Understanding effect of Teflon room temperature phase transition on coax cable delay in order to improve the measurement of TE signals of deuterated polarized targets

A half-wavelength long Teflon cable is part of a tuned circuit for the measurement of polarization in nuclear polarized targets. In trying to improve this measurement, the author noticed a large change in electrical cable length as the Teflon went through a room temperature chemical-molecular phase transition. Some test results on commercially available cables are reported. Teflon has room temperature phase transitions. The measurements indicated that the electrical length of the cable changed by 1000 ppm over a 13-19 degrees C change. The thermal equilibrium signal peak is equivalent to a change of 1 ppm in the cable length. In the experiment the cables were heated to 26 degrees C and hence improved this measurement by more than two orders of magnitude.<
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