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A polypropylene (PP) film is usually employed as the main insulation of the peaking capacitor, which is important in an electromagnetic pulse simulator to generate high-amplitude nanosecond pulse. The flashover voltage of PP films under nanosecond pulse limits the highest working voltage of a peaking capacitor. Surface fluorination was employed to increase the flashover voltage of PP. The flashover voltages of PP samples with different fluorination times (0, 4, and 6 h) were tested in an oven with nanosecond pulse voltage. The results showed that the flashover voltage of the PP film with 6-h surface fluorination was increased about 15% than the untreated film in the air. To clarify the influential mechanism, the physicochemical properties of PP film samples were tested and characterized. The results of thermally stimulated depolarization current (TSDC) showed that the trap density of the PP film increased obviously after fluorination treatment. With the increase in treatment time, the trap depth and density were increased obviously. The surface conductivity of PP films slightly decreased with the increase in fluorination time. The mechanism of surface fluorination on the influence of the flashover performance of the PP film under nanosecond pulse is discussed. It is concluded that surface fluorination significantly increases the carbon–fluorine (C–F) bond of the PP film, resulting in the increase in the depth and density of the surface trap, and then, a large amount of homocharges trapped in the surface trap reduces the electric field near the electrode. [ABSTRACT FROM AUTHOR]

B-dot sensor, as an important device, is extensively employed to measure the current flowing in the magnetically insulated transmission line (MITL). To shield the output signal of the B-dot sensor from electron flow and high electrical field in the MITL anode-cathode (A-K) gap and also avoid the electrical breakdown in the A-K gap, the sensor is often covered with the metallic film and located in a conductor cavity penetrating the MITL electrode hole simultaneously. The frequency response properties of such kind of sensor are investigated. The experiment results indicate that the upper limited response frequencies of the sensors with and without the attached $5-\mu $ m-thick Ni-Chrome foil are 50 MHz and 148 MHz, respectively. Moreover, as a result of penetration of magnetic flux into the cavity’s wall and the wire loops wound to form the sensor, the low-frequency components of the B-dot sensor output signal are amplified, consequently the falling edge of the waveform given by the B-dot probe will be distorted. We have proposed a method to make a first-order correction for such effect by using a passive resistor-capacitor integrator instead of the numerical process suggested previously. The integrator combines the behaviors of integration and compensation of the B-dot sensor output. The actual measured current waveform can be directly obtained by multiplying the output signal of the integrator by the sensitivity of the B-dot monitor. The B-dot sensors and this post-processing method have been successfully used on a pulsed power accelerator. [ABSTRACT FROM AUTHOR]