Lamb-Dip Laser-Induced Fluorescence Spectroscopy for Measuring Magnetic Field in a Plasma

Abstract

We have developed a Lamb-dip laser-induced fluorescence (LIF) system to precisely measure the local magnetic field strength in a plasma. Utilizing the hole burning effect, we made sharp dips on the LIF spectrum as the frequency markers and accurately determined the Zeeman splitting by reading the frequency interval of the dips. The method is valid even in the conditions where the Doppler broadening of the LIF spectrum is larger than the Zeeman shift. The newly developed LIF system is capable of determining a magnetic field strength on the order of 10 À4 T. It has been demonstrated that the Lamb-dip LIF system can successfully reproduce a very small field inhomogeneity in the HYPER-I linear device.

Lamb-Dip Laser-Induced Fluorescence Spectroscopy in a Supersonic Plasma Jet for Isotope Identification

“…Compared with the fluorescence signal observed using a single laser pass, the fluorescence signal intensity can be intensified using two laser beams. 18) A clear Lamb-dip was successfully observed by counterpropagating laser beams at the back of the sleeve. However, it must be noted that only the most abundant isotope, 88 Sr, was detectable by this Lamb-dip.…”

“…However, it must be noted that only the most abundant isotope, 88 Sr, was detectable by this Lamb-dip. The frequency profile of a fluorescence signal with one Lamb-dip is modeled by the equation below: 18) S A…”

“…A Lamb-dip is a Doppler-free spectrum caused by the hole-burning effect that can then distinguish a narrow nonhomogeneous broadening for each isotope. [18][19][20][21] In addition, the fluorescence signal is amplified due to the double beam. When the plasma jet is used under low-pressure conditions, the pressure broadening effect is negligible.…”

Asymmetry of velocity distribution function and inhomogeneity-induced flow associated with neutral depletion structure in an ECR plasma

“…Velocity resolution of laser-induced fluorescence (LIF) spectroscopy 1 has been greatly improved by using diode lasers. [2][3][4][5][6][7][8][9][10] Precise measurement of velocity distribution function has become possible in the experiments. We have measured the velocity distribution function of neutrals in an electron cyclotron resonance (ECR) plasma, and examined the relationship between asymmetric distribution function and flow generated by inhomogeneity.…”

“…This structure is considered to be suitable for examining the relationship between asymmetry of distribution function and inhomogeneity-induced flow. A high resolution LIF method 9,10 has been used to measure the distribution functions with velocity component parallel and perpendicular to the neutral density gradient. It has been found that the asymmetry of distribution function is generated in the direction of density gradient of neutrals.…”