Coexistence of Vagus Nerve Stimulation and Epicardial Implantable Cardioverter-Defibrillator System, Possible Interference: A Case Report and Systematic Review of the Literature

Vagus nerve stimulation (VNS) is an effective treatment for drug-resistant epilepsies in adults [1] and children [2]. Although VNS is generally well tolerated, rare cases of severe bradycardia..

Novel 4π Detection System for the Measurement of the 6Li(n,α)3H Reaction Cross-Section

A dedicated one-dimensional Time Projection Chamber (1D-TPC) was designed and produced at IRMM to determine the 6Li(n,α)3H cross section, in the 0.4-2.8 MeV energy range, aiming at 5% accuracy. The basic TPC components were a twin gridded ionisation chamber (GIC) with interwired electrodes and fast digitisation of the anode and cathode signals. The energy of both reaction products emitted from a thin 6LiF sample at the common TPC cathode was measured. A Kr(97%)CO2(3%) mixture was used as the detector gas at a pressure up to 3.5 bar. A 238U sample mounted on the cathode of an ionisation chamber without grid was used as the neutron flux monitor. Special care was taken to reduce the experimental sources of uncertainty. The beam-monitor 238U sample was characterised at IRMM by low-geometry α-counting with an accuracy of 0.1%. A 6Li sample was produced at IRMM by vacuum evaporation of 6LiF onto transparent aluminium backing. The number of 6Li atoms will be measured via Thermal Neutron Depth Profiling with an expected accuracy of 2% with respect to an IRMM Standard Reference Material. First test measurements were performed using a monoenergetic neutron beam produced by the T(p,n)3He reaction at the IRMM 7MV Van de Graaff accelerator. The experimental method and preliminary results are presented.JRC.D.4-Nuclear physic

Anti-coincidence rejection of SiPM dark pulses for improved detection of low energy radiation

Neutron and gamma detectors of the CSIRO air cargo scanner are based on scintillators readout by photodiodes (PD). The scanner imaging resolution is limited by the scintillator size. It, in turns, is limited by the number of interactions that can be detected by the PD. Silicon photomultipliers (SiPM) could be used in place of PDs to improve the neutron and gamma detector efficiency. It would ultimately improve the scanner performance in terms of speed, cargo size and image quality. Efficient use of SiPM requires gain stabilisation and dark counts suppression. This work presents a technique to strip the dark counts and the electronic noise off the genuine source-induced spectrum. The method requires the use of a pair of SiPM coupled to the same scintillator. By rejecting the events not detected by both the SiPMs, the background counts were reduced by more than 99%

Preparation of 6LiF deposits and characterisation via Monte Carlo simulations and Neutron Depth Profiling

The Institute for Reference Materials and Measurements (IRMM) is measuring the 6Li(n,t)4He cross section aiming at extending its status of standard over the MeV energy range. We developed a protocol to stretch-mount 0.75 micronmeter, 1.5 micronmeter, 8 micronmeter, and 20 micronmeter thick aluminium foils onto 0.5 mm thick tantalum rings. 6LiF samples were produced by depositing, by vacuum evaporation onto the aluminium backings, a layer of lithium fluoride 95.5% enriched in 6Li. We engineered dedicated tools and containers to handle and transport the resulting samples. These were characterised first at IRMM by differential weighing, then by Neutron Depth Profiling (NDP) at the TU Delft. These two measurements were found to be consistent for a selected sample, probed by a thermal neutron beam in three different regions to measure the 6LiF layer thickness and uniformity (defined as variation of the thickness relative to its average). The latter was found to be 0.8%, and the 6Li thickness to be 7.30 +/- 0.12, 7.35 +/- 0.12, and 7.29 +/- 0.12 micronmeter/cm2 in the three regions. We performed Monte Carlo simulations to estimate the uniformity of the 6LiF layer, and benchmarked the calculation against the NDP measurements. They were consistent with respect to the deposit uniformity although the simulations were found to overestimate the thickness of the layer.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Considerazioni sulla terapia chirurgica nel trattamento delle exotropie intermittenti

Presentato al Congresso Nazionale Associazione Italiana Ortottisti "Sviluppo ed alterazione della visione" Roma il 23-25 settembre 199

Kinematics of the 6Li(n,t)4He reaction and experimental scenarios for cross-section measurement

An approach is presented for the measurement of the 6Li(n,t)4He reaction cross section based on complementary measurements benchmarked against kinematic simulations. Key aspects of the approach include taking advantage of the particle leaking (PL) effect, and using a one-dimensional time projection chamber (1D-TPC) and an ionization chamber to detect the reaction products from monoenergetic and white neutron beams, respectively. We have derived analytical expressions describing the PL region in both the laboratory and the center-of-mass reference systems. Two complementary 1D-TPC experiments are discussed, using 6LiF deposits onto transparent aluminum foils, in the backward and forward orientations, respectively. The 6Li(n,t)4He reaction kinematics is discussed for 2-MeV neutrons and extended to the energy range from thermal to 3 MeV to reflect the experimental capability of the Institute for Reference Materials and Measurements Van de Graaff and Geel Electron Linear Accelerator facilities.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard

Ambiguities in the grid-inefficiency correction for Frisch-Grid Ionization Chambers

Ionization chambers with Frisch grids have been very successfully applied to neutron-induced fission-fragment studies during the past 20 years. They are radiation resistant and can be easily adapted to the experimental conditions. The use of Frisch grids has the advantage to remove the angular dependency from the charge induced on the anode plate. However, due to the Grid Inefficiency (GI) in shielding the charges, the anode signal remains slightly angular dependent. The correction for the GI is, however, essential to determine the correct energy of the ionizing particles. GI corrections can amount to a few percent of the anode signal. Presently, two contradicting correction methods are considered in literature. The first method adding the angular-dependent part of the signal to the signal pulse height; the second method subtracting the former from the latter. Both additive and subtractive approaches were investigated in an experiment where a Twin Frisch-Grid Ionization Chamber (TFGIC) was employed to detect the spontaneous fission fragments (FF) emitted by a 252Cf source. Two parallel-wire grids with different wire spacing (1 and 2 mm, respectively), were used individually, in the same chamber side. All the other experimental conditions were unchanged. The 2 mm grid featured more than double the GI of the 1 mm grid. The induced charge on the anode in both measurements was compared, before and after GI correction. Before GI correction, the 2 mm grid resulted in a lower pulse-height distribution than the 1 mm grid. After applying both GI corrections to both measurements only the additive approach led to consistent grid independent pulse-height distributions. The application of the subtractive correction on the contrary led to inconsistent, grid-dependent results. It is also shown that the impact of either of the correction methods is small on the FF mass distributions of 235U(nth, f).JRC.D.4-Nuclear physic

On the Frisch–Grid signal in ionization chambers

A recent theoretical approach concerning the grid-inefficiency (GI) problem in Twin Frisch–Grid Ionization Chambers was validated experimentally. The experimental verification focused on the induced signal on the anode plate. In this work the investigation was extended by studying the grid signal. The aim was to verify the grid-signal dependency on the grid inefficiency σ. The measurements were made with fission fragments from , using two different grids, with 1 and 2 mm wire distances, leading to the GI values: σ=0.031 and σ=0.083, respectively. The theoretical grid signal was confirmed because the detected grid pulse-height distribution was smaller for the larger σ. By applying the additive GI correction approach, the two grid pulse heights were consistent. In the second part of the work, the corrected grid signal was used to deduce emission angles of the fission fragments. It is inconvenient to treat the grid signal by means of conventional analogue electronics, because of its bipolarity. Therefore, the anode and grid signals were summed to create a unipolar, angle-dependent pulse height. Until now the so-called summing method has been the well-established approach to deduce the angle from the grid signal. However, this operation relies strongly on an accurate and stable calibration between the two summed signals. By application of digital-signal processing, the grid signal's bipolarity is no longer an issue. Hence one can bypass the intermediate summation step of the two different pre-amplifier signals, which leads to higher stability. In this work the grid approach was compared to the summing method in three cases: , and . By using the grid directly, the angular resolution was found equally good in the first case but gave 7% and 20% improvements, respectively, in the latter cases.JRC.D.4-Nuclear physic

10B and 6Li nuclear data measurements for incident neutron energies up to 3 MeV

We present experimental methods for the measurement of the 10B(n,α)7Li and the 6Li(n,t)4He reactions for neutron energies up to 3 MeV, and preliminary data for the 10B(n,α0)/10B(n,α1γ) branching ratios. The experimental facilities were installed at GELINA and the Van de Graaff generator of the Institute for Reference Materials and Measurement of the European Commission. Our results show the need to investigate the MeV region for these reactions, since the ENDF/B-VII.1 evaluation agrees with our data up to 1.3 MeV and overestimates above this limit.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard