Spectrometer and magnet design

The magnets utilized in these systems are typically neodymium-iron or samarium-cobalt disks with appropriately designed pole shoes that are placed with a variable air gap between them to accommodate an NMR probe designed to allow sample tubes (or flow probes) of 5 0 mm diameter. The magnet disks are typically wrapped along their sides with double wound wire to heat magnets to maintain a stable 35 °C operating 

Shim Power Supply Magnet Fleater Power Supply 

In these discnssions we will concentrate on the details of the HR-NMR spectrometer and magnet system. They represent the most complex configuration of process NMR technology. Similar process TD-NMR instrnmentation is typically less complex. 

Enclosure The main cabinet is divided into two compartments one for the magnet, and one for the electronics. The magnet compartment is maintained at a temperature of 24 + 1 °C for ultimate permanent magnet stability. The electronics compartment is on a separate air conditioner and is less rigorously temperature controlled. Fignre 10.11 shows several pictures of a Qualion Process NMR spectrometer in a NEMA enclosure configured for implementation on-line. 

Probe The probe is constrncted of stainless steel and has Swagelok fittings top and bottom for attachment to the process sample line. The constrnction of the probe inclndes a Dewar that reduces the sample heat transfer throngh the walls of the probe to the magnet components. At the sampling zone the inner wall of the probe is constrncted of alnmina ceramic which is specialty welded to the stainless. The probe is pressure tested to 1.035 x 10 Pa (103.4 bar, 1500 psi). The duplexor and preamplifier are built into the base of the probe. 

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