Versatile 4 K nuclear magnetic resonance probe and cryogenic system for small-bore high-field Bitter magnets

Abstract

A complete design for a versatile nuclear magnetic resonance cryostat/probe system specifically adapted for small 32 mm bore bitter magnets is described. The probe solves two main problems associated with constrained environments (1) high voltage arcing across cold tuned circuits in helium atmosphere and (2) loss of temperature control due to helium bubbles in a long Dewar tail at high fields. The probe implements a variable cold-tuned system with an evacuated space for tuning capacitors to avoid high voltage breakdown. The cryostat makes use of a unique counterflow design. The simple construction and disassembly ensures reliability and allows quick repair and replacement of parts.