Radiation Dosimeter is a device, instrument or system that measures or evaluates, either directly or indirectly, the quantities exposure, kerma, absorbed dose or equivalent dose, or their time derivatives (rates), or related quantities of ionizing radiation. A dosimeter along with its reader is referred to as a dosimetry system. Ionizing radiation, such as X-rays, alpha rays, beta rays, and gamma rays, remains undetectable by the senses, and the damage it causes to the body is cumulative, related to the total dose received. Therefore, workers who are exposed to radiation, such as radiographers, nuclear power plant workers, doctors using radiotherapy, workers in laboratories using radionuclides, and some hazmat teams are required to wear dosimeters so their employers can keep a record of their exposure, to verify that it is below legally prescribed limits.

Dosimeters measure an individual’s or an object’s exposure to something in the environment — particularly to a hazard inflicting cumulative impact over long periods of time, or over a lifetime. This article concentrates on the radiation dosimeter, which measures exposure to ionizing radiation, but other dosimeters also exist, such as sound dosimeters, ultraviolet dosimeters, and electromagnetic field dosimeters.

To function as a radiation dosimeter, the dosimeter must possess at least one physical property that is a function of the measured dosimetric quantity and that can be used for radiation dosimetry with proper calibration. In order to be useful, radiation dosimeters must exhibit several desirable characteristics. For example, in radiotherapy exact knowledge of both the absorbed dose to water at a specified point and its spatial distribution are of importance, as well as the possibility of deriving the dose to an organ of interest in the patient. In this context, the desirable dosimeter properties will be characterized by accuracy and precision, linearity, dose or dose rate dependence, energy response, directional dependence and spatial resolution. Obviously, not all dosimeters can satisfy all characteristics. The choice of a radiation dosimeter and its reader must therefore be made judiciously, taking into account the requirements of the measurement situation.

Common types of wearable and portable dosimeters for ionizing radiation include:

  • Quartz Fiber Dosimeter – The quartz fiber dosimeters have to be prepared, usually daily, with a positive charge from either a hand-wound or battery-powered charging unit. As the gas in the dosimeter chamber becomes ionized by nuclear radiation the charge leaks away causing the fiber indicator to rise up the graduated scale.
  • Film-Badge Dosimeter – Film-badge dosimeters for one-time use. The level of radiation absorption is indicated by a change of color on the film badge’s surface, which is compared to an indicator chart.
  • Thermoluminescent Dosimeter
  • Solid State Dosimeter (MOSFET or silicon diode)

Manufacturing processes that treat products with ionizing radiation, such as food irradiation, use dosimeters to calibrate doses. These are different from personal dosimeters because they usually must have a greater range. They often consist of small blocks of material such as perspex. One can also carry out the dosimetry of neutron radiation with a few specialized devices such as superheated drop detectors.