Current interests

John Sephton works in both the Chemical Dosimetry section of the Dosimetry Group and the Radioactivity Group. His main interests are extending the application of alanine dosimetry and the development of detector systems and instrumentation for dosimetry and radioactivity measurements.

Biography

John joined NPL in 1984 after receiving a PhD in proportional counter physics from the University of Leicester and carrying out research into pulsed CO₂ lasers at the University of Strathclyde.

Dosimetry projects have included the development of a radiation hard real time dosemeter for industrial irradiation, a cryostat for low temperature irradiations and a calorimeter for industrial linear accelerators. Radioactivity projects have included the development of a three channel liquid scintillation counter, an overload protected pulse amplifier, an ion chamber electrometer and a high pressure proportional counter. He is also closely involved with radioactive gas counting.

He is working on EMRP projects concerned with radioactivity measurements at nuclear power stations and waste repositories. He is a member of a CCRI(II) Working Group designing a new reference standard ionisation chamber for radioactivity measurement.

He has co-authored more than 25 papers that have been published in peer-reviewed journals.

Selected publications

• The use of ionisation chambers for dose rate measurements at industrial irradiation plants
  J. P. Sephton, P. H. G. Sharpe and R. D. H. Chu
  Radiat. Phys. Chem., 76 (3-6), pages 789-792 (2002)
• Dose mapping of a Co60 industrial irradiation plant using an electronic data recording system, static measurements and mathematical modelling
  J. P. Sephton, P. H. G. Sharpe, R. D. H. Chu, K. P. J. O'Hara, F. Abdel-Rehim and A. Abdel Fattah
  Radiat. Phys. Chem., 76 (11-12), pages 1820-1825 (2007)
• The behaviour of alanine dosimeters at temperatures between 100 and 300 K
  P. H. G. Sharpe, J. P. Sephton and C. A. Gouldstone
  Radiat. Phys. Chem., 78 (7-8), pages 477-479 (2009)
• Validation of a new TDCR system at NPL
  L. C. Johansson and J. P. Sephton
  Appl. Radiat. Isot., 68 (7-8), pages 1537-1539 (2010)
• Standardisation of positron-emitters in gas with the NPL primary gas counting system
  M. Marouli, J. C. J. Dean, J. P. Sephton and N. M. Spyrou
  Appl. Radiat. Isot., 68 (7-8), pages 1378-1382 (2010)
• A low noise preamplifier with optoelectronic overload protection for radioactivity measurement
  J. P. Sephton, J. M. Williams, L. C. Johansson and H. C. Phillips
  Appl. Radiat. Isot. (in print)

Contact details

E-mail: john.sephton@npl.co.uk
Tel: 020 8943 6526