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Related Concept Videos

IR Spectrometers01:25

IR Spectrometers

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There are two main infrared (IR) spectrophotometers: dispersive IR spectrometers and Fourier transform infrared (FTIR) spectrometers. In a dispersive IR spectrometer, a beam of infrared radiation produced by a hot wire is divided into two parallel equal-intensity beams using mirrors. One beam passes through the sample, while another is a reference beam. The beams then move through the monochromator, which separates the radiations into a continuous spectrum of different frequencies. The...
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Infrared (IR) Spectroscopy: Overview01:09

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When electromagnetic radiation passes through a material, atoms or molecules transition from a lower to a higher energy state by absorbing radiation corresponding to the energy difference between the two states. The absorption of infrared (IR) radiation causes transitions between vibrational energy levels in a molecule. Therefore, IR spectroscopy is a useful analytical tool for determining the molecular structure of molecules.
Different compounds display unique properties due to their...
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IR Spectroscopy: Molecular Vibration Overview01:24

IR Spectroscopy: Molecular Vibration Overview

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When Infrared (IR) radiation passes through a covalently bonded molecule, the bonds transition from lower to higher vibrational levels. The fundamental vibrational motions that result in infrared absorption can be classified as stretching or bending vibrations.
Stretching vibrations are vibrational motions that occur along the bond line, changing the bond length or distance between two bonded atoms. They are further distinguished as symmetric or asymmetric. In symmetric stretching, the...
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IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations01:08

IR Spectrum Peak Splitting: Symmetric vs Asymmetric Vibrations

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Identical bonds within a polyatomic group can stretch symmetrically (in-phase) or asymmetrically (out-of-phase). Similar to hydrogen bonding, these vibrations also influence the shape of the IR peak. Generally, asymmetric stretching frequencies are higher than symmetric stretching frequencies. For example, primary amines exhibit two distinct IR peaks between 3300–3500 cm−1 corresponding to the symmetric and asymmetric N-H stretching, while secondary amines exhibit a single...
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IR Spectrum01:19

IR Spectrum

1.6K
When infrared (IR) radiation passes through a molecule, the bonds stretch or bend by absorbing the radiation. This absorption creates the molecule's absorption spectrum, which is the plot of its percentage transmittance versus wavenumber.
Transmittance is defined as the ratio of the radiant power passing through a sample to that from the radiation's source. Multiplying the transmittance by 100 gives the percent transmittance (%T), which varies between 100% (no absorption) and 0%...
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IR Frequency Region: X–H Stretching01:24

IR Frequency Region: X–H Stretching

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In IR spectroscopy, signals produced by the X−H bonds (such as C−H, O−H, or N−H) can be observed in the frequency range of  2700–4000 cm–1. The C−H stretching vibration forms sharp bands in the region 2850–3000 cm–1. The presence of the O−H stretching vibration leads to the forming of an absorption band in the frequency range 3650–3200 cm−1. At the same time, N−H stretching can be confirmed by absorption bands in...
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Multi-chord IR-visible two-color interferometer on KSTAR.

June-Woo Juhn1, K C Lee1, T G Lee1

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|July 10, 2021
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Summary
This summary is machine-generated.

Upgrades to the KSTAR interferometer enhance multi-chord density measurements using a new laser and digital processing. This enables stable plasma density control and promises future real-time profile control.

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Area of Science:

  • Plasma Physics
  • Interferometry
  • Fusion Energy Research

Background:

  • Accurate plasma density measurements are crucial for controlling fusion devices like KSTAR.
  • Previous KSTAR interferometer systems required upgrades for multi-chord operation and improved real-time feedback.

Purpose of the Study:

  • To upgrade the KSTAR infrared-visible two-color interferometer (TCI) for multi-chord operation.
  • To enhance real-time plasma density measurement and control capabilities.

Main Methods:

  • Replaced the HeNe laser with a diode-pumped-solid-state (DPSS) laser (660 nm) for improved beam power and coherence.
  • Integrated vacuum-compatible vibration isolators with titanium retro-reflectors to mitigate fringe skips.
  • Implemented full digital phase comparators using Field-Programmable Gate-Array (FPGA) modules with CORDIC algorithm for high-speed fringe counting.

Main Results:

  • The upgraded TCI system successfully operates in a multi-chord configuration.
  • Digital phase comparators achieve high-speed signal output (up to 1.25 MHz), effectively resolving fringe skip issues.
  • Demonstrated stable single-input-single-output operation of KSTAR density control using the enhanced TCI.

Conclusions:

  • The upgraded KSTAR TCI provides robust, real-time multi-chord plasma density measurements.
  • The system facilitates stable density control and shows potential for future real-time density profile control.
  • Technological advancements in lasers, vibration isolation, and digital signal processing are key to improved fusion plasma diagnostics.