Electro-optic Kerr effect measurements of intense pulsed electric fields in water

Loughborough University (UK) and the University of Pau (France) have begun a joint research activity into a novel and non-invasive pulsed electric field food processing technique. As part of this programme, the reliable measurement of the intense transient electric fields generated in the near field of an antenna immersed in water is essential. Both research centres are currently developing fast electro-optic measurement systems based on the Kerr effect in water, as this approach offers considerable advantages over conventional D-dot sensors. A short list of these includes the important facts that an optical measurement is non-invasive, with only a laser beam traversing the water media, and has complete immunity to any perturbing electromagnetic influence from nearby powerful and usually very `noisy´ repetitive high-voltage generators. The paper will present the main results obtained from the initial phase research effort into the accurate determination of the Kerr constant in water, for an electric field strength exceeding 300 kV/cm. This will be followed by details of the design of a Kerr sensor operating in the near field of an immersed high-voltage electrode. The paper will conclude with a mention of the intended way forward.