National Physical Laboratory

Electron beam calibration service for radiotherapy (absorbed dose)

Absorbed Dose
Parallel plate electron chamber in the
calibration water phantom

Calibration of an ionisation chamber in terms of absorbed dose to water, based on primary standard electron-beam graphite calorimeter. Available in spring each year.

  • This service is designed to be used with the current IPEM Code of Practice (2003), which is based on this service. The IAEA Technical Report No.398 can also be used, but this report is not recommended by the IPEM.
  • Calibration of NACP-02, Roos (PTW and Wellhöfer) and graphite-walled Farmer chambers (NE2571, PTW30004).
  • Uses R50 alone as beam quality specifier to define reference depth. Beam qualities presently covered in the range R50=1.6 cm to 8.9 cm (nominal incident electron energies 4 MeV to 22 MeV).
  • Uncertainties for direct calibration ±2 % at the 95 % confidence level.
  • Characterisation of recombination behaviour of each chamber in terms of dose per pulse


Customer Services tel: +44 20 8943 8695

Last Updated: 9 Aug 2016
Created: 17 Apr 2007


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