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We propose a stabilization method for a Q-switched composite YAG/Yb:YAG/Cr:YAG laser configured for use as a laser igniter. The method is based on reducing the fluctuations in the magnitude of the initial seed signal caused by interference of the initial resonator modes. We have shown that a stable laser output could be achieved using a Fabry-Perot etalon, which can reduce the number of modes, to reduce the initial noise fluctuation in a resonator.

The Ignitor tokamak nuclear fusion research project is one of the most ambitious initiatives undertaken under the long-term scientific cooperation program between the Russian Federation and the Italian Republic. Currently, negotiations are underway to develop the engineering design of the Ignitor tokamak to be sited at JSC SRC TRINITI (Troitsk Institute for Innovation and Fusion Research) in Troitsk, Moscow. The Ignitor tokamak differs essentially from other tokamaks currently under development. It will have an ultra-powerful magnetic field of 13 T, in which a powerful plasma current of 11 MA will flow at a pulse discharge of about 10 s. The fusion reaction will be ignited mainly by ohmic heating. On the basis of the inspection of practically all the basic components of the energy and supporting infrastructure of the TRINITI Strong-Field Tokamak (SFT) experimental test facility, including steady-state and pulsed power supply systems, vacuum, cryogenic, and fuel systems, and diagnostic equipment, as well as on the analysis of the technical requirements for the tokamak support systems, the proposals for modernizing the TRINITI SFT experimental test facility for the implementation of the Ignitor Project were developed.

The wireless power transfer (WPT) for directly driving the high-intensity discharge (HID) lamp is proposed and implemented. In this article, the HID lamp is ignited and operated solely on the resonator without using any ignitor, ballast, or additional LC tank. Meanwhile, the key characteristics in the ignition and running phases are generally analyzed with the consideration of compensation schemes and number of coils. The even-coil series–series (SS) and odd-coil series–parallel (SP) WPT are identified to be more competent for wireless lighting with short and long transfer distances, respectively. In addition, the resonant frequency of 400 kHz is chosen to improve the luminous efficacy up to 150 lm/W. For exemplification, two-coil SS, three-coil SP, four-coil SS, and five-coil SP wireless HID lamps have been built and developed with the overall distances of 20, 40, 68, and 100 cm, and the transfer efficiencies are 94.1%, 89.6%, 83.1%, and 69.2%, respectively. Both the theoretical and experimental results are given to validate the feasibility and flexibility of the proposed system.

The ignition stage of deuterium-tritium fuel in inertial confinement fusion is a challenging task affected by many undesirable processes especially material mixing processes in the hot-spot region. In this research, an alternative proposal of the enhanced energy deposition in the proton fast ignition has been suggested. It consists of two primary assumptions of the beam-plasma system. In the first place, we have adopted the proton beam generated by TNSA or RPA mechanisms, each described by a Maxwellian or Gaussian energy distributions. Next, a realistic, non-uniform fuel plasma was adopted. Then, the cumulative stopping power of a proton beam of 10 kJ energy, penetrating the low content metal-contaminated deuterium-tritium fuel has been examined. It has been shown that in the case of the very low impurity fractions, irregular spatial fluctuations in the cumulative stopping power relative to pure fuel plasma emerges. However, at the higher concentrations, a systematic pattern becomes visible such that the contribution of the deep layers in the stopping power reduces. We observe the enhanced energy deposition close to the corona/dense core interface. It has been shown that the corona/dense core energy deposition ratio differs by up to 2.5% between pure and contaminated DT plasma. In the contaminated fuel plasma, energy deposition in the TNSA regime will effectively heat the plasma corona. While in the RPA counterpart, at a similar level of contamination, most of the incident beam energy remains inside the core fuel region.

The tokamak Ignitor project is one of the main topics of long-term scientific cooperation between the Russian Federation and the Italian Republic. The tokamak Ignitor has a super-strong magnetic fi...

In 2015, the development of the conceptual design of IGNITOR, a Russian–Italian experimental thermonuclear tokamak, was completed, and the parameters of all the systems, including the fuel system, were determined. In this work, an integrated design of arrangement of all the tritium-containing gas and secondary water streams expected in the operation of the IGNITOR tokamak was proposed on the basis of analyzing the designs of the fuel cycles of the large thermonuclear facilities JET, TFTR, and ITER. This design includes the storage of deuterium and tritium in a system of gas cylinders at a pressure of 0.4 MPa, the purification of the exhaust gas mixture from the plasma chamber using a “hot getter,” the separation of the deuterium–tritium isotope mixture by displacement gas chromatography, the purification of the process gas and air streams in a wet scrubber, and the detritiation of the water streams by chemical isotope exchange of hydrogen with water. The main technical parameters of equipment in the proposed design were estimated.

The IGNITOR tokamak project is one of main directions of scientific collaboration between Russia and Italy. The project is entering the stage of technical design for the location of the machine at the TRINITI site in Troitsk of the Moscow region. The IGNITOR machine differs considerably from other machines based on the tokamak concept by using a super strong magnetic field (13 T) and plasma current (11 MA). It will operate with short pulses (of approximately 10 s in length) and will not have a tritium breeding blanket. The requirements of the tritium fuel cycle are high because three tritium pulses per day are foreseen with a total amount of approximately 10 g to be processed daily. Fuelling will be based on gas injection. It necessary to provide a full tritium processing cycle including the storage and supply of the tritium, plasma exhaust purification, separation of the hydrogen isotopes, detritiation of gaseous and water streams, and tritium recovery from the plasma facing components. This paper considers tritium storage and delivery system as part of the fuel cycle.

Ignition characteristics in a strut-equipped dual mode combustor fueled with liquid kerosene were observed and discussed in this paper. A series of experiments and numerical simulations were carried out in the combustor both at the high-speed mode (Ma = 2.8) and at the low-speed mode (Ma = 2.0). Combustion establishment process and flame characteristics were captured and analyzed with the method of high-speed photography. Results indicated that two flammable regions, namely the recirculation region and the shear layer, generated in the combustor with the assistance of strut. Then, the optimization of ignitor parameters, including installation location of ignitor and ignitor power, had been conducted to achieve a stable flame successfully in these two flammable regions. During the flame establishment process, the ignition delay characteristics and the fluctuation energy of flame, adopted as the main parameters to estimate the ignition characteristics, were analyzed and discussed in different experimental conditions, which were mainly affected by operating Mach number, equivalence ratio of fuel, and mass flow of oxygen. The analysis results of these impacts on ignition process in this paper was beneficial to the optimization of ignition scheme in dual mode combustor for future investigations.

Analysis of hydrogen risk and the effectiveness of hydrogen mitigation systems during shutdown conditions is of great importance to support the development of the low power and shutdown (LPSD) probabilistic safety assessment (PSA) model and improve the capacity of nuclear power plants (NPPs) to reduce the hydrogen risk during shutdown conditions. This study deals with the identification of hydrogen risk and optimization of current hydrogen mitigation systems in the CPR1000 nuclear power plant during shutdown conditions before vessel head open. A detailed MELCOR input is developed, which includes detailed containment nodalization, accurate configuration of the passive autocatalytic recombiner (PAR) systems, and realistic boundary conditions based on design data and technical specifications. Three cases that represent different coolant inventory and specific hydrogen release paths are selected, and the accident progression and hydrogen risk are analyzed subsequently. The analysis indicates that the hydrogen risk is still an important issue during shutdown conditions, although the accident progression is relatively slow. PAR systems with the current configuration are added to the plant model to verify the effectiveness of the hydrogen mitigation system in the CPR1000 during shutdown conditions. The results indicate that the current configuration of PAR systems is still effective in mitigating the hydrogen risk following accidents during cold shutdown POS with PZR manhole close but is insufficient to mitigate the hydrogen risk during an accident with PZR manhole open. Therefore, two strategies to improve the hydrogen mitigation systems are proposed, and their effectiveness are compared. It is concluded that at least 12 additional PAR systems or an ignitor should be added to the PZR room to avoid severe hydrogen risk during shutdown conditions, and the additional PAR systems is the prior consideration.

The new Affordable Robust Compact (ARC) fusion reactor, which, compared to larger machines like ITER, aims to achieve its goal of fusion energy in a less expensive and smaller but even more...

This work evaluates the oxygen reduction system (ORS) approach to fire prevention in large-scale fire tests. A two-tier fuel array of standard commodities is used in a rack-storage configuration within an enclosure. A constant nitrogen/air mixture flow is supplied to the enclosure at a desired oxygen concentration. The oxygen concentration varies from 9% to 17%. A premixed propane ignitor is used as ignition source. The tested materials include five standard commodities of Class 3, CUP, CEP, UUP and UEP. The results of fire propagation success are obtained for the five standard commodities under different oxygen concentrations with a sustained igniter (hard limits) and without a sustained igniter (soft limits). The resulting limiting oxygen concentration (LOC) values are shown to be generally lower than the oxygen design concentrations recommended by existing standards including VdS 3527 and EN 16750 due to different test conditions. The hard limits are close to the fundamental LOC values for gases and vapors and do not depend significantly on the ignition duration and array size, while the soft limits vary significantly with the size and configuration of the fuel array and ignition duration. It is concluded that the hard limits are more suitable for ORS design purposes.

With the advent of proton fast driven ignition and more efficient energy transport of the ignitor beam, we might be interested to try successful ignition of the targets mixed with advanced fuels where DT main fuel acts simply as a seed. Here, we have examined the ignition and burn conditions of a DT–3He pre-compressed fuel pellet driven by proton ignitor beam generated separately by the well-known laser-accelerated ion mechanism. We have, first, derived the zero-dimensional model of the energy balance equations of one fluid, three temperatures (i.e. electron, ion and radiation temperatures) including the most important gain and loss processes. Then, in order to evaluate the feasibility of the system and its energy gain, these coupled equations are solved numerically. It has been shown that the system energy gain quickly responses and is sensitive to the initial concentration of He-3, proton beam power and total areal density of fuel. A saturation in energy gain for ρR > 8 g/cm2 has been demonstrated which is equivalent to burn fraction of higher than 0.4. Enhancement in energy gain exceeds 33 percent. Moreover, in a complete catalytic regime of both tritium and He-3 ions, as much as an order of magnitude reduction in neutron flux is observed.

A planar ignitor-based on low temperature co-fired ceramic (LTCC) and pyrotechnical micro electro mechanical system (PyroMEMS) technologies was designed and prepared in this paper. The planar ignitor is mainly composed of output charge layer, silicon safe and arm (Si-S&A) layer, and LTCC circuit base. Si/Pb3O4, C6H2(NO2)3OK/KClO4, and B/KNO3 were selected as ignition charge, gas charge, and transfer charge, respectively. The ignition circuit and main structure of the planar igniter were made by the LTCC process. Si-S&A was etched from monocrystalline silicon, which does not need environmental force to disarm. Preparation process of main components of planar ignitor that is suitable for mass production was introduced in detail. Simulation of PyroMEMS S&A actuation based on pendulum method was performed to save time for proof test. Finally, experimental verification on PyroMEMS S&A actuation and combustion propagation of B/KNO3 transfer charge were completed successfully. Results show that the idea of a planar ignitor inserted with PyroMEMS S&A device is feasible. [2018-0075]

With the development of small size and high energy output of initiators, how to improve the safety of the system becomes an urgent problem. Therefore, a novel Micro-electro-mechanical System (MEMS) initiator with a built-in safety-and-arming (S&A) device is introduced in this paper. The MEMS initiator is composed of the MEMS ignitor and the MEMS S&A device. A movable barrier with a fire hole is controlled by the MEMS S&A device. Driven by the electro-thermal principle, the barrier can be moved backward or forward to open or close the fire channel, and the status conversion between the armed mode and the safe mode can be realized. The test results show that under specific control signals, the MEMS S&A device can generate 1 mm output displacement. Under the armed mode, the flame can burst out from the fire channel when stimulated by 64 V pulse voltage. Under the safe mode, the barrier hit by the flame can stay intact, and the explosion energy is blocked in the fire channel successfully. The silicon wafer and silicon-on-insulator wafer are used to fabricate the MEMS S&A device. Integrated with the MEMS ignitor, the total chip size is 11 × 12 × 1.2 mm3.

A fusion reactor is an artificial sun created under laboratory conditions of high temperature and pressure to produce inexhaustible energy. When two nuclei of hydrogen isotopes are forced to fuse, under high temperature and high pressure, the reaction produces huge amount of energy and the heavier atoms of helium. The tokamak concept for magnetic confinement of plasma in a fusion reactor made the use of superconducting magnets most attractive and a natural choice. This chapter gives an account of the fusion process, the Lawson-Criterion for realizing ‘ignition’, different methods of plasma confinement and the superiority of tokamak concept. In a tokamak plasma is confined in a torus by an axial field generated by a set of toroidal coils distributed around the torus and a poloidal field generated by a set of poloidal coils. A high field central solenoid induces current in the plasma to heat it to high temperature through ramping of the field. This current in turn also produces poloidal field. We discuss the superconducting magnet systems built for most important fusion reactors so far, namely, T-7 of Russia, Tore Supra of France, JT-60 SA of Japan, KSTAR of Korea, EAST of China and SST-1 of India. The magnet systems of ITER, has been discussed in greater details. Two tokamaks, namely, TFTR of USA and JET at Culham UK both using normal magnets have also been included for they had many firsts and the data collected from them contributed significantly to the design of ITER. Two more futuristic reactors, the stellarator W7-X being built in Germany and IGNITOR an Italian–Russian joint fusion reactor being built in Russia have also been included towards the end of the chapter.

This work reviews the further development of the Italian–Russian bilateral project IGNITOR. One of the primary tasks for the execution of the project is the determination of the different types of engineering systems that will be required to support the engineering infrastructure of the IGNITOR tokamak. The tritium fuel cycle and detritiation systems, which provide tritium reprocessing and confinement during the operation of the scientific program, will be the most important systems. For the location of the IGNITOR, Russia proposed the Troitskii Institute and Thermonuclear Research (TRINITI) site near Moscow. The scope of this work is the investigation of the engineering concept of the tritium fuel cycle and detritiation systems for air and water with regard to the operation of the IGNITOR with tritium plasma at the TRINITI site.

In the framework of fusion energy research based on magnetic confinement, pulsed high-field tokamaks such as Alcator and FTU have made significant scientific contributions, while several others have been designed to reach ignition, but not built yet (IGNITOR, FIRE). Equivalent stellarator concepts, however, have barely been explored. The present study aims at filling this gap by: (1) performing an initial exploration of parameters relevant to ignition and of the difficulties for a high-field stellarator approach, and, (2) proposing a preliminary high-field stellarator concept for physics studies of burning plasmas and, possibly, ignition. To minimize costs, the device is pulsed, adopts resistive coils and has no blankets. Scaling laws are used to estimate the minimum field needed for ignition, fusion power and other plasma parameters. Analytical expressions and finite-element calculations are used to estimate approximate heat loads on the divertors, coil power consumption, and mechanical stresses as functions of the plasma volume, under wide-ranging parameters. Based on these studies, and on assumptions on the enhancement-factor of the energy confinement time and the achievable plasma beta, it is estimated that a stellarator of magnetic field B ~ 10 T and 30 m3 plasma volume could approach or reach ignition, without encountering unsurmountable thermal or mechanical difficulties. The preliminary conceptual device is characterised by massive copper coils of variable cross-section, detachable periods, and a lithium wall and divertor.

As alternative energy sources increase the proportion of intermittent energy supplies in power grids, coal-fired power plants have come to play an important role in flexible peak power regulation. The burner is the core of the pulverized-coal boiler, and so its performance greatly affects the ability to achieve stable combustion at low boiler loads and also determines the load adjustment range. A novel coal-igniting-fuel technology using intermediate frequency induction heating has been proposed as a means of obtaining better combustion stability at low and variable loads. This method involves the combustion of a small quantity of coal particles in the ignitor to form a central pilot flame that subsequently ignites the surrounding pulverized coal in the main burner to achieve stable combustion. The present work utilized numerical simulations and full-scale experiments to systematically investigate the coal ignition and combustion characteristics associated with this technology. The numerical results show that coal particles inside the ignitor are rapidly heated and ignited, after which the resulting flame is gathered and accelerated by the flame extension tube, thereby forming a pilot flame near the ignitor outlet. When applied to a direct current (DC) burner, this ignitor is able to ignite the primary coal/air flow in a timely manner to form a second high-temperature zone near the burner nozzle. Compared with the absence of an ignitor, the flame center area appears roughly 1.6 m ahead. In an experiment using a single ignitor, it is found that the induction heating coil can quickly heat coal particles, thereby generating a stable high-temperature heat source within 80 s. The application of this ignitor to a DC burner allows the rapid start of the burner at a low initial ambient temperature, and the load can be adjusted over wide ranges of 17.6% – 100% and 13.6% – 100% when burning Shenhua coal and Blended coal, respectively. The degree of coal burnout is found to gradually improve as the thermal load of the burner is increased, reaching a maximum of approximately 93% at full load.

In the framework of the joint Russian – Italian collaboration on the development of the IGNITOR project some preliminary estimates of the risk factors that may be occurring during the realization of the project were recently carried out. A distinctive feature of the IGNITOR project is the fact that it contains some innovative solutions in the areas of research, engineering and technology, often having no analogues not only in industry but also outside the specific laboratories and research centers responsible for the development of necessary components. In addition, it is necessary to point out several peculiarities of the IGNITOR project, which distinguish it from other large-scale scientific projects in the sphere of controlled thermonuclear fusion with magnetic confinement, implemented on the basis of the tokamak technology, and which are risk-related in terms of the project realization: 1. The super strong magnetic fields (up to 13 T); 2. The high plasma current discharge (up to 11 MA); 3. Ohmic heating as the main mechanism of ignition of the thermonuclear fusion reaction. During of the risk analysis investigation the following categories of risks were identified: ● political; ● economical; ● achievement of the main goal of the project; ● technical and technological risks; ● risks of implementation of the scientific research program; ● environmental, safety and socio-economical risks. The different impact factors on the realization phase of the IGNITOR project are shown and analyzed. The conclusions of the risks analysis that were obtained are summarized in the joint Table, where the risk category, the description of the problem, circumstances, risk mitigation method and comments are displayed.

CANDOR is a high-field advanced fusion fuel cycle experiment based on Ignitor, but with larger dimensions and higher fusion power: it is a feasibility study of a high-field Deuterium-Helium-3 (D3He) experiment of larger dimensions and higher fusion power than Ignitor, still based on the core Ignitor technologies. Results of investigations on the feasibility of D3He burning and side neutrons production in D3He plasmas and specifically in CANDOR show that, with the initial use of DT triggering, the need for an intense auxiliary heating would be considerably alleviated. The total released 14 MeV neutron energy during the 16-second burning sums to about 210 MJ. DT and DD neutron currents incoming in the CANDOR plasma chamber wall and the Neutron Wall Loads have been computed. D3He ignition could be studied in CANDOR, with modest and conservative developments of the present technology. CANDOR has a low neutron wall loading, softer neutron spectrum, low radiation damage, and - consequently - lower neutr...

The poloidal current induced in the tokamak wall during fast transient events is analytically evaluated. The analysis is based on the electromagnetic relations coupled with plasma equilibrium equations. The derived formulas describe the consequences of both thermal and current quenches. In the final form, they give explicit dependence of the wall current on the plasma pressure and current. A comparison with numerical results of Villone et al. [F. Villone, G. Ramogida, G. Rubinacci, Fusion Eng. Des. 93, 57 (2015)] for IGNITOR is performed. Our analysis confirms the importance of the effects described there. The estimates show that the disruption-induced poloidal currents in the wall should be necessarily taken into account in the studies of disruptions and disruption mitigation in ITER.

This paper describes recent progress at the NASA Glenn Research Center (GRC) in the development and demonstration of an integrated high-propellant throughput small spacecraft electric propulsion (HT-SSEP) system based on a Hall-effect thruster. A center-mounted cathode and an innovative magnetic circuit topology were implemented in the design of the Hall-effect thruster to achieve high-propellant throughput, high performance, and efficient packaging. To minimize technical risk, the HT-SSEP development approach sought to limit design features and materials to those with a clear path-to-flight. A propellant throughput capability of greater than 100 kg at a minimum thruster efficiency of 50% was targeted. The proof-of-concept NASA-H64M laboratory model (LM) thruster was designed, fabricated, and tested at GRC in fiscal year 2018. The thruster development leveraged heritage Hall-effect thruster design and manufacturing processes wherever appropriate. Recent NASA advances in Hall-effect thruster technology were also leveraged. A scalable discharge power supply (DPS) capable of powering the H64M-LM was developed, then demonstrated as part of an integrated system test. The DPS uses commercial off-the-shelf components with spaceflight equivalents. A keeper supply with DC ignitor was breadboarded, then demonstrated with a laboratory cathode. Finally, feed system trade studies were performed to ascertain what feed system architecture might be appropriate for an HT-SSEP system. This paper details the motivations for the project, the development approach, the chosen sub-system architectures, design considerations, and test results.

Due to an unfortunate oversight this paper was published with typographical errors in Keywords and Eq. (5).