Lateral shield

Abstract: Neutron energy spectra were measured behind the lateral shield of the CERF (CERN-EU High Energy Reference Field) facility at CERN with a 120 GeV/c positive hadron beam (a mixture of mainly protons and pions) on a cylindrical copper target (7-cm diameter by 50-cm long). An NE213 organic liquid scintillator (12.7-cm diameter by 12.7-cm long) was located at various longitudinal positions behind shields of 80- and 160-cm thick concrete and 40-cm thick iron. The measurement locations cover an angular range with respect to the beam axis between 13 and 133°. Neutron energy spectra in the energy range between 32 MeV and 380 MeV were obtained by unfolding the measured pulse height spectra with the detector response functions which have been verified in the neutron energy range up to 380 MeV in separate experiments. Since the source term and experimental geometry in this experiment are well characterized and simple and results are given in the form of energy spectra, these experimental results are very useful as benchmark data to check the accuracies of simulation codes and nuclear data. Monte Carlo simulations of the experimental set up were performed with the FLUKA, MARS and PHITS codes. Simulated spectra for the 80-cm thick concrete often agree within the experimental uncertainties. On the other hand, for the 160-cm thick concrete and iron shield differences are generally larger than the experimental uncertainties, yet within a factor of 2. Based on source term simulations, observed discrepancies among simulations of spectra outside the shield can be partially explained by differences in the high-energy hadron production in the copper target.

Abstract: Shielded dental contact marker has a thin, supple support layer which carries thereon a thin marker layer, such as carbon. A thin, hard protective shield layer of wax overlies the carbon layer. The shield layer is of such thickness and appropriate density as to compensate for periodontal ligament compression so that only forceful dental contact will penetrate the protective shield layer and only those points of forceful contact pressure between teeth are marked. The wax layer is sufficiently thin and hard that lateral shield layer flow does not smear or distort the mark on the dental surface.

Abstract: CYSP-BEAM is a directional neutron spectrometer formed by a thick polyethylene cylindrical collimator followed by a sensitive capsule that contains several active thermal neutron detectors located at different depths along the cylindrical axis. Due to a thick lateral shield made of polyethylene and borated rubber, only neutrons from the direction identified by the collimating aperture can reach the internal detectors. As the response function of the internal detectors tend to peak at increasing energies as the detector depth increases, the device has spectrometric properties. This type of moderated spectrometer, whose prototype was the CYSP (CYlindrical SPectrometer), is capable to combine the functionalities of Bonner Spheres in a single device, thus requiring only one exposure to measure all the energy components of the incident beam, from thermal up to GeV neutrons. The neutron spectrum is obtained via few-channel unfolding methods. With respect to the original CYSP, the new CYSP-BEAM device is optimized to operate in the direct intense beam of neutron producing installations, such as large scale neutron science facilities. Compared with CYSP, CYSP-BEAM has narrower collimating aperture and the internal detectors have sensibility a factor 100 lower. Its response matrix was simulated using MCNPX. This paper describes the new device focusing on the internal detectors, the response matrix and the test measurement performed using the 14 MeV beam produced at the ENEA Frascati Neutron Generator (FNG).