The 3-D Plasma Distribution Function Analyzers with Time-of-Flight Mass Discrimination for Cluster, FAST, and Equator-S

2013 ◽  
pp. 243-248 ◽  
Author(s):  
E. Möbius ◽  
L. M. Kistler ◽  
M. A. Popecki ◽  
K. N. Crocker ◽  
M. Granoff ◽  
...  
Keyword(s):  
Distribution Function ◽  
Time Of Flight ◽  
Mass Discrimination ◽  
Plasma Distribution

scholarly journals Precise implications for real-space pair distribution function modeling of effects intrinsic to modern time-of-flight neutron diffractometers

2018 ◽  
Vol 74 (4) ◽  
pp. 293-307 ◽  
Author(s):  
Daniel Olds ◽  
Claire N. Saunders ◽  
Megan Peters ◽  
Thomas Proffen ◽  
Joerg Neuefeind ◽  
...  
Keyword(s):  
Distribution Function ◽  
Pair Distribution Function ◽  
Amorphous Materials ◽  
Best Practice ◽  
Time Of Flight ◽  
Real Space ◽  
Mitigation Strategies ◽  
Total Scattering ◽  
Conventional Analysis ◽  
Pdf Analysis

Total scattering and pair distribution function (PDF) methods allow for detailed study of local atomic order and disorder, including materials for which Rietveld refinements are not traditionally possible (amorphous materials, liquids, glasses and nanoparticles). With the advent of modern neutron time-of-flight (TOF) instrumentation, total scattering studies are capable of producing PDFs with ranges upwards of 100–200 Å, covering the correlation length scales of interest for many materials under study. Despite this, the refinement and subsequent analysis of data are often limited by confounding factors that are not rigorously accounted for in conventional analysis programs. While many of these artifacts are known and recognized by experts in the field, their effects and any associated mitigation strategies largely exist as passed-down `tribal' knowledge in the community, and have not been concisely demonstrated and compared in a unified presentation. This article aims to explicitly demonstrate, through reviews of previous literature, simulated analysis and real-world case studies, the effects of resolution, binning, bounds, peak shape, peak asymmetry, inconsistent conversion of TOF to d spacing and merging of multiple banks in neutron TOF data as they directly relate to real-space PDF analysis. Suggestions for best practice in analysis of data from modern neutron TOF total scattering instruments when using conventional analysis programs are made, as well as recommendations for improved analysis methods and future instrument design.

Suprathermal plasma distribution functions with relativistic cut-offs

2019 ◽  
Vol 491 (3) ◽  
pp. 3967-3973
Author(s):  
H-J Fahr ◽  
M Heyl
Keyword(s):  
Distribution Function ◽  
Heat Transport ◽  
Distribution Functions ◽  
The Other ◽  
Pressure Reduction ◽  
Plasma Distribution ◽  
Order Of Magnitude ◽  
Low Mass ◽  
Velocity Moments ◽  
Free Plasma

ABSTRACT In typical plasma physics scenarios, when treated on kinetic levels, distribution functions with suprathermal wings are obtained. This raises the question of how the associated typical velocity moments, which are needed to arrive at magnetohydrodynamic plasma descriptions, may appear. It has become evident that the higher velocity moments in particular, for example the pressure or heat transport, which are constructed as integrations of the distribution function, contain unphysical contributions from particles with velocities greater than the velocity of light. In what follows, we discuss two possibilities to overcome this problem. One is to calculate a maximal, physically permitted, upper velocity, which can be realized in view of the underlying energization processes, and to stop the integration there. The other is to modify the distribution function relativistically so that no particles with superluminal (v ≥ c) velocities appear. On the basis of a typical collision-free plasma scenario, like the plasma in the heliosheath, we obtain the corresponding expressions for electron and proton pressures and can show that in both cases the pressures are reduced compared with their classical values; however, electrons experience a stronger reduction than protons. When calculating pressure ratios, it turns out that these are of the same order of magnitude regardless of which of the two methods is used. The electron, as the low-mass particle, undergoes the more pronounced pressure reduction. It may turn out that electrons and protons constitute about equal pressures in the heliosheath, implying that no pressure deficit need be claimed here.

Mass discrimination using the inferred depth of maximum through the particle densities measured at observation level

2015 ◽  
Vol 24 (10) ◽  
pp. 1550080 ◽  
Author(s):  
G. Rastegarzadeh ◽  
S. Khoshabadi
Keyword(s):  
Distribution Function ◽  
Energy Range ◽  
Linear Relationship ◽  
Distribution Functions ◽  
Mass Discrimination ◽  
Observation Level ◽  
Sensitive Parameter ◽  
Low Energies ◽  
Good Potential ◽  
Sensitive Parameters

In the present work, the shower depth of maximum (X max e) and (X max μ) (the depth at which the number of muons of shower get their maximum) has been calculated from the particles densities at the observation level. It is noteworthy that these are both mass sensitive parameters. Based on CORSIKA simulations a relationship between slope of the lateral distribution functions (η) of electrons and muons (at the observation level) and their X max have been investigated. An accurate linear relationship between them is found. The higher the energy, the deeper the X max and the steeper the distribution function is. Simulations have been done for heavy and light primaries in the energy range of 1014–1015 eV. Better ability for mass discrimination of η of the muons, due to less deflection of muons with the atmosphere is demonstrated. This method has got better results for low energies. Therefore a mass sensitive parameter, with good potential for mass discriminating between light and heavy primaries is presented.

scholarly journals Kinetic entropy-based measures of distribution function non-Maxwellianity: theory and simulations

2020 ◽  
Vol 86 (5) ◽  
Author(s):  
Haoming Liang ◽  
M. Hasan Barbhuiya ◽  
P. A. Cassak ◽  
O. Pezzi ◽  
S. Servidio ◽  
...  
Keyword(s):  
Distribution Function ◽  
Magnetic Reconnection ◽  
Entropy Density ◽  
Distribution Functions ◽  
Local Distribution ◽  
Particle In Cell ◽  
Maxwellian Plasma ◽  
Plasma Distribution ◽  
Maxwellian Distribution Function ◽  
Quantitative Understanding

We investigate kinetic entropy-based measures of the non-Maxwellianity of distribution functions in plasmas, i.e. entropy-based measures of the departure of a local distribution function from an associated Maxwellian distribution function with the same density, bulk flow and temperature as the local distribution. First, we consider a form previously employed by Kaufmann & Paterson (J. Geophys. Res., vol. 114, 2009, A00D04), assessing its properties and deriving equivalent forms. To provide a quantitative understanding of it, we derive analytical expressions for three common non-Maxwellian plasma distribution functions. We show that there are undesirable features of this non-Maxwellianity measure including that it can diverge in various physical limits and elucidate the reason for the divergence. We then introduce a new kinetic entropy-based non-Maxwellianity measure based on the velocity-space kinetic entropy density, which has a meaningful physical interpretation and does not diverge. We use collisionless particle-in-cell simulations of two-dimensional anti-parallel magnetic reconnection to assess the kinetic entropy-based non-Maxwellianity measures. We show that regions of non-zero non-Maxwellianity are linked to kinetic processes occurring during magnetic reconnection. We also show the simulated non-Maxwellianity agrees reasonably well with predictions for distributions resembling those calculated analytically. These results can be important for applications, as non-Maxwellianity can be used to identify regions of kinetic-scale physics or increased dissipation in plasmas.

scholarly journals Non-hydrodynamic Contributions to the End Effects in Time of Flight Swarm Experiments

1987 ◽  
Vol 40 (4) ◽  
pp. 519 ◽  
Author(s):  
Russell K Standish
Keyword(s):  
Distribution Function ◽  
Power Series ◽  
Transport Coefficients ◽  
Time Of Flight ◽  
Lithium Ions ◽  
End Effects ◽  
Flight Experiment ◽  
Drift Length ◽  
Order Of Magnitude ◽  
Hydrodynamic Effects

The hydrodynamic part of the distribution function of a swarm is separated from its nonhydrodynamic part using a projection operator, leading to an explicit expression for the timedependent transport coefficients. These are then related to a time of flight experiment. The contribution from non-hydrodynamic effects to the measured drift velocity is shown to be a power series in 11 d, where d is the drift length. A calculation based on an exactly soluble Fokker-Planck model shows that the correction to mobility measurements of lithium ions in helium due to non-hydrodynamic effects is of the same order of magnitude as those observed experimentally.

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