Comparing active and passive Bonner Sphere Spectrometers in the 2.5 MeV quasi mono-energetic neutron field of the ENEA Frascati Neutron Generator (FNG)

Bonner Sphere Spectrometer (BSS) equipped with passive detectors are used to replace active BSS in radiation environment characterized by high fluence rate, large photon background and pulsed time structure as those encountered near particle accelerators. In this work a newly developed passive Bonner Sphere Spectrometer, using Dysprosium activation foils as central detectors (Dy-BSS), was tested through comparison with a well-established active BSS. As a suitable neutron field, where both systems can correctly operate, the 2.5 MeV quasi mono-energetic beam of the ENEA Frascati Neutron Generator (FNG) was chosen. The two spectrometers are based on substantially different operation principles, therefore their response matrix are very different. In addition, the BSS are independently calibrated in different reference neutron fields. The exercise took place at 90 � and at a fixed distance from the neutron emitting deuterated target. As reference data, the results obtained by unfolding the active BSS data were used. The FRUIT unfolding code, ver. 5 was used. The results of the Dy-BSS are fully comparable with those of the active BSS, in terms of both total fluence and shape of the neutron spectra. For the energy range studied in this exercise, the expected level of accuracy of the Dy-BSS and its suitability for operational neutron monitoring are fully confirmed

Design and validation of a photon insensitive multidetector neutron spectrometer based on Dysprosium activation foils

Abstract This communication describes a photon insensitive passive neutron spectrometer consisting of Dysprosium (Dy) activation foils located along three perpendicular axes within a single moderating polyethylene sphere. The Monte Carlo code MCNPX 2.6 was used to optimize the spatial arrangement of the detectors and to derive the spectrometer response matrix. Nearly isotropic response in terms of neutron fluence for energies up to 20 MeV was obtained by combining the readings of the detectors located at the same radius value. The spectrometer was calibrated using a previously characterized 14 MeV neutron beam produced in the ENEA Frascati Neutron Generator (FNG). The overall uncertainty of the spectrometer response matrix at 14 MeV, assessed on the basis of this experiment, was ±3%

Mixed n–γ fields dosimetry at low doses by means of different solid state dosimeters

Abstract A Mock-up of the inboard shield of the ITER International nuclear fusion reactor was realized at the Frascati Neutron Generator (FNG) at ENEA Frascati with the scope to measure the nuclear heating (total dose) in the superconducting coils. High sensitivity MCP-6 and MCP-7 dosimeters were used to measure the low

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 from99Mo/99mTc generators as pertechnetate ion, which is the ubiquitous starting material for the preparation of99mTc radiopharmaceuticals.99Mo in such generators is currently produced in nuclear fission reactors as a by-product of235U fission. Here we investigated an alternative route for the production of99Mo 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 final99mTc-pertechnetate was carried out by means of solvent extraction. Monte Carlo simulations allowed reliable predictions of99Mo 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 1015s−1, may potentially supply an appreciable fraction of the current99Mo 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 of99Mo

Results from silicon photo-multiplier neutron irradiation test

Silicon photo-multipliers, often called "SiPM", are semiconductor photon detectors built from a square matrix of avalanche photo-diodes on common silicon substrate. SiPM have been proposed for several different applications in High Energy Physics, in particular where a large detection granularity is needed. In this presentation the results of a radiation hardness test performed at the Frascati Neutron Generator are presented. Several SiPM of different manufacturers have been irradiated integrating up to 7 1010 1-MeV-equivalent neutrons per cm2. For the first time, their performance have been recorded during the neutron irradiation and a gradual deterioration of their properties was found to happen already after an integrated dose of the order of 108 1-MeV-equivalent neutrons per cm2. The Frascati Neutron Generator (FNG) FNG uses a deuteron beam accelerated up to 300 keV impinging on a deuteron target to produce a nearly isotropic 2.5 MeV neutron output via the D(d,n)3He fusion reaction. The beam current at the target can be regulated up to 1 mA resulting in a maximum neutron production rate of 5 108 neutrons on the whole solid angle per second. Through the monitoring of the rate of associated emitted particles, protons or alpha, the neutron emission rate can be monitored on-line. This gives the unique possibility of measuring the effect of neutrons as long as the irradiation takes place. On-Line Measurements Six devices produced by the IRST and four produced by the Hamamatsu have been tested with neutrons. Depending on the distance from the production point, in four days of test, the SiPM integrated between 0.18 and 7.32 1-MeV-equivalent neutron per cm2. The current drawn by each device and its dark counting rate were continuously monitored and recorded while being irradiated. Fig. 1 shows that the current drawn by the SiPM starts to increase soon after the beginning of the irradiation. No differences between the current behavior of tested devices were found. The effects of the different neutron fluences are not visible at the level we operated. The neutron flux was kept off for a whole night while the currents were recorded. No significant recovery effects appeared. The absolute value of the current and the increasing rate, once the flux was back on, didn't change. The neutron beam has been paused several times in order to perform low voltage scans during the irradiation runs and to measure the effects on the dark currents and on the dark counting rates for different bias values. In the low voltage scans the current behavior changed rapidly with the integrated dose as it is shown in Fig.2. Off-Line Measurements The SiPM have been tested with cosmic rays before and after the neutron irradiation and the charge spectra obtained are shown in Fig 3. After the neutron irradiation, the gain was found to be about the half of the initial one (Fig.3 Bottom) and the noise pedestals (Fig. 3 Top) are much broader. The main effect is an important reduction of the detection efficiency from more than 95% to about 70%. Fig2: Measured currents as a function of the low voltage supply after different integrated doses Fig3: SiPM charge spectra with cosmic rays before (top) and after (bottom) the neutron irradiation. Fig1: Increasing factor of the current drawn by the SiPM as a function of the integrated neutron dose

Neutron Detectors Based Upon Artificial Single Crystal Diamond

This paper reports about state-of-the-art artificial Single Crystal Diamond (SCD) neutron detectors based on a multilayered structure and grown by chemical vapour deposition (CVD) technique. Multilayered SCD detectors covered with a thin layer of 6LiF allow the simultaneous detection of both slow and fast neutrons and can operate in pulse and current mode. These detectors can also be produced with a thin layer of Boron. Application of SCD detectors to neutron detection around fusion tokamak is reported. Some problems related to the processing of the very fast electrical pulse produced by diamond are addressed and the achieved and foreseen development of the processing electronics is reported as well

Management of Pediatric Urinary Tract Infections: A Delphi Study

Urinary tract infection (UTI) is one of the most common infectious diseases in the pediatric population and represents a major cause of antibiotic consumption and hospitalization in children. Considering the ongoing controversies on the management of pediatric UTI and the challenges due to increasing antimicrobial resistance, the aim of the present study was to evaluate the level of agreement on UTI management in pediatric age in Emilia-Romagna Region, Italy, and to assess on the basis of recent studies whether there is the need to change current recommendations used by primary care pediatricians, hospital pediatricians, and pediatric surgeons in everyday clinical practice to possibly improve outcomes. This consensus provides clear and shared indications on UTI management in pediatric age, based on the most updated literature. This work represents, in our opinion, the most complete and up-to-date collection of statements on procedures to follow for pediatric UTI, in order to guide physicians in the management of the patient, standardize approaches, and avoid abuse and misuse of antibiotics. Undoubtedly, more randomized and controlled trials are needed in the pediatric population to better define the best therapeutic management in cases with antimicrobial resistance and real usefulness of long-term antibiotic prophylaxis

Cryo-EM structures of the SARS-CoV-2 endoribonuclease Nsp15 reveal insight into nuclease specificity and dynamics.

Nsp15, a uridine specific endoribonuclease conserved across coronaviruses, processes viral RNA to evade detection by host defense systems. Crystal structures of Nsp15 from different coronaviruses have shown a common hexameric assembly, yet how the enzyme recognizes and processes RNA remains poorly understood. Here we report a series of cryo-EM reconstructions of SARS-CoV-2 Nsp15, in both apo and UTP-bound states. The cryo-EM reconstructions, combined with biochemistry, mass spectrometry, and molecular dynamics, expose molecular details of how critical active site residues recognize uridine and facilitate catalysis of the phosphodiester bond. Mass spectrometry revealed the accumulation of cyclic phosphate cleavage products, while analysis of the apo and UTP-bound datasets revealed conformational dynamics not observed by crystal structures that are likely important to facilitate substrate recognition and regulate nuclease activity. Collectively, these findings advance understanding of how Nsp15 processes viral RNA and provide a structural framework for the development of new therapeutics