Abstract
Sub-micron defects represent a well-known fundamental problem in manufacturing since they can significantly affect performance and lifetime of virtually any high-value component. Positron annihilation lifetime spectroscopy is arguably the only established method capable of detecting defects down to the sub-nanometer scale but, to date, it only works for surface studies, and with limited resolution. Here, we experimentally and numerically show that laser-driven systems can overcome these well-known limitations, by generating ultra-short positron beams with a kinetic energy tuneable from 500 keV up to 2 MeV and a number of positrons per shot in a 50 keV energy slice \color{black} of the order of $10^3$. Numerical simulations of the expected performance of a typical mJ-scale kHz laser demonstrate the possibility of generating MeV-scale narrow-band and ultra-short positron beams with a flux exceeding $10^5$ positrons/s, of interest for fast volumetric scanning of materials at high resolution.
Highlights
Positron annihilation lifetime spectroscopy (PALS) [1] is arguably one of the most successful techniques for the noninvasive inspection of materials and identification of small-scale defects
The performance of the system is extracted from Monte-Carlo simulations and validated in a proof-ofprinciple experiment using the TARANIS laser hosted by the Centre for Plasma Physics at Queen’s University Belfast [22]
We show that positron beams with a high flux per second and a short duration per energy slice can be generated using this class of laser systems
Summary
Positron annihilation lifetime spectroscopy (PALS) [1] is arguably one of the most successful techniques for the noninvasive inspection of materials and identification of small-scale defects. Typical machines designed for PALS routinely operate at a positron energy in the keV range and bunch durations of the order of hundreds of picosecond The performance of the system is extracted from Monte-Carlo simulations and validated in a proof-ofprinciple experiment using the TARANIS laser hosted by the Centre for Plasma Physics at Queen’s University Belfast [22] The extension of these results to the use of a kHz mJ-level laser system, such as SYLOS2 [23] at ELIALPS, indicates that more than 105 MeV-scale positrons per second in a 50 keV energy slice can be generated, with a full width half maximum duration of the order of 50 ps, i.e., shorter than the typical timescales of positron annihilation in materials [3].
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