A minimal cavity and its capacitive coupling for in vivo EPR measurements on mice.

A very simple ring resonator for in vivo L-band EPR spectroscopy was built and characterised. It employs a special capacitive coupling that allows measurents to be made on large biological samples which are not possible with other resonators. In spite of its intrinsic low Q it has a sensitivity almost equivalent to that obtained from high Q resonators. These features were tested down to a nitroxide concentration of 10 mu M in high conductivity phantoms.