SOFTWARE FOR PULSED & FT ESR SPECTROMETERS

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. 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. At the current stage of instrumentation development for pulsed and FT ESR, software issues become necessary and time-consuming matters. They include: writing hardware level code for embedded microprocessors, drivers for MS Windows operating systems, friendly and intuitive user interfaces, data acquisition and processing software, and script interpreters. We wrote the following Win32 applications: program for code download and communication with the SHARC DSP that controls our timing systems;and programs for setting time intervals in new timing systems that are used in workbench hardware testing. The Win32 console version of data acquisition software was written for the existing X/Ku-band FT ESR spectrometer, whose timing is based on popular DG535 delay generators. Data capture is provided by an Acqiris AP240 1Gsps transient signal averager. In addition, a program for pulse sequence calibration and correction is developed. Its purpose is to account for timing errors accumulated on the path from the programmed value to the TWTA output. The pulse sequences currently are captured by 4Gsps 1.5 GHz DSO. We plan to make use of a 1 GHz AP240 ADC card for building look-up tables for DSP, which will correct pulse sequences accordingly. Using the Acqiris card in this regime will require adding RF switches to steer the ADC inputs between the bridge outputs and RF detector and implementing a 2 GHz external time-base for ADC clocking in order to guarantee precise timing. The Visual C++ GUI program in the final stage of development will provide pulse sequence set up and data acquisition using Acqiris AP240 dual-channel 1 Gsps ADC averager and new timing hardware.