Document Detail


Novel pulsed switched power supply for a fast field cycling NMR spectrometer.
MedLine Citation:
PMID:  14698404     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
In this paper, we outline the operating principles of a pulsed switched power supply for a fast field-cycling nuclear magnetic resonance spectrometer. The power supply uses a variant of a four-quadrant chopper with a duty cycle that defines the average output current. With this topology only two semiconductors are necessary to drive hundreds of amperes with an output power of several kilowatts. The output current ripple has a well-defined shape that can be reduced to acceptable values by a careful design of the semiconductors' controlling circuits and drivers. A power supply prototype was tested with a home build air-core magnet operating with fields between 0 and 0.21 T. The system is computer controlled using pulse generator and data acquisition PC cards, and specific user-friendly home-developed software. A comparative proton relaxometry study in two well-known liquid crystal compounds 5CB and MBBA was performed to check the reproducibility of the T1 measurements.
Authors:
D M Sousa; P A L Fernandes; G D Marques; A C Ribeiro; P J Sebastião
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Solid state nuclear magnetic resonance     Volume:  25     ISSN:  0926-2040     ISO Abbreviation:  Solid State Nucl Magn Reson     Publication Date:  2004 Jan 
Date Detail:
Created Date:  2003-12-30     Completed Date:  2004-04-06     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  9306181     Medline TA:  Solid State Nucl Magn Reson     Country:  Netherlands    
Other Details:
Languages:  eng     Pagination:  160-6     Citation Subset:  -    
Affiliation:
Instituto Superior Técnico, Av. Rovisco Pais, 1049-001 Lisboa, Portugal.
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