ESR MICROSCOPE TIMING SYSTEM UPGRADE

Cornell University, Ithaca NY

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Abstract

This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. Advances in the efficiency of coupling MW power into the resonator of the pulse ESR microscope (Subproject 0102) have made reduction of the [unreadable]/2 and [unreadable] pulse widths and more precise absolute timing of the subsequent digitizing trigger desirable. However, the original timing pattern generator card for our ESRM (SpinCore, Inc. model PB24-100-32K) is only capable of pattern features down to 50ns and resolution to 10ns, limiting us to pulse widths of approximately 55 ns, minimum, and non-optimal timing of the gradient pulses and digitizer triggers. From the same vendor, a similar timing generator card of 25 ns pattern feature generation and 5 ns absolute timing resolution is now available (i.e., 2x master clock rate;SpinCore, Inc. model PBESR-200-4K PCI). However, this newer model is physically configured somewhat differently than the original card that we intended to replace with it. To utilize the newer timing card as a replacement upgrade in our pulse ESRM, we have fabricated an add-on panel plate with adaptor connecters compatible with the existing ESRM multicircuit timing connector, and we have also successfully updated the ESRM LabView VI routines as required to correctly program the faster timing card. In operational tests with the new timing card and with improved coupling efficiency at the probe resonator, a [unreadable]/2 pulse of ~30ns is obtained. The reduced deadtime and increased signal magnitude from this timing upgrade has resulted in improved system SNR and has contributed significantly to the recent order-of-magnitude advance in ESRM volumetric resolution.