Neutron monitors and muon detectors for solar modulation studies: 2. ϕ\phi time series

The level of solar modulation at different times (related to the solar activity) is a central question of solar and galactic cosmic-ray physics. In the first paper of this series, we have established a correspondence between the uncertainties on ground-based detectors count rates and the parameter $\phi$ (modulation level in the force-field approximation) reconstructed from these count rates. In this second paper, we detail a procedure to obtain a reference $\phi$ time series from neutron monitor data. We show that we can have an unbiased and accurate $\phi$ reconstruction ($\Delta\phi/\phi\simeq 10\%$). We also discuss the potential of Bonner spheres spectrometers and muon detectors to provide $\phi$ time series. Two by-products of this calculation are updated $\phi$ values for the cosmic-ray database and a web interface to retrieve and plot $\phi$ from the 50's to today (\url{http://lpsc.in2p3.fr/crdb}).Comment: 15 pages, 5 figures, 2 tables. AdSR, in press. Web interface to get modulation parameter phi(t): new tab in http://lpsc.in2p3.fr/crd

Atmospheric radiation environment analyses based-on CCD camera, neutron spectrometer and multi-physics modeling

International audienceIn this paper, high-altitude measurements of both radiation environment and effects are described. Measurements are made using a neutron spectrometer and CCD camera. MUSCA SEP3 software is used to correlate both measurement approaches. Analyses of the charge levels in pixels induced by radiation events are proposed. Then, cross-comparison analyses based on a CCD camera and HERMEIS neutron spectrometer are performed to investigate radiation dynamic properties, including neutron/proton and muon contributions. © 2013 IEEE

MULTI-PHYSICS MODELLING CONTRIBUTIONS TO INVESTIGATE THE ATMOSPHERIC COSMIC RAYS ON THE SINGLE EVENT UPSET SENSITIVITY ALONG THE SCALING TREND OF CMOS TECHNOLOGIES

International audienceParticles originating from primary cosmic radiation, which hit the Earth's atmosphere give rise to a complex field of secondary particles. These particles include neutrons, protons, muons, pions, etc. Since the 1980s it has been known that terrestrial cosmic rays can penetrate the natural shielding of buildings, equipment and circuit package and induce soft errors in integrated circuits. Recently, research has shown that commercial static random access memories are now so small and sufficiently sensitive that single event upsets (SEUs) may be induced from the electronic stopping of a proton. With continued advancements in process size, this downward trend in sensitivity is expected to continue. Then, muon soft errors have been predicted for nano-electronics. This paper describes the effects in the specific cases such as neutron-, proton-and muon-induced SEU observed in complemen-tary metal-oxide semiconductor. The results will allow investigating the technology node sensitivity along the scaling trend

Characterization of the neutron environment at the CERN-EU High Energy Reference Field and at the Pic du Midi

International audienceA new platform dedicated to the long-term characterization of the Atmospheric Natural Radiative Environment at mountain altitude (Pic du Midi, +2885 m) is presented. The performance of a high energy neutron spectrometer is established by comparison with the neutron monitors

Characterization of the IRSN neutron multisphere spectrometer (HERMEIS) at European standard calibration fields

International audienceThe Institute for Radiological Protection and Nuclear Safety (IRSN) has developed a new spectrometry system for neutron energies from 10-9 MeV to 10 GeV. This high energy range multisphere extended IRSN system (HERMEIS) is a high gas pressure3He-based Bonner spheres set. It is adapted to low neutron fluence rate measurements and one of its main application concerns the determination of cosmic-ray-induced neutron spectra at ground level and mountain altitudes. The neutron fluence response matrix of the set of 13 Bonner spheres, including three extended ones with tungsten and lead shells, was calculated with the radiation transport code MCNPX-2.6f. Reliable fluence responses being mandatory for a correct evaluation of the atmospheric neutron spectra, HERMEIS was characterized at standard monoenergetic, quasi-monoenergetic and realistic neutron fields facilities. Measurements with monoenergetic neutron beams of 144 keV, 565 keV, 5 MeV and 17 MeV were performed at the NPL standard Van de Graaff facility. For the characterization of the response functions at higher energies, measurements were done at the Svedberg Laboratory, with 46 MeV and 144 MeV quasi-monoenergetic neutrons. Finally, to demonstrate the suitability of the system for broad cosmic-ray neutron spectra, measurements were performed at the TSL Atmospheric-like Neutrons from thIck TArget (ANITA) and also at the CERN European Realistic Field (CERF) facilities. Data from the realistic spectra were unfolded with the GRAVEL unfolding code and as a whole, a good agreement was found between the experimental and Monte-Carlo calculated neutron fluence energy distributions. © 2012 IOP Publishing Ltd and Sissa Medialab srl

Accuracy assessment of a Lucas-Kanade based correlation method for 3D PIV

International audienceWe introduce and characterize a new 3D cross-correlation algorithm, which relies on gradient-based iterative volume deformation. The algorithm, FOLKI3D, is the extension to 3D PIV of the approach introduced by Champagnat et al. 2011. It has a highly parallel structure and is implemented on GPU. Additionally to the gradient approach for displacement estimation, we implemented a high-order interpolation scheme (with cubic B-Splines) in the volume deformation step, at a reasonable computational cost. Performance tests on synthetic volumic distributions first allow to characterize the spatial transfer function of the algorithm, and to confirm the efficiency of this interpolator, comparable to that of standard image deformation methods in planar PIV. A second series of synthetic tests then investigates the response of FOLKI3D to sources of noise specific to the tomographic PIV context, i.e. ghost particles. Depending on the tests, the algorithm is found as efficient or more robust than the state-of-the-art. The gain brought by the high-order interpolation is also confirmed in a situation with a large number of ghosts, and different reconstructed particle shapes

Experimental measurements of the cosmic-ray induced neutron spectra at various mountain altitudes with HERMEIS

Measurements performed with the High Energy Range Multisphere Extended IRSN System (HERMEIS) acquired by the French Aerospace Lab are presented and discussed. The detectors were calibrated at the Low Noise Underground Laboratory of Rustrel. Atmospheric neutron spectra were obtained at three altitudes (+500 m, +1000 m and +2885 m) and the first results about the continuous measurements of the Natural Radiative Environment at the Pic du Midi are presented with a discussion about the uncertainties. © 2012 IEEE

Computationally efficient sparse algorithms for tomographic PIV Reconstruction

\u93Back to physical particles\u94 is the idea behind this paper. We introduce the physically sound Point Spread Function (PSF) model for tomographic PIV reconstruction, that aims at sparse and spiky reconstructions. Using the PSF, we show that the tracer particles are quasi-systematically in the direct vicinity of local maxima of reconstructions obtained with MLOS. Taking advantage of both the PSF model and this local maxima extraction (which we call \u93LocM\u94), we manage to dramatically reduce the dimensionality of the reconstruction that follows. For this reconstruction, we consider the SMART algorithm applied on this local maximum restriction, and also introduce a sparse algorithm, CoSaMP. We investigate the performances of LocM-SMART and LocM-CoSaMP, compared to the traditional, blob-like, MLOSSMART used in particular by [2]. LocM-XX methods combine dramatic computational gains and a very good reconstruction accuracy. LocM-CoSaMP in particular reaches equivalent or better performances than classical MLOSSMART especially if a voxel to pixel ratio equal to 1/2 is adopted

On factors affecting the quality of tomographic reconstruction

In this paper we present experimental factors affecting the quality of tomographic PIV reconstruction. Our main contribution is to introduce a new factor built on the geometrical considerations applied to the cameras field of views and the laser volume. By performing numerical tests, we show the influence of this parameter the reconstruction using different quality measurements. We also analyze the reconstruction quality loss when illuminating larger volumes and when defocussing occurs. Finally, the effects of light scattering in the Mie regime on the reconstruction are studied. We show how Mie scattering effects ultimately lead to a signal to noise ratio loss in the reconstruction volume

Tomographic PIV: Particles vs blobs

We present an alternative approach to tomo-PIV that seeks to recover single voxel particles rather than blobs of extended size. Our approach follows the classical MLOS-SMART method with a weight matrix built with the system\u92s Point Spread Function coefficients. As such an approach requires only a few voxels to explain the image appearance, it yields much more sparse reconstructed volumes. We carefully justify our method for building the weight matrix and show on synthetic PIV images with a large exploration of generating conditions that it always leads to better results than MLOS-SMART