Halo current rotation scaling in post-disruption plasmas

2021 ◽  
Author(s):  
Alex Ryan Saperstein ◽  
J P Levesque ◽  
Michael E Mauel ◽  
Gerald Navratil
Keyword(s):  
Field Strength ◽  
Scaling Law ◽  
Rotation Frequency ◽  
Toroidal Field ◽  
Tokamak Plasma ◽  
Minor Radius ◽  
Drift Frequency ◽  
Asymmetric Component

Abstract Halo current (HC) rotation during disruptions can be potentially dangerous if resonant with the structures surrounding a tokamak plasma. We propose a drift-frequency-based scaling law for the rotation frequency of the asymmetric component of the HC as a function of toroidal field strength and plasma minor radius (frot ∝ 1/BT a2 ). This scaling law is consistent with results reported for many tokamaks and is motivated by the faster HC rotation observed in the HBT-EP tokamak. Projection of the rotation frequency to ITER and SPARC parameters suggest the asymmetric HC rotation will be on the order of 10 Hz and 60 Hz, respectively.

scholarly journals Figures of merit for stellarators near the magnetic axis

2021 ◽  
Vol 87 (1) ◽  
Author(s):  
Matt Landreman
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Axis ◽  
Configuration Design ◽  
New Paradigm ◽  
First Order ◽  
Figures Of Merit ◽  
Minor Radius ◽  
Error Field ◽  
Quantities Of Interest

A new paradigm for rapid stellarator configuration design has been recently demonstrated, in which the shapes of quasisymmetric or omnigenous flux surfaces are computed directly using an expansion in small distance from the magnetic axis. To further develop this approach, here we derive several other quantities of interest that can be rapidly computed from this near-axis expansion. First, the $\boldsymbol {\nabla }\boldsymbol {B}$ and $\boldsymbol {\nabla }\boldsymbol {\nabla }\boldsymbol {B}$ tensors are computed, which can be used for direct derivative-based optimization of electromagnetic coil shapes to achieve the desired magnetic configuration. Moreover, if the norm of these tensors is large compared with the field strength for a given magnetic field, the field must have a short length scale, suggesting it may be hard to produce with coils that are suitably far away. Second, we evaluate the minor radius at which the flux surface shapes would become singular, providing a lower bound on the achievable aspect ratio. This bound is also shown to be related to an equilibrium beta limit. Finally, for configurations that are constructed to achieve a desired magnetic field strength to first order in the expansion, we compute the error field that arises due to second-order terms.

scholarly journals Poloidal Rotation and Edge Ion Temperature Measurements Using Spectroscopy Diagnostic on Aditya-U Tokamak

Atoms ◽  
2019 ◽  
Vol 7 (3) ◽  
pp. 93
Author(s):  
Gaurav Shukla ◽  
Malay B. Chowdhuri ◽  
Kajal Shah ◽  
Nandini Yadava ◽  
Ranjana Manchanda ◽  
...  
Keyword(s):  
High Resolution ◽  
Line Emission ◽  
Rotation Velocity ◽  
Spectral Lines ◽  
Tokamak Plasma ◽  
Vacuum Vessel ◽  
Ion Temperature ◽  
Minor Radius ◽  
Impurity Ion ◽  
Poloidal Rotation

The impurity ion poloidal rotation and ion temperature from the Aditya-U tokamak plasma have been measured using a high-resolution spectroscopic diagnostic. It comprises of a high resolution, 1 m, f/8.7, Czerny-Turner configuration spectrometer along with charge coupled device (CCD) detector. The system monitors the spectral line emission of C2+ impurity ions at 464.74 nm from the top port of the Aditya-U vacuum vessel with the lines of sight covering the plasma minor radius from r = 11.55 cm to 21.55 cm. The impurity ion poloidal rotation velocity and temperature have been estimated using the Doppler shift and Doppler broadening of the spectral lines respectively. The maximum poloidal rotation at a radial location of 21.55 cm in the edge of the plasma during the plasma current flat top was observed to be ~4 km/s for the analyzed discharges and the ion temperatures measured in the edge were in the range of 32–40 eV.

scholarly journals The Finite Beta Effects on the Toroidal Field Ripple in a Tokamak Plasma

2013 ◽  
Vol 15 (2) ◽  
pp. 115-118 ◽  
Author(s):  
M. Bunno ◽  
Y. Nakamura ◽  
Y. Suzuki ◽  
K. Shinohara ◽  
G. Matsunaga ◽  
...  
Keyword(s):  
Toroidal Field ◽  
Tokamak Plasma ◽  
Toroidal Field Ripple

scholarly journals Numerical Simulations of Solar Flares

2000 ◽  
Vol 195 ◽  
pp. 445-446
Author(s):  
T. Yokoyama ◽  
K. Shibata
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Heating Rate ◽  
Magnetic Field Strength ◽  
Mass Density ◽  
Scaling Law ◽  
Coronal Magnetic Field ◽  
Mhd Equations ◽  
Numerical Code ◽  
Volumetric Heating

We study reconnection and chromospheric evaporation in flares using a numerical code including nonlinear, anisotropic heat conduction (Yokoyama & Shibata 1998). The two-dimensional, nonlinear, time-dependent, resistive, compressible MHD equations are solved. The evolution from the rise phase to (the early part of) the decay phase of a solar flare is qualitatively reproduced in this simulation. Based on the results, we obtained a relationship between the flare temperature and the coronal magnetic field strength. We assume that the energy input to a loop balances with the conductive cooling rate, that the temperature at the loop apex is TA ≍ (2QL2/κ0)2/7, where Q is the volumetric heating rate, that L is the half-length of the loop, and that the Spitzer thermal conductivity constant is κ0 = 10−6 CGS. In our simulations, the heating mechanism is magnetic reconnection, so the heating rate is described as Q = B2/(4π) · Vin/L · l/sin Θ, where B is the coronal magnetic field strength, Vin is the inflow velocity (≍ 0.1 VA from our result and also from Petschek's theory), and Θ is the angle between the slow-mode MHD shock and the loop and is approximately given by sin Θ ≍ Vin/VA. By manipulating the equations, we find where ρ is the mass density of the corona. The simulation results show very good agreement with this scaling law.

Electrorheological Properties of Suspensions Prepared From Polythiophene Conductive Polymer

Materials ◽  
2005 ◽  
Author(s):  
Datchanee Chotpattananont ◽  
Anuvat Sirivat
Keyword(s):  
Shear Flow ◽  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Applied Stress ◽  
Volume Fraction ◽  
Scaling Law ◽  
Oscillatory Shear ◽  
Steady Shear ◽  
Er Fluid

Electrorheological (ER) fluids are typically composed of polarizable particles dispersed in a non-conducting fluid. Upon the application of an electric field, chain-like or fibrillar aggregates of the suspended particles are oriented along the direction of the electric field, thereby inducing viscoelasticity and a drastic increase in viscosity. In our study, Poly(3-thiophene acetic acid), PTAA, has been developed for using as ER material. The rheological properties of this PTAA suspension upon the application of electric field were investigated under various deformations; oscillatory shear flow, steady shear, and creep. We found that PTAA based ER fluid exhibited viscoelastic behavior and showed the excellent responses under an applied electric field. Moreover, the ER response of this PTAA fluid was amplified with increases in electric field strength, particle concentration, and particle conductivity. Under the oscillatory shear, the dynamic moduli, G′ and G″, increased dramatically by 10 orders of magnitude, when the field strength was increased to 2 kV/mm. The suspensions exhibited a transition from fluid-like to solid-like behavior as the field strength increased. While under steady shear flow, the yield stress increased with electric field strength, E, and particle volume fraction, φ, according to a scaling law of the form, τy α Eαφγ. Furthermore, the creep curves of this ER fluid consisted of both elastic and viscous responses and this fluid exhibits partially elastic recovery after the removal of applied stress. The creep properties strongly depended on the magnitude of an applied stress.

Toroidal Field Strength Requirements in Tokamak Reactors

1977 ◽  
Vol 32 (2) ◽  
pp. 142-154
Author(s):  
W. M. Stacey ◽  
K. Evans
Keyword(s):  
Field Strength ◽  
Toroidal Field ◽  
Tokamak Reactors

scholarly journals Origin of Universal Correlation between Temperature and Emision Measure for Solar/Stellar Flares

2001 ◽  
Vol 203 ◽  
pp. 318-319
Author(s):  
K. Shibata ◽  
T. Yokoyama
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Heating Rate ◽  
Magnetic Field Strength ◽  
Mass Density ◽  
Scaling Law ◽  
Coronal Magnetic Field ◽  
Mhd Equations ◽  
Numerical Code ◽  
Volumetric Heating

We study the reconnection and the chromospheric evaporation in flares using the numerical code including nonlinear anisotropic heat conduction effect (Yokoyama & Shibata 1998; 2001). The two-dimensional, nonlinear, timedependent, resistive, compressible MHD equations are solved. The evolution from the rise phase to (the early part of) the decay phase of a solar flare is qualitatively reproduced in this simulation. Based on the results, we obtained a relationship between the flare temperature and the coronal magnetic field strength. If we assume that the input of energy to a loop balances with the conduction cooling rate, the temperature at the loop apex is TA ≈ (2QL2/κ0)2/7 where Q is the volumetric heating rate, L is the half-length of the loop, and κ0 = 10−6 eGS is the Spitzer's thermal conductivity constant. In our simulations, the heating mechanism is magnetic reconnection so that the heating rate is described as Q = B2/(4π) · Vin/L · 1/sin θ, where B is the coronal magnetic field strength, Vin is the inflow velocity (≈ 0.1VA from our result and also from Petschek's theory), and θ is the angle between the slow-mode MHD shock and the loop and is approximately given by sin θ ≈ Vin/VA. By manipulating the equations, we find where ρ is the mass density of the corona. The simulation results show very good agreement with this scaling law.

Simulation of Dynamic Properties of ER Damper

2012 ◽  
Vol 215-216 ◽  
pp. 901-906
Author(s):  
Suo Kui Tan ◽  
Xiao Ping Song ◽  
Yan Song Zhang ◽  
Yu Dong Zhao ◽  
Song Ji ◽  
...  
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Electric Field Strength ◽  
Dynamic Properties ◽  
Electrorheological Fluid ◽  
Drift Frequency ◽  
Fluid Damper ◽  
Er Damper ◽  
Velocity Drift ◽  
The Relationship

By way of Matlab software simulation, the relationship among shear stress and frequency, velocity, displacement and ER properties has been researched, the damper strength -- velocity, damper strength – drift properties of shear electrorheological fluid damper has been given, the law of damper strength with frequency, gap , diameter and electric field strength has been showed that damper strength is increasing with electric field strength, the biggest damper strength is 100kN, the key facters are velocity, drift, frequency, gap and etc.

Dielectrophoretic Rotation in Budding Yeast Cells

1980 ◽  
Vol 35 (11-12) ◽  
pp. 1111-1113 ◽  
Author(s):  
Maja Mischel ◽  
Ingolf Lamprecht
Keyword(s):  
Field Strength ◽  
Electric Field ◽  
Budding Yeast ◽  
Low Frequency ◽  
Rotation Frequency ◽  
Moment Of Inertia ◽  
Yeast Cells ◽  
Uniform Electric Field ◽  
The Moment

Abstract Rotation of budding yeast cells in an alternating non-uniform electric field of low frequency was investigated. Rotation frequency was found to be proportional to field strength above a threshold, and varied from cell to cell. The threshold is inversely correlated with the moment of inertia of the cells, while the slope of rotation frequency versus field strength increases with the moment. Rotation frequencies varied between 1 and 10 cycles per second. Clear differences between the dielectrophoretic behaviour of living and heat-inactivated yeast cells were observed.

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