Radiation protection at CERN

This paper gives a brief overview of the general principles of radiation protection legislation; explains radiological quantities and units, including some basic facts about radioactivity and the biological effects of radiation; and gives an overview of the classification of radiological areas at CERN, radiation fields at high-energy accelerators, and the radiation monitoring system used at CERN. A short section addresses the ALARA approach used at CERN.Comment: 22 pages, contribution to the CAS - CERN Accelerator School: Course on High Power Hadron Machines; 24 May - 2 Jun 2011, Bilbao, Spai

Commissioning of the CNGS Extraction in SPS LSS4

The CNGS project (CERN Neutrino to Gran Sasso) aims at directly detecting νμ - Î½Ï oscillations. For this purpose an intense νμ beam is generated at CERN and directed towards LNGS (Laboratori Nazionali del Gran Sasso) in Italy, about 730 km from CERN. The neutrinos are generated from the decay of pions and kaons which are produced by 400 GeV protons hitting a graphite target. The protons are extracted from the SPS straight section 4 (LSS4) in two 10.5 ï­s batches, nominally 2.4 Ñ 1013 protons each, at an interval of 50 ms. The high intensity extracted beam can cause damage to equipment if lost in an uncontrolled way, with the extraction elements particularly at risk. In addition, the beam losses at extraction must be very well controlled to avoid unacceptably high levels of radiation. To guarantee safe operation and limit radiation, the LSS4 extraction system was thoroughly commissioned with beam during the CNGS commissioning in summer 2006. The obtained results in terms of aperture in the extraction channel, longitudinal loss patterns, extraction losses and radiation during nominal operation are summarised in this note

New radiation protection calibration facility at CERN

The CERN radiation protection group has designed a new state-of-the-art calibration laboratory to replace the present facility, which is >20 y old. The new laboratory, presently under construction, will be equipped with neutron and gamma sources, as well as an X-ray generator and a beta irradiator. The present work describes the project to design the facility, including the facility placement criteria, the ‘point-zero' measurements and the shielding study performed via FLUKA Monte Carlo simulation

A desorption model for the code SOLIDUSS and its experimental benchmarking

Acknowledgements The experiments reported in this document could be carried out thanks to the assistance of numerous colleagues at CERN. In particular, the authors would like to express their gratitude to Guilherme Correia, Karl Johnston, Juliana Schell, Sebastian Rothe, Jochen Ballof, Thierry Stora, Joachim Vollaire, Reiner Geyer, Yann Pira, Lucie Vitkova, Alexandre Dorsival, Nabil Menaa, Aurore Boscher, Giuseppe Prete, Renaud Charousset and Miranda Van Stenis.The code SOLIDUSS is a Monte Carlo based solid-state diffusion software for radiation protection. It was developed to accurately estimate the amount of radionuclides that could escape activated material affected by an accidental fire. A desorption model based on the computation of the desorption probability of those radionuclides reaching the surface of an object was introduced to upgrade the software, proven to be a significant improvement with respect to earlier stages of the code. A set of experiments was performed at CERN to estimate the out-diffusion of radionuclides from activated materials typically used in accelerator environments when exposed to high temperatures. In particular, a 49.3 µm thick Cu foil containing 60Co and a 94 µm thick Al foil with 22Na were exposed to approximately 1000 °C and 600 °C respectively for different time periods. Out-diffusion fractions of 1.5 5.5% for 60Co after 5 h and 22.5 3.1% for 22Na after 4 h were obtained. A set of SOLIDUSS simulations was carried out replicating the experimental setup and using literature diffusion and desorption activation parameters. The results obtained are in good agreement with the experimental data within error bars. A high sensitivity of the simulation results to changes in the input parameters was observed

Benchmarking the Particle Background in the Large Hadron Collider Experiments

Background benchmarking measurements have been made to check the low-energy processes which will contribute via nuclear reactions to the radiation background in the LHC experiments at CERN. Previously these processes were only evaluated with Monte Carlo simulations, estimated to be reliable within an uncertainty factor of 2.5. Measurements were carried out in an experimental set-up comparable to the shielding of ATLAS, one of the general-purpose experiments at LHC. The absolute yield and spectral measurements of photons and neutrons emanating from the final stages of the hadronic showers were made with a Bi_4Ge_3O_{12} (BGO) detector. The particle transport code FLUKA was used for detailed simulations. Comparison between measurements and simulations show that they agree within 20% and hence the uncertainty factor resulting from the shower processes can be reduced to a factor of 1.2

Prompt, Activation and Background radiation studies for the HiRadMat facility of CERN/SPS

HiRadMat (High Irradiation to Materials) is a new facility under construction at CERN designed to provide high intensity beams in order to test raw materials and accelerator components with respect to the effect caused by the impact of pulsed, high intensity particle beams. In the present note detailed Monte-Carlo simulations studies using the FLUKA code have been performed for prompt dose equivalent rates in the corresponding tunnel structure as well as surface buildings, residual dose rates (after seven cooling times) for an exemplary irradiation of an LHC collimator, as well as for the remnant background dose in the tunnels after one year of operating the facility. Moreover, calculations of the possible activation of the cooling water in the dump have been performed. The scope of this document includes the operational aspects of the facility but does not cover experiment specific hazards or waste issues as they need to be studied on an individual basis

Integration Studies and Beam Physics for the Project of the NA60+ Heavy-Ion Experiment at CERN

NA60+ is a fixed target experiment proposed in the framework of the Physics Beyond Colliders programme at CERN. It aims to precisely measure the hard and electromagnetic probes in nuclear collisions. Initially proposed for the underground cavern ECN3 with very high beam intensities, the experiment now foresees a location in the EHN1 surface hall which was shown to have a limited impact on the physics performance in spite of a significant reduction of beam intensity and detector size. The potential installation and operation of the experiment with the ion beams from the Super Proton Synchrotron (SPS) has been examined regarding detector integration, beam physics, radiation protection and shielding requirements. The integration of the experiment is considered feasible and would require a significant reconfiguration of the zone in regard to shielding and layout. The first estimate for the integration cost is 1.4 MCHF

A facility to Search for Hidden Particles (SHiP) at the CERN SPS

A new general purpose fixed target facility is proposed at the CERN SPS accelerator which is aimed at exploring the domain of hidden particles and make measurements with tau neutrinos. Hidden particles are predicted by a large number of models beyond the Standard Model. The high intensity of the SPS 400~GeV beam allows probing a wide variety of models containing light long-lived exotic particles with masses below ${\cal O}$(10)~GeV/c$^2$, including very weakly interacting low-energy SUSY states. The experimental programme of the proposed facility is capable of being extended in the future, e.g. to include direct searches for Dark Matter and Lepton Flavour Violation.Comment: Technical Proposa

Measurement of the muon flux from 400 GeV/c protons interacting in a thick molybdenum/tungsten target

The SHiP experiment is proposed to search for very weakly interacting particles beyond the Standard Model which are produced in a 400 GeV/c proton beam dump at the CERN SPS. About 1011 muons per spill will be produced in the dump. To design the experiment such that the muon-induced background is minimized, a precise knowledge of the muon spectrum is required. To validate the muon flux generated by our Pythia and GEANT4 based Monte Carlo simulation (FairShip), we have measured the muon flux emanating from a SHiP-like target at the SPS. This target, consisting of 13 interaction lengths of slabs of molybdenum and tungsten, followed by a 2.4 m iron hadron absorber was placed in the H4 400 GeV/c proton beam line. To identify muons and to measure the momentum spectrum, a spectrometer instrumented with drift tubes and a muon tagger were used. During a 3-week period a dataset for analysis corresponding to (3.27±0.07) × 1011 protons on target was recorded. This amounts to approximatively 1% of a SHiP spill