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The paper deals with space-charge interactions in the ion population trapped in the Orbitrap${}^{\mathrm{\text{TM}}}$ mass analyzer where the ions perform multiple quasi-harmonic oscillations in the axial direction. The many-particle problem for interacting ions is mathematically complicated and its solution, even numerical, is obstructed by the required precision of one per million to be maintained on a large number $(10^5-10^6)$ of oscillation periods. We develop a perturbation method based on the Bogoliubov–Krylov–Mitropolsky theory and derive averaged Hamiltonian equations in perturbations, which describe the evolution of the ions’ oscillation amplitudes and phases in so-called “slow” time. This approach provides a semi-analytical comprehensive model of resonant and nonresonant space-charge effects and allows fast and accurate numerical computation. Practical mitigation strategies for most deteriorating space-charge effects like coalescence and frequency shifts are considered.

In this paper, we review three methods to construct symplectic and self-consistent multiparticle algorithms to simulate space–charge effects in particle accelerators. The first method is based on a discrete multiparticle Hamiltonian with an interaction term that depends explicitly on the coordinates of the macroparticles. The second method derives from Low’s Lagrangian for a collisionless plasma. The third method is based on a corresponding collisionless Hamiltonian. The last two methods have been mostly developed by the plasma physics community, but are equally applicable to accelerator physics problems.

The critical-charge criterion of the stem-leader transition and the shielding effects of space charges on the streamer inception are two most contested issues on the inception of positive upward leader–streamer system (LSS). In this paper, a series of simulation experiments on the LSS inception were designed and carried out. A new critical-charge criterion in the range of 0.2–0.3 μC was proposed, and the previous criterion of 1.0 μC was proved to be harsh. The shielding effect of positive space charges on the streamer inception was verified directly by the experiment results. A theoretical formula for calculating the LSS inception voltage by the first-corona inception voltage was obtained. An appropriate first-corona inception time for getting an earlier LSS inception was proved to be existent. At last, the effects of the so-called improved lightning rods, such as the early streamer emission rod (ESE) and the controllable lightning rod (CL), were discussed, and it seemed that they would not help to extend the protective zones of the lightning rods.

A photo-stimulated discharge (PSD) method is more effective than thermal methods to characterize the deep space charge traps in dielectric materials. In this paper, a new PSD measuring system was first built up based on the optical parametric oscillator laser. The laser can generate continuously tunable wavelengths whose range are 210–420 nm and with average output pulse energy 2.3 mJ. The system overcomes the shortcoming of weak output energy in past experiments, especially in the range of ultraviolet band. The PSD current spectra of PET were measured by this system. The results show that the energy level of charge traps in the PET film is mainly distributed in 4.08~5.18 eV, and the trap density maximum is at 4.22 eV. These data can provide the experimental basis for further research and improvement on electrical properties of materials.

The MgO/low-density polyethylene nanocomposite film and the sandwich-structure LDPE/MgO-LDPE/LDPE nanocomposite film were prepared by melt blending and hot pressing. Based on the Maxwell–Wagner effect, a theoretical model of the three-layer dielectric interface polarization was set up, and the charge density of the three layers of dielectric interface polarization is obtained. Then pulsed electro-acoustic (PEA) is used to study the charge distribution characteristics of the three-layer structure while the breakdown strength of the three-layer structure is tested. The formation and transmission mechanism of the interface charge is systematically analyzed through the above two methods. The results show that the formation of space charge at the interface of sandwich-structure film is likely to be the result of the interaction between the three-layer dielectric polarization effect and the capture charge mechanism at the interface. Compared with the single-layer composite film, the sandwich-structure nanocomposite film has higher breakdown strength, the reason may be that the charge is trapped by the charge trapping mechanism at the interface during the movement of the opposite electrode to form an interfacial space charge, and as the charge accumulates continuously to form a barrier at the interface, the barrier can effectively inhibit the formation of the conductive channel, and the material is improved. The breakdown field is strong.

In this paper, titanium and tungsten films were coated on copper sheets, respectively, by plasma chemical vapor deposition (PCVD). The copper sheets before and after coating were, respectively, injected as charge into the low-density polyethylene (LDPE), the space charge accumulation in LDPE was tested by the thermally stimulated current (TSC), and the trap level of the dielectric was calculated by the TSC curve. The results show that the work function improves after the modification of the electrode material, the space charge accumulation in LDPE decreases, and the trap level of the polymer reduces. Because of the oxygen vacancies, the titanium coating electrode has significant suppression on the charge injection in LDPE under 30 kV/mm and the tungsten shows excellent inhibition under 70 kV/mm.

We have studied the intense electron beams emitted from multiple metallic, vertical and well-aligned Carbon Nanotube (CNT) field emitters. A two-dimensional (2D) particle-in-cell simulation code MAGIC2D is used to obtain the I–V characteristics near to the apex of the emitters' surface for a given applied electric field and field enhancement factor over a wide range of parameters. The effects of electron space charge and electric field shielding from neighboring emitters are compared in low current and high current regimes. It is found that the electron space charge is dominant in high current regime, where the Fowler–Nordheim (FN) law becomes the 2D Child–Langmuir (CL) law. The emitter spacing, number of emitters, and emitter's uniformity are also particularly studied, and they are more critical in low current regime. Smooth transition from the FN law to CL law is demonstrated.

Fourth generation light sources based on high gain free electron lasers require production, acceleration and transport up to the undulator entrance of high brightness (low emittance, high peak current) electron bunches. Wake field effects in accelerating sections and in magnetic bunch compressors typically contribute to emittance degradation, and hence the design of the injector and its operation constitute the leading edge for high quality beam production and for the success of the future light sources. RF and DC guns, cathode materials, laser pulse shaping and sub-picosecond synchronization systems are evolving toward a mature technology to produce high quality and stable beams. Nevertheless, reduction of thermal emittance, damping of emittance oscillations and bunch compression are still the main issues and challenges for injector designs. With the advent of energy recovery linacs, superconducting RF guns have been also considered in many new projects as a possible electron source operating in CW mode. An overview of recent advancements and future perspectives of high performance electron injectors are presented in this article.

Due to their excellent electrical insulation properties and processability, polymer materials are used in many electrical products. It is widely believed that space charge plays an important role for the electric field distribution, conduction, ageing, and electric breakdown of polymeric insulation. This paper reviews measurements and characteristics of space charge behavior which mainly determined by the pulsed electro-acoustic (PEA) measurement technique. Particular interests are the effects of the applied voltage, the electrodes, temperature, humidity, microstructure, additives, and filler materials on accumulation, distribution, transport, and the decay of space charge in polymeric materials. This review paper is to provide an overview on various space charge effects under different conditions, and also to summarize the information for polymeric materials with suppressed space charge and improved electrical behavior.

Films of Polyvinyl acetate (PVAc), cellulose acetate propionate (CAP) homopolymers and their blends of compositions 0.85/0.15, 0.7/0.3, 0.5/0.5, 0.3/0.7 and 0.15/0.85 (wt/wt) were prepared to investigate the type of electrical conduction mechanism. The current-voltage characteristics have been studied under different conditions. Also, ultraviolet/visible spectra of all samples have been studied according to their different composition ratios.

The conduction mechanisms at different temperatures and voltage ranges appear to be essentially a space charge limited current for the two individual polymers, while for the blend samples the predominance mechanism is Poole-Frenkel type. Ultraviolet/visible studies of the investigated samples showed that the blend sample of 0.5/0.5 (wt/wt) has the smallest absorption edge (4.58 eV) and highest band tail (0.61 eV).

The composition blend sample 0.5/0.5 (wt/wt) has the most proper conduction and optical properties which has attractive attention in the view of its application in electronic and optical devices.

Fourth generation light sources based on high gain free electron lasers require production, acceleration and transport up to the undulator entrance of high brightness (low emittance, high peak current) electron bunches. Wake field effects in accelerating sections and in magnetic bunch compressors typically contribute to emittance degradation, and hence the design of the injector and its operation constitute the leading edge for high quality beam production and for the success of the future light sources. RF and DC guns, cathode materials, laser pulse shaping and sub-picosecond synchronization systems are evolving toward a mature technology to produce high quality and stable beams. Nevertheless, reduction of thermal emittance, damping of emittance oscillations and bunch compression are still the main issues and challenges for injector designs. With the advent of energy recovery linacs, superconducting RF guns have been also considered in many new projects as a possible electron source operating in CW mode. An overview of recent advancements and future perspectives of high performance electron injectors are presented in this article.