Commissioning Characterization and Exploitation of the CERN Shielding Benchmark Facility (CSBF)

One of the main application of the FLUKA Monte Carlo simulation code, is in the design of new beam facilities. An indispensable part of the FLUKA code development process, is benchmarking of predictions of new features against experimental data, for example benchmarking the deep shielding penetration by the particles from high energy proton accelerator operations. For this reason, the CERN High energy AcceleRator Mixed field facility (CHARM) and the CERN Shielding Benchmark Facility (CSBF) were especially designed to obtain experimental data, for deep shielding penetration studies. The main goals of this thesis, are to design and to characterize the CSBF, both by means of FLUKA Monte Carlo simulations of the radiation spectra and their validation by activation experiments. The first prototype of the CSBF was installed, together with the entire shielding of the CHARM facility, during the Long Shut-down 1 (LS1) in 2013/2014. The CHARM facility, has been operating with 24 GeV/c proton beam, since September 2014. A first characterization of the CSBF facility was performed in July 2015, with the activation of bismuth and aluminium detectors in the CSBF. Monte Carlo simulations with the FLUKA code, have been performed to estimate the production yields of bismuth isotopes and sodium for these samples. The production yields estimated by FLUKA Monte Carlo simulations, are compared to the production yields obtained from γ-spectroscopy measurements of the samples taking the beam intensity profile into account. With the experience acquired during the activation campaign in 2015, the CSBF has been significantly upgraded during the extended year-end technical stop at the beginning of 2016. Consequently, in September 2016 there was a second activation campaign with activation of bismuth, aluminium and indium samples that were placed in the CSBF, to characterize the upgraded version of the CSBF. Monte Carlo simulations with the FLUKA code, have been performed to estimate the specific production yields of bismuth, sodium and indium isotopes, for these samples, in the new configuration, and have then been compared to the production yields obtained from γ-spectroscopy measurements of the samples taking the beam intensity profile into account. In parallel to the activation campaign in 2016, there was a series of measurements with a high-pressure ionisation chamber, filled with hydrogen gas at 20 bar, calibrated for measuring ambient dose equivalent rates, in the material test location. By comparing the dose rate measured at different positions, the neutron spectrum averaged attenuation lengths of the various commonly used shielding materials are estimated. The results obtained for the activation campaigns in 2015 and 2016, have shown that the radiation fields in the CSBF, are now well understood and well described by FLUKA. These results can be used as guidelines for similar studies at future proton accelerators and at medical facilities.