Numerical Modeling of the Thermal Force for the Kinetic Test-Ion Transport Simulation Based on the Fokker-Planck Collision Operator

2014 ◽  
Vol 54 (4-6) ◽  
pp. 394-398 ◽  
Author(s):  
Y. Homma ◽  
A. Hatayama
Keyword(s):  
Numerical Modeling ◽  
Ion Transport ◽  
Collision Operator ◽  
Transport Simulation ◽  
Simulation Based ◽  
Kinetic Test ◽  
Fokker Planck

Two temperature gas equilibration model with a Fokker-Planck type collision operator

2014 ◽  
Author(s):  
A. R. Méndez ◽  
G. Chacón-Acosta ◽  
A. L. García-Perciante
Keyword(s):  
Collision Operator ◽  
Two Temperature ◽  
Equilibration Model ◽  
Fokker Planck

scholarly journals Generalized collision operator for fast electrons interacting with partially ionized impurities

2018 ◽  
Vol 84 (6) ◽  
Author(s):  
L. Hesslow ◽  
O. Embréus ◽  
M. Hoppe ◽  
T. C. DuBois ◽  
G. Papp ◽  
...  
Keyword(s):  
Growth Rate ◽  
Electric Fields ◽  
Collision Operator ◽  
Impurity Content ◽  
Fast Electrons ◽  
Generalized Operator ◽  
Partially Ionized ◽  
High Electric Fields ◽  
Bound Electrons ◽  
Fokker Planck

Accurate modelling of the interaction between fast electrons and partially ionized atoms is important for evaluating tokamak disruption mitigation schemes based on material injection. This requires accounting for the effect of screening of the impurity nuclei by the cloud of bound electrons. In this paper, we generalize the Fokker–Planck operator in a fully ionized plasma by accounting for the effect of screening. We detail the derivation of this generalized operator, and calculate the effective ion length scales, needed in the components of the collision operator, for a number of ion species commonly appearing in fusion experiments. We show that for high electric fields, the secondary runaway growth rate can be substantially larger than in a fully ionized plasma with the same effective charge, although the growth rate is significantly reduced at near-critical electric fields. Furthermore, by comparison with the Boltzmann collision operator, we show that the Fokker–Planck formalism is accurate even for large impurity content.

Alpha Radioactivity Monitor Using Ionized Air Transport Technology for Large Size Uranium Waste: Part 2—Simulation Model Reinforcement for Practical Apparatus Design

2010 ◽  
Author(s):  
Takatoshi Asada ◽  
Yosuke Hirata ◽  
Susumu Naito ◽  
Mikio Izumi ◽  
Yukio Yoshimura
Keyword(s):  
Ion Transport ◽  
Simulation Model ◽  
Cfd Simulation ◽  
Transport Model ◽  
Model Simulation ◽  
Ion Density ◽  
Transport Simulation ◽  
Simulation Results ◽  
Alpha Radioactivity ◽  
Ionized Air

In alpha radioactivity measurement using ionized air transportation (AMAT), conversion from ion currents to radioactivity accurate is required. An ion transport simulation provides ways of complementarily determining conversion factors. We have developed an ion transport simulation model. Simulation results were compared with experiments with air speeds, faster than 1 m/s, achieving good agreement. In a practical AMAT apparatus, the air-flow at the alpha source may be slower than 1 m/s, and ion loss is likely to be large. Reinforcement of the ion transport model to cover the lower air speed region is effective. Ions are generated by an alpha particle in a very thin column. Since the ion density at this temporal stage is high, the recombination loss, proportional to the square of ion density, is dominant within a few milli-seconds. The spatial and temporal scales of this columnar recombination are too small for CFD simulation. We solve an ion transport equation during the period of columnar recombination with diffusion and recombination terms and incorporated the relation between ion loss and turbulent parameters into CFD. Using this model, simulations have been done for various air speeds and targets. Those for simulation results agree with experiments, showing improvement of simulation accuracy.

A Numerical Scheme for the Quantum Fokker-Planck-Landau Equation Efficient in the Fluid Regime

2012 ◽  
Vol 12 (5) ◽  
pp. 1541-1561 ◽  
Author(s):  
Jingwei Hu ◽  
Shi Jin ◽  
Bokai Yan
Keyword(s):  
Numerical Scheme ◽  
Landau Equation ◽  
Collision Operator ◽  
Collision Term ◽  
Fluid Regime ◽  
Quantum Operator ◽  
Simple Quantum ◽  
Dirac Distribution ◽  
Bose Einstein ◽  
Fokker Planck

Abstract We construct an efficient numerical scheme for the quantum Fokker-Planck- Landau (FPL) equation that works uniformly from kinetic to fluid regimes. Such a scheme inevitably needs an implicit discretization of the nonlinear collision operator, which is difficult to invert. Inspired by work [9] we seek a linear operator to penalize the quantum FPL collision term QqFPL in order to remove the stiffness induced by the small Knudsen number. However, there is no suitable simple quantum operator serving the purpose and for this kind of operators one has to solve the complicated quantum Maxwellians (Bose-Einstein or Fermi-Dirac distribution). In this paper, we propose to penalize QqFPL by the "classical" linear Fokker-Planck operator. It is based on the observation that the classical Maxwellian, with the temperature replaced by the internal energy, has the same first five moments as the quantum Maxwellian. Numerical results for Bose and Fermi gases are presented to illustrate the efficiency of the scheme in both fluid and kinetic regimes.

Sign in / Sign up

Export Citation Format

Share Document