Spherical fused silica cells filled with pure helium for nuclear magnetic resonance-magnetometry
- Institute of Physics, Johannes Gutenberg University, Staudingerweg 7, 55128 Mainz (Germany)
- ifw Günter-Köhler-Institut für Fügetechnik und Werkstoffprüfung GmbH, Otto-Schott-Str. 13, 07745 Jena (Germany)
High magnetic fields (>1 T) are measured by NMR magnetometers with unrivaled precision if the precessing spin sample provides long coherence times. The longest coherence times are found in diluted {sup 3}He samples, which can be hyperpolarized for sufficient signal strength. In order to have minimal influence on the homogeneity and value of the measured magnetic field, the optimal container for the {sup 3}He should be a perfect sphere. A fused silica sphere with an inner diameter of 8 mm and an outer diameter of 12 mm was made from two hemispheres by diffusion bonding leaving only a small hole for cleaning and evacuation. This hole was closed in vacuum by a CO{sub 2} laser and the inner volume was filled with a few mbars of {sup 3}He via wall permeation. NMR-measurements on such a sample had coherence times of 5 min. While the hemispheres were produced with <1 μm deviation from sphericity, the bonding left a step of ca. 50 μm at maximum. The influence of such a mismatch, its orientation, and the immediate environment of the sample is analyzed by FEM-simulations and discussed in view of coherence times and absolute field measurements.
- OSTI ID:
- 22482836
- Journal Information:
- Review of Scientific Instruments, Vol. 87, Issue 1; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
- Country of Publication:
- United States
- Language:
- English
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