S. Loreti

Lithium iron oxide as alternative anode for li-ion batteries

Lithium–iron oxide Li–Fe–O was synthesized by solid state reaction between Li2CO3 and Fe2O3. The sample was characterized by X-ray powder diffraction. The XRD patterns showed well defined reflections corresponding to α-LiFeO2 and the spinel LiFe5O8 in a molar ratio of 9:1. The material was tested as alternative anode for lithium-ion batteries. It exhibited good cyclability delivering about 120 mAh/g after 500 deep charge/discharge cycles. Unlikely, the use of the material as intercalation anode in practical cells is hindered by the irreversible uptake of lithium that takes place during the first lithium insertion. X-ray diffraction pattern showed that during this step a reduction of the lithium iron oxide occurs leading to the formation of lithium oxide and iron metal.

Photoluminescence and Thermoluminescence Investigation of Europium- and Dysprosium-Doped Dibarium Magnesium Silicate Phosphor

Europium- and dysprosium-doped barium magnesium silicate powder with different concentrations of dysprosium was synthesized using solid state reactions. The prepared phosphors were characterized using photoluminescence. Prominent green color emissions were obtained under ultraviolet excitation. The thermoluminescence glow curves of the samples were measured after various delay times. With increased delay time, the intensity of the thermoluminescence peak decays, and the position of the thermoluminescence peak shifts to higher temperatures, indicating the considerable retrapping associated with general order kinetics. Refined lattice parameters of monoclinic phosphor were calculated.

Recent advances in digital coincidence counting for Radionuclide Metrology

The radioactivity measurement techniques developed within the EURAMET EMRP “MetroFission” Joint Research Project, were aimed at performing on-site activity measurements at the primary standard level (4πβ-γ coincidence counting) for a wide range of radionuclides utilizing recent advances in high-speed digital sampling and digital signal processing. The state-of-the-art technology employed within this project provides up to 14-bit digitizer systems operating with sampling rates in the order of 108 to 109 samples-per-second, incorporating on-board FPGA devices, which greatly enhances the application of digital signal processing for the implementation of digital coincidence counting. These devices when coupled to suitable analysis software, demonstrate a significant improvement in the provision of primary standards of radioactivity. This manuscript provides a description of the systems employed, along with recommendations regarding optimization of the digital sampling of signals from photo-multiplier tubes and pre-amplifiers and compare the benefits of “off-line” versus “on-line” 4πβ-γ digital coincidence counting systems.

Radiation hardness test of un-doped CsI crystals and Silicon Photomultipliers for the Mu2e calorimeter

The Mu2e calorimeter is composed by 1400 un-doped CsI crystals coupled to large area UV extended Silicon Photomultipliers arranged in two annular disks. This calorimeter has to provide precise information on energy, timing and position. It should also be fast enough to handle the high rate background and it must operate and survive in a high radiation environment. Simulation studies estimated that, in the hottest regions, each crystal will absorb a dose of 300 Gy and will be exposed to a neutron fluency of 6 x 10^{11} n/cm^2 in 3 years of running. Test of un-doped CsI crystals irradiated up to 900 Gy and to a neutron fluency up to 9 x 10^{11} n/cm^2 have been performed at CALLIOPE and FNG ENEA facilities in Italy. We present our study on the variation of light yield (LY) and longitudinal response uniformity (LRU) of these crystals after irradiation. The ionization dose does not modify LRU while a 20% reduction in LY is observed at 900 Gy. Similarly, the neutron flux causes an acceptable LY deterioration (<15%). A neutron irradiation test on different types of SIPMs (two different array models from Hamamatsu and one from FBK) have also been carried out by measuring the variation of the leakage current and the charge response to an ultraviolet led. We concluded that, in the experiment, we will need to cool down the SIPMs to 0 C reduce the leakage current to an acceptable level.

Irradiation study of UV Silicon Photomultipliers for the Mu2e Calorimeter

The Mu2e calorimeter is composed of 1400 un-doped CsI crystals, coupled to large area UV extended Silicon Photomultipliers (SiPMs), arranged in two annular disks. This calorimeter has to provide precise information on energy, timing and position resolutions. It should also be fast enough to handle the high rate background and it must operate and survive in the high radiation environment. Simulation studies estimated that, in the highest irradiated regions, each photo-sensor will absorb a dose of 20 krad and will be exposed to a neutron fluency of 5.5×1011n1 MeV/cm2 in three years of running, with a safety factor of 3 included. At the end of 2015, we have concluded an irradiation campaign at the Frascati Neutron Generator (FNG, Frascati, Italy) measuring the response of two different 16 array models from Hamamatsu, which differ for the protection windows and a SiPM from FBK. In 2016, we have carried out two additional irradiation campaigns with neutrons and photons at the Helmholtz-Zentrum Dresden-Rossendorf (HZDR, Dresden, Germany) and at the Calliope gamma irradiation facility at ENEA-Casaccia, respectively. A negligible increment of the leakage current and no gain change have been observed with the dose irradiation. On the other hand, at the end of the neutron irradiation, the gain does not show large changes whilst the leakage current increases by around a factor of 2000. In these conditions, the too high leakage current makes problematic to bias the SiPMs, thus requiring to cool them down to a running temperature of ~0oC.

OVERVIEW OF NEUTRON MEASUREMENTS IN JET FUSION DEVICE

The design and operation of ITER experimental fusion reactor requires the development of neutron measurement techniques and numerical tools to derive the fusion power and the radiation field in the device and in the surrounding areas. Nuclear analyses provide essential input to the conceptual design, optimisation, engineering and safety case in ITER and power plant studies. The required radiation transport calculations are extremely challenging because of the large physical extent of the reactor plant, the complexity of the geometry, and the combination of deep penetration and streaming paths. This article reports the experimental activities which are carried-out at JET to validate the neutronics measurements methods and numerical tools used in ITER and power plant design. A new deuterium-tritium campaign is proposed in 2019 at JET: the unique 14 MeV neutron yields produced will be exploited as much as possible to validate measurement techniques, codes, procedures and data currently used in ITER design thus reducing the related uncertainties and the associated risks in the machine operation.

14 MeV Neutrons for 99Mo/99mTc Production: Experiments, Simulations and Perspectives

Background: the gamma-emitting radionuclide Technetium-99m (99mTc) is still the workhorse of Single Photon Emission Computed Tomography (SPECT) as it is used worldwide for the diagnosis of a variety of phatological conditions. 99mTc is obtained from 99Mo/99mTc generators as pertechnetate ion, which is the ubiquitous starting material for the preparation of 99mTc radiopharmaceuticals. 99Mo in such generators is currently produced in nuclear fission reactors as a by-product of 235U fission. Here we investigated an alternative route for the production of 99Mo by irradiating a natural metallic molybdenum powder using a 14-MeV accelerator-driven neutron source. Methods: after irradiation, an efficient isolation and purification of the final 99mTc-pertechnetate was carried out by means of solvent extraction. Monte Carlo simulations allowed reliable predictions of 99Mo production rates for a newly designed 14-MeV neutron source (New Sorgentina Fusion Source). Results: in traceable metrological conditions, a level of radionuclidic purity consistent with accepted pharmaceutical quality standards, was achieved. Conclusions: we showed that this source, featuring a nominal neutron emission rate of about 1015 s−1, may potentially supply an appreciable fraction of the current 99Mo global demand. This study highlights that a robust and viable solution, alternative to nuclear fission reactors, can be accomplished to secure the long-term supply of 99Mo.

The frascati neutron generator: Present activities and future upgrades

The 14 MeV Frascati Neutron Generator (FNG), designed and built at the ENEA Frascati research center, is a highly versatile active source of fast neutrons for research activities. Neutron generation at the FNG is based on the T(d,n)α fusion reaction, to produce 14 MeV neutrons with a flux up to 1×1011 neutrons/s in steady state or pulse mode. FNG can also produce 2.5 MeV neutrons via the D(d,n)3He fusion reaction.

High temperature operation of single crystal diamond detectors

Diamond is studied since many years as potential radiation detector material. In the last years, there has been an increasing interest about the capability of diamond to withstand harsh working conditions including high temperature. The latter capability depending upon the large band gap and the excellent thermal properties of diamond. At ENEA C.R. Frascati, diamond detectors operating at high temperature are studied since many years as candidate neutron monitors for nuclear fusion reactors. Diamond metallization was realized using different metals deposited on commercial diamond films, 100 or 500 μm thick. This paper reports the results for two detectors made with metal Cr and Ag contacts, respectively. The maximum working temperature under 14 MeV neutron irradiation, while operating the detector in spectrometric mode, was in the range 220–240 °C. The best performance was obtained using Ag metal contacts. It was also observed that once cooled down below the maximum working temperature the detector performances are recovered. Furthermore, it was observed that metallization can be damaged after long lasting operation at high temperature. In the attempt to overcame this issue a new detector was realized made with one Schottky Cr-diamond metal contact on one side and an ohmic, not metallic, contact on the other side. A commercial film 100 micron thick was used. This detector shown excellent performances well above 300°C.

Point Light Sources Based on Color Centers in LiF Films for Scanning Near‐Field Optical Microscopy

Local fluorescent probes based on low‐energy electron beam irradiated lithium fluoride (LiF) thin films were preparated and tested for their applications in Scanning Near‐Field Optical Microscopy.