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Related Concept Videos

Atomic Nuclei: Magnetic Resonance01:05

Atomic Nuclei: Magnetic Resonance

The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
Atomic Nuclei: Nuclear Relaxation Processes01:23

Atomic 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...
NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences01:17

NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences

A pulse is a short burst of radio waves distributed over a range of frequencies that simultaneously excites all the nuclei in the sample. Upon passing a radio frequency pulse along the x-axis, the nuclei absorb energy corresponding to their Larmor frequencies and achieve resonance. This shifts the net magnetization vector from the z-axis toward the transverse plane. This angle of rotation of the magnetization vector, or the flip angle, is proportional to the duration and intensity of the pulse.
Double Resonance Techniques: Overview01:12

Double Resonance Techniques: Overview

Double resonance techniques in Nuclear Magnetic Resonance (NMR) spectroscopy involve the simultaneous application of two different frequencies or radiofrequency pulses to manipulate and observe two distinct nuclear spins. One important application of double resonance is spin decoupling, which selectively suppresses coupling with one type of nucleus while observing the NMR signal from another nucleus, simplifying the spectrum and enhancing resolution.
Spin decoupling is usually achieved by...
Atomic Nuclei: Larmor Precession Frequency01:11

Atomic Nuclei: Larmor Precession Frequency

The earth's gravitational field produces a 'twisting force' perpendicular to the angular momentum of a spinning mass (such as a spinning top) that causes the mass to 'wobble' around the gravitational field axis in a phenomenon called precession. Similarly, the magnetic moment (μ) of a spinning nucleus precesses due to an external magnetic field directed along the z-axis. The precession of the magnetic moment vector about the magnetic field is called Larmor precession, and the angular frequency...
Nuclear Fusion02:45

Nuclear Fusion

The process of converting very light nuclei into heavier nuclei is also accompanied by the conversion of mass into large amounts of energy, a process called fusion. The principal source of energy in the sun is a net fusion reaction in which four hydrogen nuclei fuse and ultimately produce one helium nucleus and two positrons.
A helium nucleus has a mass that is 0.7% less than that of four hydrogen nuclei; this lost mass is converted into energy during the fusion. This reaction produces about...

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Updated: Jun 8, 2026

Experimental Methods for Trapping Ions Using Microfabricated Surface Ion Traps
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Published on: August 17, 2017

Fast-Ion Axial Bounce Resonance in a Linear Magnetic Fusion Device.

S Karbashewski1, E M Granstedt1, S Kamio1,2

  • 1TAE Technologies Inc., Lake Forest, California 92610, USA.

Physical Review Letters
|June 7, 2026
PubMed
Summary

Researchers observed an energetic-particle mode (EPM) linked to fast ion bounce resonance in plasma. This study demonstrates the EPM

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Last Updated: Jun 8, 2026

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Published on: November 11, 2013

Area of Science:

  • Plasma Physics
  • Fusion Energy Research
  • Beam-Plasma Interactions

Background:

  • Energetic-particle modes (EPMs) are crucial for understanding plasma behavior in fusion devices.
  • Fast ions, often generated by neutral-beam injection (NBI), can drive instabilities.
  • Axial bounce resonance describes the interaction between fast ions and plasma waves based on their axial motion.

Purpose of the Study:

  • To experimentally observe and characterize an energetic-particle mode (EPM) driven by axial bounce resonance.
  • To investigate the persistence and diagnostic capabilities of this mode during transitions between magnetic configurations.
  • To validate simulation models for EPMs in linear plasma devices and field-reversed configurations (FRCs).

Main Methods:

  • Utilized a linear plasma device with dynamic magnetic mirror field shaping.
  • Employed neutral-beam injection (NBI) to generate fast ions with distinct bounce motions.
  • Performed 2D simulations to model FRC formation and EPM behavior.

Main Results:

  • Observed an axisymmetric magnetic mode consistent with axial bounce resonance of fast ions.
  • Confirmed the mode's origin by repeating experiments with different NBI configurations.
  • Demonstrated the EPM's persistence during a magnetic mirror to FRC transition, enabling topology diagnosis.
  • 2D simulations accurately reproduced experimental observations, confirming resonant fast ion clustering.

Conclusions:

  • The first observation of axial bounce resonance in an FRC was achieved.
  • The EPM serves as a valuable diagnostic tool for magnetic topology in fusion devices.
  • Findings offer insights into controlling and designing linear fusion devices with significant fast ion populations.