Related Experiment Video
Updated: Jun 27, 2026
06:40
Automated Delivery of Microfabricated Targets for Intense Laser Irradiation Experiments
Published on: January 28, 2021
Subterahertz gyrotron developments for collective Thomson scattering in LHD
T Notake1, T Saito, Y Tatematsu
1FIR Center, University of Fukui, 3-9-1 Bunkyo, Fukui 910-8507, Japan.
The Review of Scientific Instruments
|December 3, 2008
Summary
Collective Thomson scattering (CTS) will measure fusion ion velocity distributions. A new 400 GHz gyrotron for Large Helical Device (LHD) plasma diagnostics has been successfully tested.
Area of Science:
- Fusion Energy Research
- Plasma Physics Diagnostics
- High-Frequency Gyrotron Technology
Background:
- Collective Thomson scattering (CTS) is crucial for diagnosing ion velocity distribution functions, including thermal, tail, and fusion-born alpha particles.
- Higher frequency gyrotrons offer advantages over conventional ones for plasma heating by reducing refraction, cutoff effects, and background noise.
- Accurate measurement of these distributions is vital for understanding and controlling fusion plasma behavior.
Purpose of the Study:
- To develop a high-power pulse gyrotron operating at approximately 400 GHz for advanced CTS applications in the Large Helical Device (LHD).
- To investigate the feasibility of using higher frequency gyrotrons to improve CTS diagnostic capabilities.
- To assess the potential of CTS for detailed plasma diagnostics in fusion devices.
Main Methods:
- Development and testing of a high-power pulse gyrotron designed for operation above 400 GHz.
- Demonstration of single-mode oscillation at frequencies exceeding 400 GHz using second-harmonic resonance.
- Conducting feasibility studies involving ray tracing, scattering spectra analysis, and electron cyclotron emission calculations.
Main Results:
- Successful demonstration of a single-mode oscillation with a frequency greater than 400 GHz in the initial stage of gyrotron development.
- Confirmation of the second-harmonic resonance principle for achieving higher operating frequencies.
- Completion of feasibility studies indicating the viability of the proposed 400 GHz CTS system.
Conclusions:
- The developed 400 GHz gyrotron is a promising tool for enhancing Collective Thomson scattering diagnostics in the LHD.
- Higher frequency gyrotrons can overcome limitations of conventional systems, enabling more accurate plasma measurements.
- The project is on track to significantly advance spatially resolved velocity distribution function measurements in fusion plasmas.
Related Concept Videos
01:19Thomson's e/m Experiment
In a beam of charged particles created by a heated cathode, the particles move at different speeds. However, many applications need a beam with uniform particle speeds. An arrangement known as a velocity selector uses electric and magnetic fields to pick particles with a particular speed from the beam.
A particle with charge q, speed v, and mass m enters an area from the top, where the magnetic and electric fields are perpendicular both to the particle's motion and to one another. The magnetic...
A particle with charge q, speed v, and mass m enters an area from the top, where the magnetic and electric fields are perpendicular both to the particle's motion and to one another. The magnetic...
01:26Inductively Coupled Plasma Atomic Emission Spectroscopy: Instrumentation
Inductively coupled plasma (ICP) is the common plasma source used in atomic emission spectroscopy (AES), a technique that detects and analyzes various elements in a sample. This method is often called inductively coupled plasma atomic emission spectroscopy (ICP-AES).
There are three main types of inductively coupled plasma atomic emission spectroscopy (ICP-AES) instruments: sequential, simultaneous multichannel, and Fourier transform instruments, with the latter being less commonly used.
There are three main types of inductively coupled plasma atomic emission spectroscopy (ICP-AES) instruments: sequential, simultaneous multichannel, and Fourier transform instruments, with the latter being less commonly used.
01:19Mass Analyzers: Common Types
The quadrupole mass analyzer consists of four cylindrical metal rods arranged in a diamond carrying a DC voltage and a radio-frequency AC voltage. The motion of ions through the quadrupole depends on the field strength, causing only ions of a certain m/z to resonate successfully and strike the detector at a given field strength. Though the transmission rate for these analyzers is high, the exact elemental composition of the sample is not determined because of low resolution; however, they are...
01:21Tandem Mass Spectrometry
Tandem mass spectrometry is a technique that uses multiple mass analyzers in series to obtain a higher selectivity and reduce chemical noise during analyte detection. Instruments with multiple analyzers separated by an interaction cell enable secondary fragmentation and selected study of the fragment ions.Secondary fragmentations occur in the interaction cell and can be induced by various factors. Fragmentation induced by collision with inert gases, such as N2, Ar, He, etc., is called...
01:11Atomic 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...
01:19Inductively Coupled Plasma Atomic Emission Spectroscopy: Principle
Inductively coupled plasma (ICP) is the most widely used plasma source in atomic emission spectroscopy (AES), also known as Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). The ICP source, or torch, consists of three concentric quartz tubes with argon gas flowing through them. A spark from a Tesla coil initiates the ionization of argon, generating a high-temperature plasma.
The ions and electrons produced interact with the fluctuating magnetic field created by a water-cooled...
The ions and electrons produced interact with the fluctuating magnetic field created by a water-cooled...