A combined matrix isolation spectroscopy and cryosolid positron moderation apparatus
- Air Force Research Laboratory, Munitions Directorate, Ordnance Division, Energetic Materials Branch, AFRL/RWME, 2306 Perimeter Road, Eglin AFB, Florida 32542-5910 (United States)
We describe the design, construction, and operation of a novel apparatus for investigating efficiency improvements in thin-film cryogenic solid positron moderators. We report results from solid neon, argon, krypton, and xenon positron moderators which illustrate the capabilities and limitations of our apparatus. We integrate a matrix isolation spectroscopy diagnostic within a reflection-geometry positron moderation system. We report the optical thickness, impurity content, and impurity trapping site structures within our moderators determined from infrared absorption spectra. We use a retarding potential analyzer to modulate the flow of slow positrons, and report positron currents vs. retarding potential for the different moderators. We identify vacuum ultraviolet emissions from irradiated Ne moderators as the source of spurious signals in our channel electron multiplier slow positron detection channel. Our design is also unusual in that it employs a sealed radioactive Na-22 positron source which can be translated relative to, and isolated from, the cryogenic moderator deposition substrate. This allows us to separate the influences on moderator efficiency of surface contamination by residual gases from those of accumulated radiation damage.
- OSTI ID:
- 22105464
- Journal Information:
- Review of Scientific Instruments, Vol. 84, Issue 3; Other Information: (c) 2013 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
ABSORPTION SPECTROSCOPY
ARGON
CRYOGENICS
ELECTRON MULTIPLIERS
INFRARED SPECTRA
KRYPTON
MATRIX ISOLATION
MODERATORS
NEON
NEUTRONS
POSITRON DETECTION
POSITRON SOURCES
POSITRONS
RADIATION EFFECTS
SODIUM 22
SURFACE CONTAMINATION
ULTRAVIOLET RADIATION
XENON