Macroscopic background gradient and radiation damping effects on high-field PGSE NMR diffusion measurements
2001 (English)In: Journal of magnetic resonance (San Diego, Calif. 1997: Print), ISSN 1090-7807, E-ISSN 1096-0856, Vol. 150, no 1, 49-56 p.Article in journal (Refereed) Published
The effects of macroscopic background gradients due to susceptibility differences at the sample interfaces and of radiation damping on pulsed-gradient spin-echo (PGSE) experiments are examined. Both phenomena can lead to the seemingly strange effect of the echo signal growing as the gradient strength increases at low applied gradient strengths. For a freely diffusing species, background gradients manifest themselves as slight concave or convex inflections in the linearized PGSE attenuation curve, depending on the polarity of the applied gradient, The various means of overcoming macroscopic background gradient problems, including bipolar gradients, and their efficacy are examined experimentally and discussed. The effects of radiation damping can also result in the attenuation curve being nonlinear but, different from the effect of background gradients, the nonlinearity does not change with the polarity of the applied gradient. The vulnerability of the stimulated echo-based PGSE sequence and variations of Hahn-based PGSE sequences is investigated. Both background gradients and radiation damping have serious implications for accurate diffusion measurement determination.
Place, publisher, year, edition, pages
2001. Vol. 150, no 1, 49-56 p.
background gradients, bipolar gradients, calibration, diffusion, PGSE, radiation damping, nuclear-magnetic-resonance, spin-echo, heterogeneous systems, restricted diffusion, demagnetizing field, multiple echoes, self-diffusion, dipolar field, water, susceptibility
IdentifiersURN: urn:nbn:se:kth:diva-20658ISI: 000168914300008OAI: oai:DiVA.org:kth-20658DiVA: diva2:339354
QC 201005252010-08-102010-08-10Bibliographically approved