Deuterium release from beryllium layers by laser induced plasma ablation and laser induced desorption coupled with quadrupole mass spectrometry

Abstract

By laser induced plasma ablation and laser induced desorption methods was studied the release of deuterium atoms contained in 1 μm beryllium layers produced by thermionic vacuum arc technology combined with a plasma torch. For such purpose was used a 1053 nm nanosecond laser source with pulse duration of 10 ns, tuned in pulse energy and repetition rate, for reaching both laser induced plasma ablation and laser induced desorption regimes. The signals of the species released from the beryllium‑deuterium layers after the laser irradiation were recorded simultaneous using a high-resolution optical spectrometer and a quadrupole mass spectrometer. In the laser ablation plasma plume, optical emission bands characteristic to BeO, BeH/BeD, H₂/D₂, and SiO species were identified. Mass spectra analysis revealed the dependence of released deuterium atoms on laser operating parameters.

The amounts of deuterium atoms detected by quadrupole mass spectrometry at different laser pulse energies and repetition rates, were compared with the total amount of deuterium (4 × 10¹⁷ D/m²) measured by Thermal Desorption Spectroscopy. The results indicated that 100 % deuterium atoms were released in the laser induced plasma ablation regime, in one second, at 1 kHz laser repetition rate, after samples exposure to 1000 laser pulses. In laser induced desorption regime, at 10 Hz laser repetition rate, the exposure to 10 laser pulses in one second, lead to 10 % deuterium atoms release, the percentage decreasing to 1 % when Be/D layers are irradiated with 3 laser pulses. A discussion on the heating effects of the laser beam, as function of its operating parameters, on the layer surface morphologies is also presented.