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. As in the case of frequency-stepping, 95 GHz field-step, or -jump, capability will permit ACERT to address the significant biological interest in expanding distance measurement techniques developed at conventional frequencies to high frequency. The unique 95GHz 1kW pulse ESR spectrometer developed in our Center holds promise for studying a wide range of samples including macroscopically-aligned ones, single-crystals with full-featured goniometry, and microliter-sized samples. The high orientation selection of high-field ESR spectrum is valuable in structural studies, with both DQC and DEER techniques presently under consideration. An experimental advantage of the field-jump technique is that it can be combined with a linear ramp to flip a larger fraction of spins with respect to frequency-step experiments, thereby increasing the signal and reducing orientation-selection effects when they are of no interest. The high Q possible with an iris-coupled confocal Fabry-Perot resonator operating in the induction mode is also an area of interest. Predicted sensitivity for this resonator configuration could be up to an order of magnitude greater than one might achieve with a low-Q configuration. For the field-step applications we propose to continue development of our advanced fast, moderate current microimaging pulse driver design, which will be scaled up in output current by an order of magnitude, and to add an approx. 7mm diameter step-field coil to the dielectrically-loaded version F-P resonator presently under development. Operational goals for the pulse driver are rectangular pulse capability of ca ?100 amperes, corresponding to ?12 mT (120 G), with a stability of 0.5%. Phase sensitivity of the DEER experiment is expected to require fast rise- and fall- times on the order of 30 ns, and plateau stability of 0.3% will be required. Development of the preliminary field-step coil driver system design will be continued during the coming year.
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