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Low power capillary discharge based pulsed plasma thrusters (CDPPTs) are electrothermally dominated thrusters and they have aroused renewed interest in the investigation and enhancement of the basic performance for the application of micro/nano satellites recently. Research on the ignition mechanism of a CDPPT has been conducted to provide insight into the optimization of the structure design and promotion of the lifetime performance. It has been found that the electrical parameters, the geometry parameters, and the cumulative effect of discharge jointly determine the discharge ignition characteristics. A single ignition process is divided into the breakdown of igniter and the development of the main discharge, while the results show that the jitter of the ignition delay time is mainly introduced from the former. Shorter ignition delay time and lower jitter can be obtained with a higher ignition energy and main charging voltage or a shorter and narrower cavity, which is positively correlated to the electric field distribution along the propellant surface. Moreover, with long duration experiments, it reveals that the surface deposits and morphology of propellant and igniter are the dominant factors that cause the dispersity of the ignition effect and main discharge characteristics. [ABSTRACT FROM AUTHOR]

The diffusion of polymer molecules across an interface is an important topic in polymer physics. Measuring this diffusion process requires a labeling experiment so that the mixing of otherwise identical molecules can be followed. Here we examine the use of nonradiative energy transfer to follow the interdiffusion of polymer molecules during the annealing of latex films. Those films are prepared from a mixture of phenanthrene (Phe, the donor)- and anthracene(An, the acceptor)-labeled poly(butyl methacrylate) (PBMA) latex particles. We examine in some detail the kinetics of direct energy transfer (DET) at an interface and the evolution of the DET kinetics as the components mix. Time resolved and steady state measurement approaches are compared, and the former is employed to examine molecular diffusion in a series PBMA latex films. Various diffusion models are considered. Diffusion coefficients are calculated by treating the data in terms of a Fickian spherical diffusion model. A film from one set of samples is similar in molecular weight to that studied by small angle neutron scattering (SANS) [K. Hahn, G. Ley, H. Schuller, and R. Oberthur, Colloid Polym. Sci. 264, 1029 (1986)]. Diffusion coefficients calculated from both sets of experiments using similar Fickian diffusion models are very similar in magnitude. [ABSTRACT FROM AUTHOR]

Coaxial peaking capacitor is a key component in high-altitude electromagnetic pulse (EMP) simulators with fast front pulse output. It poses significant technical and engineering challenges in limiting radiation field amplitude and test space. This paper presents the design and testing of a 180 pF, 3 MV coaxial peaking capacitor with improved insulation performance. In the insulation design, the length of the dielectric film is extended to reduce the background electric field on the flashover path. The electric field threshold obtained from image diagnosis is used as a reference. During capacitor testing, the insulation characteristics are diagnosed using both direct and indirect methods. The voltage measured by a D-dot probe, the output waveform of the Marx generator in the primary source, and the radiation field waveform are analyzed to understand the flashover characteristics of the capacitor and to improve the reliability of the test results. The experimental results demonstrate that the peaking capacitor can operate stably at 3.0 MV. If flashover occurring on the dropping edge of the pulse is permitted, the operating voltage can be greater than 3.7 MV without significantly affecting the radiation field waveform. The analysis on the surface flashover morphology of the peaking capacitor reveals that the flashover mainly occurs at the dropping edge of the capacitor's waveform, indicating that the damage to the film is not serious. This research significantly increases the working voltage of coaxial peaking capacitors and contributes to the development of high-altitude EMP simulation technology. [ABSTRACT FROM AUTHOR]

An electrostatic calibration technique is highly flexible in producing a wide range of force and it is widely applied for nano-newton to micro-newton thrust stand calibration. This paper proposes a novel method for electrostatic comb implementation and related experiments have been carried out. Based on the printed circuit board and commercial fins, the comb can be realized flexibly with the output force conveniently extended. The force generated by this kind of comb is theoretically analyzed. Different from the traditional comb structure, the conductive area of the comb fixed plate is minimized to improve the force consistency over engagement. The influence of fin length, fin number, applied voltage, and engagement on the output force has been studied experimentally. The final comb system is capable of producing steady force in the range 13-5040 μN with the relative error within 5%. With a high voltage pulse generator, this system could produce calibration impulse bit in the range 1-1000 μN s for which the lowest level can be far more extended to the nanonewton range with a shorter pulse width, a lower voltage, and a reduced number of fins. Moreover, the calibrator has a rather flat force-engagement characteristic when the engagement is in the range of 6 mm–16 mm, while the variation of electrostatic force is within 5%. This calibrator has a wide output range and great consistency, and it is beneficial for the thrust stand calibration. [ABSTRACT FROM AUTHOR]

In this paper, a torsional thrust balance with an asymmetrical arm is designed and tested which is effective for the microthruster performance evaluation in the vacuum facilities with limited space. An optimization design method for the key parameters of the thrust balance has been developed. By utilizing the asymmetrical arm, a great resolution can be obtained with a restrained arm length. A novel printed circuit board electrostatic comb has been applied to the thrust balance calibration. Experimental results show that the comb is capable of producing steady force in the range of about 30 μN–3300 μN and an impulse bit of 7 µNs–777 µNs which can be further extended to nano-Newton second range with a shorter pulse width and a lower voltage. The calibration results show that the thrust balance has a great repeatability and reliability. The total uncertainty of the thrust stand is estimated to be 3.33% in the 1 µNs range. [ABSTRACT FROM AUTHOR]

This paper presents the design and development of a trigger with a high repetition rate, low jitter, and compact structure for the pseudospark switch (PSS), which includes an improved Marx generator based on avalanche transistors and a corona-plasma trigger unit. The generator adopted a novel 3 × 12-stage Marx circuit based on avalanche transistors in which the failure rate of transistors in the first and second stages was significantly reduced by connecting the parallel capacitors compared to the previous similar generator. The reason for the improved performance was also discussed. The main parameters of output pulses were an amplitude of −7 kV, rise time of 6 ns, jitter of 0.2 ns, and repetition rate of 2 kHz. The corona-plasma trigger unit adopted BaTiO3 ceramics with high εr as the dielectric and was arranged in the hollow cathode of the PSS. The experiments of triggering a PSS prototype were conducted. The influence of anode voltage and pressure on the trigger delay and jitter was studied, and the minimum trigger jitter achieved <1 ns. This trigger worked for 107 shots at the repetition rate of 2 kHz continuously without obvious performance degradation and any failure of the generator. The main advantage of this trigger is the simultaneous combination of the high repetition rate, low jitter, long lifetime, and great simplicity in a compact structure. [ABSTRACT FROM AUTHOR]