We propose re-evaluating the helix for extremely limited samples in EPR, the first prototype tested is shown in Fig. 1A, simulated magnetic fields in Fig. 1B. With the self-resonant micro-helix described here, at least a factor of 10 in EPR signal intensity has been simulated and experimentally confirmed in preliminary experiments.
Three characteristics differentiate the proposed micro-helix
configuration from those described in literature:
The helix is self-resonant This means that the self-inductance per loop and self-capacitance between the loops resonate at a frequency determined by ω2LC = 1, where is the resonant frequency ω in radians/s. No external capacitors are used, minimizing losses.
The helix length is much smaller than a wavelength This increases the uniformity, and the diameter is less than 0.4 mm at X-band, which increases the resonator efficiency.
The helix is coupled by mutual inductance The coupling structure can be designed to minimize noise and maximize the EPR signal intensity.