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

clinical and functional outcome in a subject with bipolar disorder and severe white matter hyperintensities

Background and Objectives: Neuroimaging studies have found higher rates of white matter hyperintensities (WMHs) in patients with bipolar disorder (BD) of all ages, although whether BD is associated with increased rates of WMHs independently from age and cerebrovascular risk factors is still matter of debate. The outcome of BD associated with severe WMHs is generally poor, but several authors have suggested that some factors could have a protective role in BD. The aim of the present study was to report the two-year follow-up of a woman with BD type I and severe WMH/PWMH lesions who was taking high concentrations of vitamin-D in her nutrition, as well as taking lithium and haloperidol as treatment. Case presentation: A 76-year-old woman was hospitalized for a mixed state BD. She had severe WMHs. She took lithium and haloperidol during the hospitalization and was euthymic at discharge as well as after two-years of follow-up. Her nutrition had a high concentration of Vitamin-D. Unfortunately, it was not possible to give her a second MRI. Conclusions: Although there was probable persistence of WMHs, the patient improved in both mood and quality of life. The possible protective effect of lithium and Vitamin-D is discussed. Received: 12 January 2010 Revised: 5 August 2010 Accepted: 14 September 2010 Short report 42 GIANLUCA SERAFINI ET AL. Background and objectives Neuroimaging studies have found higher rates of WMHs in patients of all ages with bipolar disorder (BD), most frequently localized in the frontal lobes and the frontal/parietal junction1. WMHs may indicate astrogliosis, demyelination and loss of axons and may be relatively more common in older patients with BD, reflecting an interaction of the disease with processes of normal aging. However, WMHs are also associated with several pathological conditions among older individuals2. As a result of this, the meaning of these lesions in BD is still unclear. Although there have been inconsistent results in the research on this issue, WMHs are considered to be negative prognostic factors, associated with treatment resistance, increased hospitalization rates, cognitive impairment and increased suicide risk in individuals with BD3,4. However, several other factors may play a protective role in BD. Tsai et al.5 reported that psychiatric treatment, including medication with antipsychotics or lithium, could be a protective factor against early natural death. Here, we present the case of a 76year-old woman who had had a BD for twenty-one years and had, in addition, severe WMH/PWMH lesions, who was admitted to our psychiatric hospital for a mixed state. The patient gave written consent before being included in the study

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%

Assessment of Trace Metals in Sediments from Khnifiss Lagoon (Tarfaya, Morocco)

Surface sediments from Khnifiss lagoon (Morocco) were analyzed to evaluate the contamination degree of the area. Concentrations of V, Cr, Co, Ni, Cu, Zn, As, Cd, Hg, and Pb were determined on samples taken during the summer and the autumn of 2016. On the whole, higher concentrations were found in the summer season. The results revealed the following average concentrations (mg/kg), reported in descending order: Zn (51.7 ± 31.3) > V (38.8 ± 24.7) > Cr (26.6 ± 17.8) > Ni (16.5 ± 5.47) > As (8.50 ± 2.00) > Cu (6.60 ± 3.81) > Pb (6.13 ± 3.46) > Co (3.57 ± 2.09) > Cd (0.16 ± 0.11) > Hg (0.006 ± 0.001). Organic matter showed a positive significant correlation with some trace metals (mainly V, Cr, Co, Zn, Cd, Pb). Three pollution indices were calculated: Enrichment Factor (EF), Index of Geo−accumulation (Igeo), and Pollution Load Index (PLI). Minimal enrichments (for Zn, As, and Cd) were detected at some sampling points. Overall indices showed that the Khnifiss sediments can be classified as not contaminated, and that the trace metals amounts found are ascribable to the geogenic origin. The results of this work can be used as a starting point for further evaluations of trace metals distribution in Moroccan lagoons

Studies on Flat Sandwich-type Self-Powered Detectors for Flux Measurements in ITER Test Blanket Modules

Neutron and gamma flux measurements in designated positions in the test blanket modules (TBM) of ITER will be important tasks during ITER’s campaigns. As part of the ongoing task on development of nuclear instrumentation for application in European ITER TBMs, experimental investigations on self-powered detectors (SPD) are undertaken. This paper reports the findings of neutron and photon irradiation tests performed with a test SPD in flat sandwich-like geometry. Whereas both neutrons and gammas can be detected with appropriate optimization of geometries, materials and sizes of the components, the present sandwich-like design is more sensitive to gammas than 14 MeV neutrons. Range of SPD current signals achievable under TBM conditions are predicted based on the SPD sensitivities measured in this work

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