Injection and confinement of positron bunches in a magnetic dipole trap.

We demonstrate the efficient injection of a pulsed positron beam into a magnetic dipole trap and investigate the ensuing particle dynamics in the inhomogeneous electric and magnetic fields. Bunches of ∼10^{5}e^{+} were transferred from a buffer-gas trap into the field of a permanent magnet using a lossless E×B drift technique. The Δt≈0.

Cooling positronium to ultralow velocities with a chirped laser pulse train.

When laser radiation is skilfully applied, atoms and molecules can be cooled, allowing the precise measurements and control of quantum systems. This is essential for the fundamental studies of physics as well as practical applications such as precision spectroscopy, ultracold gases with quantum statistical properties and quantum computing. In laser cooling, atoms are slowed to otherwise unattainable velocities through repeated cycles of laser photon absorption and spontaneous emission in random directions.

Anisotropic Photodetachment of Positronium Negative Ions with Linearly Polarized Light.

We report on the anisotropic photodetachment of positronium negative ions, followed by the dissociation into p-wave electrons and positronium atoms, with a linearly polarized laser beam. We have observed a strong recoil effect of the photoelectrons on the translation momentum of the dissociated positronium atoms. With polarization angle-resolved measurements, the asymmetry parameter of the photoemission angular distribution of the ions at a photon energy of 1.

Tabular Two-Dimensional Correlation Analysis for Multifaceted Characterization Data.

We propose tabular two-dimensional correlation spectroscopy analysis for extracting features from multifaceted characterization data, essential for understanding material properties. This method visualizes similarities and phase lags in structural parameter changes through heatmaps, combining hierarchical clustering and asynchronous correlations. We applied the proposed method to data sets of carbon nanotube (CNT) films annealed at various temperatures and revealed the complexity of their hierarchical structures, which include elements such as voids, bundles, and amorphous carbon.

Formation of Nanoscale Protrusions on Polymer Films after Atomic Oxygen Exposure: Observations with Positron Annihilation Lifetime Spectroscopy.

Atomic oxygen (AO) is one of the dominant components of the residual atmosphere in low Earth orbit. AO collides with spacecraft with a translational energy of 5 eV, forming nanoscale protrusions on polymeric materials. To clarify the influences of a polymer's chemical structure on the formation of AO-induced microstructures, this study investigated the size of free-volume holes and the layer thickness that interacted with AO for polyethylene (PE), polypropylene (PP), and polystyrene (PS) by positron annihilation lifetime spectroscopy.