National Physical Laboratory

Protection and environmental level (air kerma)

Protection Level Gamma-ray Facility
Protection level Gamma-ray facility

NPL's protection-level calibration service is tailored for ionisation chambers used as secondary standards or instruments required for measurement of the greatest accuracy. Calibration of either an ionisation chamber alone or as a complete instrument is available.


  • Calibrated directly against the NPL air kerma primary standards or via specially constructed transfer chambers.
  • X-ray qualities in accordance with ISO 4037 narrow spectrum series (see table below).
  • 60Co, 137Cs and 241Am radionuclides.
  • Air kerma rates in the range 5 mGy/hr to 50 mGy/hr


  • Radionuclide calibrations are available throughout the year by arrangement, calibrations in X-ray qualities are carried out during October - December each year.
  • Under the terms of a EUROMET agreement, calibrations with 4 MeV to 7 MeV X-rays may be undertaken at the Physikalisch-Technische Bundesanstalt (PTB), Braunschweig, Germany. Enquiries in this case should be directed to Dr Sigmund Guldbakke at PTB (T: +49 531 592 6211  |  F: +49 531 592 9292)

Protection Level Gamma-ray Facility Specs


Customer Services tel: +44 20 8943 8695

Last Updated: 9 Aug 2016
Created: 17 Apr 2007


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