The application of a CAEN DT5730 digitizer unit for fast neutron metrology and applications has been explored. The standard methods implemented to obtain a calibrated light output parameter from the integrated anode output has a high sensitivity to the selection of pulse integration time. We report on measurements made at the n-lab within the Department of Physics at the University of Cape Town which explored alternative approaches to determining the light output parameter with the digital acquisition system, aiming for a high degree of consistency.

The accurate knowledge of the beam energy is of first importance in most applications using ion beams delivered by electrostatic accelerators. Regular beam energy calibration is thus required. The standard procedure is to use neutron thresholds and well known gamma-ray resonances. However, only a few calibration points are available between 2 MeV and 4 MeV despite the need of such beam energies, for instance, for nuclear reaction analyses. In this work, the suitability of Al-27(p,gamma)Si-28 and Sc-45(p,n)Ti-45 resonances has been studied in this specific energy range by comparison with well-established calibration energies. The methodology used for the experiments and data treatment is fully detailed. The usefulness of these resonances is shown through several calibration campaigns that led to a complete energy calibration of two accelerator based facilities from 500 keV up to 4 MeV.

A neutron spectrometry campaign was carried out in the AMANDE accelerator control room. These measurements had several objectives, one of which was to verify the possibility of determining, with the HERMEIS Bonner sphere system, very low fluence and ambient dose equivalent rates. These measurements were also expected to provide comparison values with calculations, performed with MCNPX 2.6.0, used for modeling the whole facility and to verify the radiological zoning implemented. Neutrons of 3.3 MeV then 15 MeV were produced in the experimental hall of AMANDE and measurements were made in the control room, behind a 40 cm thick concrete wall. The ambient dose equivalent rates derived from the measured spectra are respectively of the order of 0.2 and 10 μSv/h, which are in agreement with a LB6411 surveymeter data also involved.

The cross section of the Tb-159(n, gamma)Tb-160 reaction was measured in four mono-energetic neutron fields of energy 3.7, 4.3, 5.4, and 6.85 MeV, respectively, with the activation technique applied to metal discs of natural composition. To ensure an acceptable precision of the results all major sources of uncertainties were taken into account. Calculations of detector efficiency, incident neutron spectrum and correction factors were performed with the Monte Carlo code (MCNPX), whereas theoretical excitation functions were calculated with the TALYS-1.2 code and compared to the experimental cross section values. This paper presents both measurements and calculation leading to the cross section values. (C) 2015 Elsevier B.V. All rights reserved.

The variation in the response of instruments with neutron energy has to be determined in well-characterized monoenergetic neutron fields. The quantities associated with these fields are the neutron fluence and the mean energy of the monoenergetic neutron peak needed to determine the related dosimetric quantities. At the IRSN AMANDE facility, the reference measurement standard for neutron fluence is based on a long counter calibrated in the IRSN reference Cf-252 neutron field. In this paper, the final characterization of this device is presented as well as the method used to determine the reference fluence at the calibration point in monoenergetic neutron fields.

To ensure the validity of their national standards, National Metrology Institutes, NMIs, participate regularly in international comparisons. In the area of neutron metrology, Section III of the Consultative Committee for Ionizing Radiation is in charge of the organization of these comparisons. From September 2011 to October 2012, the eleventh key comparison, named CCRI(III)-K11, took place at the AMANDE facility of the LNE-IRSN, in France. Participants from nine NMIs came with their own primary reference instruments, or instruments traceable to primary standards, with the aim of determining the neutron fluence, at 1 m distance from the target in vacuum, per monitor count at four monoenergetic neutron fields: 27 keV, 565 keV, 2.5 MeV and 17 MeV.The key comparison reference values (KCRV) were evaluated as the weighted mean values of the results provided by seven participants. The uncertainties of each KCRV are between 0.9 % and 1.7 %. The degree of equivalence (DoE), defined as the deviation of the result reported by the laboratories for each energy from the corresponding KCRV, and the associated expanded uncertainty are also reported and discussed.

Neutron calibration facilities and monitoring techniques have been developed since the middle of the 20th century to support research and nuclear power energy development. The technical areas needing reference neutron fields and related instruments were mainly cross section measurements, radiation protection, dosimetry and fission reactors, with energy ranging from a few millielectronvolts to about 20 MeV. The reference neutron fields and calibration techniques developed for these purposes will be presented in this paper. However, in recent years, emerging fields have brought new needs for calibration facilities and monitoring techniques. These new challenges for neutron metrology will be exposed with their technical difficulties.

The ITER International Fusion Energy Organization has solicited IRSN Laboratory for Neutron Metrology and Dosimetry to study the possibility to calibrate, in monoenergetic neutron fields at 14 and 2.45 MeV, the neutron detectors to be placed inside the future fusion reactor. In addition to the estimate of the necessary irradiation times, the dose equivalent rates from some of the neutron activated beam line elements had been calculated to consider the cooling time mandatory before access. Neutron activation calculations have been performed with the Fluka Monte-Carlo code. The resulting dose equivalent rates depend strongly of the neutron beam intensity as well as the neutron energy. In the worst case, for 14 meV neutrons at an emission rate of 10(12) s(-1), a cooling time of 24 h would be needed for a close access to the shadow cone. Several days would be mandatory in the case of the target holder. (C) 2013 Elsevier Ltd. All rights reserved.

The Institute for Radiological Protection and Nuclear Safety (IRSN) has developed a new spectrometry system for neutron energies from 10−9 MeV to 10 GeV. This high energy range multisphere extended IRSN system (HERMEIS) is a high gas pressure3He-based Bonner spheres set. It is adapted to low neutron fluence rate measurements and one of its main application concerns the determination of cosmic-ray-induced neutron spectra at ground level and mountain altitudes. The neutron fluence response matrix of the set of 13 Bonner spheres, including three extended ones with tungsten and lead shells, was calculated with the radiation transport code MCNPX-2.6f. Reliable fluence responses being mandatory for a correct evaluation of the atmospheric neutron spectra, HERMEIS was characterized at standard monoenergetic, quasi-monoenergetic and realistic neutron fields facilities. Measurements with monoenergetic neutron beams of 144 keV, 565 keV, 5 MeV and 17 MeV were performed at the NPL standard Van de Graaff facility. For the characterization of the response functions at higher energies, measurements were done at the Svedberg Laboratory, with 46 MeV and 144 MeV quasi-monoenergetic neutrons. Finally, to demonstrate the suitability of the system for broad cosmic-ray neutron spectra, measurements were performed at the TSL Atmospheric-like Neutrons from thIck TArget (ANITA) and also at the CERN European Realistic Field (CERF) facilities. Data from the realistic spectra were unfolded with the GRAVEL unfolding code and as a whole, a good agreement was found between the experimental and Monte-Carlo calculated neutron fluence energy distributions.

Neutrons are a relevant background in rare events physics. Detectors based on fast neutron-induced nuclear reactions are commonly used for fast neutron spectroscopy. In this subject, scintillating bolometers provide an excellent energy resolution and particle discrimination by the simultaneous measurement of the heat and emitted light. Our group has constructed several Li-6 and B-10 based massive scintillating bolometers (LiF, Li6Eu(BO3)(3), Li6Gd(BO3)(3)), with energy resolutions ranging from 16 to 200 keV. First results of a 32 gr (LiF)-Li-6 scintillating bolometer enriched at 95% in Li-6 operated at 20 mK are presented. The use of this material in a multi-target cryogenic dark matter experiment, like EURECA, would allow monitoring the incident neutron flux in the detector during the data-taking.

In some branches of metrology the quantity, or quantities, to be measured and the requirements for standards of this quantity, or these quantities, are clear-cut, although the accuracies required may not always be obvious. Good examples are time, length and mass. The quantities measured in neutron metrology and the requirements and uses of these quantities are less well known. This paper lays the foundation for subsequent more detailed discussions of the problems and issues faced by national metrology institutes when developing and providing standards.

The calibration of a neutron-sensitive device can range from a simple calibration factor at a single energy or energy distribution to a full response characterization over the entire energy range to which the device is sensitive. As the responses of neutron-sensitive devices and the fluence-to-dose-equivalent conversion coefficients can vary with neutron energy and incident angle, both simulation and experiments in standard neutron fields are required. Although several ISO standards present calibration principles in general and detailed discussion on many specific areas, there are certain omissions and limitations that this paper intends to highlight, along with some new recommendations derived from the recent literature, mainly focused on the effective centre, corrections for geometry and neutron scattering, as well as the problem of calibrating in terms of personal dose equivalent.

The SIGMA facility consisted of six Am-Be neutron sources, of 0.56TBq each, which were located in a graphite moderator block of 150×150×150 cm on side. In total, the neutron sources strength was about 1.9×10 s. As explained in the last report, the more than 10 years old Am-Be sources should be evacuated, due to the French regulations, stopping the use of this facility beginning of 2006. We used this as an opportunity to improve the thermal components of the field. As a first step, it was decided to place a 6.3 GBq (170 mCi) Cf source at the center of the existing graphite moderator block resulting in 95% of neutrons with energy below 0.5 eV generating 88% of the neutron total dose equivalent. However, it has not been possible in the last years to get the Cf source with reasonable cost and delay. This situation resulted in the cancellation of IRSN participation to the CCRI key comparison K-8 as announced in 2009. Since the last CCRI meeting, IRSN

In order to develop reference low-energy monoenergetic neutron fields, the (45)Sc(p,n) reaction is being studied within the framework of a scientific cooperation between NPL, PTB, IRMM and IRSN. The first study is dedicated to the selection of the most suitable backing material for scandium targets. It must be able to sustain high proton beam currents to compensate for the low cross section of the (45)Sc(p,n) reaction. Targets with backings made of Mo, Al, W, Ag, Pt and Ta were irradiated during several hours at a few tens of mu A at the NPL neutron reference facility. Target thickness and composition were analysed with the RBS method at the AIFIRA facility before and after NPL irradiations leading to the selection of tantalum as the best choice for backing material. (C) 2010 Elsevier Ltd. All rights reserved.

NPL, FIB, IRMM and IRSN are involved, within a scientific cooperation, in a comprehensive study aimed at developing reference low-energy monoenergetic neutron fields. This paper will explain the importance of such developments, highlighted by the over response of neutron survey meters in the key energy range, and also describe the main difficulties encountered. The variation of the neutron yield with ion beam energy from the neutron threshold up to about 50 key has been measured at IRSN AMANDE facility for the (45)Sc(p,n), (65)Cu(p,n), (51)V(p,n), (57)Fe(p,n) and (37)Cl(p,n) reactions. (C) 2010 Elsevier Ltd. All rights reserved.

The variation of the response of instruments as a function of neutron energy has to be determined in well-characterized mono-energetic neutron fields. These fields are measured in terms of neutron fluence and mean energy of the mono-energetic neutron peak, providing values that are required to determine the related dosimetric quantities. At the IRSN AMANDE facility, the reference measurement standard for neutron energy is based on the time of flight (ToF) method, i.e. on a determination of the neutron velocity, requiring a pulsed beam and fast detectors. In this study, we describe the experimental and theoretical aspects of the development of this method for neutron energies above 1MeV using liquid scintillators. We present the adopted experimental protocol and give full details of the estimation of uncertainties associated with the neutron energy measurement. To extract as accurately as possible the mean energy from the experimental neutron ToF distribution, a simulated energy distribution is fitted to the measurements. This simulation includes a detailed analysis of the energy resolution, taking into account all the contributions influencing the ToF measurements. Comparison with neutron energy calculated from kinematics leads to the conclusion that the ToF method at the AMANDE facility can be considered as a reference measurement standard for neutron energies between 1MeV and 20MeV, with a relative uncertainty lower than 1.5%.

The neutron metrology and dosimetry laboratory has developed a long counter, on the basis of optimization work using Monte-Carlo simulations. The calibration of this new device was performed at the IRSN standard radionuclide source facility. Measurements were also realized at the monoenergetic neutron fields facility, AMANDE, to determine the dead time correction, the effective center and efficiency as a function of neutron energy. A good agreement was observed between the long counter results and the monoenergetic neutron fluence values determined with proton recoil counters. The results of the experimental characterization of the IRSN long counter are presented in this paper.