HIGH-SENSITIVITY NUCLEAR MAGNETIC RESONANCE FOR THE QUANTITATIVE ANALYSIS OF BODY FLUIDS.
Final rept. 1 Aug 66-1 Feb 67,
SOUTHWEST RESEARCH INST SAN ANTONIO TEX DEPT OF INSTRUMENTATION RESEARCH
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Magnetic resonance measurements on the electronic free radicals and nuclear protons moments in diphenylpicrylhydrazil were made using a superconducting tuned circuit as the sensing element. Two operating frequencies, 30 MHz and 0.95 MHz, were used in these experiments. Signal-to-noise improvements between 5,000 and 16,000 were obtained over the non-superconducting mode. The quality factor of the superconducting resonant circuits ranged from a low of 10,000 to a high of 2,800,000. A major limitation to high quality factor was the low temperature loss properties of the dielectrics used in the construction of the tuned circuit. Three types of detection schemes were used 1 Rollins type, 2 Rollins type with MOS Fet amplifier held at 4.2K., and 3 Robinson-type marginal oscillator. Design criteria are presented to circumvent line broadening due to magnetic flux expulsion of the Meissner effect from the superconducting radiofrequency coil. Author
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