Breakdown Mechanism Research Articles

Enhancing mechanisms of arc-erosion resistance for copper tungsten electrical contact using reduced graphene oxides in situ modified by copper nanoparticles

To solve critical issues of premature failure for copper tungsten (CuW) based electrical contacts during arc erosion at the moment of arc breakdown, we proposed a new strategy of using metal doped reduced graphene oxides (rGOs) and in-situ formed tungsten carbides to inhibit movements of cathode spots during the arc ablation process. CuW composites were reinforced with Cu modified rGO nanopowders (i.e. Cu@rGO) using combined processes of chemical co-reduction, ball milling and spark plasms sintering (SPS). Effects of Cu@rGO addition on microstructure, arc erosion resistance and arc ablation resistance of the CuW composites were systematically investigated. Results showed that tungsten carbides with irregular shapes were formed through in-situ reactions of rGO and tungsten during the SPS process. Arc erosion resistance of CuW composites was significantly improved owing to introduction of nanostructured Cu@rGO. Compared with those of CuW composites, the ablation areas of Cu@rGO/CuW ones were much smaller and the ablation craters were shallower, and the average strengths of dielectric vacuum breakdowns of the CuW composites with 3 wt% Cu@rGO were increased by 28.9%. The arc breakdown mechanisms of Cu@rGO/CuW composites were identified as: (1) The nanostructured Cu@rGO increases the viscosity of molten metal Cu, thus inhibiting its fast flow and splashing; (2) Lower work functions of carbon (i.e. rGO) and tungsten carbide restrain the electron emissions during arc breakdown; and (3) The tungsten carbides with their good stability and high melting point shorten the solidification time of molten copper liquid and extend the service life time of the Cu@rGO/CuW composites.

Analysis of overload induced arc formation and beads characteristics in a residential electrical cable

The process and mechanism of breakdown induced cable insulation exposed to conductor heating caused by overload were investigated. The time from the beginning of the overload to the occurrence of an electrical arcing event was measured. A mathematical equation between the average time of the initial breakdown and current was established for 220 VAC distribution systems. The phenomena in these experiments were captured with a high-speed camera. The times and durations of arcing events occurring repeatedly were documented throughout the whole process, which could present some information associated with the possibility of this fault to ignite combustibles. The formation process of breakdown was evaluated theoretically. The established mathematical equation to calculate the average time of the initial breakdown could be employed to predict the interval between overload occurrence and breakdown arcing. The formation process of arc beads was affected by the hot environment created by breakdown and insulation combustion. Kinds of metallographic microstructure of arc beads might be found during a test, such as dendritic segregation structure, equiaxed recrystallized grains, and cylindrical crystals. This work could provide basic data for determining the breakdown occurrence attributed to overload.

Field cycling behavior and breakdown mechanism of ferroelectric Al0.78Sc0.22N films

The effects of field cycling of Al0.78Sc0.22N capacitors on ferroelectric properties are investigated. In the first hundreds of switching cycles, the reduction in the switching voltage was observed, possibly due to the formation of nitrogen-vacancy to facilitate the atom displacements. With further switching cycles, fatigue effect was observed, especially for domains with low switching voltage. The leakage current analysis indicates continuous downward band bending with the number of switching cycles, effectively reducing the Schottky barrier height for electrons. The breakdown of Al0.78Sc0.22N films is triggered by the Joule heat due to excessive leakage current. The mechanism is in contrast to conventional ferroelectric materials, where the breakdown is triggered by Joule heat at the local conductive filaments.

Influence of food macrostructure on the kinetics of acidification in the pig stomach after the consumption of rice- and wheat-based foods: Implications for starch hydrolysis and starch emptying rate

How the stomach can serve as a biochemical environment for starch digestion and the implications on starch emptying are not well-understood. Biochemical changes during gastric digestion of cooked wheat- and rice-based diets of varying particle size and microstructure were investigated using a growing pig model. In larger-particle size diets (rice grain, rice noodle, pasta), pH >3 was maintained in the proximal stomach digesta even until 240 min digestion, resulting in extended remaining amylase activity and accumulation of maltose from starch hydrolysis in the stomach. In smaller-particle size diets (couscous, rice couscous, semolina porridge), gastric acidification occurred faster to produce homogeneous intragastric pH and deactivated amylase. The hypothesis of the study was that food macrostructure would impact gastric acidification kinetics, and the resulting biochemical environment for starch hydrolysis in the stomach may further affect the mechanisms of food breakdown in the stomach and gastric emptying of starch.

Resting state functional brain networks associated with emotion processing in frontotemporal lobar degeneration

This study investigated the relationship between emotion processing and resting-state functional connectivity (rs-FC) of the brain networks in frontotemporal lobar degeneration (FTLD). Eighty FTLD patients (including cases with behavioral variant of frontotemporal dementia, primary progressive aphasia, progressive supranuclear palsy syndrome, motor neuron disease) and 65 healthy controls underwent rs-functional MRI. Emotion processing was tested using the Comprehensive Affect Testing System (CATS). In patients and controls, correlations were investigated between each emotion construct and rs-FC changes within critical networks. Mean rs-FC of the clusters significantly associated with CATS scoring were compared among FTLD groups. FTLD patients had pathological CATS scores compared with controls. In controls, increased rs-FC of the cerebellar and visuo-associative networks correlated with better scores in emotion-matching and discrimination tasks, respectively; while decreased rs-FC of the visuo-spatial network was related with better performance in the affect-matching and naming. In FTLD, the associations between rs-FC and CATS scores involved more brain regions, such as orbitofrontal and middle frontal gyri within anterior networks (i.e., salience and default-mode), parietal and somatosensory regions within visuo-spatial and sensorimotor networks, caudate and thalamus within basal-ganglia network. Rs-FC changes associated with CATS were similar among all FTLD groups. In FTLD compared to controls, the pattern of rs-FC associated with emotional processing involves a larger number of brain regions, likely due to functional specificity loss and compensatory attempts. These associations were similar across all FTLD groups, suggesting a common physiopathological mechanism of emotion processing breakdown, regardless the clinical presentation and pattern of atrophy.

Effects of SiNX passivation on GaN-HEMT DC characteristics

In this paper, the effects of tensile/compressive stress induced charge by silicon nitride (SiNX) passivation on electrical characteristics of D-mode high electron mobility transistor (HEMT), i.e., GAN were investigated by SILVACO simulation tools and fabrication results were also shown as its counterpart. The influence of Al-fraction and surface state were also discussed and analyzed. The results of stress-induced SiNx impact shows the tensile stress increase the 2-dimensional electron gases (2DEG) density. The compressive stress will not only decrease the sheet charge density but also format 2-dimensional hole gases (2DHG) at the heterojunction of GaN/AlGaN. Besides, the possible mechanism of breakdown resulting from 2DHG is discussed which results in the breakdown of device more easily. This study also shows the performance of the real device based on the design of the simulation model. Finally, D-mode GaN MIS-HEMTs was fabricated to verify the physical model. We also designed different kinds of Gate-to-Drain length in this study. The Ron of LGD = 5, 10 and 15 μm were 12.9, 15.04 and 16.48 mΩ cm2, respectively. The highest breakdown voltage was observed for LGD = 10 μm because of the field plate.

Mechanisms of aggregate breakdown in (sub) tropical soils: Effects of the hierarchical resistance

The soil system is a dynamic component of the earth. Aggregate stability is critical for soil quality and ecosystem services. In tropical and subtropical soils, the role of clay, soil organic carbon, aluminum, and iron oxides on aggregate stability is somewhat controversial. In addition, aggregates develop a hierarchical organization; however, this process is poorly evaluated in the context of aggregate stability on different breakdown mechanisms such as raindrop impact, slaking (entrapped air), breakdown by differential swelling, and abrasion. Therefore, the objective of this study was: 1) to evaluate the aggregate stability of (sub) tropical soils in terms of four different breakdown mechanisms; 2) to ascertain the existence of hierarchical resistance to break down mechanism of pre-selected aggregates classes; 3) to determine whether soil chemical–mineralogical attributes influence aggregate stability. Five Oxisols originated from igneous rocks along a transect were evaluated. The soil aggregate stability responded according to hierarchical resistance, but differently to each breakdown mechanism: abrasion, slaking, differential swelling, and raindrop impact. Overall, the larger aggregates (4–8 mm) corresponded to a lower resistance to abrasion and raindrop impact. In contrast, the smaller aggregates (1–2 mm) were more affected by slaking than raindrop impact. Soil organic carbon, except for large aggregates, and soil texture did not show a significant role on aggregate stability. Silicon oxides increased the resistance to abrasion, while iron oxides increased the resistance to slaking. In contrast, aluminum oxides decreased the aggregate stability (slaking). The aggregate stability was influenced by method deployed and pre-selected classes of aggregate size. In this study, rainfall simulation (raindrop impact) and wet sieving (fast wetting) were the recommended methods to evaluate (sub) tropical soil aggregate stability. An aggregate size of 2–4 mm is preferable if a single class is selected.

Prebiotics and the Human Gut Microbiota: From Breakdown Mechanisms to the Impact on Metabolic Health.

The colon harbours a dynamic and complex community of microorganisms, collectively known as the gut microbiota, which constitutes the densest microbial ecosystem in the human body. These commensal gut microbes play a key role in human health and diseases, revealing the strong potential of fine-tuning the gut microbiota to confer health benefits. In this context, dietary strategies targeting gut microbes to modulate the composition and metabolic function of microbial communities are of increasing interest. One such dietary strategy is the use of prebiotics, which are defined as substrates that are selectively utilised by host microorganisms to confer a health benefit. A better understanding of the metabolic pathways involved in the breakdown of prebiotics is essential to improve these nutritional strategies. In this review, we will present the concept of prebiotics, and focus on the main sources and nature of these components, which are mainly non-digestible polysaccharides. We will review the breakdown mechanisms of complex carbohydrates by the intestinal microbiota and present short-chain fatty acids (SCFAs) as key molecules mediating the dialogue between the intestinal microbiota and the host. Finally, we will review human studies exploring the potential of prebiotics in metabolic diseases, revealing the personalised responses to prebiotic ingestion. In conclusion, we hope that this review will be of interest to identify mechanistic factors for the optimization of prebiotic-based strategies.

Temporal evolution characteristics and mechanism analysis of CCD breakdown induced by nanosecond and picosecond pulse lasers

Studies on the interaction between laser irradiation and charge-coupled devices (CCDs) have been reported to potentially bring new opportunities in the field of photoelectric countermeasures. It is known that the complete failure of CCD caused by pulsed laser originates from the destruction of CCD internal structure, but the detailed damage mechanism of laser-induced CCD breakdown is still a dilemma. Here, the thermal-mechanical coupling model of CCD irradiated by laser is established by finite element method, and the damage threshold and damage characteristics of CCD in point damage, line damage, black-and-white split screen and complete damage stages are characterized. The results show that the temperature rise effect of silicon substrate damage is predominant in the lateral direction, which increases by 300–3000 K; while it only increases by 300–400 K in the longitudinal direction. The complete damage threshold of CCD irradiated by nanosecond laser is 509 mJ/cm2; while that irradiated by picosecond laser is 190 mJ/cm2. When the silicon dioxide insulation layer is completely ablated, CCD completely fails due to the clock confusion caused by a short circuit between silicon electrodes.

Degradation of bisphenol A and S in wastewater during cold atmospheric pressure plasma treatment

Developing novel, fast and efficient ecologically benign processes for removing organic contaminants is important for the continued development of water treatment. For this reason, this study investigates the implementation of Cold Atmospheric pressure Plasma (CAP) generated in ambient air as an efficient tool for the removal of Bisphenol A (BPA) and Bisphenol S (BPS)—known endocrine disrupting compounds in water and wastewater, by monitoring degradation kinetics and its transformation products. The highest removal efficiencies of BPA (>98%) and BPS (>70%) were obtained after 480 s of CAP exposure. A pseudo-first-order kinetic revealed that BPA (−kt = 4.4 ̶ 9.0 ms−1) degrades faster than BPS (−kt = 0.4 ̶ 2.4 ms−1) and that the degradation is also time- and CAP power-dependent, while the initial concentration or matrix type had a negligible effect. This study also tentatively identified three previously reported and one novel transformation product of BPA and four novel transformation products of BPS. Their postulated structures suggested similar breakdown mechanisms, i.e., hydroxylation followed by ring cleavage. The results demonstrate that CAP technology is an effective process for the degradation of both BPA and BPS without the need for additional chemicals, indicating that CAP is a promising technology for water and wastewater remediation worthy of further investigation and optimization.

Enhancing high-temperature capacitor performance of polymer nanocomposites by adjusting the energy level structure in the micro-/meso-scopic interface region

The interface plays a major role in the conduction and breakdown behaviors of dielectric materials. Enhancing interface compatibility and Schottky barrier to reduce conduction loss and enhance breakdown strength of nanocomposites has been widely studied. Nevertheless, there are few reports on the effect of the energy level structure in filler/polymer and electrode/dielectric interface region on the breakdown strength and high-temperature energy storage performances. Herein, the polyimide (PI) films sandwiched by Al2O3 layers and filled with SiO2 shell-coated high-K BaTiO3 nanofibers were prepared. Our results reveal that the wide bandgap oxide layer can regulate the energy level structure of the interface region, introduce deep traps in the nanocomposites and increase the Schottky barrier at the electrode/dielectric interface to impede charge injection and transport. Moreover, the nanocomposites combine the advantages of anisotropic dielectric properties from the Al2O3 layer, SiO2 shell, and BaTiO3 core, enhancing dielectric constants of the nanocomposites. The optimal nanocomposites show greatly enhanced discharge energy density and breakdown strength at 150 °C, which are 370% and 38% higher than those of PI, respectively. This work provides more insight into the mechanism of electrical conduction and breakdown in polymer nanocomposites and offers an effective strategy for developing polymer nanocomposites with superior capacitive performance at elevated temperatures.

Analysis of breakdown mechanism based on contact area and field enhancement factor of different electrode‐material combinations

Analysis of breakdown mechanism based on contact area and field enhancement factor of different electrode‐material combinations

Structural Remodelling of the Carbon‐Phosphorus Enzymatic Machinery by a Dual ATP‐Binding Cassette Module

Phosphorus (P) is an essential macronutrient that can be extracted from the environment by several metabolic pathways. In E. coli, phosphate deprivation activates the the 14‐cistron phn operon that encodes carbon‐phosphorus (C‐P) lyase. C‐P lyase confers the ability to extract phosphorus from a wide range of phosphonate compounds containing the chemically highly stable C‐P bond.1 Phosphonates are widespread in nature and due to their similarity to phosphate esters, have important applications in agriculture and biomedicine, as pesticides (glyphosate, RoundUp) and antibiotics, respectively. C‐P lyase catalyses a complex multi‐step pathway that directly depends on 10 of the encoded proteins (PhnGHIJKLMNOP). Of these, the PhnJ subunit was shown to be responsible for cleavage of the C‐P bond via a strict anaerobic glycyl radical mechanism that requires an iron‐sulphur (Fe4S4) cluster and S‐adenosyl methionine (SAM) for radical activation. Surprisingly, however, this mechanism was not immediately compatible with the crystal structure of a PhnGHIJ C‐P lyase core complex, which placed key residues at a significant distance, thus leaving a large gap in our understanding of the mechanism of phosphonate breakdown.2,3 The phn operon also encodes two ATP‐binding cassette (ABC) proteins with homology to the nucleotide‐binding domains of ABC transporters, PhnK and PhnL, for which no function has been assigned. Here, we present four high‐resolution (~2 Å), single‐particle cryo‐electron microscopy structures of 300+ kDa C‐P lyase complexes in several key, functional states. Together, these structures reveal how the PhnGHIJ core complex interacts with a unique double dimer of PhnK and PhnL subunits, in which PhnK, in a tight ATP‐bound conformation, bridges the core complex and PhnL. We also show using additional structures determined under ATP turnover conditions, that ATP hydrolysis in PhnK induces a dramatic remodelling of the core complex, leading to opening and large‐scale movement of several subunits. Moreover, we show that ATP hydrolysis and binding of both ABC subunits is required for growth of E. coli on phosphonate. Finally, we demonstrate that C‐P lyase in the closed state binds substrate at a metal‐binding site located at the interface between the PhnI and PhnJ subunits, and that ATP hydrolysis leads to a reorganisation of this active site in a way likely contributes to substrate/product exchange. In summary, we provide several novel insights into the elusive process of phosphonate breakdown by C‐P lyase in microorganisms and represent a solid structural basis for understanding the catalytic process. Our structural data also uncover a hitherto unknown configuration of ABCs in which two ABC dimers directly interact with each other that have broad implications for our understanding of the role of this module in biological systems.1. Metcalf, W. W. & Wanner, B. L. Gene 129, 27‐32, (1993).2. Kamat, S. S., Williams, H. J., Dangott, L. J., Chakrabarti, M. & Raushel, F. M. Nature 497, 132‐136, (2013).3. Seweryn, P. et al. Nature 525, 68‐72, (2015).

Observation of breakdown wave mechanism in avalanche ionization produced atmospheric plasma generated by a picosecond CO2 laser

Understanding the formation and long-timescale evolution of atmospheric plasmas produced by ultrashort, long-wavelength infrared (LWIR) pulses is an important but partially understood problem. Of particular interest are plasmas produced in air with a peak laser intensity ∼1012 W/cm2, the so-called clamping intensity observed in LWIR atmospheric guiding experiments where tunneling and multi-photon ionization operative at near-IR or shorter wavelengths are inoperative. We find that avalanche breakdown on the surface of aerosol (dust) particles can act to seed the breakdown of air observed above the 200 GW/cm2 threshold when a train of 3 ps 10.6 μm laser pulses separated by 18 ps is used. The breakdown first appears at the best focus but propagates backward toward the focusing optic as the plasma density approaches critical density and makes forward propagation impossible. The velocity of the backward propagating breakdown can be as high as 109 cm/s, an order of magnitude greater than measured with ns pulse-produced breakdown, and can be explained rather well by the so-called breakdown wave mechanism. Transverse plasma expansion with a similar velocity is assisted by UV photoionization and is observed as a secondary longitudinal breakdown mechanism in roughly 10% of the shots. When a cm-size, TW power beam is propagated, interception of aerosol particles is guaranteed and several (40 cm−3) breakdown sites appear, each initially producing a near-critical density plasma. On a 10 ns–1 μs timescale, shockwaves from each site expand radially and coalesce to produce a large hot gas channel. The radial velocity of the expansion agrees well with the prediction of the blast wave theory developed for ultrafast atmospheric detonations.

Impact of Anode Thickness on Breakdown Mechanisms in Vertical GaN PiN Diodes with Planar Edge Termination

GaN vertical PiN diodes with different anode thicknesses were fabricated on three native GaN wafers with the same p-layer doping concentrations, and planar hybrid edge termination. The breakdown behavior in terms of the breakdown voltage and the electroluminescence were studied as functions of the anode thickness. A repeatable avalanche breakdown and highest breakdown voltage were measured with the thinnest anode of 300 nm and with the thinnest edge termination region. This indicates the efficacy of the nitrogen-implanted hybrid edge termination design that comprises of junction termination and guard rings hybrid design. As the anode thickness increases, the edge termination thickness increases, and the devices exhibit lower breakdown voltages and less robust breakdown characteristics, often destructive. From this study, we also conclude that a very high p-layer doping of 2 × 1019 cm−3 is not s practical doping level, because it is too sensitive to the edge termination thickness.

Investigation of ON-State Breakdown Mechanism in AlGaN/GaN HEMTs with AlGaN Back Barrier

The temperature-dependent ON-state breakdown BVON loci of AlGaN/GaN high-electron-mobility transistors (HEMTs) with an AlGaN back barrier were investigated using the gate current extraction technique. The impact ionization of acceptor-like traps was revealed to be responsible for the ON-state breakdown in HEMTs as a 2D electron gas (2DEG) channel is marginally turned on. The characteristic electric field Ei of impact ionization was extracted, exhibiting a U-shaped temperature dependence from 40 to −30 ∘C, with minimum Ei occurring at −10 ∘C. The impurity scattering effect of acceptor-like traps in AlGaN/GaN heterostructures is suggested to be responsible for the negative temperature dependence of BVON and Ei below −10 ∘C.

Autophagy in muscle regeneration: potential therapies for myopathies.

Autophagy classically functions as a physiological process to degrade cytoplasmic components, protein aggregates, and/or organelles, as a mechanism for nutrient breakdown, and as a regulator of cellular architecture. Its biological functions include metabolic stress adaptation, stem cell differentiation, immunomodulation and diseases regulation, and so on. Current researches have proved that autophagy dysfunction may contribute to the pathogenesis of some myopathies through impairment of myofibres regeneration. Studies of autophagy inhibition also indicate the importance of autophagy in muscle regeneration, while activation of autophagy can restore muscle function in some myopathies. In this review, we aim to report the mechanisms of action of autophagy on muscle regeneration to provide relevant references for the treatment of regenerating defective myopathies by regulating autophagy. Results have shown that one key mechanism of autophagy regulating the muscle regeneration is to affect the differentiation fate of muscle stem cells (MuSCs), including quiescence maintenance, activation and differentiation. The roles of autophagy (organelle/protein degradation, energy facilitation, and/or other) vary at different myogenic stages of the repair process. When the muscle is in homeostasis, basal autophagy can maintain the quiescence state and stemness of MuSCs by renewing organelle and protein. After injury, the increased autophagy flux contributes to meet biological energy demand of MuSCs during activation and proliferation. By mitochondrial remodelling, autophagy during differentiation can promote the metabolic transformation and balance mitochondrial‐mediated apoptosis signals in myoblasts. Autophagy in mature myofibres is also essential for the degradation of necrotic myofibres, and may affect the dynamics of MuSCs by affecting the secretion spectrum of myofibres or the recruitment of supporting cells. Except for myogenic cells, autophagy also plays an important role in regulating the function of non‐myogenic cells in the muscle microenvironment, which is also essential for successful muscle recovery. Autophagy can regulate the immune microenvironment during muscle regeneration through the recruitment and polarization of macrophages, while autophagy in endothelial cells can regulate muscle regeneration in an angiogenic or angiogenesis‐independent manner. Drug or nutrition targeted autophagy has been preliminarily proved to restore muscle function in myopathies by promoting muscle regeneration, and further understanding the role and mechanism of autophagy in various cell types during muscle regeneration will enable more effective combinatorial therapeutic strategies.

Impact of MgO spacer layer on microwave performance of MgZnO/ZnO HEMT

This article analyzes the direct current and small-signal parameters of MgZnO/ZnO (MZO) HEMT for microwave application. Further, the impact of the MgO spacer layer on the microwave performance parameters such as transconductance (g m), cut-off frequency (f T), maximum oscillation frequency (f max) and Johnson’s figures of merit (J-FOM) of MZO HEMT has been analyzed. MZO HEMT with MgO spacer results in the enhanced values of two-dimensional electron gas (2DEG) density of 7.2 × 1013 cm−2 and g m of 91 mS mm−1. The values of f T and f max exhibit 3-fold enhancement to 5.57 GHz and to 7.8 GHz, respectively, and J-FOM is increased by 2.93 times with the introduction of MgO spacer layer in HEMT structure. Moreover, the impact of MgO spacer is studied on the off-state breakdown mechanism of MZO HEMT. The off-state breakdown voltage (V br) of MZO HEMT is ∼25 V higher than that for MZO HEMT with an MgO layer. Therefore, there is a trade-off between the microwave performance and the device off-state breakdown voltage. This work is significant for the development of large-area and cost-effective ZnO-based HEMTs for microwave applications.

Improving the reliability of MOS capacitor on 4H-SiC (0001) with phosphorus diffused polysilicon gate

The interface states and reliability of 4H-SiC metal-oxide-semiconductor field effect transistors (MOSFETs) with thermal gate oxides have been researched widely. Several reports have researched the gate oxide process itself, but the effects of subsequent processes should not be ignored. In this paper, the reliability of thermal gate oxide films followed by polysilicon gate (poly-gate) process, which are widely used in MOSFET manufacture, and Al gates were compared. The poly-gate samples markedly affected the performance measured by time-zero dielectric breakdown and time-dependent dielectric breakdown methods because the phosphorus content diffused during poly-gate formatting; this was especially advantageous in reducing leakage current and improving the charge-to-breakdown (Q BD). After electronic characteristics measurements, scanning electron microscopy cross-sections were also used to analyze the breakdown mechanism. We observed an intermediate layer between the Al gate and the oxide that may cause the barrier height to be smaller than that of the poly-gate. The Al work function and polysilicon Fermi level determine the gate leakage currents and the resultant gate oxide reliability, whereas the Al2O3 gate sample has a smaller work function offset (0.7 eV) than ideal Al gate and poly-gate samples. The results imply that the reliability of the Al gate samples may be an intrinsic problem.

Understanding the electromagnetic topology during the ohmic breakdown in tokamaks considering self-generated electric fields

The physical mechanisms of the ohmic breakdown in a tokamak have been understood based on the classical Townsend avalanche theory. However, a new systematic theory (Yoo et al 2018 Nat. Commun. 9 3523) recently demonstrated that electron avalanches during the ohmic breakdown are completely different from the Townsend avalanche due to strong self-generated electric fields. In this study, we elucidate the multi-dimensional effects of the self-generated electric field on plasma dynamics during the ohmic breakdown. We also propose a novel electromagnetic topology analysis method that can easily predict the overall plasma behavior and where the main plasma is generated. The topology analysis method is validated by a state-of-art particle simulation for various magnetic configurations. New physical insights into the complex electromagnetic topology would facilitate designing more reliable and optimized ohmic breakdown scenarios in future tokamaks, such as ITER and beyond.