The President-Elect's Message

It is my great pleasure to inform you that the Accelerator Section's nominee for the G. William Morgan Lecturer Award has been approved by the Health Physics Society (HPS) Emeritus Committee. The Accelerator Section’s Morgan Lecturer for this year is Dr. Graham R. Stevenson, senior physicist (retired) with the Radiation Protection Group at the European Laboratory for Particle Physics (CERN), Geneva, Switzerland. Dr. Stevenson is one of the best known and internationally renowned health physicists in the field of high-energy accelerators. His outstanding contributions cover a period of about four decades. His research is described in several hundred publications in the scientific literature and laboratory reports. He is also the co-author of two books.

Dr. Stevenson started his scientific career as a research assistant in the Cosmic Ray Group at Bristol University studying cascades induced by very high-energy cosmic rays. He then accepted an appointment as a member of the Neutron Group at the headquarters of the Radiological Protection Service of the United Kingdom at Sutton, Surrey, in 1963. He was involved in studies of the use of nuclear track emulsion type A (NTA) film in neutron personal dosimetry, low-energy neutron dosimetry, and shielding. From 1966 to 1971, Dr. Stevenson served as a senior scientific officer in the Radiological Protection Group of the Rutherford Laboratory. During this period, his work included research in the fields of neutron spectrometry, accelerator shielding, dose equivalent estimation, and the production of induced activity from particle accelerators. From 1969 to 1971, he held a concurrent appointment as lecturer in the Radiation Physics Department at the University of Surrey.

From 1971 until his retirement in 2003, Dr. Stevenson worked at CERN in Geneva as a senior physicist with the Radiation Protection Group. He was engaged in the radiological design of the 450-GeV Super Proton Synchrotron (SPS) in the 1970s and more recently was involved in the design of the Large Electron Positron Collider (LEP). For the final 15 years, he worked on the radiological hazards associated with CERN's Large Hadron Collider (LHC), the 7-TeV proton-proton collider being installed in the LEP tunnel. He was also a member of the project group formed to build the target station for the CERN Neutrinos to Gran Sasso (CNGS) project, designed to send neutrinos from CERN in Geneva to the Gran Sasso Laboratory in Italy. His research interests included hadronic cascade development from an experimental and theoretical viewpoint, skyshine, muon production and shielding, dosimetry, and production of induced radioactivity.

Dr. Stevenson is a long-time member of the UK Society for Radiological Protection and the French Société Française de Radioprotection. He served on the Task Group on External Radiation of Committee 3 of the International Commission on Radiological Protection (ICRP) which led to Publication 51 in 1987. He has been consulted to assist in radiation protection issues of major high-energy accelerator projects in the US and in Japan. Most recently, he served on the US Department of Energy (DOE) committee reviewing Fermilab's NuMI Project that sends neutrinos from Chicago to the Soudan mine facility in Minnesota.

Graham will talk on the role of approximations and empiricism in predicting parameters of radiological importance at accelerator facilities. An abstract of his talk follows.

Modern computer technology has enabled the creation of programs that simulate the transport of radiation of a nearly infinite number of particle types in a nearly infinite number of geometrical configurations, thus enabling one to predict (sometimes with a nearly infinite degree of accuracy) the doses to operators, users, maintenance personnel, components, and the environment, where these doses are due to the operation of particle accelerators. However, these programs require significant knowledge, experience, investment of time, and dedication on the part of the user, even if the hardware required to run these programs is available in the offices of most health physicists. In many situations, predictions of sufficient accuracy can be obtained by using simple approximations or empirical formulae to describe the real physical situation.

A number of these simple techniques as applied to the prediction of the radioactivity induced at accelerator facilities and the determination of shielding against the electromagnetic, hadron, and muon components of the radiation field are described in this presentation. The selection of these examples is not exhaustive but based on the experience of the author over 30 years of designing accelerators. Their benefits are considerable, but in certain situations their use can lead to considerable errors in the predictions, and in consequence Monte-Carlo simulation programs such as FLUKA, MCNPX, and MARS are essential to describe the radiation field. Examples are given to illustrate when it was necessary to use these more complex techniques at CERN and elsewhere to design facilities within acceptable norms.

As our section president noted in his column, there will once again be a special session of the Accelerator Section at the HPS meeting in Washington, D.C. The session is scheduled from 8:15 to 11:45 AM and from 2:30 to 5:00 PM on Tuesday, July 13. The schedule for the presentations is listed at the HPS website (page 24).

I look forward to seeing you all in Washington, DC.