ESR MICROSCOPE HAVERSINE GRADIENT COIL DRIVER UPGRADE

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This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff. A significant goal of our upgrade effort for the 16GHz pulse ESR microscope has been improving the reliability of electronic sub-systems which comprise this instrument. To avoid significant additional future downtime caused by spotty reliability of the existing haversine gradient coil driver, this subsystem has been disassembled and critical sections have been redesigned and rebuilt. Since the rebuild, we have not experienced any further operational interruptions due to this unit. Upgraded sections include the isolation power converters, the MOSFET drivers, reconstruction of the output network and feedback network revisions to the narrow-band z-axis constant-current driver for stability enhancement. Engineering refinements developed in the course of making these upgrades are presently being applied to design and construction of next-generation hybrid gradient driver systems of higher peak power capability.