Generation Of Runaway Electrons Research Articles

Runaway dynamics in reactor-scale spherical tokamak disruptions

Understanding generation and mitigation of runaway electrons in disruptions is important for the safe operation of future tokamaks. In this paper we investigate the runaway dynamics in reactor-scale spherical tokamaks, focusing on a compact nominal design with a plasma current of 21 megaamperes (MA), 1.8 T magnetic field on axis and major radius of approximately 3 m. We study both the severity of runaway generation during unmitigated disruptions, and the effect that typical mitigation schemes based on massive material injection have on runaway production. The study is conducted using the numerical framework dream (Disruption Runaway Electron Analysis Model). We find that, in many cases, mitigation strategies are necessary to prevent the runaway current from reaching multi-MA levels. Our results indicate that, with a suitably chosen deuterium–neon mixture for mitigation, it is possible to achieve a tolerable runaway current and ohmic current evolution. However, this does not account for the runaway source due to wall activation, which has been found to severely limit successful mitigation at conventional aspect ratios, but whose definition requires a more complete wall specification. Furthermore, the majority of the thermal energy loss is found to happen through radial transport rather than radiation, which poses a risk of unacceptable localised heat loads.

Confinement of passing and trapped runaway electrons in the simulation of an ITER current quench

Runaway electrons (REs) present a high-priority R&D issue for ITER but little is known about the extent to which RE generation is affected by the stochastic field intrinsic to disrupting plasmas. RE generation can be modelled with reduced kinetic models and there has been recent progress in involving losses due to field stochasticity, either via a loss-time parameter or radial transport coefficients which can be estimated by tracing test electrons in 3D fields. We evaluate these terms in ITER using a recent JOREK 3D MHD simulation of plasma disruption to provide the stochastic magnetic fields where RE markers are traced with the built-in particle tracing module. While the MHD simulation modelled only the current quench phase, the case is MHD unstable and exhibits similar relaxation as would be expected during the thermal quench. Therefore, the RE simulations can be considered beginning right after the thermal quench but before the MHD relaxation is complete. The plasma is found to become fully stochastic for 8 ms and the resulting transport is sufficient to overcome RE avalanche before flux surfaces are reformed. We also study transport mechanisms for trapped REs and find those to be deconfined as well during this phase. While the results presented here are not sufficient to assess the magnitude of the formed RE beam, we show that significant RE losses could be expected to arise due to field stochasticity.

Numerical Study on the Effect of Plasma Density on Runaway Electron Suppression in the ADITYA-U Tokamak

Runaway Electrons (REs) generated during plasma disruptions in fusion grade tokamaks have the potential to severely damage the plasma-facing components. Designing optimal plasma discharge scenarios for RE suppression in future experiments requires interpretative modeling of current experiments. Multiple experiments have been carried out on ADITYA-U tokamak to design optimal plasma discharge scenarios for RE avoidance and suppression. In this article, we have numerically studied two representative pairs of ADITYA-U plasma discharges. In the first pair of discharges, plasma density was increased by gas puffs during the flap-top phase which is shown to suppress RE generation. In the second pair of the representative discharges, the effect of a lower ratio of peak electric field during breakdown to the pre-fill pressure is shown on RE generation. We simulate these plasma discharges using the PREDICT code to study the dynamics of Res. The results are consistent with the experimental Hard X-Ray diagnostic observations for both the pair of representative discharges. Additionally, the lowest RE-current is obtained in the discharges with a low ratio of the peak electric field during breakdown to the pre-fill pressure and high plasma density during the flap-top phase due to gas puffs. The suppression of REs is demonstrated by showing the effect of increasing plasma density on the separatrix in momentum space between thermal electrons and REs.

Runaway electron generation during tokamak start-up

Tokamak start-up is characterized by low electron densities and strong electric fields, in order to quickly raise the plasma current and temperature, allowing the plasma to fully ionize and magnetic flux surfaces to form. Such conditions are ideal for the formation of superthermal electrons, which may reduce the efficiency of ohmic heating and prevent the formation of a healthy thermal fusion plasma. This is of particular concern in ITER where engineering limitations put restrictions on the allowable electric fields and limit the prefill densities during start-up. In this study, we present a new 0D burn-through simulation tool called STREAM (STart-up Runaway Electron Analysis Model), which self-consistently evolves the plasma density, temperature and electric field, while accounting for the generation and loss of relativistic runaway electrons. After verifying the burn-through model, we investigate conditions under which runaway electrons can form during tokamak start-up as well as their effects on the plasma initiation. We find that Dreicer generation plays a crucial role in determining whether a discharge becomes runaway-dominated or not, and that a large number of runaway electrons could limit the ohmic heating of the plasma, thus preventing successful burn-through or further ramp-up of the plasma current. The runaway generation can be suppressed by raising the density via gas fuelling, but only if done sufficiently early. Otherwise a large runaway seed may have already been built up, which can avalanche even at relatively low electric fields and high densities.

Formation and termination of runaway beams during vertical displacement events in tokamak disruptions

A simple 0D model which mimics the plasma surrounded by the conducting structures (Kiramov and Breizman 2017 Phys. Plasmas 24 100702) and including self-consistently the vertical plasma motion and the generation of runaway electrons during the disruption is used for an assessment of the effect of vertical displacement events on the runaway current formation and termination. The total plasma current and runaway current at the time the plasma hits the wall is estimated and the effect of injecting impurities into the plasma is evaluated. In the case of ITER, with a highly conducting wall, although the total plasma current when the plasma touches the wall is the same for any number of injected impurities, however the fraction of the plasma current carried by runaway electrons can significantly decrease for large enough amounts of impurities. The plasma velocity is larger and the time when the plasma hits the wall shorter for lower runaway currents, which are obtained when larger amounts of impurities are injected. When the plasma reaches the wall, the scraping-off of the runaway beam occurs and the current is terminated. During this phase, the plasma vertical displacement velocity and electric field can substantially increase leading to the deposition of a noticeable amount of energy on the runaway electrons (∼hundreds of MJ). It is found that an early second impurity injection reduces somewhat the amount of energy deposited by the runaways. Also larger temperatures of the companion plasma during the scraping-off might be efficient in reducing the power fluxes due to the runaways onto the PFCs. The plasma reaches the q a = 2 limit before the runaway electron current is terminated and by that time the amount of energy deposited on the runaway electrons can be substantially lower than that expected until the beam is fully terminated. Negligible additional conversion of magnetic into runaway kinetic energy is predicted during the runaway deconfinement following the large magnetic fluctuations after q a = 2 is crossed for characteristic deconfinement times lower than 0.1 ms which is a characteristic timescale for ideal MHD instabilities to develop.

Observation of electron runaway in a tip-plane air gap under negative nanosecond pulse voltage by PIC/MCC simulation

The initial stage of the gas breakdown with the generation of runaway electrons was investigated using particle-in-cell/Monte Carlo collision simulations. The parameters of the solved problem are a 1 mm long atmospheric air gap between tip-plane electrodes applied with a nanosecond pulse voltage. The pulse is 5.2 ns in rising time (10%–90%), 10 ns in pulse width (FWHM) and 40 kV in amplitude. The cathode is a cone-shaped electrode, the tip of which is defined by the elliptic equation (the major axis is 4 mm and the minor axis is 1 mm), and the minimum radius of curvature is 0.125 mm. As it is found in the simulation that the development of the discharge channel from the cathode to the anode only takes about tens to hundreds of picoseconds, especially at high overvoltages with runaway electrons, it is assumed that the gap voltage applied in such a short time is nearly constant. Depending on the voltage at the breakdown, different behavior of the energetic electrons is observed. When the voltage is low, about 12 kV, energetic electrons are only produced in the tip cathode layer, where the electric field is the highest; no runaway electrons leading the discharge channel are observed. When the voltage is higher, about 15 kV, the energetic electrons begin to run away at the head of the discharge channel, where the electric field is high enough. When the voltage is even higher, the energetic electrons run away, even at the beginning of the discharge, and from the cathode to the anode. Pre-ionization of the gas ahead of the discharge channel by the runaway electrons is observed, which may play an important role in the fast breakdown of the gas under the nanosecond short pulse.

Advances in physics and applications of 3D magnetic perturbations on the J-TEXT tokamak

In the last two years, three major technical improvements have been made on J-TEXT in supporting of the expanded operation regions and diagnostic capabilities. (1) The successful commission of the 105 GHz/500 kW/1 s electron cyclotron resonance heating (ECRH) system increasing the core electron temperature from 0.9 keV up to around 1.5 keV. (2) The poloidal divertor configuration with an X-point in the high-field side has been achieved. In particular, the 400 kW electron cyclotron wave has also been successfully injected into the diverted plasma. (3) A 256-channel electron cyclotron emission imaging diagnostic system and two sets of four-channel Doppler backscattering diagnostics have been successfully developed on J-TEXT, allowing detailed measurement of the electron temperature and density fluctuations for turbulence and MHD research. The locked mode (LM), especially the 2/1 LM, is one of the biggest threats to the plasma operation. Both the thresholds of 2/1 and 3/1 LM are observed to vary non-monotonically on electron density. The electrode biasing was applied successfully to unlock the LM from either a rotating or static resonant magnetic perturbation (RMP) field. In the presence of 2/1 LM, three kinds of standing wave (SW) structures have been observed to share a similar connection to the island structure, i.e. the nodes of the SWs locate around the O- or X-points of the 2/1 island. The control and mitigation of disruption is essential to the safe operation of ITER, and it has been systematically studied by applying a RMP field, massive gas injection (MGI) and shattered pellet injection on J-TEXT. When the RMP-induced 2/1 LM is larger than a critical width, the MGI shutdown process can be significantly influenced. If the phase difference between the O-point of LM and the MGI valve is +90° (or −90°), the penetration depth and the assimilation of impurities can be enhanced (or suppressed) during the pre-thermal quench (TQ) phase and result in a faster (or slower) TQ. A secondary MGI can also suppress the runaway electron (RE) generation, if the additional high-Z impurity gas arrives at the plasma edge before TQ. When the secondary MGI has been applied after the formation of the RE current plateau, the RE current can be dissipated, and the dissipation rate increases with the injected impurity quantity but saturates with a maximum of 28 MA s−1. The non-local transport is experimentally observed in the ion transport channel. The electron thermal diffusivity significantly increases with the ECRH power. Theoretical work shows that significant intrinsic current can be driven by electromagnetic turbulence, and the robust formation mechanism of the E × B staircase is identified from the Hasegawa–Wakatani system.

On the role of preexisting MHD activity for the plasma response to massive deuterium injection

As part of a reliable disruption mitigation system (SPI) for ITER, pure deuterium shattered pellet injection (SPI) has been proposed as a way of avoiding hot tail runaway electron generation. It offers the possibility of diluting the plasma and, thereby, cooling it down by a large factor without immediately triggering a thermal quench (TQ). However, the reliability of this and similar SPI approaches could be reduced by preexisting MHD modes, which are usually present during the pre-TQ phase, when the disruption mitigation scheme is being triggered. To address this question, this theoretical study investigates massive deuterium injection into an MHD active ASDEX Upgrade plasma using the non-linear MHD code JOREK. Cases with and without preexisting 2/1 islands are studied. Scans are performed in the preexisting island size, the number of atoms injected, and the relative phase of the injection location with respect to the island. Realistic values of resistivity and heat diffusion anisotropy are considered. This provides insights into the physical mechanisms at play and the relevant time scales involved. Results largely indicate that plasma dilution by deuterium also seems to work reliably in the presence of preexisting MHD activity. Nevertheless, when injecting in phase with the X-point of a large preexisting island, the TQ can occur earlier than without. Altogether, simulations increase confidence in the reliability of plasma dilution by deuterium injection and its applicability to ITER.

Influence of Nanoparticles and Metal Vapors on the Color of Laboratory and Atmospheric Discharges.

Currently, electrical discharges occurring at altitudes of tens to hundreds of kilometers from the Earth’s surface attract considerable attention from researchers from all over the world. A significant number of (nano)particles coming from outer space burn up at these altitudes. As a result, vapors of various substances, including metals, are formed at different altitudes. This paper deals with the influence of vapors and particles released from metal electrodes on the color and shape of pulse-periodic discharge in air, nitrogen, argon, and hydrogen. It presents the results of experimental studies. The discharge was implemented under an inhomogeneous electric field and was accompanied by the generation of runaway electrons and the formation of mini-jets. It was established that regardless of the voltage pulse polarity, the electrode material significantly affects the color of spherical- and cylindrical-shaped mini jets formed when bright spots appear on electrodes. Similar jets are observed when the discharge is transformed into a spark. It was shown that the color of the plasma of mini-jets is similar to that of atmospheric discharges (red sprites, blue jets, and ghosts) at altitudes of dozens of kilometers and differs from the color of plasma of pulsed diffuse discharges in air and nitrogen at the same pressure. It was revealed that to observe the red, blue and green mini-jets, it is necessary to use aluminum, iron, and copper electrodes, respectively.

Approximate atomic models for fast computation of the Fokker–Planck equation in fusion plasmas with high-Z impurities and suprathermal electrons

With the choice of tungsten as a material for the ITER plasma facing components, the suprathermal electron interaction with non-fully ionized impurities emerged as an important issue in plasma modeling. Microwave heating and current drive systems, especially lower hybrid current drive, can generate a significant population of suprathermal electrons in the plasma. Also, in the case of the runaway electron generation and mitigation by massive gas injection, the collisions with impurities can have a significant impact on the electron drag force. A correct description of the fast electrons collisions with non-fully ionized impurities requires calculation of the atomic form factor. This can be done with ab initio models that are accurate, though time consuming in practical applications. In this paper, we compare existing approximations of the form factors, based on the Thomas–Fermi or Pratt–Tseng models. Ab initio density functional theory (DFT) calculations are used as a reference method to determine the accuracy of the compared models. Based on this analysis, we propose some modifications of the existing models, tuned with numerical parameter optimization, which provide a higher accuracy while maintaining a short computation time. These modifications include multiple exponents in the Pratt–Tseng model and fitting the parameters of the form factor equation to the DFT-based results. Some applications of the presented models to the calculation of the elastic and inelastic collision frequencies for Fokker–Planck equation are presented, showing a good agreement between the results obtained with the DFT method and the proposed models.

Modeling the complete prevention of disruption-generated runaway electron beam formation with a passive 3D coil in SPARC

The potential formation of multi-mega-ampere beams of relativistic ‘runaway’ electrons (REs) during sudden terminations of tokamak plasmas poses a significant challenge to the tokamak’s development as a fusion energy source. Here, we use state-of-the-art modeling of disruption magnetohydrodynamics coupled with a self-consistent evolution of RE generation and transport to show that a non-axisymmetric in-vessel coil will passively prevent RE beam formation during disruptions in the SPARC tokamak, a compact, high-field, high-current device capable of achieving a fusion gain Q > 2 in deuterium–tritium plasmas.

Numerical investigation of a high-pressure gas medium preionization by runaway electrons

A comparative simulation of the generation and acceleration of runaway electrons in the discharge gap during the initiation of the discharge by nanosecond and subnanosecond pulses is carried out. We used a numerical model based on the PIC-MCC method. Calculations were carried out for N2 6 atm pressure. Numerical simulation of a formation process of the electron avalanche initiated by an electron field-emitted from the top of the cathode microspike was carried out taking into account the motion of each electron in the avalanche. Characteristic runaway electron trajectories, runaway electron energy gained during the motion through the discharge gap, times required for runaway electrons to reach the anode were calculated. We compared our results with calculations using well-known differential equation of electron acceleration using braking force in Bethe approximation. We solved this equation also for braking force based on real (experimental) ionization cross section. The reasons for the discrepancy in the calculation results are discussed.

Development and experimental qualification of novel disruption prevention techniques on DIII-D

Novel disruption prevention solutions spanning a range of control regimes are being developed and tested on DIII-D to enable ITER success. First, a new real-time control algorithm has been developed and tested for regulating nearness to stability limits and maintaining safety-margins. Its first application has been for reliable prevention of vertical displacement events (VDEs) by adjusting plasma elongation (κ) and the inner-gap between the plasma and inner-wall in response to real-time open-loop VDE growth rate (γ) estimators. VDEs were robustly prevented up to average open-loop growth rates of 800 rad s−1 with initial tunings, with only applying shape modification when near safety limits. Second, the disruption risk during fast, emergency shutdown after large tearing and locked modes can be significantly improved by transitioning to a limited topology during shutdown. More than 50% of emergency limited shutdowns after locked modes reach a final normalized current I N < 0.3 before terminating, scaling to the 3 MA ITER requirement. This is in contrast to diverted shutdowns, the majority of which disrupt at I N > 0.8. Despite improvements, these results highlight the critical importance of early prevention. Third, a novel emergency shut down method has been developed which excites instabilities to form a warm, helical core post-thermal quench. The current quench extends to ∼100 ms and avoids VDEs and runaway electron generation. Novel real-time machine learning disruption prediction has been integrated with the DIII-D proximity controller, and a real-time compatible multi-mode MHD spectroscopy technique has been developed. Results presented here were enabled by a focused effort, the disruption free protocol, in DIII-D’s 2019–20 campaign to complement disruption prevention experiments with a large piggy-back program. In addition to testing novel techniques, it is estimated to have helped avoid 32 potential disruptions in piggyback operations with rapid, early shutdowns after large rotating n = 1 or locked modes.

Reflectometry of Picosecond Emission and Discharge Processes in a Gas-Filled High-Voltage Coaxial Line

Emission and discharge processes during the passage of high-voltage subnanosecond pulses with variable amplitude and duration along a gas-filled coaxial transmission line (CTL) are studied. Homogeneous CTL as well as CTL with special disk inserts (electric field enhancers initiating electron emission processes) on its central electrode were used. Data on the propagation and distortion of pulses were obtained and analyzed for different gases (nitrogen, hydrogen, SF6, and air) in a wide range of pressures. The voltage/field ranges and pulse durations are established where the role of runaway electrons (RAEs) appearing near the enhancer is essential in the breakdown development. It is shown that the effect of RAEs can be suppressed by shortening the voltage pulse even for hydrogen, which has a reduced static breakdown field and a high rate of ionization. It is also demonstrated that the RAE generation is abruptly replaced by the explosive electron emission from the enhancer edge with decreasing pressure from atmospheric to technical vacuum.

Pressure Response Optimization of an Eddy Current-Driven Flyer Plate Valve for the ITER Shattered Pellet Injection System

One technique for mitigating disruptions in a tokamak is shattered pellet injection (SPI). SPI is a process in which a large solid pellet consisting of deuterium, neon, or argon is desublimated in a pipe gun barsrel and launched downstream. Pellets are shattered just before entering the plasma by an impact with an angled tube. Injection of these materials into the plasma radiates stored thermal energy, limits current decay rates, suppresses the generation of runaway electrons, and dissipates runaway electrons if necessary. A critical element of the SPI system is a fast-acting valve that releases high-pressure gas to dislodge and accelerate pellets directly, or indirectly via a mechanical punch. A prototype valve sized for the ITER SPI system has been designed and fabricated. A pulsed high-voltage power supply energizes the valve’s internal magnetic coil, which induces eddy currents in the adjacent flyer plate resulting in a repulsive force between the flyer plate and the coil. The flyer plate action lifts a valve seat, allowing high-pressure gas to flow from the valve plenum to the downstream (breech) location of the pellet or mechanical punch. All of the valve’s internal components are designed to operate in ITER-level static background magnetic fields. A study was conducted to optimize the downstream pressure response for a range of valve sizes and operating pressures. In particular, the study analyzes the breech pressure response associated with varying plenum pressures as well as varying breech volumes. A computational fluid dynamics simulation was built in STAR-CCM+ and validated against data from laboratory experiments. The resulting simulation outputs, in the form of downstream responses for a variety of initial plenum pressures and breech volumes, will be used as a complement to experimental data to ensure the pressure pulse is suitable for pellet survivability. These data, combined with studies on pellet shear strength and shock response, will be applied to optimization of overall operating parameters of the ITER SPI system.

Modes of runaway electron beams during formation of diffuse discharges in air and nitrogen

Investigations of the generation of runaway electron beams (REs) and the for-mation of diffuse discharges during breakdown of gaps with a cathode, which has a small radius of curvature, have been carried out. In air and nitrogen at elevated pressure, based on the registration and analysis of the characteristics of radiation from discharge, as well as parameters of the RE beam current and dynamic dis-placement current, it is shown that, depending on the conditions (E/N, gas type and its pressure, design and material of the cathode, amplitude and front of the voltage pulse), diffe-&#x0D; rent modes of generation of runaway electron beams are realized. It was found that the ratio of the velocity of the front of the ionization wave (streamer) and the runaway electrons, as well as the design of the cathode and the delay time before the explosion of cathode microinhomogeneities, significantly affect the generation of runaway electrons. The conditions for the realization of various modes are de-termined; oscillograms of the beam current pulses and photographs of the glow of the gap are presented.

Modelling of runaway electron dynamics during argon-induced disruptions in ASDEX Upgrade and JET

Disruptions in tokamak plasmas may lead to the generation of runaway electrons that have the potential to damage plasma-facing components. Improved understanding of the runaway generation process requires interpretative modelling of experiments. In this work we simulate eight discharges in the ASDEX Upgrade and JET tokamaks, where argon gas was injected to trigger the disruption. We use a fluid modelling framework with the capability to model the generation of runaway electrons through the hot-tail, Dreicer and avalanche mechanisms, as well as runaway electron losses. Using experimentally based initial values of plasma current and electron temperature and density, we can reproduce the plasma current evolution using realistic assumptions about temperature evolution and assimilation of the injected argon in the plasma. The assumptions and results are similar for the modelled discharges in ASDEX Upgrade and JET. For the modelled discharges in ASDEX Upgrade, where the initial temperature was comparatively high, we had to assume that a large fraction of the hot-tail runaway electrons were lost in order to reproduce the measured current evolution.

Streak investigations of the dynamics of subnanosecond discharge developing in nitrogen at a pressure of 6 atm with the participation of runaway electrons

The results of an investigation of a self-sustained subnanosecond discharge in nitrogen at a pressure of 6 atm are presented. A high voltage pulse with a front of approximately 770 ps at the level of 0.1–0.9 in amplitude was applied to the studied gas gap. In this case, the voltage rise rate in the discharge gap at the prebreakdown stage was 1.45 × 1014 V s−1. A breakdown occurs at the end of the front of the voltage pulse. The cathode geometry used provided a 3.3-fold enhancement of an electric field in the near-cathode spatial domain. It is shown that at the initial stage the discharge is of a volumetric form which turns into a spark form further. The discharge contraction starts from a cathode and an anode almost simultaneously. The propagation rate of ionization waves accompanying the spark channel development is 4.2 × 108 cm s−1. The initial volumetric form of the discharge is provided by preliminary ionization of a gas medium by runaway electrons. The generation of runaway electrons takes place in the enhanced electric field area formed near a microprotrusion on the cathode surface, while the macro-geometry of the discharge gap does not ensure enhancing of the electric field up to the value which is sufficient to the implementation of the runaway electron generation criterion. Numerical simulation of a formation process of the electron avalanche initiated by an electron field-emitted from the top of the cathode microprotrusion was carried out taking into account the motion of each electron in the avalanche. To simulate electron motion through the discharge gap, the 3D Monte-Carlo technique was employed. The following runaway electron parameters were calculated: characteristic runaway electron trajectories; runaway electron energy gained during the motion through the discharge gap; and times required for runaway electrons to reach the anode.

Main modes of runaway electron generation during a breakdown of high-pressure gases in an inhomogeneous electric field

Using our recently proposed method, we have identified three modes of runaway electron generation. This method is based on the recording of a dynamic displacement current using a current collector. It makes it possible to unambiguously interpret the dynamics of ionization processes occurring at the stage of formation of a high-voltage nanosecond discharge in a strongly inhomogeneous electric field and dense gaseous media. Simultaneous and separate recording by the current collector of a runaway electron beam current and the dynamic displacement current as well as the recording of discharge characteristics and high-speed framing of plasma glow at the breakdown stage made it possible to interpret the runaway electron generation modes in terms of the rate of ionization processes. It has been shown how the reduced electric field strength, the gas kind, the design and material of a high-voltage cathode with a small radius of curvature, the amplitude and rise time of a voltage pulse as well as the delay in the onset of the explosive emission process at the cathode affect the implementation of one or another generation mode.

Generation of runaway electrons in plasma after a breakdown of a gap with a sharply non-uniform electric field strength distribution

The paper is devoted to the study of the initiation and formation of a negative streamer in a sharply inhomogeneous electric field and the generation of runaway electrons (REs) in air and helium at atmospheric pressure and below, as well as in sulfur hexafluoride at low pressure. Nanosecond voltage pulses of negative polarity with an amplitude of 18 kV were applied across a point-to-plane gap 8.5 mm long. The studies were carried out using broadband measuring sensors and equipment with picosecond time resolution, as well as using a four-channel ICCD camera. Using a special method for measuring the dynamic displacement current caused by the redistribution of the electric field during streamer formation, the waveforms of voltage, discharge current, RE current, and dynamic displacement current were synchronized to each other, as well as to ICCD images. Data on the generation of REs with respect to the dynamics of streamer formation were obtained. It was found that REs are generated not only during the breakdown of the gap, but also after that. It has been found that the formation time of explosive emission centers affects the generation of REs after breakdown. Based on the measurement data of the voltage, discharge current, and dynamic displacement current, the electron concentration in the plasma channel after breakdown and the electric field strength near the surface of the grounded electrode were calculated.