Radiation protection study related to the future post-accelerator of the HIE-ISOLDE project

The HIE-ISOLDE project aims at expanding the physics programme of the ISOLDE facility at CERN. In particular, the addition of a superconducting linac will allow the post-acceleration of radioactive ion beams up to 10 MeV/u. However, because of field emission in the superconducting cavities and the possibility of neutron production for ion interactions above the Coulomb barrier, new radiological hazards need to be mitigated. Measurements of dose rate levels close to cavity prototypes were used to determine the intensity of the source of X ray due to field emission for a single cavity. The results were extrapolated to the operation of the 32 cavities that will be installed, and a detailed FLUKA calculation was performed to determine the required shielding to minimise the exposure of personnel present in the ISOLDE experimental hall during operation. FLUKA was also used to determine the maximum ambient dose equivalent rate levels in the accessible part of the hall due to ion beam losses for the envelope energies and intensities

Evaluation of the radiation field and shielding assessment of the experimental area of HIE-ISOLDE

The ISOLDE facility at CERN is one of the first facilities in the world dedicated to the production of the radioactive ion beams (RIB) and during all its working time underwent several upgrades. The goal of the latest proposed upgrade, ‘The High Intensity and Energy ISOLDE’ (HIE-ISOLDE), is to provide a higher performance facility in order to approximate it to the level of the next generation ISOL facilities, like EURISOL. The HIE-ISOLDE aims to improve significantly the quality of the produced RIB and for this reason the increasing of the primary beam power is one of the main objectives of the project. An increase in the nominal beam current (from 2 to 6 μA proton beam intensity) and energy (from 1.4 GeV to 2 GeV) of the primary proton beam will be possible due to the upgrade of CERN’s accelerator infrastructure. The current upgrade means reassessment of the radiation protection and the radiation safety of the facility. However, an evaluation of the existing shielding configuration and access restrictions to the experimental and supply areas must be carried out. Monte Carlo calculations were performed in order to evaluate the radiation protection of the facility as well as radiation shielding assessment and design. The FLUKA—Monte Carlo code was used in this study to calculate the ambient dose rate distribution and particle fluxes in the most important areas, such as the experimental hall of the facility. The results indicate a significant increase in the ambient dose equivalent rate in some areas of the experimental hall when an upgrade configuration of the primary proton beam is considered. Special attention is required for the shielding of the target area once it is the main and very intensive radiation source, especially under the upgrade conditions. In this study, the access points to the beam extraction and beam maintenance areas, such as the mass separator rooms and the high voltage room, are identified as the most sensitive for the experimental hall from the radiation protection point of view

Radiation protection, radiation safety and radiation shielding assessment of hie-isolde

The high intensity and energy ISOLDE (HIE-ISOLDE) project is an upgrade to the existing ISOLDE facility at CERN. The foreseen increase in the nominal intensity and the energy of the primary proton beam of the existing ISOLDE facility aims at increasing the intensity of the produced radioactive ion beams (RIBs). The currently existing ISOLDE facility uses the proton beam from the proton-synchrotron booster with an energy of 1.4 GeV and an intensity up to 2 mA. After upgrade (final stage), the HIE-ISOLDE facility is supposed to run at an energy up to 2 GeV and an intensity up to 4 mA. The fore-seen upgrade imposes constrains, from the radiation protection and the radiation safety point of view, to the existing experi-mental and supply areas. Taking into account the upgraded energy and intensity of the primary proton beam, a new assessment of the radiation protection and radiation safety of the HIE-ISOLDE facility is necessary. Special attention must be devoted to the shielding assessment of the beam dumps and of the experimental areas. In this work the state-of-the-art Monte Carlo particle transport simulation program FLUKAwas used to perform the computation of the ambient dose equiva-lent rate distribution and of the particle fluxes in the projected HIE-ISOLDE facility (taking into account the upgrade nominal primary proton beam energy and intensity) and the shielding assessment of the facility, with the aim of identifying in the existing facility (ISOLDE) the critical areas and locations where new or reinforced shielding may be necessary. The conse-quences of the upgraded proton beam parameters on the operational radiation protection of the facility were studied

(Im-)possible ISOL beams

Refractory elements, i.e. elements with very high melting point and low vapor pressure, cannot be released in atomic form from an ISOL target. Therefore most of these elements are presently not available as ISOL beams. However, when reactive gases are introduced into the target, they may form volatile compounds with the refractory elements, allowing for an easier transport to the ion source. Particularly useful are high-temperature stable fluorides and oxides. By these chemical evaporation methods so far ISOL beams of the refractory elements C, Zr, Hf and Ta have been produced. We discuss how ISOL beams of B, Ti, Nb, Mo, Tc, Ru, W, Re, Os and Ir could be produced in a similar way