Abstracts of Accelerator Session Presentations and Posters
For those readers who were not able to attend the 49th Annual Meeting of the Health Physics Society in Washington, DC, in July, we've once again provided several abstracts of the presentations.
L. S. Walker and J. C. Liu
The ANSI N43 committee established a writing committee to rewrite the ANSI N43.1 accelerator safety standard in 1994. James Liu and Scott Walker were appointed as co-chairs. Compared to the old standard, the new standard is aimed at having a broader application, up-to-date requirements, and recommendations for best practices. The new standard uses a hazard-based graded approach to address radiation safety programs for accelerators with various energies, beam currents, and applications (excluding medical accelerators which are covered by another standard). Thus the standard fulfills the goal of the committee to prepare a standard with unlimited application to industrial and research accelerators. The standard is largely complete with chapters as follows: 1) scope, 2) definitions, 3) radiation safety program (facility safety program, radiation safety planning, organizational considerations, safety assessment, review, and performance evaluation), 4) radiation safety system (prompt radiation, safety system features, reliability and fail-safety, tamper resistance, quality control, configuration control, adventitious production of radiation, and induced radioactivity), 5) personnel access control system (including graded approach, postings, barriers, beam-inhibiting devices and interlocks), 6) radiation control system (passive shielding and active systems), 7) accelerator operation (including readiness reviews, maintenance and testing, bypasses and deviation from procedure, operating practices, emergencies), 8) operational health physics, and 9) training. The document also has appendices regarding how to determine the safety and operations envelope, guidance for computer-based access control systems, and radiation measurements at accelerators.
The Duke Free Electron Laser Laboratory (DFELL) is currently being upgraded by adding a booster synchrotron to an existing linac and storage ring. The injection energy will be increased from 270 MeV to 1.2 GeV and the injection power may increase by as much as a factor of 200. DFELL has the capacity to produce high-intensity photon beams by back-scattering UV photons from its wiggler off energetic electrons in the storage ring. In the current configuration pencil gamma beams with up to 1.0E+6 photons per second and energies between 2 and 20 MeV have been generated. After the upgrade, the upper gamma energy limit will be 225 MeV, with expected intensities of 1.0E+8 to 1.0E+9 photons per second. When the energy of the photon back-scattered off an electron exceeds 50 MeV, that electron loses too much energy to be recirculated in the ring and will be therefore lost. This implies that production of gamma beams above 50 MeV will require continuous injection, call the "top-off" mode.
The Fermilab project Neutrinos at the Main Injector (NuMI) will try to answer intriguing questions about mass and flavor oscillation of neutrinos. Neutrinos produced at Fermilab will be aimed at a detector in the Soudan mine in northern Minnesota. The target, magnetically focusing horns, a decay pipe, and a hadron absorber are water-cooled devices that will help in focusing the primary beam that will eventually produce the neutrinos. The calculations of the induced radioactivity, hydrogen gas evolution, shielding, and other radiological issues associated with these systems are described.