Subsequent Pulses Research Articles

Surface plasma wave excited by laser pulse obliquely incident on a double-layer plasma target and ts application

Surface plasma wave (SPW) will significantly affect the subsequent mutual coupling between laser and plasma, so there are many important applications such as particle acceleration driven by laser pulses and transmission enhancement. In this work, the properties of the SPW produced by an ultra-short and ultra-intensity laser pulse incident on a double-layer plasma target are studied by using the all-electromagnetic large-scale two-dimensional particle in cell (PIC) simulations. It is shown that the high-intensity laser incident with a large angle, <i>θ</i> =75°, can drive the electrons of the low-density layer to form a transportable periodic structure with the propagation speed close to light speed, and excite electrostatic wave whose wavelength is similar to that of the incident laser and is numerically close to the theoretical result according to previous theory. In order to excite the SPW, the laser intensity needs to reach a certain threshold. Besides, the ratio of the surface wave intensity to the incident laser intensity in the double-layer target case obviously deviates from the theoretical result of the single-layer target case, showing a nonlinear relationship. In the second part of the simulation, it is found that the SPW can significantly enhance the transmission of subsequent laser pulse, allowing the subsequent laser to break through the "black barrier" due to the dense plasma. A pre-laser irradiates the double-layer plasma target at <i>θ</i> = 75°, and then the subsequent laser is normally incident after a delay of Δ<i>t</i> = 23<i>T</i>. As a result, an obvious electromagnetic wave with the same direction as the sub-laser can be observed behind the target, which indicates that the sub-laser absolutely transmits the dense plasma. In comparison, when a single laser is normally incident on the target without pre-laser while other conditions keep unchanged, no obvious wave can be distinguished behind the target, that is, the field is nearly zero. Another simulation where a single-layer target is injected by pre-laser and sub-laser in order but the wave behind the target is also unobservable, proves that it is SPW that plays the main role in transmission enhancement instead of accelerated hot electrons on the target which can also transport the laser energy.

Reducing laser beam fluence and intensity fluctuations in symmetric and asymmetric compressors

Abstract All space–time coupling effects arising in an asymmetric optical compressor consisting of two non-identical pairs of diffraction gratings are described analytically. In each pair, the gratings are identical and parallel to each other, whereas the distance between the gratings, the groove density and the angle of incidence are different in different pairs. It is shown that the compressor asymmetry does not affect the far-field fluence and on-axis focal intensity. The main distinctive feature of the asymmetric compressor is spatial noise lagging behind or overtaking the main pulse in proportion to the transverse wave vector. This results in a degraded contrast but reduces beam fluence fluctuations at the compressor output. Exact expressions are obtained for the spectrum of fluence fluctuations and fluence root mean square that depends only on one parameter characterizing compressor asymmetry. The efficiency of small-scale self-focusing suppression at subsequent pulse post-compression is estimated.

Effective combined surface hardening processes of structural steels using ultrasound

The effectiveness of hardening of the surface layer of machine parts is evaluated by the operational properties of the surface layer and depends on many conditions that characterize the specific features of the technological process in which this method of hardening is carried out. The surface plastic deformation of structural steels with the use of ultrasound is studied. Four variants of hardening are considered: ultrasonic treatment with continuous supply of ultrasonic energy, pulse ultrasonic treatment, combination of ultrasonic treatment with subsequent pulse treatment, ultrasonic treatment after hardening with induction heating. It is shown that ultrasonic treatment increases microhardness of surface layer of structural steels by 1.5 times, HF hardening by more than 2 times, HF hardening + UZO combination by 3 times and HF hardening + IUZO combination by 3.2 times. Ultrasonic treatment increases compression stresses occurring in steel surface hardened by HFI hardening. The compressive stresses increase especially strongly after pulse ultrasonic treatment with five passes and reach the value of 1200 Pa.

Bound-state formation in time-dependent potentials

We study the temporal formation of quantum-mechanical bound states within a one-dimensional attractive square-well potential by first solving the time-independent Schr\"odinger equation and then studying a time-dependent system with an external time-dependent potential. For this we introduce Gaussian potentials with different spatial and temporal extensions and generalize this description also for subsequent pulses and for random noisy potentials. Our main goal is to study the timescales in which the bound state is populated and depopulated. Particularly, we clarify a likely connection between the uncertainty relation for energy and time and the transition time between different energy eigenstates. We demonstrate that the formation of states is not delayed due to the uncertainty relation but follows the pulse shape of the perturbation. In addition we investigate the (non-)applicability of first-order perturbation theory on the considered quantum system.

Pulse Burst Generation and Diffraction with Spatial Light Modulators for Dynamic Ultrafast Laser Materials Processing.

A pulse burst optical system has been developed, able to alter an energetic, ultrafast 10 ps, 5 kHz output pulse train to 323 MHz intra-burst frequency at the fundamental 5 kHz repetition rate. An optical delay line consisting of a beam-splitting polariser cube, mirrors, and waveplates transforms a high-energy pulse into a pulse burst, circulating around the delay line. Interestingly, the reflected first pulse and subsequent pulses from the delay line have orthogonal linear polarisations. This fact allows independent modulation of these pulses using two-phase-only Spatial Light Modulators (SLM) when their directors are also aligned orthogonally. With hybrid Computer Generated Holograms (CGH) addressed to the SLMs, we demonstrate simultaneous multi-spot periodic surface micro-structuring on stainless steel with orthogonal linear polarisations and cylindrical vector (CV) beams with Radial and Azimuthal polarisations. Burst processing produces a major change in resulting surface texture due to plasma absorption on the nanosecond time scale; hence the ablation rates on stainless steel with pulse bursts are always lower than 5 kHz processing. By synchronising the scan motion and CGH application, we show simultaneous independent multi-beam real-time processing with pulse bursts having orthogonal linear polarisations. This novel technique extends the flexibility of parallel beam surface micro-structuring with adaptive optics.

Plasmon guided assembly of nanoparticles in solids

Light manipulation of metallic nanoparticles (NPs) with outstanding plasmonic properties attracts broad interest in multiple areas owing to the significant field enhancement and localization effect mediated by plasmons. So far, optical migration of NPs has only been achieved on platforms such as gases, solutions, and mesoporous thin films (TiO2), while not been realized for NPs inside large macroscopic transparent materials due to the high density and viscosity of a host matrix. The high localization of light intensity by plasmons allows the laser pulses to deposit energy via near-field at the nanoscale at reduced thermal modification and ablation over extended regions inside a host material. This makes it possible to achieve directed and guided migration of NPs within large macroscopic transparent materials. Here, we propose a plasmon-enhanced method using ultrafast laser direct writing to manipulate metal NPs inside a glass. The optical potential between closely spaced NPs increases significantly under laser irradiation, leading to guided energy deposition by ionization, and light interference which leads to the self-assembly of NPs into nanostructures under irradiation of subsequent pulses. In this work, ordered subwavelength NP gratings are fabricated, which exhibit polarization dependence and show promise for applications in information encoding and optical storage. This study provides a new physical case for ultrafast laser-driven guided self-assembly of NPs, where the dynamic evolution via their fragmentation and migration is observed, contributing to the understanding of the origin of self-assembled gratings and opening up new research directions for light manipulation of NPs.

Electric charge build-up and dissipation at pulsed streamer corona by EFISH and probe measurements

This work examines the dynamics of volumetric electric charge deposited by a single pin electrode streamer corona in atmospheric air at ambient conditions. Recent studies show that, at pulse-periodic operation, electric charge remains in surrounding air after the first discharge. This residual charge significantly affects the electric field distribution and morphology of discharges at subsequent pulses. In this study, the residual electrical potential/field was measured during and after dissipation of a pulsed 80 kV streamer corona of alternating polarity. This was accomplished using electrostatic probes and the electric field induced second harmonic method (EFISH generation). The residual volumetric charge of a positive pulse polarity streamer corona occupies a zone of up to 80 mm from the electrode. The subsequent application of a negative polarity pulse leads to partial neutralization of the previous charge and the generation of a region with a high-amplitude electric field. The propagation of following positive polarity pulses is limited by the residual positive volumetric charge. The EFISH method reveals the magnitude of the electric field at discharge propagation and electrostatic probes inform the polarity. Intensified imaging acquisition was used to evaluate the spatial distribution and dynamics of corona discharge during the alternating polarity waveform.

Increase in end-tidal carbon dioxide after defibrillation predicts sustained return of spontaneous circulation during out-of-hospital cardiac arrest

IntroductionGuidelines recommend monitoring end-tidal carbon dioxide (ETCO2) during out-of-hospital cardiac arrest (OHCA), though its prognostic value is poorly understood. This study investigated the relationship between ETCO2 and return of spontaneous circulation (ROSC) after defibrillation in intubated non-traumatic OHCA patients. MethodsThis retrospective, observational cohort analysis included adult OHCA patients who received a defibrillation shock during treatment by an urban EMS agency from 2015 to 2021. Peak ETCO2 values were determined for the 90-second periods before and after the first defibrillation in an intubated patient (shock of interest [SOI]). Values were analyzed for association between the change in ETCO2 from pre- to post-shock and the presence of ROSC on the subsequent pulse check. ResultsOf 518 eligible patients, mean age was 61, 72% were male, 50% had a bystander-witnessed arrest, and 62% had at least one episode of ROSC. The most common arrest etiology was medical (92%). Among all patients, peak ETCO2 during resuscitation prior to SOI was 36.8 mmHg (18.6). ETCO2 increased in patients who achieved ROSC immediately after SOI (from 38.3 to 47.6 mmHg; +9.3 CI: 6.5, 12.1); patients with sustained ROSC experienced the greatest increase in ETCO2 after SOI (from 37.8 to 48.2 mmHg; +10.4 CI: 7.2, 13.6), while ETCO2 in patients who did not achieve ROSC after SOI rose (from 36.4 to 37.8 mmHg; +1.4 CI: −0.1, 2.8). ConclusionsETCO2 rises after defibrillation in most patients during cardiac arrest. Patients with sustained ROSC experience larger rises, though the majority experience rises of less than 10 mmHg.

Rate-dependent ferroelectric switching in barium titanate ceramics from modified PUND experiments

Predicting and controlling the rate-dependent electro-mechanical switching in ferroelectric ceramics is challenging due to our current lack of understanding the underlying domain switching mechanisms at short time scales or high rates. Therefore, we propose an experimental protocol, which is a modification of the so-called Positive Up Negative Down (or PUND) experiment, to probe the rate-dependent competition between domain nucleation, domain growth, and variant selection in barium titanate ceramics as a representative material. Our experiments use a pump electric field pulse to switch the sample from a poled state at electric field rates spanning five orders of magnitude (10−2−102 MV/m⋅s). The remanent microstructures at the end of different pump pulses are probed using a subsequent probe electric field pulse, which is applied at a constant quasistatic rate. Results reveal reduced polarizability at higher electric field rates, indicating reduced domain switching. In addition, this pump-probe experiment shows an increase in domain wall nucleation vs. growth at higher rates. Simultaneous mechanical strain measurements using stereographic digital image correlation indicate a difference in nucleated domain wall variants while switching anti-parallel vs. parallel to the pre-poled direction. The data shows that ferroelastic 90° domain nucleation is preferred in the former case, while ferroelectric 180° nucleation is preferred in the latter. Our study highlights the importance of quantifying microscopic kinetics of domain nucleation, domain wall growth, and the effect of mobile defects in modeling the short-time electro-mechanical response of ferroelectric ceramics.

Effects of bubble behaviors in femtosecond laser machining of silicon wafer in liquids

In this article, the effects and mechanism of how bubble behaviors would affect liquid-assisted femtosecond laser cutting of silicon wafer are investigated. There are two kinds of bubbles generated during laser ablation in liquids, including the cavitation bubbles and the persistent bubbles. First, evolutions of the laser-induced cavitation bubbles are recorded by time-resolved shadowgraph imaging. The maximum height of the cavitation bubbles is shown to be 42 μm at the pulse energy of 18.15 μJ. The cavitation bubbles are shown to cause the defocusing effect on subsequent pulses, resulting in non-uniform ablated microgrooves. To improve the microgrooves morphology, the time interval between adjacent pulses is adjusted on basis of lifetime of the cavitation bubbles. The defocusing effect becomes alleviative when the time interval exceeds 100 μs. Next, the persistent bubbles are induced after the collapse of the cavitation bubbles and whose behaviors are studied. The results show that drastic explosions occur once the laser interacts with the persistent bubbles covered on the microgroove, and cause detrimental effects on surface morphology. The ethanol solution is chosen to improve surface wettability on basis of the dwell property of the persistent bubbles. Finally, the shielding effect of the persistent bubbles for incoming laser pulses is studied, which shows a decrease in the microgroove depth by 53 % in the 2 wt% ethanol solution. This work illustrates how the bubbles affect the cutting of silicon wafer under liquid, and how uniform microgrooves with fine surface morphology are achieved by utilizing the bubble behaviors.

Possible origin of the spatiotemporal evolution of the 2008 earthquake swarm in Northwest-Bohemia, Czech Republic

The phenomenon ‘earthquake swarm’ is well known from numerous locations on Earth but its mechanism and trigger process are still an enigma. The influence of fluids on fluid-driven seismicity is generally well accepted but the temporal behaviour and the migration of activated phases is still an open question. We attempt to answer these open questions by combining the results of research on induced-seismicity with new reliable analyses of full moment tensors (FMTs) of the swarm earthquakes of 2008 to 2018 in Northwest-Bohemia, Czech Republic by Vavryčuk et al. (2017, 2021). The FMTs reveal evidence of compressive fracturing as the prevailing focal mechanism during the swarms. Our proposed hypotheses considered these earthquakes as the origin of subsequent pore pressure pulses in the respective active swarm phase. The diffusion of these pore pressure pulses, which could trigger the nearby earthquakes as well as the successive swarm phase in the vicinity after a respective diffusion process in space and time, are the target of this studies. Missing information regarding the real diffusion distances are compiled by a strict statistical approach of a one-to-one analysis of the swarm earthquakes. The analyses suggest that parts of the swarm earthquakes could be triggered by pore pressure diffusion with an estimated diffusivity range of approximately D = 0.01 to 3.0 m2/s. In exceptional cases, which make about 5% of all cases, we have to consider also diffusivities up to 15 m2/s. Examples of hydraulic diffusivities observed in our region of interest confirm this range. Such a process can also be assumed during further swarms in the years 2011 to 2018 because of the continuous and predominant occurrence of compressive fracturing as a focal mechanism beside pure shear and tensile fracturing. Our results could explain for the first time the missing link regarding the temporal and spatial migration of the subsequent swarm phases in our studied region at Nový Kostel (Northwest-Bohemia, Czech Republic).

Effects of phase accumulation in frequency-comb-based multidimensional coherent spectroscopy

In recent years, frequency-comb-based multidimensional coherent spectroscopy has emerged as a very powerful optical method for studying samples with long dephasing times. It enables the measurement of comb resolution multidimensional coherent spectra in seconds as opposed to hours or even days required by traditional mechanical stage-based spectrometers. However, for some samples (e.g., cold atoms and molecules) the dephasing times could be longer than the repetition periods of the excitation lasers which means that the generated signal will not fully decay between the pulses. Depending on the relative phase or time between the pulses, the signals generated by the subsequent laser pulses can constructively or destructively interfere with each other. In this paper we study this behavior by solving the optical Bloch equations and provide a theoretical description of frequency-comb-based multidimensional coherent spectroscopy.

Trapped Fields >1 T in a Bulk Superconducting Ring by Pulsed Field Magnetization

One potential application of magnetized RE-Ba-Cu-O (where RE = rare earth or Y) bulk superconductors is as a high-field alternative to conventional permanent magnets in desktop NMR and MRI systems. Pulsed field magnetization (PFM) is one of the most promising practical methods of magnetizing such bulks. However, the trapped fields obtained by PFM are much lower than those obtained using quasi-static methods like field-cooling magnetization (FCM) due to heating during PFM. Furthermore, bulk superconducting rings have proved more difficult to magnetize via PFM than discs. The reported trapped fields in single bulk superconducting rings magnetized by PFM are less than 0.35 T at the centre of the bore due to thermomagnetic instabilities. In this work, systematic PFM measurements on a bulk Gd-Ba-Cu-O ring were carried out and a trapped field of 1.3 T at 55 K was achieved using a multi-pulse, stepwise cooling (MPSC) method. In the MPSC method, a sequence of pulsed fields is used to magnetize the ring bulk. The pulsed field is increased in small increments and the sample temperature is decreased sequentially. Consequently, as some field is already trapped after the first pulse, the motion of the flux for subsequent pulses will be reduced, leading to less heat generated in the bulk sample. This greatly improves the thermomagnetic stability of the PFM process, enabling larger trapped fields.

Silicon surface patterning by regular stripes of laser-induced periodic surface structures

Laser-induced periodic surface structures (LIPSS) formation on the surface of mono-crystalline silicon is reported for a specific fabrication regime of large-area structuring. Using a femtosecond laser at 1030 nm wavelength, a particular range of fluence and beam overlap in two-dimensional scanning scheme has been identified where LIPSS-covered areas organize into stripes perpendicular to the scanning direction. The stripes, where the LIPSS appear, are regularly spaced and located in between the centers of two subsequent Gaussian pulses while the regions receiving the peak pulse fluence are free of LIPSS. The formation of the LIPSS stripes is examined by analyzing local integrated fluence, N-on-1 pulse damage geometry and thresholds of modifications. Processes at play in the generation of such stripes of LIPSS are discussed and an explanation based on interpulse feedback from amorphized areas is proposed.

Thermal unrest of a fumarolic field tracked using VIIRS imaging bands: The case of La fossa crater (Vulcano Island, Italy)

Detecting precursory signals before an eruption is one of the main objectives of applied volcanology. Among these signals, the variation of the emitted heat flux is certainly an important indicator of a state of disequilibrium within the magmatic system. Here we report the results of a detailed analysis of VIIRS (Visible Infrared Imaging Radiometer Suite) imaging bands (at 375 m spatial resolution) focused on measuring the Volcanic Radiative Power (VRP) emitted by the fumarole field of La Fossa crater (Vulcano Island, Italy) over the past decade (2012–2022). The analysis reveals that the long-term, steady-state VRP (baseline ∼0.17 MW) was perturbed in 2020–2021 when a prolonged period of lower than normal (<-2σ) radiant flux preceded the major unrest phase that began in mid-September 2021. By early October the anomalous VRP had peaked at ∼1.2 MW (6–8 times the baseline) then started to gradually decline in the following months. A subsequent thermal pulse was recorded in May–July 2022 and was accompanied by a period of seawater discoloration that affected the Baia di Levante (a shallow sea bay ∼1.4 km north of La Fossa crater). The concomitance of these phenomena suggests the occurrence of a second pressurization phase driven by the arrival of deep magmatic fluids within both the central and distal degassing fumarolic zones. These results provide a complementary, important contribution to the understanding of the unrest of La Fossa crater and highlight the potential of VIIRS in detecting pre-eruptive signals at other poorly-monitored volcanoes characterized by high-temperature fumarolic activity.

Retinal ganglion cell desensitization is mitigated by varying parameter constant excitation pulse trains.

Retinal prostheses partially restore vision in patients blinded by retinitis pigmentosa (RP) and age-related macular degeneration (AMD). One issue that limits the effectiveness of retinal stimulation is the desensitization of the retina response to repeated pulses. Rapid fading of percepts is reported in clinical studies. We studied the retinal output evoked by fixed pulse trains vs. pulse trains that have variable parameters pulse-to-pulse. We used the current clamp to record RGC spiking in the isolated mouse retina. Trains of biphasic current pulses at different frequencies and amplitudes were applied. The main results we report are: (1) RGC desensitization was induced by increasing stimulus frequency, but was unrelated to stimulus amplitude. Desensitization persisted when the 20 Hz stimulation pulses were applied to the retinal ganglion cells at 65 μA, 85 μA, and 105 μA. Subsequent pulses in the train evoked fewer spikes. There was no obvious desensitization when 2 Hz stimulation pulse trains were applied. (2) Blocking inhibitory GABAA receptor increased spontaneous activity but did not reduce desensitization. (3) Pulse trains with constant charge or excitation (based on strength-duration curves) but varying pulse width, amplitude, and shape increased the number of evoked spikes/pulse throughout the pulse train. This suggests that retinal desensitization can be partially overcome by introducing variability into each pulse.

Suppression of fibrillatory dynamics consisting of stable rotors by periodic pacing

Recent experimental studies have shown that a sequence of low-energy electrical far-field pulses is able to terminate fibrillation with substantially lower per-pulse energy than a single high-energy electric shock (see S Luther et al Nature 475 235–39). During this low-energy antifibrillation pacing (LEAP) procedure only tissue near sufficiently large conduction heterogeneities, such as large coronary arteries, is activated. In order to understand the mechanism behind LEAP, we have carried out a statistical study of resetting a medium filled by one or more stable spirals (‘rotors’) in a two-dimensional electrophysiological model of cardiac tissue perforated by blood vessels to the resting state (‘defibrillation’). We found the highest success probabilities for this defibrillation for underdrive pacing with periods 10–20 percent larger than the dominant period of the stable rotors in the unperturbed dynamics. If a sufficiently large number pulses is applied and an optimal pacing period chosen, the energy per pulse required for successful defibrillation is about 75–80 percent lower than the energy needed for single-shock defibrillation. Optimal conditions to control and suppress fibrillation based on stable rotors, hence, are similar to the ones in found for the case of an electrophysiological model displaying spatiotemporal chaos (‘electrical turbulence’) in an earlier study (see P Buran et al 2017 Chaos 27 113110). The optimal pacing period is found to increase with increasing strength of the electrical field strength used in the model. The success probability also increases strongly until the fourth or fifth pulse administered, which is strongly correlated to an observed increase of the fraction of re-excitable tissue with each subsequent pulse. Monitoring the fraction of excitable tissue in the model as key quantity of the excitable medium, moreover, enabled us to successfully predict the optimal pacing period for defibrillation.

Математическое моделирование динамики тепловых ударных волн в нелинейных локально-неравновесных средах

We performed a mathematical simulation of heat transfer in a local non-equilibrium medium whose transfer characteristics are functions of the temperature distribution. A homogeneous polynomial of arbitrary degree represents nonlinearities in thermal conductivity and thermal diffusivity. The mathematical model consists of a hyperbolic nonlinear heat transfer wave equation, initial conditions and nonlinear boundary conditions of the second and first kind. To solve this problem, we used a conservative homogeneous finite-difference scheme along the upper time grid line (implicitly). We then used the tridiagonal matrix algorithm of the second order in the spatial variable and of the first order in time to solve the resulting system of linearised algebraic equations. A periodic series of rectangular temperature or heat flux pulses form the boundary conditions of the first and second kind. Computation results reveal ultimate propagation rates of temperature and heat fronts featuring pronounced first-kind discontinuities with attenuating magnitudes. As the process unfolds, the initial pulses heat the region between the boundary and the heat wave front, while the subsequent pulses traverse this region at a higher velocity due to thermal diffusivity being a function of temperature, their fronts "catching up" with the previous fronts, increasing the discontinuity magnitude at the initial pulse front, that is, forming a thermal shock wave front similar to that of a shock wave in gas dynamics. We obtained such thermal shock waves for boundary conditions of both the first and the second kind. We also analysed kinematic and dynamic characteristics of thermal waves

Sediment deposition characteristics in shallow saturation excess overland flow for urban Stormwater applications

AbstractOver the last several decades, urban stormwater management has grown to include green infrastructure, such as bioswales. However, little is known about the fate of particulate contaminants after depositing in bioswales and similar systems, in part due to limited understanding of sediment transport dynamics in the shallow (water depths comparable to bed roughness height), near‐saturated flow conditions typical of such systems. To better understand the sediment deposition characteristics, a flume study was performed with natural sediment and flow characteristics similar to those encountered in bioswales. A fluorescent, paramagnetic sediment tracer was used to mimic silt sized particles carried by stormwater flows, and a photographic hood was used to image the tracers deposited on the flume surface after subsequent pulses of tracer slurry, where the image intensity was established to be a reliable proxy for surface tracer concentration. These data were analysed to calculate the sediment trapping efficiency, that is, the rate of sediment deposition onto the soil surface per unit time, and samples of the flume effluent were collected to provide an independent mass balance of the deposited tracer. Experimentally determined sediment trapping efficiencies were found to decrease with increasing bed slope angle, which indicates soils at greater bed slopes will be less capable of retaining particulate‐associated contaminants, and were found to decrease over time as the soil surface became saturated with fine particles. These trapping efficiencies were also compared with mathematical models from the literature, augmented with a formula representing the observed surface‐saturation effect. The results of this study can lead to the development of more realistic models for predicting the removal performance of current stormwater remediation designs in regard to fine sediment associated contaminants.

Theoretical analysis on the forced ignition of a quiescent mixture by repetitive heating pulse

Recently, forced ignition by nanosecond-repetitive-pulsed-discharge (NRPD) has received great attention since it can greatly promote ignition. However, there is no theoretical analysis on ignition induced by multiple heating pulses such as NRPD. Therefore, this work attempts to provide a theoretical interpretation on the ignition of a quiescent, flammable mixture by multiple discharges and to assess the effects of repetitive pulse on ignition characteristics. Based on fully transient formulation, analytical expressions describing ignition kernel propagation induced by multiple pulses are derived. The key parameters of multiple pulse heating, such as energy distribution among individual pulse, intermittent duration between neighboring pulse and total pulse numbers are appropriately incorporated, and their effects on ignition characteristics are assessed. It is found that because of memory effect, the flame kernel continues to propagate after switching off the external heating source. Sequentially introducing identical heating pulses at appropriate intermittent duration repetitively exploits the memory effect during ignition kernel development and thus extends propagating distance of the flame front. The repetitive pulse heating can promote ignition capability due to the flame revitalization effect, i.e., ignition reinforcement to the flame front thanks to additional thermal energy supplied by subsequent pulse. This is consistent with the synergistic effect of NRPD observed in previous experimental studies. In particular, as the pulse number increases, the minimum ignition energy decreases and approaches to an asymptotic value. In the limit of large pulse number, it is found that the integration of the implicit expressions describing the ignition kernel evolution does not depend on the pulse number explicitly. This substantiates the invariance of minimum ignition energy with heating pulse number. The present theory explains the effects of multiple discharges on ignition and provides insights on ignition enhancement.