Speaker
Description
Spin polarized positron beams are employed in investigations of magnetic and electronic structure dynamics [1, 2] and may also be useful in the production of a positronium Bose-Einstein condensate [3]. Slow positron beams derived from radioactive sources are naturally spin polarized due to the non-conservation of parity in the beta decay process [4] although measuring the polarization can be challenging. Existing polarimetry techniques involve either strong magnetic field (~ 1 T) [5], high density beams (1016 cm-3) [6] or high beam energies (100 keV) [7]. Since the polarisation is conserved in positronium formation, a technique involving depletion of magnetic sub-levels of triplet positronium via irradiation by microwaves may be more desirable. In this work we describe such an approach where the spin polarisation of a positron beam is deduced from depletion of the asymmetric population of magnetic sub levels of a metastable positronium beam [8] using circularly polarised microwave radiation. We present the experimental method and recent progress of the investigation.
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[5] Y. Nagai et al., Nucl. Instrum. Methods Phys. Res. B 171 199 (2000)
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[8] D. M. Newson et al. Rev. Sci. Instrum. 94 083201 (2023)
