The Radiation Dosimetry group is concerned with the dosimetry of x- and γ-rays, and charged particles such as electrons and protons. We develop, maintain and disseminate the UK national measurement standards for these radiations and engage in research on radiation interactions to address the needs of industry, healthcare and government.

The group is also involved in promoting the role of traceability in quality assurance, international and national specification standards and measurement protocols, for example through training.

Air kerma calibration services are provided for a wide range of photon energies and intensities ranging from the lowest air kerma rates required for environmental monitoring (nGy/h) to those employed for radiotherapy (Gy/min). These services are provided in response to the requirements of legislation or Codes of Practice such as those published by the Institute of Physics and Engineering in Medicine.

In each case, traceability to a primary standard is an essential feature. A range of primary standards is required, each standard covering a particular photon energy band, and each is used to support the provision of a number of calibration services carried out by the group.

Absorbed dose to water is the preferred quantity for measurements of ionising radiation in many contexts, and the design and development of existing primary standards have been driven by this need to realise absorbed dose. All high-energy, electron and photon calibration services, at therapy-level and industrial-level doses and dose-rates are traceable to these primary standards.

Modelling using radiation transport Monte Carlo simulations plays an increasingly important role in support of our measurements, from the design of new primary standards to the modelling of industrial radiation processes. Monte Carlo training courses and application workshops are held at NPL on a regular basis.

The Radiation Dosimetry group maintains a number of ionising radiation facilities enabling research and the provision of the calibration services. All of the facilities are available for hire with technical support from experienced specialists who carry out the work to procedures accredited to ISO9001. Many users find the measurement advice they provide invaluable and the authority lent to the measurements by NPL's internationally recognised expertise of significant commercial benefit.