Threshold Electric Field Research Articles

Electric-field-temperature phase diagram and electromechanical properties in lead-free (Na0.5Bi0.5)TiO3-based incipient piezoelectric ceramics

In this work, the (1-x)(0.8Na0.5Bi0.5TiO3-0.2K0.5Bi0.5TiO3)-xSrTiO3 (NKBT-xST) incipient piezoelectric ceramics with x=0–0.07 (0ST-7ST) were prepared by the solid-state reaction method and their structural transformation and electromechanical properties were investigated as a function of ST content. As the ST content increases, the long-range ferroelectric order is disrupted, and the ferroelectric-relaxor phase transition temperature (TFR) shifts to around room temperature for NKBT-5ST ceramics, accompanied by a relatively high electrostrain of 0.3% at 6kV/mm. The large strain response associated with the vanished ferroelectric properties around TFR can be attributed to the reversible relaxor-ferroelectric phase transition. The electric-field-temperature (E-T) phase diagrams were established, and the transition between the two field-induced long-range ferroelectric states were found to take place via a two-step switching process through an intermediate relaxor state. The threshold electric field to trigger the conversion between ferroelectric state and relaxor state depends strongly on the dynamics of polarization relaxation, which is influenced by temperature and composition.

On the measurement of the threshold electric field for runaway electron generation in the Frascati Tokamak Upgrade

Experiments have been carried out to evaluate the threshold electric field for runaway generation during the flat-top phase of ohmic discharges in the Frascati Tokamak Upgrade tokamak. An investigation of the conditions for runaway electron generation and suppression has been performed for a wide range of plasma parameter values. The measured threshold electric field is found to be significantly larger (∼2−5 times) than predicted by the relativistic collissional theory of runaway generation, ER=ne e3 lnΛ/4π ε02 me c2, and can be explained to a great extent by an increase of the critical electric field due to the effect of the electron synchrotron radiation losses. These findings are consistent with the results of an ITPA joint experiment to study the onset, growth, and decay of relativistic runaway electrons [Granetz et al., Phys. Plasmas 21, 072506 (2014)]. Confirmation of these results for disruptions with high electric field might imply significantly lower requirements on electron densities for suppression and prevention of runaway formation in ITER.

Lower Electric Field-Driven Magnetic Phase Transition and Perfect Spin Filtering in Graphene Nanoribbons by Edge Functionalization.

Perfect spin filtering is an important issue in spintronics. Although such spin filtering showing giant magnetoresistance was suggested using graphene nanoribbons (GNRs) on both ends of which strong magnetic fields were applied, electric field controlled spin filtering is more interesting due to much easier precise control with much less energy consumption. Here we study the magnetic/nonmagnetic behaviors of zigzag GNRs (zGNRs) under a transverse electric field and by edge functionalization. Employing density functional theory (DFT), we show that the threshold electric field to attain either a half-metallic or nonmagnetic feature is drastically reduced by introducing proper functional groups to the edges of the zGNR. From the current-voltage characteristics of the edge-modified zGNR under an in-plane transverse electric field, we find a remarkable perfect spin filtering feature, which can be utilized for a molecular spintronic device. Alteration of magnetic properties by tuning the transverse electric field would be a promising way to construct magnetic/nonmagnetic switches.

Runaway electron generation and control

We present an overview of FTU experiments on runaway electron (RE) generation and control carried out through a comprehensive set of real-time (RT) diagnostics/control systems and newly installed RE diagnostics. An RE imaging spectrometer system detects visible and infrared synchrotron radiation. A Cherenkov probe measures RE escaping the plasma. A gamma camera provides hard x-ray radial profiles from RE bremsstrahlung interactions in the plasma. Experiments on the onset and suppression of RE show that the threshold electric field for RE generation is larger than that expected according to a purely collisional theory, but consistent with an increase due to synchrotron radiation losses. This might imply a lower density to be targeted with massive gas injection for RE suppression in ITER. Experiments on active control of disruption-generated RE have been performed through feedback on poloidal coils by implementing an RT boundary-reconstruction algorithm evaluated on magnetic moments. The results indicate that the slow plasma current ramp-down and the simultaneous reduction of the reference plasma external radius are beneficial in dissipating the RE beam energy and population, leading to reduced RE interactions with plasma facing components. RE active control is therefore suggested as a possible alternative or complementary technique to massive gas injection.

Size effect on polarization switching kinetics of P(VDF-TrFE) copolymer nanodots

We demonstrate polarization switching kinetics of poly(vinylidene fluoride-ran-trifluoroethylene) P(VDF-TrFE) nanodots depending on their sizes. Ferroelectric copolymer P(VDF-TrFE) nanodots, ranging from 20 to 250 nm in lateral size, were deposited on a Nb-doped SrTiO3 substrate by a position-controlled dip-pen nanolithography technique. Ferroelectric switching characteristics of P(VDF-TrFE) nanodots was investigated by piezoresponse force microscopy. Asymmetric switching behavior was observed during switching process, indicating that the threshold electric fields for polarization reversal were measured differently under the same conditions according to the switching polarity. Significantly, when the size of P(VDF-TrFE) nanodot approached around 250 nm, electric fields for polarization switching were compatible with those of the P(VDF-TrFE) thin film. We suggest that the electric fields required for polarization reversal of the P(VDF-TrFE) nanodots present asymmetric switching behaviors, and asymptotic behavior be observed as the nanodots increase in lateral size.

Electro–optic response in thin smectic C* film with chevron structures**Project supported by the Russian Foundation for Basic Research (RFBR) (Grant Nos. 16-32-00043 and 14-02-97026).

The effects in electrostatic models of chevron surface-stabilized ferroelectric liquid crystals are investigated through numerical modeling. To study smectic C* director distribution within the cell, we consider two nonlinear approaches: the chevron interface does not interplay with the electric field; the electric field interplays with the chevron interface. The obtained results of the director field distribution are compared with the earlier linearized studies. We find that whether or not the electric field interplays with the chevron interface, the electro–optic response requires a generalized approach for its description. The threshold electric field, which is necessary for switching between two stable director states in the chevron cell is evaluated. This study suggests that, in many cases of practical interest, electro–optic response to the electric field and the threshold electric field can be precisely estimated. We argue that, beside being numerically efficient, our approach provides a convenient and a novel standpoint for looking at the electro–optic response problem.

Orientational control of liquid crystal molecules via carbon nanotubes and dichroic dye in polymer dispersed liquid crystal

ABSTRACTPolymer dispersed liquid crystals (PDLCs) using nematic liquid crystal and photo-curable polymer (NOA 65) were prepared by polymerisation-induced phase separation technique, in equal ratio (1:1) of polymer and liquid crystal (LC). We demonstrate that doping of small amount (0.125%, wt./wt.) of multiwall carbon nanotubes (CNTs) and orange azo dichroic dye in PDLC generously controlled the molecular orientation, dynamics of LC in droplet and size of droplets. The effects of multiwall CNTs and dye on PDLCs were studied in terms of transition temperature, droplet morphology, transmittance characteristic, contrast ratio and response time. The results exhibited that the values of the threshold electric fields were reduced from 8 V/µm (pure PDLC) to 1.18 and 1.72 V/µm, doped with multiwall CNTs and dye, respectively. The CNTs-doped PDLC shows faster switching response as compared with pure PDLC and dye-doped PDLC. However, dye-doped PDLC shows much higher contrast among all PDLC samples. Further, the results also illustrate that the birefringence value of LC in PDLCs was changed with doping of CNTs and dye.

RESISTANCE OF THE SUBCUTANEOUS INTERNAL CARDIOVERTER DEFIBRILLATOR TO 60 HZ ELECTRIC FIELDS

The technology behind implantable cardioverter defibrillators (ICDs) is constantly evolving. Although improved shielding and other manufacturing features have rendered them more immune to electromagnetic interference (EMI), there remains safety concerns in high-risk exposure situations. Based on the International Standards Organization standard ISO 14117 and the calculations that can be made based on annex F of European norm EN 50-527-2-1 ICDs on the market are presumed immune at least up to ICNIRP’s general public exposure limit (4.2 kV/m for 60 Hz electric fields).. The goal of this study was to expose the subcutaneous ICD (S-ICD) to electric fields up to 20kV/m, so to determine the electric field threshold for interference. Such high electric field levels can be encountered in industrial settings (power utility substations) and in the right of way of high voltage (735 kV) power lines (theoretically up to about 8,5 kV/m at midspan).

Model for Stress Generation and Flow in Anodic Oxides

Porous anodic oxide (PAO) films are grown by electrochemical polarization of Al, Ti, and other metals in baths that dissolve the oxide. Procedures to grow films with highly ordered and controllable arrangements of nanoscale pores have led to the extensive use of PAO films in nanofunctional devices. Experiments and calculations show that transport in the oxide occurs by electrical migration coupled with oxide flow driven by mechanical stress (1-3). Pores initiate by a morphological instability at the oxide-solution interface when the initially formed barrier oxide reaches a critical thickness (4). In another presentation at this meeting, we showed that this instability is preceded by the buildup of compressive stress due to localized electric field-induced electrolyte anion incorporation at the oxide-solution interface. The instability is modeled by competition between stabilizing oxide formation at the oxide-solution interface and destabilizing oxide flow driven by gradients of anion-induced surface stress. The model predicts important features of self-ordered PAO growth on many metals: the pore separation-voltage scaling ratio, the narrow ranges of anodizing efficiency, and the threshold electric field. Characteristics of anodic oxides that enable self-organized PAO formation include their ability to flow and to accumulate highly localized stress at interfaces due to electrochemical reactions. Here we report a new model for coupled interfacial reactions, electrochemical transport and mechanics of amorphous anodic oxides. In the model, ionic conduction occurs by high-field electrical migration of oxygen and metal vacancy type defects. In contrast with other point defect models, vacancies are created and destroyed homogeneously within the oxide by electric-field stimulated localized relaxations of the amorphous network. Vacancy creation expands the oxide network generating compressive stress, while vacancy destruction contracts the network producing tensile stress. Field-stimulated vacancy formation and removal affect the conductance of anodic films and hence may be probed by electrochemical impedance spectroscopy (EIS). Impedance measurements during steady-state Al anodizing in sulfuric and oxalic acids are presented. The spectra reveal inductive loops between 1 and 100 Hz as reported elsewhere (5). The characteristic time constant and resistance of the inductive loop are shown to be determined by the kinetic parameters of the vacancy formation/removal reaction. The values of these parameters are independent of anodizing current density or solution composition. The kinetic model for vacancy formation/removal identified by EIS was used to simulate evolution of stress distributions in the oxide during Al anodizing in phosphoric acid at a constant current density of 5 mA/cm2 (6). Calculations demonstrate that vacancies are continuously generated at the oxide-solution interface to accommodate incorporation of large electrolyte oxyanions. This process is shown to be quantitatively consistent with localized compressive stress buildup at this interface as revealed by in situ stress measurements, the precursor for oxide flow and pore formation. At the metal interface, vacancies produced by metal oxidation are destroyed continuously at the metal interface, consistent with the buildup of localized tensile stress found experimentally. Finally we discuss implications of vacancy formation/removal for oxide flow. It is argued that at sufficiently high stress levels, this reaction can account for displacement of oxide volume driven by stress gradients. Such a process is equivalent to vacancy creep and can explain the apparent viscous flow of anodic oxides reported in several papers (1-3,7). ACKNOWLEDGMENT This work was supported by the the National Science Foundation through NSF-CMMI-100748. REFERENCES 1. S. J. Garcia-Vergara et al., Electrochim. Acta. 52, 681 (2006). 2. J. E. Houser and K. R. Hebert, Nature Mater. 8, 415 (2009). 3. J. Oh and C. V. Thompson, Electrochim. Acta, 56, 4044 (2011). 4. K. R. Hebert et al., Nature Mater. 11, 162 (2012). 5. M. Curioni et al., Electrochim. Acta 55, 7044 (2010). 6. Ö. Ö. Çapraz, et al., Electrochim. Acta 167, 404 (2015). 7. D. H. Bradhurst and J. S. L. Leach, J. Electrochem. Soc., 113, 1245 (1966).

(Invited) Stress-Assisted Formation of Self-Organized Porous Anodic Oxides

Porous anodic oxide (PAO) films are grown by electrochemical polarization of Al, Ti, and other metals in baths that dissolve the oxide. Procedures to grow films with highly ordered and controllable arrangements of nanoscale pores have led to the extensive use of PAO films in nanofunctional devices. Experiments and calculations show that transport in the oxide occurs by electrical migration coupled with plastic flow driven by mechanical stress in the oxide, and suggest that flow may play a role in formation of self-ordered PAO (1-3). Pores initiate by a morphological instability at the oxide-solution interface when the initially formed barrier oxide reaches a critical thickness (4). Herein is reported a combined experimental and modeling investigation of the formation and self-ordering of PAO. Experiments were carried out to identify stress generation mechanisms during galvanostatic formation of Al barrier films in 0.4 M H3PO­4. Stress distributions in these films were measured by monitoring stress-induced sample curvature changes during oxide formation followed by open circuit dissolution of the films (5). Elevated compressive stress reaching several GPa was found to build up within a few nanometers of the oxide-solution interface, coinciding with high phosphorus contamination in the same layer revealed by GDOES (6). The compressive surface stress is likely due to electric field-induced phosphate incorporation. The experimentally characterized surface stress was incorporated in our anodizing model based on transport by coupled viscous flow and electrical migration (2). Morphological stability analysis of the model reveals pattern formation consistent with the well-established characteristic pore spacing to voltage relationship of PAO (7). Pore formation is governed by competition between stabilizing oxide formation at the solution interface and destabilizing flow driven by gradients of anion incorporation-induced surface stress. The model successfully predicts the critical threshold electric field and the narrow ranges of anodizing efficiency characterizing PAO formation on many metals (3,4). A compelling analogy exists between the mechanisms of PAO ordering and formation of hexagonally-ordered Marangoni patterns in thin liquid films.

(Invited) Resistive Switching in Mott Insulators: From Fundamentals to Mott Memories

The application of short electrical pulses on narrow gap Mott insulators gives rise to a new phenomenon of resistive switching. This transition is volatile above threshold electric fields of a few kV/cm and stabilizes into a non-volatile RS for higher electric fields. Our works have shown that this phenomenon is driven by the electric field, which triggers an electronic avalanche [1]. This avalanche provokes the collapse of the Mott insulating state at the nanoscale [2] and generates the formation of granular conductive filaments. The resulting non-volatile transition is reversible and these materials have the ability to switch back and forth between two resistance states with possible intermediate levels. This phenomenology was first evidenced on the family of chalcogenide compounds AM4Q8 (A=Ga,Ge; M=V,Nb,Ta,Mo; Q=S,Se), either on single crystals or on thin films [3]. We have recently demonstrated that these properties are actually universal to all canonical Mott insulators such as (V1-xCrx)2O3 or NiS2-xSex [4]. In the V2O3:Cr system, these new results indicate that, beyond temperature for V2O3 and pressure for (V1-xCrx)2O3, a third tuning parameter, electric field E, is prone to induce an reversible Insulator to Metal transition. This is particularly interesting since these E-induced transitions can occur at room temperature and are hence suitable for applications. Our last results demonstrate that (V1-xCrx)2O3 thin films can be deposited by reactive magnetron co-sputtering [5]. We show that this deposition technique allows controlling the Cr content, oxidation degree and crystallinity after ex-situ annealing. Our last results demonstrate that (V1-xCrx)2O3 thin films can be deposited by reactive magnetron co-sputtering [5]. We show that this deposition technique allows controlling the Cr content, oxidation degree and crystallinity after ex-situ annealing. Our first results on metal-insulator-metal (MIM) devices show that we retrieve the electric-field-induced resistive switching on these TiN/(V1-xCrx)2O3/TiN symmetric ReRAM cells. The characterization of these Mott memory single cells demonstrate very competitive performances which place narrow gap Mott insulators as promising candidates for ReRAM and memristor applications [6]. [1] V. Guiot et al., Nat. Commun. 2013, 4, 1722 [2] V. Dubost et al., Nano Lett. 2013,13, 3648 [3] V. Ta Phuoc et al., Phys. Rev. Lett. 2013, 110, 037401 ; A. Camjayi et al., Phys. Rev. Lett. 2014, 113, 086404 ; E. Souchier et al., Phys. Stat. solidi-RRL 2011, 5, 53 ; J. Tranchant et al., Thin Solid Films 2013, 533, 61 [4] P. Stoliar et al., Adv. Mater. 2013, 25, 3222 ; E. Janod et al., Adv. Funct. Mater. 2015, 25(40), 6287 [5] M. Querré et al., Thin Solid Films 2015, doi: 10.1016/j.tsf.2015.12.043[6] L. Cario et al. – Patent PCT/EP2008/052968 ; M.P. Besland et al. – Patent PCT/EP2010/053442; L. Cario et al. – Patent PCT/EP2013/057500.

An investigation of the possibility of detecting gamma‐ray flashes originating from the atmosphere of Venus

AbstractThe Runaway Electrons Avalanche Model Monte Carlo simulation is used to study the propagation of runaway electrons and gamma‐ray flashes originating from the atmosphere of Venus, and the possibility of detecting these high‐energy gamma rays at low‐Venus orbit is also investigated. Relativistic Runaway Electron Avalanche (RREA) lengths and energy spectra at the Venus middle cloud levels have similar values to those of Earth at sea level, with a similar RREA threshold electric field (~286 kV/m). If electrified clouds in Venus make similar numbers of gamma rays as are made by thunderstorms on Earth during Terrestrial Gamma‐ray Flashes (TGFs), then the calculated gamma‐ray fluences at low‐Venus orbit (~550 km) have an approximate range of 10−3 photons/cm2 to 4 photons/cm2 for the source altitude between 58 km and 70 km. These gamma‐ray fluences are similar to those measured by spacecraft in low‐Earth orbit from TGFs. Therefore, if TGF‐like events initiate in the middle and upper clouds of Venus, they would be detectable by spacecrafts at low‐Venus orbit.

The influence of Ag nanoparticles on random laser from dye-doped nematic liquid crystals

The threshold energy and electric field response characteristic of random laser have been investigated in dye-doped nematic liquid crystal (DDNLC) with the addition of different concentrations of Ag nanoparticles (NPs). Due to the localized surface plasmon resonance (LSPR) induced by Ag NPs, random laser from DDNLC with Ag NP doping had a lower threshold energy. From another point of view, nematic liquid crystals (LCs) in a DDNLC cell with the addition of Ag NPs could be more easily influenced by the electric field, which allowed the random laser to be controlled at a lower applied voltage. The turn-off time and turn-on time of random laser also decreased in the DDNLC cells with increasing the concentration of Ag NPs. This is due to the enhancement of the electro-optical characteristic of LC and the restoring force imparted by the locally ordered LCs induced by the Ag NPs, respectively.

Field emission properties and strong localization effect in conduction mechanism of nanostructured perovskite LaNiO3

We report the potential field emission of highly conducting metallic perovskite lanthanum nickelate (LaNiO3) from the nanostructured pyramidal and whisker shaped tips as electron emitters. Nano particles of lanthanum nickelate (LNO) were prepared by sol-gel route. Structural and morphological studies have been carried out. Field emission of LNO exhibited high emission current density, J = 3.37 mA/cm2 at a low threshold electric field, Eth = 16.91 V/μm, obeying Fowler–Nordheim tunneling. The DC electrical resistivity exhibited upturn at 11.6 K indicating localization of electron at low temperature. Magnetoresistance measurement at different temperatures confirmed strong localization in nanostructured LNO obeying Anderson localization effect at low temperature.

Encaged molecules in external electric fields: A molecular "tug-of-war".

Response of polar molecules CH3OH and H2O2 and a non-polar molecule, CO2, as "guests" encapsulated in the dodecahedral water cage (H2O)20 "host," to an external, perturbative electric field is investigated theoretically. We employ the hybrid density-functionals M06-2X and ωB97X-D incorporating the effects of damped dispersion, in conjunction with the maug-cc-pVTZ basis set, amenable for a hydrogen bonding description. While the host cluster (cage) tends to confine the embedded guest molecule through cooperative hydrogen bonding, the applied electric field tends to rupture the cluster-composite by stretching it; these two competitive effects leading to a molecular "tug-of-war." The composite remains stable up to a maximal sustainable threshold electric field, beyond which, concomitant with the vanishing of the HOMO-LUMO gap, the field wins over and the cluster breaks down. The electric-field effects are gauged in terms of the changes in the molecular geometry of the confined species, interaction energy, molecular electrostatic potential surfaces, and frequency shifts of characteristic normal vibrations in the IR regime. Interestingly, beyond the characteristic threshold electric field, the labile, distorted host cluster fragmentizes, and the guest molecule still tethered to a remnant fragment, an effect attributed to the underlying hydrogen-bonded networks.

Physical implication of transition voltage in organic nano-floating-gate nonvolatile memories

High-performance pentacene-based organic field-effect transistor nonvolatile memories, using polystyrene as a tunneling dielectric and Au nanoparticles as a nano-floating-gate, show parallelogram-like transfer characteristics with a featured transition point. The transition voltage at the transition point corresponds to a threshold electric field in the tunneling dielectric, over which stored electrons in the nano-floating-gate will start to leak out. The transition voltage can be modulated depending on the bias configuration and device structure. For p-type active layers, optimized transition voltage should be on the negative side of but close to the reading voltage, which can simultaneously achieve a high ON/OFF ratio and good memory retention.

Direct observation of λ-DNA molecule reversal movement within microfluidic channels under electric field with single molecule imaging technique**Project supported by the National Natural Science Foundation of China (Grant No. 61378083), the International Cooperation Foundation of the National Science and Technology Major Project of the Ministry of Science and Technology of China (Grant No. 2011DFA12220), the Major Research Plan of National

The electrodynamic characteristics of single DNA molecules moving within micro-/nano-fluidic channels are important in the design of biomedical chips and bimolecular sensors. In this study, the dynamic properties of λ-DNA molecules transferring along the microchannels driven by the external electrickinetic force were systemically investigated with the single molecule fluorescence imaging technique. The experimental results indicated that the velocity of DNA molecules was strictly dependent on the value of the applied electric field and the diameter of the channel. The larger the external electric field, the larger the velocity, and the more significant deformation of DNA molecules. More meaningfully, it was found that the moving directions of DNA molecules had two completely different directions: (i) along the direction of the external electric field, when the electric field intensity was smaller than a certain threshold value; (ii) opposite to the direction of the external electric field, when the electric field intensity was greater than the threshold electric field intensity. The reversal movement of DNA molecules was mainly determined by the competition between the electrophoresis force and the influence of electro-osmosis flow. These new findings will theoretically guide the practical application of fluidic channel sensors and lab-on-chips for precisely manipulating single DNA molecules.

Dependence of Electroporation Detection Threshold on Cell Radius: An Explanation to Observations Non Compatible with Schwan's Equation Model.

It is widely accepted that electroporation occurs when the cell transmembrane voltage induced by an external applied electric field reaches a threshold. Under this assumption, in order to trigger electroporation in a spherical cell, Schwan's equation leads to an inversely proportional relationship between the cell radius and the minimum magnitude of the applied electric field. And, indeed, several publications report experimental evidences of an inverse relationship between the cell size and the field required to achieve electroporation. However, this dependence is not always observed or is not as steep as predicted by Schwan's equation. The present numerical study attempts to explain these observations that do not fit Schwan's equation on the basis of the interplay between cell membrane conductivity, permeability, and transmembrane voltage. For that, a single cell in suspension was modeled and the electric field necessary to achieve electroporation with a single pulse was determined according to two effectiveness criteria: a specific permeabilization level, understood as the relative area occupied by the pores during the pulse, and a final intracellular concentration of a molecule due to uptake by diffusion after the pulse, during membrane resealing. The results indicate that plausible model parameters can lead to divergent dependencies of the electric field threshold on the cell radius. These divergent dependencies were obtained through both criteria and using two different permeabilization models. This suggests that the interplay between cell membrane conductivity, permeability, and transmembrane voltage might be the cause of results which are noncompatible with the Schwan's equation model.

Modeling of Nanotips Fabricated by Local Electron Bombardment

Nanotips have attracted increasing interest in several aspects of nanotechnology, particularly in nanotip-based microscopy and nano-characterization. Therefore, fabricating nanotips with well-defined shapes and in a highly controlled process is vital for these applications. Here, we present some characterization analysis of nanotips fabricated by the recently developed local electron bombardment method. We highlight the importance of using spherical crystal models to reproduce the nanotip atomic structure as a way to estimate the nanotip size, rather than using the conventional ring counting method. The nanotip shape is modeled by building the crystal structure of the nanotip apex to estimate its size. Then, the overall nanotip shape is estimated by sequentially destructing the entire nanotip and utilizing finite element simulation tools to build the nanotip model. The simulation model is made in a way to generate the same threshold electric field, in the field ion microscope, before and after the nanotip destruction.

Study on statistical breakdown delay time in argon gas using a W-band millimeter-wave gyrotron

In this study, we investigated plasma initiation delay times for argon volume breakdown at the W-band frequency regime. The threshold electric field is defined as the minimum electric field amplitude needed for plasma breakdown at various pressures. The measured statistical delay time showed an excellent agreement with the theoretical Gaussian distribution and the theoretically estimated formative delay time. Also, we demonstrated that the normalized effective electric field as a function of the product of pressure and formative time shows an outstanding agreement to that of 1D particle-in-cell simulation coupled with a Monte Carlo collision model [H. C. Kim and J. P. Verboncoeur, Phys. Plasmas 13, 123506 (2006)].