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[en] Measurements were performed of six reference neutron spectra at the Nuclear Research Institute, Rez. The reference spectra are produced by means of a 252Cf source moderated with iron and polyethylene layers. A detailed description is given of the Bonner spectrometer used in the measurements. The results are presented in a number of tables and show a good agreement with results of similar measurements carried out in 1988. (A.K.) 5 figs., 15 tabs., 11 refs
[en] The spherical moderator system, generally known as Bonner spheres, is a well known instrument used for low intensity neutron spectra measurement. The spectrometric method has been promoted by T.W.Bonner in the 60.s. The present experimental setup developed at INR is formed by 7 HD polyethylene shells, from 60 to 433 mm external diameter, respectively from 4 to 191 mm thick covering a 5 cm diameter spherical BF3 filled neutron detector with isotropic response. It was a remarkable effort to find appropriate technical solutions for polyethylene parts manufacturing. The response matrix has been obtained by MCNP computation. The calibration procedure uses a Pu-Be fast neutron source and shadow cone measurements. For spectrum unfolding the SAND II code, usually used for multi-foil activation techniques, has been adapted. For signal processing a pulse mode electronic chain has been installed. The Bonner spheres spectrometer is now ready for use. (authors)
[en] Neutron spectrometric measurements in the positive ion accelerators is a mandatory requirement to assess the neutron doses accurately and thereby controlling the radiation hazards associated with the radiation fields. Bonner sphere based measurements using passive dosimeters is one of the well-established methodologies of measurement. This paper presents a methodology and testing of a single sphere (with multi-detectors) spectrometer designed and fabricated in-house. This system is portable and convenient for measurements in the fields
[en] Highlights: • The BSS, WENDI II, LINUS and LUPIN agree amongst them and with the FLUKA simulations within one sigma of uncertainty. • The LB6411 underestimates up to 35% as compared to FLUKA and the extended rem counters. • The PRESCILA overestimates the high-energy component and underestimate the evaporation part. Therefore, the PRESCILA overestimates the H*(10) on the CT and underestimates it on the IT. • Concerning the two TEPC, they agree within their range of uncertainty for all positions. The agreement with FLUKA is satisfactory on the CT/CS but the TEPCs show underestimation on the IT. This paper discusses an instrument intercomparison performed in the high-energy field at the CERF facility at CERN between 2015 and 2017 (October 2015, May 2016, November 2016 and June 2017). Measurements were performed in several reference exposure locations with the CERN extended-range Bonner Sphere Spectrometer (BSS), a Berthold LB4611, the LINUS rem counter from CERN, the LUPIN rem counter from ELSE Nuclear, the FHT 762 Wide Energy Neutron Detection Instrument (WENDI-II) from Thermo Scientific, the LUDLUM MODEL 42–41 PRESCILA NEUTRON PROBE and two models of Tissue-equivalent proportional counters (TEPCs) from Far West Technologies. All results are compared with the latest FLUKA reference values from simulations performed in 2017.
[en] Accelerator-based neutron beams are becoming popular tools for material testing, radiation hardness and soft errors studies. The characterization of these beams in terms of dosimetric and spectrometric quantities is a challenging task, mainly due to their wide energy interval (from thermal up to hundreds MeV) and, in certain facilities like VESUVIO - ISIS (RAL, UK), to their small dimension (few cm in radius). Extended Range Bonner Sphere Spectrometers (ERBSS) would be a valuable tool, due to their wide energy range, good photon discrimination and possibility to choose among different central detectors according to the intensity, photon component and time structure of the field. Nevertheless, the non-uniform irradiation of the spheres could lead to important systematic errors. With the aim of bringing the advantages of ERBSS into the characterization of collimated beams, a dedicated study was performed using the VESUVIO spallation-based collimated beam at ISIS (Rutherford Appleton Laboratory, Oxford). Here a 3.21 cm radius collimated beam was characterized using a Dysprosium activation foil-based ERBSS whose response matrix was recalculated for this specific beam diameter. Besides the results of the experimental campaign, this paper presents the calculation of the response matrix and its dependence on the beam dimension.
[en] A set-up intended to replicate neutron spectra encountered at workplaces is presented. Such a facility can provide means of calibrating dosemeters in spectral conditions similar to those of their use for radiation protection purposes. Results of a computational approach are compared with Bonner Multisphere Spectrometer measurements. (author)
[en] A qualitative estimation of several neutron spectra unfolding methods using data obtained with a multispheric spectrometer is presented. An algorithm is proposed using a multiparametric regularizing functional. To unfold the spectra by the algorithm mockup experiments have been conducted. The results show that if the original data are known with the accuracy of 3%, therefore the spectra unfolding errors are not more than 20-30%
[en] A new computer code, NEWSPEC, is in development at the University of Arkansas. The NEWSPEC code allows a user to unfold, fold, rebin, display, and manipulate neutron spectra as applied to Bonner sphere measurements. The SPUNIT unfolding algorithm, a new rebinning algorithm, and the graphical capabilities of Microsoft (MS) Windows and MS Excel are utilized to perform these operations. The computer platform for NEWSPEC is a personal computer (PC) running MS Windows 3.x or Win95, while the code is written in MS Visual Basic (VB) and MS VB for Applications (VBA) under Excel. One of the most useful attributes of the NEWSPEC software is the link to Excel allowing additional manipulation of program output or creation of program input