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Lanthanum halide scintillation crystals represent the state of the art of the scintillators technology for gamma ray spectroscopy. They feature a short decaying time (< 30 ns), high light yield, good detection efficiency and an optimal energy resolution (< 2.9% at 662 keV). Lanthanum halides also present an intense intrinsic background caused by the radioactive decay of 138La and 227Ac contaminations, which cover all the lower energies up to 3 MeV. Despite being a limitation in low counting rate experiments, this intrinsic background can be exploited to perform energy calibration of the pulse height spectra, refraining from the employment of dedicated external sources. The intense electron capture peak of 138La at 1471 keV, which is the most relevant feature for this purpose, has been deeply characterized in literature in many aspects. In this work, a detailed analysis of the lanthanum bromide intrinsic background was performed on several scintillation crystals, unveiling a feature with an average energy of 1515 keV not yet described in the current literature. [ABSTRACT FROM AUTHOR]

Abstract: Single crystal diamond (SDD) detectors coupled to fast digital data acquisition were tested as monitors of fast neutrons at the ISIS pulsed spallation neutron source. The ISIS pulsed neutron beams are generated by proton induced spallation on a tungsten tantalum target at 50Hz repetition rate. The SDD signal was digitized at 1GHz to reconstruct the deposited energy and time of flight (t ToF) of each detection event. The SDD system was used reliably and almost continuously over a period of several days. The results of the biparametric measurements are in qualitative agreement with predictions based on the proton beam pulse structure and the energy deposited in the SDD by the main neutron interaction processes. [Copyright &y& Elsevier]

Silicon Carbide (SiC) is a relatively new entry in the world of solid-state detectors. Although SiC response to neutrons is more complex than the one obtained with diamonds, the measured energy resolution (FWHM/ E d < 4 %) makes SiC an interesting alternative to diamond and silicon detectors for fast neutrons. The results obtained from the measurements of the response of a 100 μ m thick SiC detector to neutrons in the energy range between 3 and 20 MeV at the n_TOF spallation source at CERN are presented in this paper. By selecting the neutron energy by means of the time of flight, the detector response to quasi-mono-energetic neutrons was measured. The main neutron-induced nuclear reactions were identified in the measured pulse height spectrum. Detection efficiency as a function of neutron energy was measured and interpreted based on available neutron cross section and by making use of Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

In this work we present the response of a new large volume 4H Silicon Carbide (SiC) detector to 14 MeV neutrons. The device has an active thickness of 100 μ m (obtained by epitaxial growing) and an active area of 25 mm2. Tests were conducted at the ENEA-Frascati Neutron Generator facility by using 14.1 MeV neutrons. The SiC detector performance was compared to that of Single-Crystal Diamond (SCD) detectors. The SiC response function was successfully measured and revealed a very complex structure due to the presence in the detector of both Silicon and Carbon atoms. Nevertheless, the flexibility in the SiC manufacturing and the new achievements in terms of relatively large areas (up 1x1 cm2) and a wide range of thicknesses makes them an interesting alternative to diamond detectors in environments where limited space and high neutron fluxes are an issue, i.e. modern neutron cameras or in-vessel tokamak measurements for the new generation fusion machines such as ITER. The absence of instabilities during neutron irradiation and the capability to withstand high neutron fluences and to follow the neutron yield suggest a straightforward use of these detectors as a neutron diagnostics. [ABSTRACT FROM AUTHOR]

Abstract The ITER project requires additional heating by two neutral beam injectors, each accelerating up to 1 MV a 40 A beam of negative deuterium ions for one hour. Such requirements have never been reached, so it was decided to build in Padova a facility (PRIMA) that hosts two experimental devices: SPIDER, a 100 kV negative H/D RF beam source, and MITICA, a full-scale injector for the ITER NBI. SPIDER has begun operation in 2018, while MITICA is expected to start after 2020. In both devices the accelerated deuterium beam impinges on an actively cooled beam dump used to stop the deuterons. Detection of fusion neutrons produced between beam–deuterons and dump-embedded deuterons will be used as a means to resolve the horizontal beam intensity profile. A neutron detection system called Close-contact Neutron Emission Surface Mapping (CNESM) is installed right behind the SPIDER beam dump, with the aim to provide the neutron emission map of the beam dump surface. The core of this diagnostic system is an nGEM (neutron-Gas Electron Multiplier) detector which will be able to reconstruct the fast neutron beam profile with an efficiency of about 10−4. A crucial point in order to correctly reconstruct the profile of the deposited D − power is the directionality discrimination capability of the detector. This paper reports on the results of the characterization of the nGEM directionality capabilities, performed at the Frascati Neutron Generator (FNG) using 2.5 MeV neutrons, before installation of the detector inside the SPIDER vacuum vessel. [ABSTRACT FROM AUTHOR]

Fusion experiments put many challenges on the neutron detection methods, since they require fast neutron counters and spectrometers with good energy resolution capable of operating in harsh environments under a large range of neutron flux intensities. Recently, SiC detectors were proposed for these roles due to their outstanding properties. Among those, the operation of SiC with partial polarization is of interest since it might allow for a fast neutron detector with efficiency tunable online, which would allow a good functionality under a large range of flux intensities. This paper describes the characterization of a series of SiC detectors operated with a fraction of the polarization needed to achieve full depletion. The characterization is performed through I/V measurements, alpha irradiation in vacuum and neutron irradiation. A functionality with excellent detection characteristics is demonstrated, reaching an energy resolution of 1.05 % for 5.5 MeV alphas and 2.05 % for 14 MeV neutrons. Some limitations on the maximum bias will be also discussed, pointing out some challenges for the manufacturing of thick SiCs in the future. [ABSTRACT FROM AUTHOR]

Abstract A study of the response of three Δ E-E telescopes to fragments produced in nuclear interactions at 40 AMeV is presented. All the employed telescopes feature silicon carbide (SiC) detectors for at least one detection stage. Two identification methods have been used and their performance discussed: the Δ E-E technique and the Pulse Shape Analysis technique (for identification of nuclear fragments stopped in a single SiC layer). Identification capabilities similar to those obtained with the best available silicon detectors have been found for the SiC detector prototypes studied in this work. [ABSTRACT FROM AUTHOR]

The recently developed Cs 2 LiYCl 6 :Ce (CLYC) crystals are interesting scintillation detectors not only for their gamma energy resolution (<5% at 662 keV) but also for their capability to identify and measure the energy of both gamma rays and fast/thermal neutrons. The thermal neutrons were detected by the 6 Li(n,α)t reaction while for the fast neutrons the 35 Cl(n,p) 35 S and 35 Cl(n,α) 32 P neutron - capture reactions were exploited. The energy of the outgoing proton or α particle scales linearly with the incident neutron energy. The kinetic energy of the fast neutrons can be measured using both the Time Of Flight (TOF) technique and using the CLYC energy signal. In this work, the response to monochromatic fast neutrons (1.9–3.8 MeV) of two CLYC 1″×1″ crystals was measured using both the TOF and the energy signal. The observables were combined to identify fast neutrons, to subtract the thermal neutron background and to identify different fast neutron-capture reactions on 35 Cl, in other words to understand if the detected particle is an α or a proton. We performed a dedicated measurement at the CN accelerator facility of the INFN Legnaro National Laboratories (Italy), where the fast neutrons were produced by impinging a proton beam (4.5, 5.0 and 5.5 MeV) on a 7 LiF target. We tested a CLYC detector 6 Li-enriched at about 95%, which is ideal for thermal neutron measurements, in parallel with another CLYC detector 7 Li-enriched at more than 99%, which is suitable for fast neutron measurements. [ABSTRACT FROM AUTHOR]

The light response of two thin inorganic scintillators based on YAP:Ce and LaBr 3 :Ce crystals has been measured with protons in the 4–8 MeV energy range at the Uppsala tandem accelerator and in the 8–26 MeV energy range at the Legnaro tandem accelerator. The crystals have been calibrated in situ with 137 Cs and 60 Co γ-ray sources. The relative light yields of protons with respect to gammas have been measured and are here reported to be (96±2)% and (80±2)% for YAP:Ce and LaBr 3 :Ce, respectively. The results open up to the development of a Telescope Proton Recoil spectrometer based on either of the two crystals as alternative to a silicon based spectrometer for applications to high neutron fluxes. [ABSTRACT FROM AUTHOR]

The ITER neutral beam test facility under construction in Padova will host two experimental devices: SPIDER, a 100 kV negative H/D RF beam source, and MITICA, a full scale, 1 MeV deuterium beam injector. SPIDER will start operations in 2016 while MITICA is expected to start during 2019. Both devices feature a beam dump used to stop the produced deuteron beam. Detection of fusion neutrons produced between beam-deuterons and dump-implanted deuterons will be used as a means to resolve the horizontal beam intensity profile. The neutron detection system will be placed right behind the beam dump, as close to the neutron emitting surface as possible thus providing the map of the neutron emission on the beam dump surface. The system uses nGEM neutron detectors. These are Gas Electron Multiplier detectors equipped with a cathode that also serves as neutron–proton converter foil. The cathode is designed to ensure that most of the detected neutrons at a point of the nGEM surface are emitted from the corresponding beamlet footprint (with dimensions of about 40×22 mm 2 ) on the dump front surface. The size of the nGEM detector for SPIDER is 352 mm×200 mm. Several smaller size prototypes have been successfully made in the last years and the experience gained on these detectors has led to the production of the full size detector for SPIDER during 2014. This nGEM has a read-out board made of 256 pads (arranged in a 16×16 matrix) each with a dimension of 22 mm×13 mm. This paper describes the production of this detector and its tests (in terms of beam profile reconstruction capability, uniformity over the active area, gamma rejection capability and time stability) performed on the ROTAX beam-line at the ISIS spallation source (Didcot-UK). [ABSTRACT FROM AUTHOR]

The crystal Cs 2 LiYCl 6 :Ce (CLYC) is a very interesting scintillator material because of its good energy resolution and its capability to identify γ-rays and fast/thermal neutrons. The crystal Cs 2 LiYCl 6 :Ce contains 6 Li and 35 Cl isotopes, therefore, it is possible to detect thermal neutrons through the reaction 6 Li(n, α)t while 35 Cl ions allow to measure fast neutrons through the reactions 35 Cl(n, p) 35 S and 35 Cl(n, α) 32 P. In this work two CLYC 1″×1″ crystals were used: the first crystal, enriched with 6 Li at 95% (CLYC-6) is ideal for thermal neutron measurements while the second one, enriched with 7 Li at >99% (CLYC-7) is suitable for fast neutron measurements. The response of CLYC scintillators was measured with different PMT models: timing or spectroscopic, with borosilicate glass or quartz window. The energy resolution, the neutron-γ discrimination and the internal activity are discussed. The capability of CLYC scintillators to discriminate γ rays from neutrons was tested with both thermal and fast neutrons. The thermal neutrons were measured with both detectors, using an AmBe source. The measurements of fast neutrons were performed at the Frascati Neutron Generator facility (Italy) where a deuterium beam was accelerated on a deuterium or on a tritium target, providing neutrons of 2.5 MeV or 14.1 MeV, respectively. The different sensitivity to thermal and fast neutrons of a CLYC-6 and of a CLYC-7 was additionally studied. [ABSTRACT FROM AUTHOR]

The response of a 3″×3″ LaBr 3 (Ce) scintillator to 14 MeV neutron irradiation has been measured at the Frascati Neutron Generator and simulated by means of a dedicated MCNP model. Several reactions are found to contribute to the measured response, with a key role played by neutron inelastic scattering and (n,2n) reactions on 79 Br, 81 Br and 139 La isotopes. An overall 43% efficiency to 14 MeV neutron detection above an experimental threshold of 0.35 MeV is calculated and confirmed by measurements. Post irradiation activation of the crystal has been also observed and is explained in terms of nuclear decays from the short lived 78 Br and 80 Br isotopes produced in (n,2n) reactions. The results presented in this paper are of relevance for the design of γ-ray detectors in burning plasma fusion experiments of the next generation, such as ITER, where capability to perform measurements in an intense 14 MeV neutron flux is required. [ABSTRACT FROM AUTHOR]

Abstract: Fast neutron detectors with a sub-millimetric space resolution are required in order to qualify neutron beams in applications related to magnetically-controlled nuclear fusion plasmas and to spallation sources. A nGEM detector has been developed for the CNESM diagnostic system of the SPIDER NBI prototype for ITER and as beam monitor for fast neutrons lines at spallation sources. The nGEM is a triple GEM gaseous detector equipped with polypropylene and polyethylene layers used to convert fast neutrons into recoil protons through the elastic scattering process. This paper describes the results obtained by testing a nGEM detector at the ISIS spallation source on the VESUVIO beam line. Beam profiles (σ x =14.35mm, σ y =15.75mm), nGEM counting efficiency (around 10-4 for 3MeV