Triggered Spark Research Articles

Gas mixture conditions conducive to backdraft phenomenon

This work examines the influence of gas mixture compositions on backdraft phenomenon. A series of experiments were conducted in a reduced-scale enclosure subjected to various fire configurations, including a 25.0 kW and a 37.5 kW methane fire and a 16.7 kW and a 25.0 kW propane fire. Three different metrics were used to evaluate backdraft phenomenon: (1) internal conditions within the enclosure before an anticipated backdraft; (2) ignition of a local gas mixture resulting in a backdraft; and (3) intensity of resulting backdraft. The gas mixture composition within the compartment before a backdraft was determined using measurements obtained from an enhanced phi meter and gas analyzer. Ignition resulting in a backdraft was evaluated from the equivalence ratio and gas species concentration measurements surrounding a triggered spark ignitor. Backdraft intensity was analyzed by quantifying the total heat release of the exiting fireball via carbon dioxide generation calorimetry. Real-time equivalence ratio measurements showed the progressive state of the gas mixture composition within the compartment before ignition. Backdraft was observed to occur when the gas mixture surrounding the ignition soure was greater than stoichiometric conditions. The total heat release of backdrafts was found to correspond to the initial mass fraction of fuel residing within the compartment for experiments with propane fires.

Critically Evaluated Atomic Data for the Au iv Spectrum

A spectral investigation of triply ionized gold (Au iv) has been carried out in the wavelength region of 500–2106 Å. The gold spectra were photographed at the National Institute of Standards and Technology, USA, on a 10.7 m normal incidence vacuum spectrograph (NIVS) using a sliding spark source as well as on a 3 m NIVS at the Antigonish laboratory in Canada with a triggered spark source. Our analysis is theoretically supported by the pseudorelativistic Hartree–Fock (HFR) formalism with a superposition of configuration interactions implemented in Cowan's suite of codes. Radiative transition parameters are also calculated using the HFR+CPOL (core polarization effects) model and the multiconfiguration Dirac–Hartree–Fock approach, and their comparisons are used to evaluate the transition rate data. All the previously reported levels of the 5d 8, 5d 76s, and 5d 76p configurations are confirmed, except one, and three are newly established. The missing 1 S 0 level of 5d 8 is now established at 55,277.8 cm−1. A total of 981 observed lines (E1 type), classified to 1031 transitions, including 133 newly identified, enabled us to optimize 139 energy levels. Several astrophysically important transitions, forbidden (M1- and E2-type) lines of 5d 8 and 5d 76s, are provided with their Ritz wavelengths and radiative parameters. A critically evaluated set of energy levels, observed and Ritz wavelengths along with their uncertainties, transition rates, and uniformly scaled intensities of Au iv lines have been presented. Also, large-scale atomic data to compute the opacity of Au iv in the kilonova ejecta have been supplemented in this work.

Energy levels, wavelengths and radiative rates for transitions in Hg-like Bismuth

The fourth spectrum of bismuth (Bi IV) has been investigated in the vacuum ultraviolet region. Recordings of bismuth spectra were made on a 3-m normal incidence vacuum spectrograph at Antigonish laboratory in Canada using a triggered spark light source. The theoretical interpretation for this spectrum was made with the pseudo-relativistic Hartree-Fock approach implemented in Cowan's code. The previous analysis of the energy level structure of Bi IV is confirmed and extended with the identifications of the 6p2 1S0 and 5d96s26p 3D2 levels, which were not reported earlier. Two new doubly excited configurations 6p6d and 6p7s were studied for the first time with the identification of 56 spectral lines. In total, 84 energy levels were located in the 5d10[6s2+ 6snp (n = 6, 7) + 6p2 + 6snd (n = 6, 7) + 6s5f], 6p6d, 6p7s, 5d96s2np (n = 6–10) and 5d96s2nf (n = 5–13) configurations, among which fifteen were newly established. A total of 552 spectral lines have now been classified in Bi IV in the region 193–5000 Å. We also present the optimized energy level values, transition rates and Ritz wavelengths along with their uncertainties evaluated using the least-squares fitting procedure.

Response Time of Surge Protective Devices Employing Spark Gap Technology

The transient behavior of commercially available low-voltage surge protective devices (SPDs) is experimentally investigated by employing standard lightning and switching impulse voltages. The response time of an SPD that integrates a triggered spark gap between the power lines and earth is on focus; a novel definition of the response time is proposed. Surprisingly, the experimentally derived response time varies beyond the upper limit declared by the SPD manufacturer. This work stresses the need for an update of international standards to incorporate a definition of the response time of SPDs covering a wide range of transients.

Energy structure investigations in triply ionized mercury: Hg IV

We report energy level structure of triply ionized mercury (Hg IV). The spectrum was recorded on a 3-m normal incidence vacuum spectrograph in the wavelength region 300 – 2000 Å, using a triggered spark source at the spectroscopy laboratory, St. Francis Xavier University, Antigonish in Canada. Wavelength measurement and the corresponding uncertainties caused by calibration procedures are carefully analyzed. Based on the analysis of original measurements, the energy levels are optimized, which resulted in an improved set of energy level values. A complete disentanglement of the origin of these energy levels may well be impossible; therefore, new configurations have been extended in our theoretical calculations using Cowan's pseudo-relativistic Hartree-Fock code with superposition of interacting configurations. All preceding results were confirmed, and the 5d8(6d + 7s) mixed configurations have been newly established with the aid of experimental data supported by theoretical calculations. Along with the optimized energy eigenvalues, the observed and Ritz wavelengths, transition rates, and eigenvector compositions of Hg IV are also given. The energy level values were optimized using a computer code LOPT.

Miniature solid-state switched spiral generator for the cost effective, programmable triggering of large scale pulsed power accelerators

This paper presents the design and testing of several different configurations of spiral generator, designed to trigger high current switches in the next generation of pulsed power devices. In particular, it details the development of spiral generators that utilize new ultrafast thyristor technology as an input switch, along with a polarity dependent output gap to improve the efficiency of the spiral generator design. The generator produced 50 kV from a 3.6 kV charging voltage, with a rise time of only 50 ns and a jitter of 1.3 ns---directly comparable, if not better than, a generator employing a triggered spark gap as the input switch. The output gap was constructed in house from commonly available components and a 3D printed case, and showed remarkable repeatability and stability---simple alterations to the output gap could further reduce the rise time. The entire spiral generator, along with control and charging electronics, fitted into a case only $210\ifmmode\times\else\texttimes\fi{}145\ifmmode\times\else\texttimes\fi{}33\text{ }\text{ }\mathrm{mm}$.

Assessment of MOV dimensioning principles, TRV risk management and cost-effectiveness of gapless FSC in Finnish series compensated system by utilizing EMT simulations

Between years 1997 and 2016 eleven fixed series capacitors (FSCs) have been built to enhance the interarea transmission capability of Finnish 400 kV transmission system. During these years, Fingrid (Finnish transmission system operator) has experienced various reliability issues with the existing FSCs. In early 2017 Fingrid launched a development project with target to improve the reliability and cost-effectiveness of Fingrid’s FSC fleet by developing the FSC specification, project and maintenance practices. As a part of the project, possibilities to develop FSC overvoltage protection requirements were studied for more robust, reliable and cost-effective technical solution. To compare investment costs and risks of FSC protection with and without forced triggered spark gap, an extensive EMT study was carried out. The study consisted of MOV energy and TRV-risk assessments including extensive sensitivity analysis covering 11 existing and 2 new FSC installations. Based on results of the study, new improved MOV dimensioning principles and the line circuit breakers’ TRV requirements were established to address for future FSC investments and refurbishments.

Plasma triggered spark gap switch for multiple switch synchronization.

A four-electrode plasma based triggered spark gap switch is designed for pulsed power applications, which consists of an anode and cathode of a main spark gap switch and an anode and cathode for a trigger pin. The anode and cathode of the trigger pin are coaxially arranged, and the gap between electrodes is 25 μm. A trigger voltage of 200 V is applied across the trigger gap with the help of a switching insulated gate bipolar transistor. With the breakdown of the trigger gap, plasma is generated, which is injected into the main gap. The trigger pin is placed axisymmetric to the main spark gap in the cathode. The main discharge channel of the spark gap has 0.6 mm space between two electrodes, which is charged to 1000 V. When the spark gap is triggered, the discharge current has a peak value of 6.1 kA with a quarter cycle time period of 0.97 µs. The four-electrode spark gap switch results are compared with those of a three-electrode trigatron switch, which has the peak current of 6 kA with 1.01 µs as quarter-cycle time period. Four similar four-electrode spark gap switches are triggered with the same scheme and synchronized within 10 ns as peak values of currents with jitter as less than 5 ns.

Cathode Assembly of a High-Current Electron Gun with Multichannel Initiation of Emission by Breakdown on the Surface of a Dielectric

A new scheme of the cathode assembly of a high-current electron gun is presented. The initiation of explosive emission is carried out using of 69 parallel triggered spark gaps, the electrodes and tubular ceramic insulators of which are built into the disk explosive-emission cathode. The efficiency of the proposed scheme and the high emissivity of the cathode assembly, which is approximately 1.5–1.7 times higher than the emissivity that is characteristic for a traditional gun scheme with a plasma anode and a copper-braided explosive emission cathode, are demonstrated.

The Effect of Removing the High Power Pulse Transformer on the Microwave Pulse Duration in the Preionization Phase in Taban Tokamak

In this study, a simple, economical and efficient preionization system (2.45 GHz, 1 kW) was constructed to assist the current startup in Taban tokamak ( $B_{T}= 0.7$ T, $R = 0.45$ m, a = 0.15 m). Power pulse transformer is a part of the preionization circuit, and its removal from the system can have impact on the performance of microwave duration and plasma preionization. In the present system, the magnetron was connected directly to the capacitor using a triggered spark gap. This new preionization system allows studying the electron cyclotron emission (ECR) preionization phenomenon at different toroidal magnetic fields. The toroidal magnetic field ripple was also used to determine the entrance moment of the ECR layer into the chamber. As a result, the exact moment of sending microwave can be determined using the moment of the ECR layer formation inside the chamber for maximum absorption of wave power.

Spectral analysis of triply ionized silver (Ag IV)

The spectral investigation of triply ionized silver (Ag IV) has been carried out in the vacuum ultraviolet region. Silver spectra excited through a triggered spark source were photographed on a 3-m normal incidence vacuum spectrograph at St. F. Xavier University, Antigonish in Canada. The theoretical study of the spectrum was made through the quasi-relativistic Hartree-Fock formalism in Cowan's code. The previous work of Ag IV on the 4d75p-(4d8+4d75s) transition array was confirmed but with some revisions. The study of a new transition array 4d7(5d+6s)-4d75p resulted in the establishment of 27 energy levels of 4d75d and 4d76s configurations. A total of 182 energy levels of 4d8, and 4d7nℓ (ℓ=0, 1, 2, and n=5, 6) configurations were optimized, through the classification of 1146 transitions.

Electrode Erosion and Lifetime Performance of a Compact and Repetitively Triggered Field Distortion Spark Gap Switch

The electrode erosion and lifetime performance of a compact and repetitively triggered field distortion spark gap switch were studied at a repetitive frequency rate of 30 Hz, a peak current of 8.5 kA, and a working voltage of ±35 kV when the switch was filled with a gas mixture of 30% SF6 and 70% N2 at a pressure of 0.3 MPa. The variations of the time-delay jitter and the self-breakdown voltage were both studied for the whole service lifetime of the spark gap switch. The morphology of both the electrodes and the plate insulator, before and after the service lifetime tests, is also analyzed. The results show that during these tests, the time-delay jitter is basically synchronized with the self-breakdown voltage jitter, and both undergo firstly a process of rapidly decreasing their values, then remaining stable, and finally and gradually increasing after 70 000 pulses. The change in the electrode surface roughness (i.e., surface profile) is caused by erosion and chemical deposits in the switch cavity, which are mainly the two factors that affect the time-delay jitter of the switch. Tip protrusions on the electrode surface, due to electrode erosion, contribute to reducing the time-delay jitter. However, due to chemical reactions, fluorides and sulfides are deposited on the switch components, as well as metal particles caused by electrode erosion sputtering. Slowly, after a large number of shots, all these phenomena affect the self-breakdown performance resulting in an increased self-breakdown voltage jitter, which also causes the time-delay jitter to increase. Although there are a number of reasons that contribute to the deterioration of the performance of the switch, it is fortunate that if a switch suffering a degraded performance is reassembled, with the electrodes mechanically polished and all the components cleaned, the optimal performance of the switch can be restored. If maintenance work is carried out regularly to preserve the condition of the switch’s inner components, the service lifetime of the switch can be prolonged.

Revised and extended analysis of doubly ionized gold: Au III

The spectrum of doubly ionized gold (Au III) photographed in the region 450–2106 Å has been investigated. The gold spectra have been recorded at two places viz. at the National Institute of Standards and Technology (USA) on a 10.7-m normal incidence vacuum spectrograph (NIVS) using a sliding spark source as well as on a 3-m NIVS at the Antigonish laboratory in Canada with a triggered spark source. Au III has a ground configuration [4f14]5p65d9 with 2D5/2 as its lowest level. Excited configurations are quite complicated as the first excited odd parity configuration 5d86p alone contains 45 energy levels. Excitation of a single electron from the valence 5d shell produces configurations of the type 5d8nl. Various configurations arise due to multiple excitation of the 5d9 subshell, e.g., 5d76s6p, 5d76s2, 5d66s26p, 5d76p2, etc. Theoretical predictions were made using Cowan's quasi-relativistic Hartree-Fock code with the superposition of configurations involving 5p6 [5d9 + 5d8ns (n = 6–8) + 5d8nd (n = 6–8) + 5d76l2(l = 0–2)+5d7(6s6d+ 6s7s+ 6d7s)] in the even parity system and 5p5 [5d10 + 5d96s] + 5p6 [5d8np (n = 6–8) + 5d8nf (n = 5–7) + 5d7 (6s6p+ 6s7p+ 6p7s+ 6p6d+ 6s5f+ 6s6f) + 5d66s26p] in the odd parity matrix. A total of 262 energy levels belonging to the 5d9 + 5d8[6s+7s+6d+6p] + 5d7[6s2 + 6s6p] configurations have been established, 69 being new including three revised levels, one from each of the 5d86d, 5d87s and 5d76s6p configurations. In the process, 1504 spectral transitions have been classified in the wavelength region 570–3310 Å. The accuracy of the wavelength measurements for sharp and unblended lines is ±0.005 Å. The final interpretation of the results was made on the basis of least squares fitted parametric calculations. The level optimization was achieved with a computer program LOPT.

Revised analysis of the third spectrum of mercury: Hg III

The doubly charged mercury (Hg III) is having the closed sub-shell 5d10(1S0) as its ground state and the first exited configuration(s) of the type 5d9nl (n ≥ 5). The spectrum of mercury was recorded on a 3-m normal incidence vacuum spectrograph at the spectroscopy laboratory of St. F. X. University in Canada. The excitation source used was a triggered spark in the wavelength region of 300–2000 Å. The theoretical calculations (inclusive of extended configurations) for the ion were accomplished by means of Cowan's quasi-relativistic Hartree-Fock code with superposition of configurations for appropriate interpretation of energy levels. Least squares fitted parametric calculations were used to elucidate the observed level structure. The obtained energy level values were optimized using a level optimization program (LOPT). A gross set of energy eigenvalues along with their LS-compositions, wavelengths and weighted transition probabilities of Hg2+ in the wavelength range 590 Å to 8200 Å are given. The ionization potential of Hg III was found to be 278,200 ± 400 cm−1 (34.49 ± 0.05 eV).

Revised and extended analysis of the third spectrum of silver: Ag III

The spectrum of doubly ionized silver (Ag III) having the ground configuration 4p64d9 has been investigated. The silver spectra were recorded on a 3-m normal incidence vacuum spectrograph at St. Francis Xavier University, Antigonish (Canada) using a triggered spark source. Theoretical predictions based on the Hartree–Fock method were made using superposition of interacting configurations and relativistic corrections. For proper interpretation of configuration interaction, the configurations 4p6[4d9, 4d8ns (n=5–9), 4d8nd (n = 5–9), 4d8ng (n=5–7), 4d75s2 and 4d75p2] and 4p54d10, 4p6[4d8np (n=5–7), 4d8nf (n = 4–6), 4d8nh (n = 6–7), 4d75s5p and 4d75s4f] were incorporated in the even and odd parity systems, respectively. The previous analyses were checked thoroughly; five levels of 4d85p were revised and two configurations, viz., 4d85d and 4d86s have been investigated for the first time. A total of 124 energy levels were established belonging to the configurations 4p6[4d9+4d8(5s + 6s + 5p + 5d)], among which 64 levels of 4p64d8(5d + 6s) were newly established. Least squares fitting parametric calculations were carried out to interpret the observed energy level structure. The observed energy levels were optimized to fit the measured wavelengths.

Development of longitudinally excited CO2 laser

Simple, compact, and affordable discharged-pumped CO2 laser controlled by a fast high voltage solid state switch has been developed. In this study, longitudinal excitation scheme has been adapted for simple configuration. In the longitudinal excitation scheme, the discharge is produced along the direction of the laser axis, and the electrodes are well separated with a small discharge cross-section. Triggered spark gap switch is usually used to switch out the high voltage because of simple and low cost. However, the triggered spark gap operates in the arc mode and suffer from recovery problem causing a short life time and low efficiency for high repetition rate operation. As a result, there is now considerable interest in replacing triggered spark gap switch with solid state switches. Solid state switches have significant advantages compared to triggered spark gap switch which include longer service lifetime, low cost and stable high trigger pulse. We have developed simple and low cost fast high voltage solid state switch that consists of series connected-MOSFETs. It has been installed to the longitudinally excited CO2 laser to realize the gap switch less operation. Characteristics of laser oscillation by varying the discharge length, charging voltage, capacitance and gas pressure have been evaluated. Longer discharge length produce high power of laser oscillation. Optimum charging voltage and gas pressure were existed for longitudinally excited CO2 laser.

The Third Spectrum of Indium: In III

The present investigation reports on the extended study of the third spectrum of indium (In III). This spectrum was previously analyzed in many articles, but, nevertheless, this study represents a significant extension of the previous analyses. The main new contribution is connected to the observation of transitions involving core-excited configurations. Previous data are critically evaluated and in some cases are corrected. The spectra were recorded on 3-m as well as on 10.7-m normal incidence spectrographs using a triggered spark source. Theoretical calculations were made with Cowan’s code. The analysis results in the identifications of 70 spectral lines and determination of 24 new energy levels. In addition, the manuscript represents a compilation of all presently available data on In III.

Corona pre-ionized gas switches with an increased lifetime for Marx generator of the lightning test complex

A new design of triggered spark gas switches with an increased operation life and stable dynamic performances for 2.4 MV, 4 MJ Marx generator of the lightning test complex is developed. An operation mode of switches in the test complex is the following: the total voltage – up to 80 kV, the discharge current – up to 50 kA, the charge flowing – up to 3.5 C/pulse, the working gas – dry air at an atmospheric pressure. An increased operating life is achieved by using the torus-shaped electrodes with an increased working area and by the application of a thick disk with a hole, as a trigger electrode, installed between the two torus-shaped electrodes. A short breakdown time delay and a high stability of the breakdown voltage under dynamic conditions are provided by gas pre-ionization in the spark gap by UV-radiation of an additional corona discharge in the axial region of the switch.

Two-Part Synthetic Test Procedures for the Testing of Medium-Voltage Load Break Switches

Though synthetic test methods are widely used for testing high-power circuit breakers (CBs), synthetic testing has not been reported in the literature as being extended to the testing of medium-voltage (MV) load break switches (LBS). This paper investigates the possibility of type testing of MV LBS using synthetic test procedures. The transient recovery voltage (TRV) required is calculated from both IEC and IEEE standards and it is shown that the IEC TRV specification results in a more severe TRV. It is found that testing with a basic Weil circuit requires two-part testing. In one test, a low-amplitude TRV with a fast rate of rise stresses the early region associated with thermal failure. In the other test, a higher-amplitude slowly rising TRV stresses the later dielectric region. However, the two-part test using the unmodified Weil circuit is shown to cause significant TRV overstressing. Insertion of a precharged capacitor and additional damping resistors into the Weil circuit at critical times using triggered spark gaps are found to be effective to reduce overstressing. Simulation results show that it is possible to use a modified synthetic test circuit to test LBS with voltage ratings of up to 38 kV and load currents of 800 A.

Eighth spectrum of palladium: Pd VIII

The spectrum of seven-times ionized palladium (Pd VIII) has been studied in the 170–310 Å region for the first time. Spectra were obtained on a 3 m 3600 lines/mm grazing incidence spectrograph with a triggered vacuum spark as a source of excitation. 178 lines of 4d3–4d25p transitions were identified with the use of parametric calculation based on the orthogonal operator technique. All 19 and 45 energy levels respectively in the 4d3 ground configuration and in the 4d25p excited configuration were determined. Using Cowan code calculations 183 lines of the 4d3–(4d24f + 4p54d4) transition array were classified, 51 levels of the mixed 4d24f + 4p54d4 configurations were located.