High-yield thermalized positronium at room temperature emitted by morphologically tuned nanochanneled silicon targets

Abstract Nanochanneled silicon targets with high positron/positronium (Ps) conversion rate and efficient Ps cooling were produced. Morphological parameters of the nanochannels, such as their diameter length, adjusted to get a large fraction thermalized at room temperature being emitted into vacuum. measurements conducted combining single-shot positron annihilation lifetime spectroscopy Doppler 1 3 S → 2 P transition. γ –3 ratio also performed estimate positron/Ps efficiency. In converter nanochannel 7–10 nm depth 3.89 μ m, ∼28% implanted positrons an energy 3.3 keV was found be transverse kinetic 11 ± meV. The reduction nanochannels 1.13 without changing diameter, result in less cooling, highlighting presence reflection from bottom end nanochannels.