Nuclear signal simulation applied to gas ionizing chambers

Conference of 4th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, ANIMMA 2015 ; Conference Code:121554International audienceParticle transport codes used in detector simulation allow the calculation of the energy deposited by charged particles produced following an interaction. The pulses temporal shaping is more and more used in nuclear measurement into pulse shape analysis techniques. A model is proposed in this paper to simulate the pulse temporal shaping and the associated noise level thanks to the output track file PTRAC provides by Monte-Carlo particle transport codes. The model has been dedicated to ion chambers and more especially for High Pressure Xenon chambers HPXe where the pulse shape analysis can resolve some issues regarding with this technology as the ballistic deficit phenomenon. The model is fully described and an example is presented as a validation of such full detector simulation

« Apports croisés entre fiction et théorie du Dark Side en entreprise : le cas de la fiction The Challenger Disaster (2013) »

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Paternal supervisor gatekeeping: How supervising fathers hinder other fathers at work in their uptake of flexible work arrangements

This study explores the role that supervisors play in the low uptake of Flexible Work Arrangements (FWA) among fathers in France. We draw on 28 interviews with fathers who had requested access to FWA and reported on the reaction of their supervisors. These supervisors were all fathers themselves and had previously benefitted from such arrangements themselves, but did not grant such policies to other fathers. To understand these unexpected findings, we conducted an additional 16 interviews with supervising fathers in organizations who had previously enjoyed similar FWA. The findings show that supervising fathers can act as barriers to other fathers in their organizations who try to push for more gender equality. We identified four ways in which supervisors tend to dissuade fathers from accessing policies to which they are entitled: gender-role confirming discourses; career threats; practical reasons as a justification; and a lack of paternal workplace support. The findings highlight the role of men (in this case, supervising fathers) in the lack of increasing gender equality at work. By showing that fathers can function as ‘paternal supervisor gatekeepers’ for other fathers in their organizations, we open up new fruitful ways for studying gender equality in organizations

Implementation of a nonlinear filter for online nuclear counting

International audienceNuclear counting is a challenging task for nuclear instrumentation because of the stochastic nature of radioactivity. Event counting has to be processed and filtered to determine a stable count rate value and perform variation monitoring of the measured event. An innovative approach for nuclear counting is presented in this study, improving response time and maintaining count rate stability. Some nonlinear filters providing a local maximum likelihood estimation of the signal have been recently developed, which have been tested and compared with conventional linear filters. A nonlinear filter thus developed shows significant performance in terms of response time and measurement precision. The filter also presents the specificity of easy embedment into digital signal processor (DSP) electronics based on field programmable gate arrays (FPGA) or microcontrollers, compatible with real-time requirements

Détecteur de fission à basse température (77 °K)

La section efficace de fission par des neutrons de 16 eV à 35 keV du 239Pu a été mesurée à l'accélérateur linéaire de 45 MeV de Saclay par la méthode du temps-de-vol avec un scintillateur gazeux d'un type nouveau contenant 1 g de matière fissile et refroidi à la température de l'azote liquide. La résolution nominale était de 1 ns/m et les résultats obtenus sont comparés à des mesures antérieures

Gadolinium for neutron detection in current nuclear instrumentation research: A review

International audienceNatural gadolinium displays a number of remarkable physical properties: it is a rare earth element, composed of seven stable or quasi-stable isotopes, with an exceptionally high magnetization and a Curie point near room temperature. Its use in the field of nuclear instrumentation historically relates to its efficiency as a neutron poison in power reactors. Gadolinium is indeed the naturally occurring element with the highest interaction probability with neutrons at thermal energy, shared between Gd-157 (15.65%, 254000 b cross section) and Gd-155 (14.8%, 60900 b) isotopes. Considering that neutron capture results in an isotopic change, followed by a radiative rearrangement of nuclear and atomic structures, Gd may be embodied not merely as a neutron poison but as a neutron converter into a prompt photon and an electron source term. Depending on the nature and energy of the reaction products (from a few-keV Auger electrons up to 8 MeV gamma rays) that the detector aims at isolating as an indirect neutron signature, a variety of sensor media and counting methods have been introduced during the last decades. This review first draws a theoretical description of the radiative cascade following Gd(n,gamma) capture. The cascade may be subdivided into regions of interest, each corresponding to dedicated detection designs and optimizations whose current status is detailed. This inventory has allowed the authors to extract and benchmark key figures of merit for the definition of a detection scheme: neutron attenuation, neutron sensitivity (cps/nv), gamma rejection, neutron detection limit in a mixed field, intrinsic or extrinsic moderation, and transportability. On this basis, the authors have identified promising paths for Gd-based neutron detection in contemporary instrumentation

Nuclear counting filter based on a Centered Skellam Test and a double Exponential Smoothing

Conference of 4th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, ANIMMA 2015 ; Conference Code:121554International audienceOnline nuclear counting represents a challenge due to the stochastic nature of radioactivity. The count data have to be filtered in order to provide a precise and accurate estimation of the count rate, this with a response time compatible with the application in view. An innovative filter is presented in this paper addressing this issue. It is a nonlinear filter based on a Centered Skellam Test (CST) giving a local maximum likelihood estimation of the signal based on a Poisson distribution assumption. This nonlinear approach allows to smooth the counting signal while maintaining a fast response when brutal change activity occur. The filter has been improved by the implementation of a Brown's double Exponential Smoothing (BES). The filter has been validated and compared to other state of the art smoothing filters. The CST-BES filter shows a significant improvement compared to all tested smoothing filters

Hypothesis tests for the detection of constant speed radiation moving sources

Conference of 4th International Conference on Advancements in Nuclear Instrumentation Measurement Methods and their Applications, ANIMMA 2015 ; Conference Code:121554International audienceAs a complement to single and multichannel detection algorithms, inefficient under too low signal-to-noise ratios, temporal correlation algorithms have been introduced to detect radiological material in motion. Test hypothesis methods based on the mean and variance of the signals delivered by the different channels have shown significant gain in terms of a tradeoff between detection sensitivity and false alarm probability. This paper discloses the concept of a new hypothesis test for temporal product detection methods, taking advantage of the Poisson nature of the registered counting signals, and establishes a benchmark between this test and its empirical counterpart. The simulation study validates that in the two relevant configurations of a pedestrian source carrier under respectively high and low count rate radioactive backgrounds, the newly introduced hypothesis test ensures a significantly improved compromise between sensitivity and false alarm, while guaranteeing the stability of its optimization parameter regardless of signal-to-noise ratio variations between 2 to 0.8

Gadosphere: a high-scale plastic scintillator sphere with a metal gadolinium core for thermal neutron detection and counting

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