A5069203486- Magnetic confinement fusion research
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Princeton Plasma Physics Laboratory
2008-2024
Princeton University
2002-2023
University of Wisconsin–Madison
2003-2019
University of California, Los Angeles
2002-2003
University of Wisconsin System
1989-2002
University of Chicago
2002
Sterling Research Group
2002
Lawrence Livermore National Laboratory
1997-1998
University of Washington
1998
General Atomics (United States)
1998
An auxiliary poloidal inductive electric field applied to a reserved pinch plasma reduces the current density gradient, slows growth of m=1 tearing fluctuations, suppresses their associated sawteeth, and doubles energy confinement time. Small sawteeth occur in improved state but with m=0 precursors. By requiring change toroidal flux embedding plasma, profile drive is transient, improvement encourges program reversed transport suppression using control.
A potentially attractive next-step towards fusion commercialization is a pilot plant, i.e. device ultimately capable of small net electricity production in as compact facility possible and configuration scalable to full-size power plant. key capability for pilot-plant programme the high neutron fluence enabling nuclear science technology (FNST) research. It found that physics assumptions between those assumed ITER nth-of-a-kind it provide FNST-relevant wall loading devices. Thus, may be...
With the addition of inductive poloidal current drive for profile control in Madison Symmetric Torus (MST) reversed field pinch, magnetic fluctuation amplitude halves, leading to reduced energy and particle transport. A four- five-fold increase confinement time ${\ensuremath{\tau}}_{E}\ensuremath{\sim}5\mathrm{ms}$ with both decreased Ohmic input power increased stored thermal coincides record low high electron temperature $\ensuremath{\sim}600\mathrm{eV}$ (for MST)....
We report the results of an experimental and theoretical international project dedicated to study quasi-single helicity (QSH) reversed field pinch (RFP) plasmas. The has involved several RFP devices numerical codes. It appears that QSH spectra are a robust feature common all experiments. Our expand reinforce evidence formation self-organized states with one dominant helical mode (Ohmic SH state) is approach complementary active control magnetic turbulence improve confinement in steady state RFP.
The local electron energy flux produced by magnetic fluctuations has been measured directly in the MST reversed field pinch (over radial range r/a>0.75).The flux, electrons traveling parallel to a fluctuating magentic field, is obtained from correlation between heat and field. fluctuation induced large (100 kW/${\mathrm{cm}}^{2}$) ``core'' (r/a0.85) small (10--30 edge.
In the Madison Symmetric Torus (MST) reversed-field pinch [Fusion Technol. 19, 131 (1991)] magnetic oscillations become stationary (locked) in lab frame as a result of process involving interactions between modes, sawteeth, and field errors. Several helical modes phase locked to each other form rotating localized disturbance, disturbance locks an impulsive error generated at sawtooth crash, fields grow monotonically after locking (perhaps due unstable interaction error), over tens...
Electron current fluctuations are measured with an electrostatic energy analyzer at the edge of MST reversed-field pinch plasma. The radial flux fast electrons ($E>{T}_{\mathrm{ea}}$) due to parallel streaming along a fluctuating magnetic field is determined locally by measuring correlated product $〈{\stackrel{\ifmmode \tilde{}\else \~{}\fi{}}{J}}_{e}{\stackrel{\ifmmode \~{}\fi{}}{B}}_{r}〉$. Particle transport small just inside last closed surface...
Reduction of core-resonant m=1 magnetic fluctuations and improved confinement in the Madison Symmetric Torus [Dexter et al., Fusion Technol. 19, 131 (1991)] reversed-field pinch have been routinely achieved through control surface poloidal electric field, but it is now known that has limited part by edge-resonant m=0 fluctuations. Now, refined field control, plus toroidal possible to reduce simultaneously This allowed high-energy runaway electrons, possibly indicative flux-surface...
We report the first experimental verification of magnetohydrodynamic (MHD) dynamo in reversed-field pinch (RFP). A burst MHD electric field is observed during sawtooth crash, followed by an increase local parallel current Madison Symmetric Torus RFP edge. By measuring each term, mean-field Ohm's law to hold within error bars both between and crashes.
New developments in Faraday rotation polarimetry have provided the first measurements of current density profile and core magnetic fluctuations a high-temperature reversed field pinch. This has been achieved by fast-polarimeter system with time response up to 1 μs phase resolution <1 mrad. Recent experiments on Madison Symmetric Torus directly measured radial plasma interior amplitude 33 G, ∼1%. A broad spectrum is observed 100 kHz. Relaxation at sawtooth crash occurs timescale μs....
The change in magnetic energy and helicity has been measured during the sawtooth relaxation Madison Symmetric Torus reversed-field pinch. larger decay of (4.0%--10.5%), relative to (1.3%--5.1%), modestly supports conservation hypothesis Taylor's theory. However, observed is than simple magnetohydrodynamics prediction. Enhanced fluctuation-induced transport observed.
New profile measurements have allowed the electron thermal diffusivity to be estimated from power balance in Madison Symmetric Torus where magnetic islands overlap and field lines are stochastic. The show that (1) energy transport is conductive not convective, (2) measured diffusivities good agreement with numerical simulations of stochastic transport, (3) greatly reduced near reversal surface diffusion small.
Improved confinement has been achieved in the MST through control of poloidal electric field, but it is now known that improvement limited by bursts an edge-resonant instability. Through refined field control, plus toroidal we have suppressed these bursts. This led to a total beta 15% and reversed-field-pinch-record estimated energy time 10 ms, tenfold increase over standard value which for first substantially exceeds scaling characterized most reversed-field-pinch plasmas.
A high current plasma electron emitter based on a miniature source has been developed. The emitting is created by pulsed gas discharge. emission 1 kA at 300 V with pulse duration of 10 ms. prototype injector described in this paper will be used for 20 electrostatic injection experiment the Madison symmetric torus reversed-field pinch. replicated order to attain total requirement. simple design and proven very reliable operation. current, small size (3.7 cm diameter) low impurity generation...
Energy confinement comparable with tokamak quality is achieved in the Madison Symmetric Torus (MST) reversed field pinch (RFP) at a high beta and low toroidal magnetic field. Magnetic fluctuations normally present RFP are reduced via parallel current drive outer region of plasma. In response, electron temperature nearly triples doubles. The time increases ten-fold (to ∼10 ms), which L- H-mode scaling values for same plasma current, density, heating power, size shape. Runaway evidenced by...
The fluctuation-induced Hall electromotive force, [deltaJ x deltaB]/nee, is experimentally measured in the high-temperature interior of a reversed-field pinch plasma by fast Faraday rotation diagnostic. It found that dynamo effect significant, redistributing (flattening) equilibrium core current near resonant surface during reconnection event. These results imply effects beyond single-fluid MHD are important for and magnetic reconnection.
Characteristics of electrostatic and magnetic turbulence in the edge tokamaks, stellarators reversed field pinches are compared contrasted. Scalings turbulent fluctuation levels wave numbers discussed. Electrostatic is shown to explain density scale lengths all three device types. fluctuations also determine thermal transport tokamaks stellarators, while runaway electron stellarators.
Plasma flow velocity fluctuations have been directly measured in the high-temperature magnetically confined plasma Madison Symmetric Torus (MST) Reversed-Field Pinch (RFP) [R. N. Dexter et al., Fusion Technol. 19, 131 (1991)]. These measurements show that are correlated with magnetic field such electromotive force 〈ṽ×B̃〉 approximately balances parallel Ohm’s law, E∥+〈ṽ×B̃〉∥=ηJ∥. This initial measurement is subject to limitations of spatial localization and other uncertainties, but evidence...
Evidence of a self-organized collapse towards narrow spectrum magnetic instabilities in the Madison Symmetric Torus [R. N. Dexter, D. W. Kerst, T. Lovell, S. C. Prager, and J. Sprott, Fusion Technol. 19, 131 (1991)] reversed field pinch device is presented. In this collapsed state, dubbed quasi-single helicity (QSH), modes condenses spontaneously to one dominant mode more completely than ever before observed. The amplitudes all but largest m=1 decrease QSH states. New results about thermal...
First measurements of the current-density profile in core a high-temperature reversed-field pinch are presented. The is observed to peak during sawtooth cycle and broaden promptly at crash. This change can be linked magnetic relaxation dynamo which predicted drive antiparallel current plasma core. For high-confinement discharges, suppressed strongly peak.
In general, the linear two-fluid tearing instabilities are driven by shear Alfvén (SA), compressional (CA), and slow magnetoacoustic (MA) modes modified on short scales effects. Previous theories were devoted to either hot plasma case where coupling of SA MA waves dominates, or cold limit, β=0, instability is CA waves. Taking into account compressibility Hall term, we derive general equations that cover two limiting cases transition between them. particular, in case, derived depend factor...
Magnetic field fluctuations (and the associated current perturbation) have been measured in core of a high-temperature reversed-field pinch using newly developed fast-polarimetry system. Radial magnetic fluctuation levels approximately 1% are standard-reversed-field discharges which increase to 4% during sawtooth crash (enhanced dynamo). The level is reduced fourfold for high-confinement plasmas where core-resonant tearing modes suppressed.
Three-wave nonlinear coupling of spatial Fourier modes is measured in the MST reversed field pinch by applying bispectral analysis to magnetic fluctuations at plasma edge 64 toroidal locations and 16 poloidal locations, permitting observation over 8 polodial 32 modes. Comparison bispectra predicted resistive MHD computation indicates reasonably good agreement. However, during crash phase sawtooth oscillation strongly enhanced, concomitant with a broadened (presumably nonlinearly generated) k...
Edge equilibrium, turbulence and transport related plasma parameters from the Advanced Toroidal Facility (ATF) [Fusion Technol. 10, 179 (1986)] torsatron, ZT-40M 8, 1571 (1985)] reversed-field pinch, Phaedrus-T [Nucl. Fusion 32, 2040 (1992)] tokamak, Texas Experimental Tokamak (TEXT) 1, 479 (1981)], Test Reactor (TFTR) [in Plasma Physics Controlled Nuclear Research, 1990 (International Atomic Energy Agency, Vienna, 1991), Vol. p. 9] have been obtained using a standardized Langmuir probe...
The fluctuation-induced dynamo <v x b> has been investigated by direct measurement of v and b in the edge a reversed-field pinch is found to be significant balancing Ohm's law. velocity fluctuations producing emf have poloidal mode number m = 0, consistent with MHD calculations contrast core 1 dynamo. exhibit parity relative their resonant surface predicted linear theory.