A powerful NMR field-cycling device using GTOs and MOSFETs for relaxation dispersion and zero-field studies

Abstract A fast electronic field switch is described for field-dependent NMR experiments (relaxation dispersion, zero-field spectra, cross relaxation, etc.), which makes use of high-voltage thyristors and transistors (GTOs, MOSFETs) and thus allows production of cycles of the magnetic flux density B with much shorter transit intervals to the maximum field level than instruments previously reported in the literature. The switch controls a 3 kW power supply and gives dB dt max = 6 × 10 2 T/s for Bmax = 0.21 T; a projected extension of the device to 50 kW driving power will increase either the maximum switching rate or the maximum field level by one order of magnitude. The performance of the switch is by measurements of the proton spin relaxation dispersion of samples with rather short relaxation times, namely in the millisecond range. Also shown are proton zero-field spectra of such systems, which cannot be obtained by means of the recently reported, inherently slow mechanical cycling devices because of the presence of fast longitudinal relaxation processes.

[1]  F. Noack,et al.  Kernmagnetische Relaxation und Korrelation in Zwei-Spin-Systemen , 1964 .

[2]  D. Suter,et al.  Time-domain zero-field magnetic resonance with field pulse excitation , 1985 .

[3]  A. Pines,et al.  Zero field NMR and NQR with selective pulses and indirect detection , 1985 .

[4]  Warner Fite,et al.  Precision High Speed Current Regulators for Occasionally Switched Inductive Loads , 1968 .

[5]  S. Meiboom,et al.  NUCLEAR MAGNETIC RESONANCE STUDY OF THE PROTON TRANSFER IN WATER , 1961 .

[6]  I. Solomon,et al.  Nuclear Magnetic Interactions in the HF Molecule , 1956 .

[7]  M. Stohrer,et al.  Molecular motion in solid odd‐numbered paraffin C19H40: Proton spin relaxation spectroscopy from 5.8 kHz to 86 MHz , 1977 .

[8]  L. Hwang,et al.  Proton spin relaxations in solutions of paramagnetic complex with S=3/2 in slow motion region , 1985 .

[9]  F. Noack,et al.  NMR field-cycling spectroscopy: principles and a]lications , 1986 .

[10]  P. Coppens,et al.  Methyl Zeeman-tunnel resonance and nuclear spin relaxation in copper acetate , 1983 .

[11]  S. H. Koenig,et al.  Protein rotational relaxation as studied by solvent 1H and 2H magnetic relaxation. , 1976, Biochemistry.

[12]  R. Kimmich,et al.  Chain fluctuations in the amorphous regions of polyethylene as indicated in proton relaxation spectroscopy , 1980 .

[13]  F. Noack,et al.  Proton spin T1 relaxation dispersion in liquid H2O by slow proton‐exchange , 1980 .

[14]  Walter Kauzmann,et al.  The Structure and Properties of Water , 1969 .

[15]  L. Nordenskiöld,et al.  Theory of nuclear spin relaxation in paramagnetic systems in solution , 1985 .

[16]  D. Edmonds.  Nuclear quadrupole double resonance , 1977 .

[17]  F. Noack.  NMR Studies of Self-Diffusion in Some Homologous Nematic Liquid Crystals , 1984 .