High-field facilities at the Francis Bitter National Magnet Laboratory

Abstract

Publisher Summary This chapter highlights the features of high-field facilities at the Francis Bitter National Magnet Laboratory (FBNML). The laboratory features over two dozen water-cooled, superconducting, and combination magnets with fields ranging up to 30 teslas in a 3.3 cm bore and a homogeneous 25 τ in a 5.4 cm bore. The facility is available free of charge; this attracts scientists worldwide. The power supply consists of two identical shafts of rotating machinery. Each includes a 4.6 MW synchronous motor fed from a 4.16 kV substation, a pair of 240 V direct-current generators, and an 80-ton flywheel to help smooth field ripple and to store energy for multisecond pulses. Together, the four generators can deliver 40 kA continuously. The control system provides a current stability of ∼ 0.1% peak-to-peak; a 6 Hz ripple is the major component of this noise. All of the laboratory's high-field magnets are of the Bitter design. The laboratory's new hybrid system, brought on-line in early 1981, offers two combinations of field and bore: 30 τ in a 3.3 cm bore and a homogeneous 25 τ in a 5.4 cm bore. One of the facilities at FBNML is a group of four spectrometers operating at proton-observed frequencies of 272, 304, 306, and 498 MHz. The last of these incorporates a superconducting magnet generating 11.7 τ by means of niobium–titanium operating at 2.3 K.