Low energy neutral beam production by laser vaporization of metals

Abstract

We have quantitatively studied the production of low energy (0.1-10 eV) metal neutral beams by laser vaporization of thin metal foils. For the experimental geometry available on the TFR tokamak, this technique results in the injection of 1015 neutrals in a time of ∼ 300 μs

Fluctuation measurements on the Wendelstein 7-AS stellarator by means of repetitive lithium laser blow-off

“…Laser blow-off has been discussed as a source for 1-10 eV atoms for the first time in the seventies [13][14][15]. A laser blow-off source consists of a laser and a substrate which is transparent for the laser wavelength.…”

Laser blow-off with photodiode detection system at the helically symmetric experiment

“…Various metals have been used in previous and current experiments such as iron [7,12,15] and titanium [2]. Aluminum has been used as an LBO tracer element at various experiments [3,[11][12][13]15] and a thorough characterization is documented by the laser blow-off system that was designed for use on the French Tokamak TFR [2].…”

“…Various metals have been used in previous and current experiments such as iron [7,12,15] and titanium [2]. Aluminum has been used as an LBO tracer element at various experiments [3,[11][12][13]15] and a thorough characterization is documented by the laser blow-off system that was designed for use on the French Tokamak TFR [2]. Aluminum was chosen for HSX because it radiates sufficiently to provide a bright photodiode signal at HSX electron temperatures and density, even in low concentrations.…”

“…Other terms needed are the specific plasma minor radius at the actual point of injection (where the distance between the last closed flux surface and the magnetic axis is 7 cm), 𝑇 𝑒 and 𝑛 𝑒 measurements, atomic data from ADAS, and the energy of the injected aluminum neutrals when starting at the wall, 2 eV. The energy is estimated using the neutral energy spectrum from the LBO characterization study [2] described in section 4.…”

New Seeding Methodology for Gas Concentration Measurements

“…The evolution of the resulting ablation plume is also complex, as it is sensitive to the environment under which the ablation is conducted. For this reason, most of the previous studies that reported on the generation of neutral atomic species, such as sodium, 16 aluminum, 17 and indium 18 atoms, using the laser ablation method were typically performed under low-pressure environments to reduce the impact of gas collisions on the resulting plumes. Hence, insufficient information is available from the literature to assess its potential to be used to seed carrier gas at atmospheric pressure.…”