HiPER – time resolution


HiPER operates in induction mode using circular smooth or corrugated shorted waveguide as a sample-holder. Induction mode means the sample is excited by a linearly polarised beam but detection is via the orthogonal linearly polarised mode. Power transfer to the orthogonal mode will occur whenever a circular polarised state is absorbed or emitted due to electron paramagnetic resonance. This scheme has the huge advantage that it isolates the source from the detector, reducing the requirements for receiver protection and reducing issues associated with amplifier saturation. With careful set-up, 80 dB of isolation can be achieved between the two orthogonal modes. Combined with the large 1 GHz instantaneous bandwidth, this allows high time resolution measurements to be made during a high-power pulse. This allows both T1 and T2 relaxation times to be made down to a few nanoseconds with applications in molecular dynamics and characterisation of samples for Dynamic Nuclear Polarisation.

Examples of coherent transient responses measured during high power (up to kW) excitation are shown above. Analysis of transients as a function of power allow T1’s and T2’s to be calculated down to a few nanoseconds.