We describe here the design and construction of a modern, state-of-the
-art nuclear magnetic resonance (NMR) field-cycling instrument. Fourie
r transform NMR spectra of both liquid and solid samples can be measur
ed, and spin-lattice relaxation times (T-1Z) investigated over a broad
range of magnetic field strengths ranging from 0 to 2 T. The instrume
nt is based upon an existing personal computer-based NMR spectrometer
[C. Job, R. M. Pearson, and M. F. Brown, Rev. Sci. Instrum. 65, 3354 (
1994)] which has been expanded into a fully computer-controlled field-
cycling instrument. The magnetic field cycling is accomplished electro
nically by utilizing fast switching thyristors and a storage capacitor
based on the Redfield energy storage concept. Unique aspects of the d
esign include the field-cycling magnet, which can reach fields as high
as 2 T; the personal computer-based NMR spectrometer and associated w
aveform electronics; and the use of a commercially available pulse wid
th modulation switching current amplifier, having low internal power d
issipation and a fast current settling time. Using this new technology
T-1Z relaxation times as short as 1 ms can be readily measured. (C) 1
996 American Institute of Physics.