Laser spectroscopy for measuring the parameters of a plasma containing helium and argon

LIF measurements on an atomic helium beam in the edge of a fusion plasma

“…The factor amounts to 15% and hence this is about the accuracy of the rate coefficient, provided all other parameters are known. On the other hand, once the rate coefficient σ v 3 3 P o →3 3 D has been measured with sufficient accuracy, the decay of the fluorescence signal at λ = 587.6 nm following a laser pulse at λ = 388.9 nm could possibly be used to derive the local electron density (n e measurements in low temperature plasmas have been reported, either from the ratio of time integrated (laser-and collision-induced) fluorescence signals [40,41] or from the time trace of the collision-induced signals at λ = 388.9 nm after a laser excitation at λ = 587.6 nm [42]). The convenience of this LIF-based measurement when compared with absolute population determination is that only relative fluorescence signals are needed (no absolute calibration of the observation system is necessary; exact laser adjustment is not crucial).…”

LIF Measurements on an Atomic Helium Beam in the Edge of a Fusion Plasma—possible derivation of the electron density

“…However, this requires additional calibration and adjustment effort. The maximum signal amplitudes of both signals at the laser wavelength and the one induced by collisions are strongly correlated to the initial population density of the lower level 2 3 S, which has a maximum at electron temperatures of T e ≅ 20 -50 eV depending on the value of n e . This is demonstrated for the collision-induced signal in FIGURE 2 (b) and for the signal at the laser wavelength in FIGURE 3 (a) − the values of population densities relative to the ground state population are plotted without rescaling.…”

“…The electron density in the range n e = 10 11 -10 12 cm -3 in a helium plasma of T e ≈ 5 eV was determined by Tsuchida et al [2] from the ratio of time integrated collision-induced (λ = 667.8 nm) and laserinduced fluorescence signals upon the laser excitation at λ = 501.6 nm in singlet helium. Shcheglov et al [3] determined electron densities of n e ≈ 5 × 10 11 cm -3 in an argon plasma (T e ≈ 10 eV) with helium content using relative collision-induced signals I 388.9 nm /I 706.5 nm upon laser excitation at λ = 587.6 nm.…”

“…The method relies on resonant laser pumping of some levels and analyzing their fluorescence after the end of the laser pulse. Such measurements were already performed in low temperature plasmas with some content of atomic helium [1,2,3]. In this paper, we discuss the applicability of this method in the fusion edge plasma in the density range of 10 12 -10 13 cm -3 when exciting helium atoms with a laser at the wavelength of λ = 388.9 nm tuned to the triplet transition 2 3 S → 3 3 P o and observing the fluorescence light at the laser wavelength and at λ = 587.6 nm (3 3 D → 2 3 P o ).…”

Power Spectral Density Optimization of the Tunable Radiation Source for the Iter Divertor Plasmas Lif Diagnostic

“…В настоящее время существуют перестраиваемые лазеры на красителях с энергией в несколько де-сятков мДж в импульсе, что вполне достаточно для проведения измерений на ИТЭР с учётом потерь энергии лазерного излучения в оптическом тракте от лазерного источника до плазмы дивертора. В мо-дельных экспериментах на установке ПН-3 [4,5] использовался лазерный источник, максимальная энер-гия импульса которого достигала 12 мДж. Низкая энергия в импульсе обеспечивает большой ресурс ра-боты без смены красителя, а также возможность производить измерения даже при значительном умень-шении пропускания оптического тракта ввода лазерного луча в область диверторной плазмы.…”