Inertial Electrostatic Confinement Fusion Device Research Articles

Analytical investigation of neutron production rate in spherical IECF devices

The radial profile of the neutron production rate in spherical inertial electrostatic confinement fusion devices (IECF) is investigated. The electrostatic potential is determined by solving the Poisson equation, and by using the potential; the fuel ion energy distribution function is determined at each radial point. From the energy distribution function, the fusion reaction rate is evaluated. Dependence of beam-beam and beam-background reaction rate on some important parameters as the spreads in the normalized angular ion energies, working pressure, and grid transparency are investigated.

Electromagnetic Design and Simulation of a New Fusion Device

A new inertial electrostatic confinement (IEC) fusion device is proposed. The device contains two ion guns which feed the plasma media by deuterium ions. The device is designed in three dimensions and the finite difference method is applied to satisfy the boundary values of the cylindrical chamber. It is the first time that both the ions and electrons are simulated in this geometry by particle in cell (PIC) technique. Ions and electrons can interact with six bar-sized cathodes of the chamber and each other as a result of many-body problem. The device has a central dc current-carrying rod, which generates a homogeneous magnetic field surrounding the six cathodes. Thus we expect a better confinement compared to the conventional devices. The simulation records the real-time position and momentum by using the electromagnetic equations together with the momentum equations. The dynamics of the particles is seen to be complicated with vibrations on the horizontal plane due to the field. DOI: http://dx.doi.org/10.5755/j01.eee.20.8.8435

Measuring time of flight of fusion products in an inertial electrostatic confinement fusion device for spatial profiling of fusion reactions

A new diagnostic has been developed that uses the time of flight (TOF) of the products from a nuclear fusion reaction to determine the location where the fusion reaction occurred. The TOF diagnostic uses charged particle detectors on opposing sides of the inertial electrostatic confinement (IEC) device that are coupled to high resolution timing electronics to measure the spatial profile of fusion reactions occurring between the two charged particle detectors. This diagnostic was constructed and tested by the University of Wisconsin-Madison Inertial Electrostatic Confinement Fusion Group in the IEC device, HOMER, which accelerates deuterium ions to fusion relevant energies in a high voltage (∼100 kV), spherically symmetric, electrostatic potential well [J. F. Santarius, G. L. Kulcinski, R. P. Ashley, D. R. Boris, B. B. Cipiti, S. K. Murali, G. R. Piefer, R. F. Radel, T. E. Radel, and A. L. Wehmeyer, Fusion Sci. Technol. 47, 1238 (2005)]. The TOF diagnostic detects the products of D(d,p)T reactions and determines where along a chord through the device the fusion event occurred. The diagnostic is also capable of using charged particle spectroscopy to determine the Doppler shift imparted to the fusion products by the center of mass energy of the fusion reactants. The TOF diagnostic is thus able to collect spatial profiles of the fusion reaction density along a chord through the device, coupled with the center of mass energy of the reactions occurring at each location. This provides levels of diagnostic detail never before achieved on an IEC device.

Prediction of potential well structure formed in spherical inertial electrostatic confinement fusion devices with various parameters

AbstractIn this paper, the theoretical analysis regarding potential structure on the inertial electrostatic confinement fusion devices has been carried out. Negatively biased grid as cathode placed at the center of the device surrounded by anode is assumed. The device is an ion-injection system and electrons may be emitted from the surface of the cathode. So the existence of both ion and electron currents inside the cathode is considered. Dependence of radial potential well structure on some important parameters as the spreads in the normalized total and angular electron and ion energies, the ratio of ion circulating current to electron circulating current, ion perveance, and grid transparency are investigated by solving Poisson equation.

Comparison of High-Energy He+ and D+ Irradiation Impact on Tungsten Surface in the IR-IECF Device

Polycrystalline tungsten specimens were irradiated in the Iranian Inertial Electrostatic Confinement Fusion device (IR-IECF) by high energy (~100 keV) and high fluency (~1019 ions/cm2) helium and deuterium plasma to investigate the implantation impact of high energetic ions on tungsten as a candidate for fusion first wall material. Comparison of the exposure by He and D2 plasma and influence of high temperature (~1,100 °C) implantation of each ion has been examined. Scanning electron microscopy was used to investigate surface morphology changes for various ion fluencies. Results showed the onset of visible surface pores formation especially for helium implanted samples which increased with higher implant fluencies, eventually resulting in a rough and flaky surface structure, unlike deuterium implanted samples on which smoothening of the surface occurred. Microhardness measurements were used to evaluate mechanical properties of implanted tungsten. Each specimen sustained surface hardening after implantation which was observed to increase with greater ion dose. The phase formation and structural evolution were studied by X-ray diffractometry method.

An inertial electrostatic confinement (IEC) device modeling and the effects of different cathode structures to the fields

A 3D electrostatic modeling of an inertial electrostatic confinement (IEC) fusion device has been realized. Finite element method is considered in order to identify the potential and electrical fields inside the spherical device. Two different material types are examined for the holder part of the cathode by comparing the field results. The different structures of cathode spheres are investigated for the determination of minimal and maximal field values; thereby the effect of structures on the fields and confinement process has been estimated. Parallel to our previous study, the porcelain holder presents better homogeneous field and at the center of the inner sphere. In addition, an increase of vertical rings on the inner grid affects the bottom corner of electrical potential, thereby ions are scattered to the entire region of the inner grid. According to the analyzes, there should be an optimal number vertical rings for the cathode grid structures so that one can achieve a better ion core at the middle of the grid for the confinement process.

New Insight into Gridded Inertial Electrostatic Confinement (IEC) Fusion Devices

Gridded inertial electrostatic confinement (IEC) devices use a 10-200 kV voltage difference to accelerate ions through a 0.1-10 mTorr background gas in a spherical or cylindrical geometry. The detailed investigation of a gridded IEC device using DD fuel has resulted in several surprises that have greatly altered our perception of how these systems operate. It was found that there are at least 4 major misconceptions that have been in place for over 15 years on how such IEC systems operate. These misconceptions range all the way from what energetic ion is causing the majority of fusions, to the energy and charge state of the reacting ions. Experimental results will illustrate some of the surprising reactions that are taking place in DD gridded system.

Study on Discharge Characteristics of a Cylindrical Inertial Electrostatic Confinement (IEC) Device for High-Yield Fusion Sources

Inertial electrostatic confinement (IEC) fusion device has been investigated as a compact fusion source to generate byproducts of fusion reactions for many applications. However, the IEC fusion device still has insufficient fusion reaction rate and stability issues in high power operation. In this work, a cylindrical IEC device is designed and discharge voltage and current at various pressures and geometries are studied to understand their effect on discharge. From this result, three key features is observed and discussed: 1) discharge voltage in IEC device increases with lower transparent cathode at the identical operating pressure, 2) high voltage and current discharge can be obtained with higher operating pressure at the identical pd value. 3) high voltage discharge without decrease of operating pressure can be obtained by considering limit length of cathode diameter in IEC device. Based on these results, it is supposed that transparency and size of cathode in an IEC device can be optimized for high voltage and current discharge with relatively high operating pressure to increase fusion reactions of beam-cathode surface and beam-background gas besides ion-ion fusion reaction in continuous IEC discharge. Consequently, these results can be reflected on design of a high-yield fusion sources.

Experimental Study of the Iranian Inertial Electrostatic Confinement Fusion Device as a Continuous Neutron Generator

Among many facilities in the field of nuclear fusion devices, inertial electrostatic confinement (IECF) device has the specific character of tendency to generate fusion products continuously. Besides the distinctive characteristics, it has become an outstanding focus of interest for many scientists because of several applications such as the ability of performing hydrogen boron fusion. This paper summarizes primary results of the design and construction of the first Iranian IECF device (IR-IECF). It consists of 13.5 cm diameter stainless steel cathode, 41 cm diameter anode with a 60 cm diameter and 60 cm height vacuum chamber. The outcomes of neutron detection rep- resent more than 10 7 neutron/s at the maximum biased voltage of -140 kV and 70 mA current with deuterium operational filling gas in the steady state regime.

慣性静電閉じ込め核融合（IECF）装置における中性子発生領域の研究

慣性静電閉じ込め核融合（IECF）装置における中性子発生領域の研究

Effects of chamber pressure variation on the grid temperature in an inertial electrostatic confinement device

Inertial electrostatic confinement fusion devices are compact sources of neutrons, protons, electrons, and x rays. Such sources have many applications. Improving the efficiency of the device also increases the applications of this device. Hence a thorough understanding of the operation of this device is needed. In this paper, we study the effect of chamber pressure on the temperature of the cathode. Experimentally, the grid temperature decreases as the chamber pressure increases; numerical simulations suggest that this is caused by the reduction of the hot ion current to the cathode as the pressure increases for constant power supply current. Such an understanding further supports the conclusion that the asymmetric heating of the cathode can be decreased by homogenizing the ion flow around the cathode.

A stationary multi-component cathode modeling and ion trajectories for an inertial electrostatic confinement fusion device

A new cathode modeling with stationary multi-component cathode approach is suggested for an inertial electrostatic confinement fusion device and some preliminary simulation studies based on the potential function of this cathode have been presented. The ions are accelerated due to the Coulomb force on a 2D plane and the central grid is assumed to have 6 point-wise and negatively charged at the middle. The model includes a repulsive force that stems from the screening effect of atoms at the vicinity of cathode. The simulations have proven that the particle trajectories are highly complex in the new potential well; in fact, the prediction of the particle route is observed to be strictly dependent on the control parameters such as the grid radius, ion current, voltage and initial position of the ion. Copyright © 2010 John Wiley & Sons, Ltd.

Effects of Grid Cathode Structure on a Low-Input-Power Inertial Electrostatic Confinement Fusion Device

The effects of grid cathode structure on a low-input-power inertial electrostatic confinement fusion (IECF) device were studied to achieve a high neutron production rate (NPR). An increase in geometric transparency of the grid cathode by decreasing the number of wire rings is known to mean that the recirculation ion current is increased. We expected that this increase would contribute to an increase in the NPR. However, our experimental results showed that the NPR in the low-input-power IECF device (V = 10:0-30:0 kV, I = 40:0 mA) increased by decreasing the transparency. We clarified this tendency by analyzing the equipotential lines near the grid. As a result, we found that the distortion of these lines near the grid was lessened by decreasing the transparency. Lessening the distortion of these lines, rather than increasing the in recirculation ion current, was effective in increasing the NPR in the low-input-power IECF device. In addition, we find that the effect of mitigating these lines depended on the applied voltage.

Effects of Grid Cathode Structure on a Low-Input-Power Inertial Electrostatic Confinement Fusion Device

The effects of grid cathode structure on a low-input-power inertial electrostatic confinement fusion (IECF) device were studied to achieve a high neutron production rate (NPR). An increase in geometric transparency of the grid cathode by decreasing the number of wire rings is known to mean that the recirculation ion current is increased. We expected that this increase would contribute to an increase in the NPR. However, our experimental results showed that the NPR in the low-input-power IECF device (V = 10:0-30:0 kV, I = 40:0 mA) increased by decreasing the transparency. We clarified this tendency by analyzing the equipotential lines near the grid. As a result, we found that the distortion of these lines near the grid was lessened by decreasing the transparency. Lessening the distortion of these lines, rather than increasing the in recirculation ion current, was effective in increasing the NPR in the low-input-power IECF device. In addition, we find that the effect of mitigating these lines depended on the applied voltage.

Study of Various Modes of Operation of an IEC Device

Inertial electrostatic confinement fusion devices are compact sources of neutrons, protons, electrons and X-rays. Such sources have many applications. Improving the efficiency of the device also increases the number of applications of this device. Hence a thorough understanding of the operation of this device is needed. In this paper we study the various modes in which an IEC device can be operated. The device seems to perform better when RF power is used. Furthermore, the amount of current that the power source can drive at a given pressure and grid voltage is dependent on the frequency applied to the grid—the higher the frequency the higher the cathode current. The device has been tested up to 320 kHz and the power supply current kept increasing up to this frequency. The higher limit was not reached by the present RF power supply. Another effect observed with the use of RF power is that the ionization source is more homogeneous relative to electron source ionization. This could mean that the heat load on the cathode is more evenly distributed. Such an even heat distribution would allow higher power operation.

The IEC Fusion-Plasma Torch - A Path for Closing the Materials Cycle

There are two interrelated requirements for achieving a sustainable modern world: 1) the availability of clean energy sources, and 2) the ability to close the materials cycle from use to reuse. Nature has always operated on a closed cycle process powered by solar energy. After the industrial revolution humans increasingly embarked upon an open cycle process extracting resources from the earth, dispersing them, and depositing the wastes into the earth’s life support systems of air, water, and soil. Fusion energy has unique capabilities for addressing the root cause of the resulting energy-environment-economy dilemma that our planet now faces. We propose an industrial evolutionary path for solving the dilemma based on the hydrogen-boron (p-11B) fusion fuel cycle and the application of ultra-high temperature plasmas (fusion plasmas) for materials recycling. This concept is known as the Fusion Torch and would return waste material back to its original 92 elemental states. An Inertial Electrostatic Confinement fusion device is proposed due to its characteristic non-Maxwellian plasma which enables burning p-B11.

Built-In Ion Source for Inertial Electrostatic Confinement in Low Pressure Regime

An inertial electrostatic confinement (IEC) fusion device driven by a ring-shaped built-in ion source is proposed and designed aiming at a reduced operating gas pressure in order to explore a possibility of a drastic enhancement in the fusion reaction rate in the envisaged beam-beam collision regime. In the present scheme ions will be extracted from a ring-shaped magnetron discharge plasma toward an IEC cathode grid placed concentrically at the center. A prototype ion source showed an accessible pressure of 5 mPa, which is hundreds times as low as the conventional glow-discharge-driven IEC. Dependence of the ion source current and extraction efficiency on the central IEC cathode voltage was studied by prototype experiments and numerical calculations. An IEC device with a built-in ion source was then designed based on these results. The expected IEC grid current is ˜0.4 mA at 5 mPa, where observation of the beam-beam fusion contribution is anticipated.

Optimization of an IEC Fusion Device to Increase Steady-State D-D Neutron Generation Rates

The University of Wisconsin-Madison Inertial Electrostatic Confinement (IEC) Fusion Research Group has been performing experiments on an IEC device known as HOMER. This device is a 65cm high, 91cm diameter cylindrical aluminum vacuum chamber that contains two concentric spherical wire grids, the outer grid acting as the anode and the inner grid as the cathode. The potential difference between the anode and cathode drives ions towards the center of the grids. Using this device, steady-state D-D fusion reactions are created in order to produce 2.45 MeV neutrons. With the goal of achieving maximum neutron production rates, the following parameters have been varied: cathode voltage, ion current, operating pressure, and the separation distance between the anode and cathode. The studies on pressure, voltage, and current have led to the discovery of trends that allow for the extrapolation of neutron rates at various conditions. The cathode/anode separation studies have offered valuable insight into how the distance between the electrodes effects the concentration of deuterium molecular ions and the ion energy spectra, and has led to the implementation of a configuration that better maximizes neutron production rates.

Neutron Production Rate of Inertial Electrostatic Confinement Fusion Device with Fusion Reaction on Surface of Electrodes

The neutron production rate (NPR) through fusion reaction on the surface of electrode(s) of an IECF (Inertial Electrostatic Confinement Fusion) device, which is expected to increase at low pressure, has been evaluated with a one dimensional simulation code and an experimental device. In the simulation, the NPR on the cathode and the anode has been evaluated individually as a function of pressure. The simulation results reveal that the NPR on the cathode increases at low pressure and that on the anodes increases at high pressure. In the experiment, titanium coated electrodes have been used in order to rise the adsorbed amount, and the results show same tendency along with the pressure as calculation results. And the maximum value increases 3 times by coating titanium.

Comparison of Spherical and Cylindrical Cathode Geometries in Inertial Electrostatic Confinement Devices

The performance of a new Inertial Electrostatic Confinement (IEC) fusion device using a cylindrical anode and two different cathode geometries, spherical and cylindrical, was compared to an existing IEC device with two different sized configurations of spherical anodes and cathodes. Experimental data was generated at -30 to -150 kilovolts, 30 milliamps steady-state, and 0.3 Pascal of Deuterium (D) and/or Helium-3 (3He). The best neutron rate achieved by the new device in a D environment was 2.7x107 neutrons per second at 145 kV and 35 mA. In a D-3He environment, the best proton rate achieved was 2.0x107 protons per second at 130 kV and 30 mA. Both the D-D neutron rate and the D-3He proton rate were approximately 40% lower than the larger volume existing IEC device.