Parallel Ion Flow Velocity Measurement Using Laser Induced Fluorescence Method in an Electron Cyclotron Resonance Plasma

Abstract

Parallel ion flow velocity along a magnetic field has been measured using a laser induced fluorescence (LIF) method in an electron cyclotron resonance (ECR) argon plasma with a weakly-diverging magnetic field. To measure parallel flow velocity in a cylindrical plasma using the LIF method, the laser beam should be injected along device axis; however, the reflection of the incident beam causes interference between the LIF emission of the incident and reflected beams. Here we present a method of quasi-parallel laser injection at a small angle, which utilizes the reflected beam as well as the incident beam to obtain the parallel ion flow velocity. Using this method, we observed an increase in parallel ion flow velocity along the magnetic field. The acceleration mechanism is briefly discussed on the basis of the ion fluid model.

Analysis of Azimuthal Doppler Shift of Anisotropically Absorbed Laguerre-Gaussian Beam Propagating in Transverse Flow

“…High-resolution spectroscopies using the resonant excitation of atoms with the narrow-band tunable diode lasers are valuable methods to measure Doppler spectra for plasma dynamics study [1][2][3][4]. In conventional laser spectroscopy, it has been taken for granted that the observed Doppler spectrum is the projection of the velocity distribution function onto the wave vector of the excitation laser.…”

Development of Ar I and Ar II Measuring System using Laser-Induced Fluorescence Methods in High-Density Helicon Plasma

“…Absolute calibrations of wavelength, i.e. fundamental wavelengths of both Ar I and Ar II were decided by the middle point between Doppler shifts by the forward and backward laser injection using a reflecting mirror [10]. In addition, our system can exclude a power-broadening problem of Doppler spectrum, because of the low power density of the pumping laser.…”

Data-volume reduction of optical vortex laser absorption spectroscopy by coarse-graining using a quadrant photodiode

“…For particle flow measurement in plasma, laser spectroscopy such as tunable diode laser absorption spectroscopy (TDLAS) and laser-induced fluorescence is a non-invasive plasma diagnostic method that can measure the velocity component parallel to the probe beam. [1][2][3][4] Therefore, using laser spectroscopic methods to measure the perpendicular particle flow entering the boundary region, the probe beam must be incident perpendicular to the boundary, making the measurement challenging. 5,6) This limitation in measurement direction is because the longitudinal Doppler shift is constrained only to the velocity component aligned with the wave vector of the plane wave used as the probe beam.…”