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Electron microscopic observations of Rb particles and pitting in 129Xe spin-exchange optical pumping cells.

Authors
  • Flower, C1
  • Freeman, M S
  • Plue, M2
  • Driehuys, B1
  • 1 Center for In Vivo Microscopy, Department of Radiology, Duke University, 311 Research Dr, Durham, North Carolina 27710, USA.
  • 2 Shared Materials Instrumentation Facility, Duke University, 101 Science Dr., Durham, North Carolina 27710, USA.
Type
Published Article
Journal
Journal of Applied Physics
Publisher
AIP Publishing
Publication Date
Jul 14, 2017
Volume
122
Issue
2
Pages
24902–24902
Identifiers
DOI: 10.1063/1.4991642
PMID: 28804157
Source
Medline
Language
English
License
Unknown

Abstract

High-volume production of hyperpolarized 129Xe by spin-exchange optical pumping (SEOP) has historically fallen short of theoretical predictions. Recently, this shortfall was proposed to be caused by the formation of alkali metal clusters during optical pumping. However, this hypothesis has yet to be verified experimentally. Here, we seek to detect the presence of alkali particles using a combination of both transmission (TEM) and scanning (SEM) electron microscopy. From TEM studies, we observe the presence of particles exhibiting sizes ranging from approximately 0.2 to 1 μm and present at densities of order 10 s of particles per 100 square microns. Particle formation was more closely associated with extensive cell usage history than short-term ([Formula: see text]1 h) SEOP exposure. From the SEM studies, we observe pits on the cell surface. These pits are remarkably smooth, were frequently found adjacent to Rb particles, and located predominantly on the front face of the cells; they range in size from 1 to 5 μm. Together, these findings suggest that Rb particles do form during the SEOP process and at times can impart sufficient energy to locally alter the Pyrex surface.

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