Effect of drifts on the diffusion of runaway electrons in tokamak stochastic magnetic fields

1992 ◽  
Vol 4 (1) ◽  
pp. 176-186 ◽  
Author(s):  
J. R. Myra ◽  
Peter J. Catto
Keyword(s):  
Magnetic Fields ◽  
Runaway Electrons ◽  
Stochastic Magnetic Fields

scholarly journals Effects of magnetic perturbations and radiation on the runaway avalanche

2021 ◽  
Vol 87 (2) ◽  
Author(s):  
P. Svensson ◽  
O. Embreus ◽  
S. L. Newton ◽  
K. Särkimäki ◽  
O. Vallhagen ◽  
...  
Keyword(s):  
Growth Rate ◽  
Runaway Electrons ◽  
Plasma Parameters ◽  
Perturbative Approach ◽  
Efficient Simulation ◽  
Strong Current ◽  
Magnetic Perturbations ◽  
Space Dynamics ◽  
Stochastic Magnetic Fields ◽  
Mitigation Methods

The electron runaway phenomenon in plasmas depends sensitively on the momentum- space dynamics. However, efficient simulation of the global evolution of systems involving runaway electrons typically requires a reduced fluid description. This is needed, for example, in the design of essential runaway mitigation methods for tokamaks. In this paper, we present a method to include the effect of momentum-dependent spatial transport in the runaway avalanche growth rate. We quantify the reduction of the growth rate in the presence of electron diffusion in stochastic magnetic fields and show that the spatial transport can raise the effective critical electric field. Using a perturbative approach, we derive a set of equations that allows treatment of the effect of spatial transport on runaway dynamics in the presence of radial variation in plasma parameters. This is then used to demonstrate the effect of spatial transport in current quench simulations for ITER-like plasmas with massive material injection. We find that in scenarios with sufficiently slow current quench, owing to moderate impurity and deuterium injection, the presence of magnetic perturbations reduces the final runaway current considerably. Perturbations localised at the edge are not effective in suppressing the runaways, unless the runaway generation is off-axis, in which case they may lead to formation of strong current sheets at the interface of the confined and perturbed regions.

Transport in sheared stochastic magnetic fields

1997 ◽  
Vol 4 (2) ◽  
pp. 270-276 ◽  
Author(s):  
E. Vanden Eijnden ◽  
R. Balescu
Keyword(s):  
Magnetic Fields ◽  
Stochastic Magnetic Fields

Electron transport studies in stochastic magnetic fields on the Compact Auburn Torsatron

1995 ◽  
Vol 2 (6) ◽  
pp. 2026-2032 ◽  
Author(s):  
H. Lin ◽  
R. F. Gandy ◽  
S. F. Knowlton ◽  
G. J. Hartwell ◽  
D. Prichard ◽  
...  
Keyword(s):  
Electron Transport ◽  
Magnetic Fields ◽  
Transport Studies ◽  
Stochastic Magnetic Fields

Nonlinear Magneto-Electric Response Characteristics of Giant Mag-Netostrictive-Piezoelectric Composite Sensors in Harmonic and Stochastic Excitation

2015 ◽  
Vol 764-765 ◽  
pp. 1339-1343
Author(s):  
Jia Xu ◽  
Chang Yi Hong ◽  
Zhi Wen Zhu
Keyword(s):  
Magnetic Fields ◽  
Piezoelectric Composite ◽  
Electric Response ◽  
Stochastic Excitation ◽  
Nonlinear Dynamic Model ◽  
Van Der Pol ◽  
Response Characteristics ◽  
Giant Magnetostrictive Material ◽  
Jump Phenomena ◽  
Stochastic Magnetic Fields

Nonlinear magneto-electric response characteristics of giant magnetostrictive-piezoelectric composite sensors in harmonic and stochastic magnetic fields were studied in this paper. Van der Pol nonlinear difference items were introduced to interpret the hysteresis phenomena of both giant magnetostrictive material and piezoelectric ceramics. The nonlinear dynamic model of giant magnetostrictive-piezoelectric composite sensors in harmonic and stochastic magnetic fields was developed. The expression of dynamic response of the system was obtained, and the bifurcation characteristics of the system were analyzed. The magneto-electric coefficient of the composite sensors was determined, and the effects of system parameters on the dynamic characteristics and magneto-electric coefficient of the system were analyzed. The simulation results show that there are stochastic Hopf bifurcation and jump phenomena of vibration amplitude in the system, and both of that can be avoided through adjusting parameters. The experimental results show that the system’s motion becomes chaotic when stochastic excitation is extremely large. The results of this paper are helpful for optimal design and improvement of giant magnetostrictive-piezoelectric composite sensors.

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