and measure different types of radiation. Knowing the basic differences between the types of radiation detectors can be a lifesaver if you find yourself in a situation where you're dealing with radiation.

Read on to know which radiation detection devices to use for your purposes, and when and where you should be using a radiation detector.

Why Do You Need A Radiation Detector?

You need a radiation detector to protect yourself from ionizing radiation and the harmful effects it can have on your health. Being able to detect and measure the radiation around you can be the difference between knowing it's safe to be in an area and knowing that you need to leave as fast as possible.

Radioactivity is an everyday phenomenon that happens when an element's unstable atoms release excess energy in the form of waves or particles. Radioactive materials often produce alpha and beta particle radiation, as well as gamma-ray radiation. The emissions from these unstable atoms are known as ionizing radiation.

Decaying radioactive materials commonly produce ionizing radiation. The radiation coming from these materials has such a high amount of energy that it can remove electrons from atoms that they interact with, including the atoms in living things.

Having electrons removed from your atoms sounds scary because it is. Ionizing radiation can damage your body on the cellular level and \result in your cells and tissues slowly dying. This can put you at high risk of developing cardiovascular and cerebrovascular diseases.

Radiation detectors measure the amount of ionizing radiation around them. It's important to have a radiation detector if you want to avoid excessive amounts of ionizing radiation and keep yourself healthy.

The first radiation detectors were very different from the radiation detectors we have available today. One of the first devices used to measure radiation was a photographic plate that would show dark/light spots or look fogged up from the radioactive exposure. This method was not very accurate but laid the foundation for future innovation in radiation detection technology.

The electroscope was another early detector that was commonly used in the early days of radiation study. The electroscope worked by using a pair of gold leaves that would be charged and repel each other. This method of measurement was much more sensitive and precise than photographic plates.

The most accurate early radiation detection device was the spinthariscope. The invention of the spinthariscope allowed scientists to measure the rate of decay of radioactive materials.

How Does A Radiation Detector Work?

Generally, a radiation detector works by reacting to ionizing radiation released by radiation sources around it. Different radiation detector types have different ways of working and measuring the amount and type of radiation that they are exposed to.

Most radiation detection devices contain a material that is responsive to ionizing radiation. The difference between these detectors comes down to the type of radiation they detect and how they show the measurement of radiation.

Want more information on radiation detection and measurement solutions? Feel free to contact us.

Additional reading:
reciprocating (or piston) compressors and rotary screw air ...
Heat Press Comparison: Clam Shell vs Swing Away ...
Animal Feed Processing Techniques and Equipment
Your Guide to Steel Strapping
How People Got Hot Water Before Water Heaters
How Modular Sorting Systems Transform Modern Workspaces?
Exploring Modular Sorting System Applications in Industry

Types Of Radiation Detectors

Three main types of radiation detection devices exist: gas-filled detectors, scintillation detectors, and solid-state detectors. Every type of detector has specific pros and cons that make them better suited to certain tasks.

Gas-Filled Detectors

The most widely used type of radiation detectors is gas-filled detectors. There are many different kinds of gas-filled detectors and each type works in a different way, but they all use the same basic principle to detect radiation. Exposure to radiation makes the gas in the chamber ionized, producing an electronic charge, which is then measured by a measurement system.

There are three main subtypes of gas-filled detectors, with each one being differentiated by the voltage applied by the detector. The main subtypes of gas-filled detectors are ionization chambers, proportional counters, and Geiger-Muller tubes.

Ion Chamber

Ionization chambers, a.k.a. ion chambers, are gas-filled detectors that use a low voltage to function. Ion chambers can only register measurements from the ion pairs that are created inside the reaction chamber.

Unlike other detector types, ion chambers tend not to suffer from dead time, making them very useful for measuring high-energy gamma-ray radiation.

Ion chambers have a couple of drawbacks, however. Firstly, they can't tell the difference between different kinds of radiation. Secondly, ion chambers can be more costly than other kinds of detectors.

Proportional Counters

Proportional counters are gas-filled detectors that are one step up from ion chambers in terms of the voltage they use. The ion pulse measured by a proportional counter is associated with the amount of energy in the field of radioactivity that is being measured.

Because of this amplified measurement, proportional counters are very sensitive and can differentiate between different radiation types, especially radiation from alpha particles and beta particles. This makes them valuable for spectroscopy applications, as well as contamination screening detectors.

Geiger-Muller Tube

Geiger-Muller (G-M) tubes are the third major subtype of gas-filled detectors and operate at the highest voltage compared to proportional counters and ion chambers. This type of detector is where the term 'Geiger counter' comes from. While popular culture has popularized the term 'Geiger counter', it's not accurate to refer to every radiation detector as a Geiger counter.
G-M tubes can experience a phenomenon called 'dead time' when exposed to higher rates of radiation. This means that there's a significant delay between the cascade of pulse detection and when the gas in the G-M tube resets to identify another pulse.

Scintillation Detectors

Another significant type of radiation detector is the scintillation detector. These radiation detectors work by using the same principle as the early spinthariscope. Scintillation detectors use a material that gives off flashes of light when exposed to radiation, which is connected to a photomultiplier (PM) tube.

Scintillation detectors are highly sensitive and can differentiate between different types of radiation in small amounts, making them useful in spectroscopy. These properties of scintillation detectors make them very good for radiation search applications, especially in the context of radiation security.

Scintillation detectors come in many forms and sizes, from handheld detectors to large monitors. The application of a scintillation detector depends on its size. Small ones can be employed to screen vessels or containers for concealed radioactive material, while bigger detectors can be used to screen entire areas and populations.

Solid-State Detectors

The third and final type of radiation detector is solid-state detectors. These detectors typically use a semiconductor material like silicon to detect radiation. Solid-state detectors work by the same principles as an ion chamber detector but at a lower voltage and smaller scale.

Solid-state detectors consist of two semiconductor material layers made of silicon. The first layer is an 'n-type' layer, which has more electrons than holes. The second layer is a 'p-type' layer, with more holes than there are electrons. The extra electrons from the n-type layer cross the space between the two layers to fill the electron holes that are in the p-type layer. This creates an area called a 'depletion zone'.

Solid-state detectors are typically small and have a very quick response time, owing to the small size of both the solid-state detector and the depletion zone. These factors make solid-state detectors great for electronic dosimetry and useful in radiation protection applications.

These detectors can withstand a much larger absorbed dose of radiation over their lifespan of usage, making solid-state detectors ideal for use in settings with very strong fields of radiation.

Where And When You Need Radiation Detectors

Radiation detectors are needed if you expect to be working near or traveling through a heavily irradiated area. However, there are also settings where you might not expect to encounter radiation. Since extended exposure to small amounts of ionizing radiation can build up in your system, it's better to be cautious.

Places where you commonly need radiation detectors are industrial and nuclear power plants, medical facilities that specialize in nuclear medicine, and places that have been irradiated by a nuclear event such as the Chornobyl Exclusion Zone.

If you know how and where you intend to use a radiation detector, you can easily determine which type of detector you'll need for the task. There are three main reasons to use a radiation detector: radiation measurement, protection, and search.

Radiation Measurement Applications

When there are radioactive materials that need to be monitored, this calls for radiation measurement.

The objective of radiation measurement is to gain awareness of the properties of radiation near a known radioactive material. The important measurements to be aware of are the boundaries of a radioactive area, strength of an established radioactive field, and spread of radioactive contamination.

Radiation detectors that are used for measurement have unique requirements, usually having relatively high measurement ranges or modifications that are used to look for a specific type of radiation.

Radiation Protection Applications

Radiation protection, like radiation measurement applications, is generally used when you expect to find radiation in a certain setting. However, radiation protection differs from radiation measurement in its objective. While radiation measurement is used to measure and monitor radioactivity itself, radiation protection is used to monitor people.

The most common example of radiation protection is radiation dosimetry. Radiation badges are worn by personnel working and traveling through radioactive settings. These badges protect personnel by giving them an awareness of the amount of radiation they've been exposed to. If a worker is aware of the amount of radiation they have been exposed to, they can avoid the most harmful effects of radiation exposure by altering their position, behavior, or schedule to minimize further exposure.

Radiation badges are most commonly worn by medical or military personnel, nuclear industry workers, and other occupationally exposed workers.

Radiation Search Applications

Radiation search is different from both radiation protection and radiation measurement. Radiation search is used to detect radiation in an area where radiation isn't expected to be, with the goal of keeping sources of radiation out of that area.

Radiation searching devices are usually used by security personnel, customs officials, border inspectors, and first responders to detect and remove radioactive sources before they can cause harm. Radiation detectors used for search applications have different requirements from those used for measurement and protection, due to the substantially different circumstances they're used in.

Radiation search needs detectors that are highly sensitive to detect small amounts of radiation emitted by a radioactive source or material that may be concealed. Radiation spectroscopy is especially useful here since it can filter out legitimate or natural sources of radiation and identify radioactive isotopes that are dangerous or unexpected.

Conclusion

If you're working around radiation or expecting to travel through a radioactive area, having a radiation detector on your person is imperative to your safety. Being aware of the amount of radiation around you can drastically change the way you should be approaching a situation.

The biggest thing you need to know before picking up a radiation detector is how you intend to use it:

• Traveling through a place and want to know if you're in a highly irradiated area? Pick up a solid-state detector ' they're small, light, and have a long lifespan.
• Planning to measure radiation for research? Gas-filled detectors may be your best bet.
• Trying to keep irradiated items away from a safe zone? Scintillation detectors are great at detecting radiation in places it shouldn't be in.

Keep safe and radiation-free by staying prepared! Knowing the basic differences between the three main types of radiation detectors will help you choose the ideal detector for your needs and use case.

Contact us to discuss your requirements of radiation protection solutions. Our experienced sales team can help you identify the options that best suit your needs.