Related Experiment Video
Updated: Jul 2, 2026
11:03
An Analog Macroscopic Technique for Studying Molecular Hydrodynamic Processes in Dense Gases and Liquids
Published on: December 4, 2017
Short-scale turbulent fluctuations driven by the electron-temperature gradient in the national spherical torus
E Mazzucato1, D R Smith, R E Bell
1Princeton Plasma Physics Laboratory, Princeton University, Princeton, New Jersey 08543, USA. mazzucato@pppl.gov
Physical Review Letters
|September 4, 2008
Summary
Turbulent fluctuations were detected in plasma using electromagnetic waves. These fluctuations, linked to electron temperature gradients, suggest a key driver of plasma turbulence.
Area of Science:
- Plasma Physics
- Fusion Energy Research
- Electromagnetic Wave Scattering
Background:
- Understanding plasma turbulence is crucial for magnetic confinement fusion.
- The National Spherical Torus Experiment (NSTX) provides a platform for studying plasma behavior.
- Turbulence can significantly impact plasma confinement and energy transport.
Purpose of the Study:
- To investigate the characteristics of turbulent fluctuations in NSTX plasmas.
- To identify the scale lengths and driving mechanisms of observed plasma turbulence.
- To validate experimental findings with theoretical models.
Main Methods:
- Utilizing coherent scattering of electromagnetic waves to probe plasma.
- Analyzing wave number spectra to determine turbulence scales.
- Employing a linear gyrokinetic stability code for numerical simulations.
Main Results:
- Detected turbulent fluctuations with wave numbers k perpendicular rho(e)=0.1-0.4.
- Determined a turbulence scale length comparable to the collisionless skin depth.
- Found experimental results consistent with numerical simulations.
Conclusions:
- The electron-temperature gradient is a likely driver of the observed plasma turbulence.
- Experimental evidence supports the theoretical understanding of turbulence in toroidal plasmas.
- Findings contribute to the broader knowledge of plasma physics and fusion energy.
Related Concept Videos
01:14Atomic Nuclei: Nuclear Spin State Population Distribution
Near absolute zero temperatures, in the presence of a magnetic field, the majority of nuclei prefer the lower energy spin-up state to the higher energy spin-down state. As temperatures increase, the energy from thermal collisions distributes the spins more equally between the two states. The Boltzmann distribution equation gives the ratio of the number of spins predicted in the spin −½ (N−) and spin +½ (N+) states.
01:24Turbulent Flow
Turbulent flow is characterized by unpredictable fluctuations in velocity and pressure, which result in a chaotic fluid movement distinct from the orderly patterns of laminar flow. While laminar flow is governed by smooth, parallel layers with minimal mixing, turbulent flow exhibits highly irregular, three-dimensional patterns. This behavior arises due to instabilities in the fluid's velocity profile, and amplifies as the flow velocity increases. Minor disturbances, known as turbulent spots,...
01:27Atomic Spectroscopy: Effects of Temperature
Atomization, converting samples into gas-phase atoms and ions, is essential for atomic spectroscopy. The flame temperature required for atomization affects the efficiency of the atomic spectroscopic methods by increasing the atomization efficiency and the relative population of the excited and ground states.
At thermal equilibrium, the relative populations of excited and ground state atoms can be estimated using the Maxwell–Boltzmann distribution. For example, an increase in temperature from...
At thermal equilibrium, the relative populations of excited and ground state atoms can be estimated using the Maxwell–Boltzmann distribution. For example, an increase in temperature from...
01:23Atomic Nuclei: Nuclear Relaxation Processes
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis. This...
01:21Carrier Transport
The generation of electrical current in semiconductors is fundamentally driven by two mechanisms: drift and diffusion. These processes are essential for the functionality and performance of semiconductor-based devices.
Drift Current:
The drift of charge carriers is started by an external electric field (E). Charged particles, such as electrons and holes, experience an acceleration between collisions with lattice atoms. For electrons, this results in a drift velocity (vd) given by:
Drift Current:
The drift of charge carriers is started by an external electric field (E). Charged particles, such as electrons and holes, experience an acceleration between collisions with lattice atoms. For electrons, this results in a drift velocity (vd) given by:
02:39Entropy
Salt particles that have dissolved in water never spontaneously come back together in solution to reform solid particles. Moreover, a gas that has expanded in a vacuum remains dispersed and never spontaneously reassembles. The unidirectional nature of these phenomena is the result of a thermodynamic state function called entropy (S). Entropy is the measure of the extent to which the energy is dispersed throughout a system, or in other words, it is proportional to the degree of disorder of a...