[en] Preliminary radiation shielding specifications are presented here for the 3 GeV BOOMERANG Australian synchrotron light source project. At this time the bulk shield walls for the storage ring and injection system (100 MeV Linac and 3 GeV Booster) are considered for siting purposes

[en] The calculations presented compare the different performances of the three Monte Carlo codes PENELOPE-1999, MCNP-4C and PITS, for the evaluation of Dose profiles from a 25 keV electron micro-beam traversing individual cells. The overall model of a cell is a water cylinder equivalent for the three codes but with a different internal scoring geometry: hollow cylinders for PENELOPE and MCNP, whereas spheres are used for the PITS code. A cylindrical cell geometry with scoring volumes with the shape of hollow cylinders was initially selected for PENELOPE and MCNP because of its superior simulation of the actual shape and dimensions of a cell and for its improved computer-time efficiency if compared to spherical internal volumes. Some of the transfer points and energy transfer that constitute a radiation track may actually fall in the space between spheres, that would be outside the spherical scoring volume. This internal geometry, along with the PENELOPE algorithm, drastically reduced the computer time when using this code if comparing with event-by-event Monte Carlo codes like PITS. This preliminary work has been important to address dosimetric estimates at low electron energies. It demonstrates that codes like PENELOPE can be used for Dose evaluation, even with such small geometries and energies involved, which are far below the normal use for which the code was created. Further work (initiated in Summer 2002) is still needed however, to create a user-code for PENELOPE that allows uniform comparison of exact cell geometries, integral volumes and also microdosimetric scoring quantities, a field where track-structure codes like PITS, written for this purpose, are believed to be superior

[en] Accelerator-produced radiation levels at the perimeter of the Ernest Orlando Lawrence Berkeley National Laboratory (the Berkeley Laboratory) reached a maximum in 1959. Neutrons produced by the Bevatron were the dominant component of the radiation field. Radiation levels were estimated from measurements of total neutron fluence and reported in units of dose equivalent (rem). Accurate conversion from total fluence to dose equivalent demands knowledge of both the energy spectrum of accelerator-produced neutrons and the appropriate conversion coefficient functions for different irradiation geometries. At that time (circa 1960), such information was limited, and it was necessary to use judgment in the interpretation of measured data. The Health Physics Group of the Berkeley Laboratory used the best data then available and, as a matter of policy, reported the most conservative (largest) values of dose equivalent supported by their data. Since the early sixties, significant improvements in the information required to compute dose equivalent, particularly in the case of conversion coefficients, have been reported in the scientific literature. This paper reinterprets the older neutron measurements using the best conversion coefficient data available today. It is concluded that the dose equivalents reported in the early sixties would be reduced by at least a factor of two using current methods of analysis

[en] The calculations presented compare the performances of two Monte Carlo codes used for the estimation of microdosimetric quantities: Positive Ion Track Structure code (PITS) and a main user-code based on the PENetration and Energy LOss of Positrons and Electrons code (PENELOPE-2000). Event by event track-structure codes like PITS are considered superior for microdosimetric applications and they are written for this purpose. PITS tracks electrons in water down to 10 eV. PENELOPE is one of the few, among widely available general purpose codes, that can simulate random electron-photon showers in any material for energies from 100eV to 1GeV. The model for the comparison is a large water cylinder with an internal scoring geometry of spheres with 1(micro)m diameter where the scoring quantities are calculated. The source is a 25 keV electron pencil beam impinging normally on the sphere surface. This work shows only the lineal energy as a function of position and lineal energy spectra at a given location since for microdosimetry and biology applications, and for discussion of radiation quality in general, these answers are more appropriate. The computed PENELOPE results are in agreement with those obtained with the PITS code and previously published in this journal. This paper demonstrates PENELOPE's usefulness at low energies and for small geometries. What is still needed are experimental results to confirm these analyses

[en] There are more and more third-generation synchrotron radiation (SR) facilities in the world that utilize low emittance electron (or positron) beam circulating in a storage ring to generate synchrotron light for various types of experiments. A storage ring based SR facility consists of an injector, a storage ring, and many SR beamlines. When compared to other types of accelerator facilities, the design and practices for radiation safety of storage ring and SR beamlines are unique to SR facilities. Unlike many other accelerator facilities, the storage ring and beamlines of a SR facility are generally above ground with users and workers occupying the experimental floor frequently. The users are generally non-radiation workers and do not wear dosimeters, though basic facility safety training is required. Thus, the shielding design typically aims for an annual dose limit of 100 mrem over 2000 h without the need for administrative control for radiation hazards. On the other hand, for operational and cost considerations, the concrete ring wall (both lateral and ratchet walls) is often desired to be no more than a few feet thick (with an even thinner roof). Most SR facilities have similar operation modes and beam parameters (both injection and stored) for storage ring and SR beamlines. The facility typically operates almost full year with one-month start-up period, 10-month science program for experiments (with short accelerator physics studies and routine maintenance during the period of science program), and a month-long shutdown period. A typical operational mode for science program consists of long periods of circulating stored beam (which decays with a lifetime in tens of hours), interposed with short injection events (in minutes) to fill the stored current. The stored beam energy ranges from a few hundreds MeV to 10 GeV with a low injection beam power (generally less than 10 watts). The injection beam energy can be the same as, or lower than, the stored beam energy. However, the stored beam power (product of stored beam current and energy), which is one of the key parameters in determining the production and hazards of gas bremsstrahlung (GB) and SR in beamlines, is quite high (MW to GW levels). Because of the similar design and dose control goals as well as similar beam parameters and operation modes among SR facilities, it is highly desired and useful for SR accelerator community to have the design and practices for radiation safety of the storage ring and SR beamlines that are professionally sound and consistent. On the other hand, it can be understood that a SR facility may need to have its specific policies and practices, due to its own technical, practical, economical and/or political considerations

[en] This work compares the design and practices for radiation safety among the five SR facilities: two low-energy sources (ALS and NSLS), one medium-energy source (SSRL), and two high-energy sources (APS and SPring8). The issues addressed in this comparison are (1) safety interlock systems for ring and beamlines, (2) beam loss scenarios and shielding design for storage ring, (3) beam loss scenarios and shielding design for SR beamlines, which cover synchrotron radiation and gas Bremsstrahlung issues, (4) radiation monitors for ring and beamlines, (5) safety control issues for top-up operation, and (6) operational issues. The goals of this work are to (1) provide a framework of radiation safety issues that need to, or may, be considered in the design and operation of a SR facility, and (2) develop sound policies and practices for radiation safety of SR facilities, when it is needed and practical to do so