Recent Developments in Toroid Cavity Autoclave Engineering
A toroid cavity autoclave (TCA) is a metal pressure vessel that simultaneously functions as an NMR resonator. Since the introduction of the TCA concept, many adaptations and optimizations were put together to suit particular applications such as catalysis in supercritical fluids, rotating-frame imaging of materials, and evaluation of transport phenomena. In this article, we present recent achievements in TCA engineering that were carried out for both major fields of research with TCAs, i.e., high-pressure and imaging studies. A new modular TCA design is introduced that makes it possible to easily access all individual parts of the autoclave for maintenance and replacement. The TCA is double tuned to a high frequency for 1H and 19F resonances and a low frequency for hetero nuclei. It withstands pressures up to 400 bar at room temperature and 300 bar at temperatures up to 100°C. The autoclave sample volume is electrically separated into two compartments with only the lower compartment NMR sensitive. With the two-compartment TCA, it is possible to monitor multiple-phase systems or gas/liquid reactions in situ without sacrificing high-resolution qualities of the probe. In addition, special features are presented, such as the utilization of a second pressure line for injecting key reagents that initiate a chemical reaction or for vigorously mixing gases with a reactive solution. A newly designed resistive heater that does not introduce stray magnetic fields is also described.
H. G. Niessen et al., "Recent Developments in Toroid Cavity Autoclave Engineering," Concepts in Magnetic Resonance Part B: Magnetic Resonance Engineering, vol. 16, no. 1, pp. 15-21, Wiley-Blackwell, Jan 2003.
The definitive version is available at http://dx.doi.org/10.1002/cmr.b.10056
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