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Secondary Radiation Production and Shielding at Proton Therapy Facilities
Published in Harald Paganetti, Proton Therapy Physics, 2018
Radiation transmission can be approximated by an exponential function over a limited range of thickness [5]. The attenuation length is defined as the distance traveled in the medium through which the intensity of the radiation is reduced to 37% of its original value. The neutron attenuation length, λ, is given by
Measurement and simulations of high-energy neutrons through a various thickness of concrete and steel shields using activation detectors at CHARM and CSBF
Published in Journal of Nuclear Science and Technology, 2023
Noriaki Nakao, Toshiya Sanami, Tsuyoshi Kajimoto, Hiroshi Yashima, Robert Froeschl, Davide Bozzato, Elpida Iliopoulou, Angelo Infantino, Eunji Lee, Takahiro Oyama, Masayuki Hagiwara, Seiji Nagaguro, Tetsuro Matsumoto, Akihiko Masuda, Yoshitomo Uwamino, Arnaud Devienne, Fabio Pozzi, Marco Tisi, Tommaso Lorenzon, Nabil Menaa, Heinz Vincke, Stefan Roesler, Markus Brugger
where J [W] is the beam loss power at the source point, H1 [(mSv/h) cm2/W] is dose rate at 1-cm distance for a unit beam-loss power, r [cm] is the distance between the beam-loss point and the estimation point, and d [cm] is the effective shield thickness. ρ [g/cm3] is the density of the shielding material and λ [g/cm2] is the attenuation length. Tesch et al. also proposed the equation of the dose rate at 90° direction for the point beam loss [2], which is almost identical to the Eq. (1), where Hcasc corresponds to H1. Where, the Hcasc parameters were summarized based on the experimental data for neutron yields from various targets that were bombarded with protons of energies up to about 1 GeV, and the λ values based on the experiment were also summarized for the lateral concrete shield [2].
Effect of fluorescent dyes on the scintillation efficiency, improved light yield and radiation hardness of polystyrene-based plastic scintillator: a comparative study
Published in Radiation Effects and Defects in Solids, 2023
Lizbeth Alex, Rajesh Paulraj, Mohit Tyagi
Blue emitting plastic phosphors are composed by the addition of scintillating dyes to the amorphous transparent-to-visible light polymer host (5), requiring an aromatic structure for the fluorescence process. Viscous liquids such as styrene, vinyltoulene polymerize on heating to form thermoplastic polymers (6). The weak fluorescence efficiency and the short attenuation length for the scintillating light do not make the polymer an effective scintillator. Only about 3% of energy is converted into photons for molecules with aromatic rings (7) and the emission wavelength of these photons does not match the quantum efficiency of the photomultiplier tubes. It is known from the literature that a concentration of 1% by weight of the fluor increases the attenuation length of the photons as well as the light yield of the scintillator (8, 9). The properties such as high solubility, photostable, chemically stable, temperature tolerant and cost effective should be taken into consideration while selecting the fluors in designing the plastic scintillator (9).
Attenuation length of high energy neutrons through a thick concrete shield measured by activation detectors at CHARM
Published in Journal of Nuclear Science and Technology, 2020
Noriaki Nakao, Toshiya Sanami, Tsuyoshi Kajimoto, Elpida Iliopoulou, Robert Froeschl, Markus Brugger, Stefan Roesler, Angelo Infantino
From the attenuation curves of the simulated radionuclide production rates, the attenuation lengths at the corresponding depth of concrete were estimated with the production rates at two points at 40-cm depth intervals. The uncertainty was less than 1% due to the statistical errors in each depth of the simulation. The results were compared for different radionuclides and with those of neutron fluxes above 20 MeV (see Figure 13). After penetration depths of 100 cm, all attenuation lengths coincided and gradually decreased from 120 to 112 g/cm2 as the concrete thickness increased from 100 to 700 cm. This indicates that the attenuation lengths beyond 100-cm depth are independent of the threshold energies of reaction because of the spectral equilibrium state in a deep concrete region. Therefore, attenuation length of high-energy neutron flux in a deep concrete region is equivalent to that estimated from the attenuation profiles of radionuclide production rates.