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Retarding field energy analyzers are commonly used for the experimental determination of the distribution of ions. Measurements require taking the first derivative of the measured current with respect to the retarding voltage, which limits the accuracy of the results. Here a commercial energy analyzer is combined with a lock-in detection and AC modulation technique to obtain ion distribution functions with an improved dynamic range. The technical realization of the method together with its theoretical motivation are presented. The various challenges for implementing the technique and ways to address them are given. The energy resolution of the method is discussed based on the concept of transfer functions, and the influence of the various adjustable parameters (grid bias voltages, frequency and amplitude of the modulation signal) on the obtained results are studied. The application of the method to an inductive discharge readily shows a dynamic range of more than three orders of magnitude. This dynamic range provides information on additional plasma parameters, such as the potential and the plasma density at the sheath edge and in the center of the discharge. Possibilities for further improvement of the technique are discussed. [ABSTRACT FROM AUTHOR]

Tunable diode laser absorption spectroscopy (TDLAS) is a commonly used technique to measure the temperature and density of atoms or molecules in a gas. In this work, we demonstrate that the TDLAS diagnostics could be effectively applied to measure the magnetic field in a low-density weakly magnetized plasma using the Zeeman splitting of the absorption spectrum of lines from noble gases. The laser wavelength is tailored to fit the 1 s 5 → 2 p 6 transition of atomic Ar with the wavelength λ = 763.51 nm . Two mechanisms of line broadening and splitting are observed: Doppler broadening and Zeeman effect. The latter is especially pronounced by applying polarization-selective observation of the absorption to the TDLAS measurements. By fitting the σ and π components of the absorption spectrum, the line-integrated magnetic field on the order of 30–50 mT is determined. The agreement between the measured values and the vacuum field (neglecting the impact of the plasma) calculations on the axis of the PSI-2 is found to be about 15–20%. [ABSTRACT FROM AUTHOR]