Design and Test of an Electric Field Sensor for the Measurement of High-Voltage Nanosecond Pulses

Abstract

D-dot sensors were designed and tested for the measurement of nanosecond high-voltage pulses. Computer simulation results showed that the I-type sensor has an acceptable response in a wide range of frequency among three types of sensors such as I, ∇, and T. The I-type sensor has coaxial cylinder shape, which consists of a brass inner conductor, a Teflon middle dielectric, and an aluminum outer conductor. Since I-type showed good linearity up to 1.2 GHz, we calibrated the sensor using relatively low frequencies. The attenuation ratio of the integrated signal of the D-dot sensor was calibrated against a standard high-voltage probe (Tektronix P6015, 75-MHz bandwidth). The measured attenuation ratio and standard deviation were 7.70×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> and 0.0608×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> , respectively. The measured attenuation ratio was in good agreement with the calculated ratio within 7.5%. The operational characteristics of the sensor were tested by measuring nanosecond voltage pulses generated from a Blumlein pulse forming line. We measured high-voltage pulses having 300 kV, 5-ns pulsewidth, and 300-ps rise time using the designed D-dot sensor. The accuracy of the sensor enabled detection of several tens of picosecond differences in the rise time of the high-voltage pulses resulting from different gap distances in the peaking switch.