The effect of parasitic capacitance Cp on DC SQUID characteristics and noise performance has been studied using a test structure consisting of 11 identical SQUID washers with Nb films of various widths covering the slit. The measured I-V characteristics are in good agreement with simulations based on a simple lumped circuit model. The energy resolution ε in seems to scale roughly according to in approximately ε ≈ γkBT √L(C+2Cp), where γ is a dimensionless constant, kB is the Boltzmann constant, T is the temperature, C is the junction capacitance, and L is the inductance.
Ryhänen, T., Cantor, R., Drung, D., Koch, H., & Seppä, H. (1991). Effect of parasitic capacitance on DC squid performance. IEEE Transactions on Magnetics, 27(2), 3013 - 3016. https://doi.org/10.1109/20.133844