Omnidirectional Photonic Electric Field Sensor for Diagnosing Nuclear Weapons Effects

High energy X-ray pulse sources used in nuclear weapons effects (NWE) tests can produce electromagnetic pulses through system generated electromagnetic pulse (SGEMP) effects. Improved diagnostics for NWE experiments is motivated by the need to accurately measure the test environment and to model the response of devices under test with reduced overall uncertainties in the presence of high energy X-ray radiation. In particular, Source Generated EMP (SGEMP) and Box Internal EMP (IEMP) experiments would greatly benefit from the development of compact, robust, non-perturbing electric and magnetic field sensors to measure the local fields induced by X-ray generated electron currents. SGEMP pulses can be as much as ten million volts per meter in strength, have rise times less than one nanosecond, and last for as much as several hundred nanoseconds. The current method of measuring electric and magnetic fields uses bulky and metallic B-dot and D-dot probes, which require an integrator to obtain the field values. At high frequencies, greater than several hundred megahertz, active integrators are required that limit the dynamic range and the low frequency response. This proposal specifically addresses the development of a photonic electric field sensor that would overcome the limitations of the D-dot electric field measurement devices. The photonic sensor optically isolates the SGEMP pulses from the measuring instrument to provide a safe and reliable measurement of high field strengths in high radiation energy environments. A compact, high speed, and omnidirectional sensor probe that does not suffer from electromagnetic field absorption and heating is the key component to an accurate SGEMP sensor. All-dielectric construction makes the proposed photonic probe technology inherently immune to EM heating effects, while highly flexible and thin optical fibers make it possible to route sensor cables through tightly confined spaces.