Towards Ultra-Thin Detector Magnet Designs by Insulating Coil Windings With V$_{2}$O$_{3}$-Epoxy Composite

We have measured temperature dependent resistivity of two types of vanadium oxide (V $_{2}$ O $_{3}$ ) epoxy composites from 77 K to room temperature. Such a composite could be used as an insulating layer between the windings of a superconducting magnet. During a magnet quench, the composite is expected to change from insulating to metallic at approximately 150 K, re-distributing the current through the heated windings. Our measurement results show significantly different phase transition characteristics of the samples. A sample mixed using 99.7% pure V $_{2}$ O $_{3}$ powder with sharp edges in particles and an average equivalent circle diameter (ECD) of 4.5 $\mu$ m has a factor of 23 resistivity change and a sample mixed using 95% pure V $_{2}$ O $_{3}$ powder with round edges in particles and an average ECD of 70 $\mu$ m has a change of three orders of magnitude, respectively. Using V $_{2}$ O $_{3}$ -epoxy composite as an insulating layer between the coil windings might allow thinner detector magnet designs since the current and heat would spread more uniformly across the magnet during a quench.