Traveling Wave Direct Energy Converter Research Articles

Examination of Efficiency Dependence on Deceleration Voltage in a Traveling Wave Direct Energy Converter Simulator

Examination of Efficiency Dependence on Deceleration Voltage in a Traveling Wave Direct Energy Converter Simulator

Experimental Analysis on Variation of the Amount of Particles Passing Through Traveling Wave Direct Energy Converter

Traveling wave direct energy converter (TWDEC) was proposed as an efficient energy recovery device for 14.7 MeV protons produced by D-3He fusion reaction. Protons are velocity-modulated and bunched up, then induce traveling wave field which traps and decelerates themselves. In simulation experiments, it was found that the amount of particles was larger during application of modulation/deceleration field in the condition providing high efficiency than other conditions. This paper treats the phenomenon and will present results of analytical experiments and discussion. We found that ions were scattered due to modulation, and variation of the number of ions was corresponding to variation of deceleration effect. The possible mechanism of the phenomenon is scattering of particles due to bunching and its suppression due to trapping by deceleration field. In other words,high efficiency would be obtained by suppression of scattering.

Analytical Experiment of Time Evolution of Deceleration Effect in Traveling Wave Direct Energy Converter Using Dual-Frequency Modulation

Analytical Experiment of Time Evolution of Deceleration Effect in Traveling Wave Direct Energy Converter Using Dual-Frequency Modulation

Examination of Bunching Effect of Dual-Frequency Modulation in a Traveling Wave Direct Energy Converter Simulator

Examination of Bunching Effect of Dual-Frequency Modulation in a Traveling Wave Direct Energy Converter Simulator

Performance improvement due to additional collectors in a secondary electron direct energy converter simulator

The structure of secondary electron (SE) direct energy converter (SEDEC), which was proposed as an additional energy recovery device settled in the downstream of traveling wave direct energy converter for D-3He fusion, was investigated to improve its performance. Additional electron collectors (A-ECs) were settled near foil electrodes for quick collection of SEs. As the location of the A-ECs was close to the proton beam, scattered protons were incident on the A-ECs, leading to a decrease in the net electron current. Blocking plates were used to suppress incident of protons. The net electron current recovered and overcame the level measured in the conventional structure. The recovered power increased by 75%.

A Study of Miniaturization of Traveling Wave Direct Energy Converter for Loading on a Spacecraft

Traveling wave direct energy converter (TWDEC) was proposed as an efficient energy recovery device for fast protons produced by D- 3 He fusion reaction. The applica- tion of TWDEC to fusion propulsion system was also studied, and its significant subject was miniaturization of the device. In TWDEC, there is a trade-off between device size and efficiency, and an employment of a decelerator of constant deceleration scheme is promising to realize miniaturization. The paper experimentally examines one of the working char- acteristics of the constant deceleration scheme by using a relative phase control method called active decelerator. The results of the experiment and corresponding numerical orbit calculation are consistent with the theory of the constant deceleration scheme.

Studies on the Axial Position of the Decelerator in Traveling Wave Direct Energy Converter

Studies on the Axial Position of the Decelerator in Traveling Wave Direct Energy Converter

One-Dimensional Semianalytical Model for Optimizing the Standing-Wave Direct Energy Converter

A method to optimize the spacing of decelerator electrodes in the standing-wave direct energy converter has been developed. The standing-wave direct energy converter is introduced as a simplified version of, and possible milestone toward, the traveling-wave direct energy converter to facilitate a general understanding of the physics of the traveling-wave direct energy converter, as well as to simplify the modeling and results. The standing-wave direct energy converter may also stand alone as an alternative to the traveling-wave direct energy converter. The method developed takes advantage of analytical simplifications in capacitance calculations to avoid the use of a computational mesh, thereby modeling the standing-wave direct energy converter system with low simulation runtimes while using explicit numerical methods to advance groups of ions, referred to as ion bunches. The optimization scheme returns the optimal electrode spacing and circuit resistance value given the inputs of the initial ion energy, ion bunch density, operating frequency, decelerator electrode radius, and number of decelerator electrodes. The method approximates the ion bunches as point charges on the axis of the device, and the limitations of this approximation are considered. The expansion of the ion bunch is treated analytically and imposes a limiting tradeoff between the density of the ion bunches and the duration of ion deceleration. Performance trends and other tradeoffs are also presented.

Characterization of Secondary Electron Collection for Energy Recovery from High Energy Ions with a Magnetic Field

A traveling wave direct energy converter (TWDEC) is expected to be used as an energy recovery device for fast protons produced during the D-3He nuclear fusion reaction. Some protons, however, are not fully decelerated and pass through the device. A secondary electron direct energy converter (SEDEC) was proposed as an additional device to recover the protons passing through a TWDEC. In our previous study, magnetic field was applied for efficient secondary electron (SE) collection, but the SEs were reflected close to the collector due to the magnetic mirror effect and the collection was degraded. Herein, a new arrangement of magnets is proposed to be set away from the collector, and experiments in various conditions are performed. An appropriate arrangement away from the collector resulted in the improvement of SE collection.

Studies on Characteristics of a Bias-Type Traveling Wave Direct Energy Converter Installed on GAMMA 10 Tandem Mirror

The operating characteristics of traveling wave direct energy converter, which is expected to be used in an advanced fusion, are discussed in the case of broad energy band flux based on the deceleration theory. Comparison of distributions in phase space between different relative phase differences shows a good agreement with the theory. The examination by narrow energy band flux roughly explained that the observed low energy component corresponded to the incident ions around the best matching energy of the decelerator.

Numerical Analysis of Particle Orbits for Modulation Process in Traveling Wave Direct Energy Converter

As for the modulation process of a traveling wave direct energy converter (TWDEC), which will be used in D-3He fusion power generation and has a principle of a reversal process of linear accelerator, numerical analysis of particle orbits has been performed. Space charge effect is taken into account to examine lower modulation effect found in simulation experiments. In the high incident particle density expected in the simulation experiments, the influences of space charge effect on modulation process have been confirmed in the view points of radial spread, axial velocity, and bunching characteristics.

Analytical Experiments Using a Bias-Type Traveling Wave Direct Energy Converter Simulator Installed on Gamma 10 Tandem Mirror

In order to investigate working characteristics of traveling wave direct energy converter (TWDEC) to flux with wide energy spread, the second-phase experiments of the research project using end-loss flux of GAMMA 10 were performed. The end-loss flux of the normal operation and that of the one-side plugging operation of GAMMA 10 were introduced to a bias-type TWDEC. The variation of effect of TWDEC operation was examined on relative phase difference between the modulator and the decelerator voltages. Both deceleration and acceleration effect were found according to the relative phase difference for the end-loss flux of both normal and one-side plugging operations.

Studies on Modulation Process of Traveling Wave Direct Energy Converter for Advanced Fusion

The first systematic study of the modulation process of traveling wave direct energy converter (TWDEC), an efficient energy recovery device for fast protons created in an advanced fusion, has been presented. The necessary conditions required for a practical TWDEC modulator were examined. The experimental investigation of modulation characteristics for half-wavelength and one-wavelength modulators was performed. In the one-wavelength modulator, the same effect as the half-wavelength modulator can be obtained by half modulation voltages of electrodes. The modulation effect is sensitive with the phase difference between two RF voltages of the one-wavelength modulator, which could be used for control of modulation effect with a fixed electrode structure.

Simulation Experiments of Traveling Wave Direct Energy Converter on GAMMA 10 Tandem Mirror

Simulation experiments of traveling wave direct energy converter (TWDEC) on GAMMA 10 tandem mirror have been performed. Following to initial experiments reported previously, full biasing system including measurement system has been constructed. The biasing system has successfully worked showing that energy distribution is shifted corresponding to the bias voltage. Examination of approximated energy distribution functions reveals that the deceleration effect by TWDEC operation is found for an appropriate relative phase difference between modulator and decelerator RFs.

Magnetically Channeled IEC Trap Array Fusion Device for Interplanetary Missions

A radical new inertial electrostatic confinement (IEC) fusion concept, the magnetically channeled IEC trap array (MCTA), is studied as a candidate power unit for interplanetary space travel. IEC fusion concepts are widely recognized to be attractive for space power because they are simple and lightweight. However, existing experimental IEC concepts, while very successful for low-level power neutron sources, do not project to high-power space applications because of poor confinement-time scaling and grid heating/losses. The MCTA concept addresses both issues: eliminating the need for a central grid by injecting energetic ions into this unique hybrid configuration and providing improved confinement by connecting a number of traps. Because of the linearly connected geometry and compatibility with an efficient traveling wave direct-energy converter, aneutronic fuels, such as D-3He, can be implemented. Thus, the MCTA concept has the potential to accomplish the demanding requirements of future deep-space propulsion and power by providing a high power-density propulsion system. This promise was amply demonstrated in an earlier, reasonably detailed design study by University of Illinois researchers that used an MCTA to accomplish a fast manned mission to Jupiter.In the present paper, we discuss the basic MCTA concept and examine stability issues that must be resolved to access the feasibility of this concept. Some important supporting data carry over from prior IEC experiments, but a full MCTA configuration has yet to be studied experimentally. If proven feasible, the MCTA development path would involve experiments at progressively higher powers aimed at the ultimate demonstration of a full-scale, several-hundred-MW propulsion unit.

Improvement of Structure of Traveling Wave Direct Energy Converter Simulator for Ion Flux with Wide Energy Spread

In D-3He fusion, most of fusion energy is carried by kinetic energy of created protons of 14.7 MeV. Concept of traveling wave direct energy converter (TWDEC) was proposed as an effective energy converter with less handling voltage. Although fundamental researches on TWDEC have been reported, the dependence on energy spread of flowing ions has not been investigated in spite of its significant effects against conversion efficiency. The paper treats this subject by an application of TWDEC simulator to GAMMA 10 tandem mirror whose end-loss flux has relatively wide energy spread. The energy distribution of the end-loss flux was measured, and a new structure of TWDEC simulator was designed according to the measured result. The conversion efficiency was estimated by one-dimensional numerical orbit calculations showing the designed structure had enough performance as TWDEC.

Deceleration in a traveling wave direct energy converter for advanced fusion

A traveling wave direct energy converter (TWDEC) is desirable for the direct energy conversion of fast protons produced by deuterium–helium-3 fusion, since the proton energy is so great that conventional electrostatic converters cannot be used. This paper presents the results of high-energy TWDEC simulation experiments as a follow-up to the previously reported proof-of-principle experiments for low energy. As the beam energy increases, the efficiency of energy recovery is expected to improve, and since the variation in the beam velocity becomes large, its effect cannot be neglected. The decelerator electrodes intervals were designed to take into account the velocity matching between the decelerated beam and the traveling wave. The variable intervals also dictate the small size of the hole in the electrode through which the beam passes. A more appropriate hole size results in deceleration efficiency over 20% for a unit wavelength. The effectiveness of the matching design was confirmed by the dependence of deceleration efficiency on the beam energy. The experimental scaling of the deceleration efficiency for a unit wavelength was extended to approach the level of a commercial-scale device.

Optimization of Decelerator Structure of Traveling Wave Direct Energy Converter Simulator for D-3He Fusion

In D-3He fusion, most of fusion energy is carried by created protons of 14.7MeV. Concept of traveling wave direct energy converter (TWDEC) is applied for the purpose to construct an energy converter with less handling voltage and higher efficiency. To improve conversion efficiency of the TWDEC, we propose two methods of optimization of decelerator structure in the view point of matching between the beam velocity and the phase velocity of the traveling wave. As the result of experiments in a TWDEC simulator based on each method, these optimizations are really effective to improve conversion efficiency. However, when the matching is disturbed by some factors, less matching results in less efficiency.

Experimental and Computational Study on the Cusp-DEC and TWDEC for Advanced Fueled Fusion

Experimental and computational results of direct energy converters (DECs) for advanced fueled fusion such as D-3He are presented. Kinetic energy of thermal component of end loss plasma is converted to electricity by using the Cusp DEC. The proof-of-principle experiments of a single slanted cusp have been carried out and verified the faculty of the configuration. To improve a separation of electrons from ions, numerical simulation shows a Helmholtz magnetic configuration with a uniform magnetic field is more effective than the Cusp DEC. The fusion-produced high-energy ions like 15 MeV protons in D-3He fueled fusion can pass through the Cusp DEC without disturbing their orbits and enter a traveling-wave direct energy converter (TWDEC). Small scale experiments have shown the effectiveness of the TWDEC and the numerical simulation on optimization of interval of electrodes in a decelerator gives high conversion efficiency up to 60 %.

Traveling-Wave Direct Energy Converter for an FRC/D3HE Reactor

Energy distribution of the 14.7MeV protons, which has energy spread of about 2 MeV due to the thermal motion of fuel ions, is derived analytically. Curvature drift of charged particles in an open magnetic field with a spiral configuration is estimated for separation of the 15MeV protons from thermal components. Numerical orbital calculation shows that amplitude of a wave about 1MV is necessary for trapping and deceleration of the proton beam in a traveling-wave direct energy converter (TWDEC). About 80% of the kinetic energy of the proton beam can be converted into electricity when bunching of the proton beam is improved by applying series of velocity modulations. Results of a computer simulation show that the TWDEC has desirable performance characteristics. The traveling wave with a designed frequency is excited spontaneously without any external power supply. The wave rapidly reaches an equilibrium state after loading, and stably responds to load fluctuations.