Recent Advances in the Design of High-Field dc Solenoid Magnets

The art of dc solenoid design is re-examined with the objective of maximizing magnetic field at the expense of volume and homogeneity, while providing axial access at the largest feasible angular aperture. Solenoids of this type would provide higher fields for the investigation of cyclotron resonance and magneto-optical effects in thin specimens at far-infrared frequencies where limitations of source intensity and detector sensitivity require large-aperture optics and preclude the use of pulsed magnets. Heat transfer experiments indicate that under conditions of nucleate boiling it is possible to transfer heat across a copper-water interface at more than ten times the rate of 200 w/cm2 which served as the basis for Bitter's design some twenty years ago. Transfer rates of 2500 w/cm2 were achieved in a 0.010×0.20-in. rectangular flow channel and at a copper temperature of only 114°C. Two modified Bitter solenoids and a new, tape-wound wide-aperture solenoid were designed to dissipate the maximum power of 1700 kw supplied by Professor Bitter's generator at MIT through a considerably reduced transfer area and thus provide higher fields in smaller volumes. The design and preliminary performance data are described.