DEVELOPMENT OF VERSATILE 8-18 GHZ FT ESR SPECTROMETER

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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. We made significant progress in finalizing the construction of a new, versatile 8-18 GHz FT-ESR spectrometer. The microwave pulse forming unit, receiver and frequency converters, internal to the microwave bridge, were assembled in their final configuration and to a large extent integrated with the new timing system designed and built at ACERT. Our latest design iteration of timing systems makes it possible to generate pulses in their sequences with 10 picosecond timing resolution and provide all necessary control signals for appropriate spectrometer components. Currently, we are in the process of writing spectrometer control firmware and data acquisition software and finalizing small hardware issues to improve overall system performance at the spectrometer level. The data acquisition is currently based on two AP240 dual-channel 1 Gsps ADC/signal averager PCI cards that capture quadrature signals and average them with very high efficiency. The new spectrometer will use new 4kW Ku-band and/or 8 kW X-band TWTAs with their output power temporarily limited to 2 kW until a new high-power high-speed active receiver protection stage is built to protect the limiting diode from damage. The spectrometer bridge is in the final stage of testing along with the pulse programmer and data collection system.