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Title: Fusion energy in an inertial electrostatic confinement device using a magnetically shielded grid

Abstract

Theory for a gridded inertial electrostatic confinement (IEC) fusion system is presented, which shows a net energy gain is possible if the grid is magnetically shielded from ion impact. A simplified grid geometry is studied, consisting of two negatively biased coaxial current-carrying rings, oriented such that their opposing magnetic fields produce a spindle cusp. Our analysis indicates that better than break-even performance is possible even in a deuterium-deuterium system at bench-top scales. The proposed device has the unusual property that it can avoid both the cusp losses of traditional magnetic fusion systems and the grid losses of traditional IEC configurations.

Authors:
; ;  [1]
  1. School of Physics, The University of Sydney, Sydney, New South Whales 2006 (Australia)
Publication Date:
OSTI Identifier:
22486442
Resource Type:
Journal Article
Resource Relation:
Journal Name: Physics of Plasmas; Journal Volume: 22; Journal Issue: 10; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
70 PLASMA PHYSICS AND FUSION TECHNOLOGY; CUSPED GEOMETRIES; DEUTERON REACTIONS; GRIDS; INERTIAL CONFINEMENT; IONS; MAGNETIC FIELDS; MAGNETIC SHIELDING; NET ENERGY; THERMONUCLEAR REACTORS

Citation Formats

Hedditch, John, E-mail: john.hedditch@sydney.edu.au, Bowden-Reid, Richard, E-mail: rbow3948@physics.usyd.edu.au, and Khachan, Joe, E-mail: joe.khachan@sydney.edu.au. Fusion energy in an inertial electrostatic confinement device using a magnetically shielded grid. United States: N. p., 2015. Web. doi:10.1063/1.4933213.
Hedditch, John, E-mail: john.hedditch@sydney.edu.au, Bowden-Reid, Richard, E-mail: rbow3948@physics.usyd.edu.au, & Khachan, Joe, E-mail: joe.khachan@sydney.edu.au. Fusion energy in an inertial electrostatic confinement device using a magnetically shielded grid. United States. doi:10.1063/1.4933213.
Hedditch, John, E-mail: john.hedditch@sydney.edu.au, Bowden-Reid, Richard, E-mail: rbow3948@physics.usyd.edu.au, and Khachan, Joe, E-mail: joe.khachan@sydney.edu.au. 2015. "Fusion energy in an inertial electrostatic confinement device using a magnetically shielded grid". United States. doi:10.1063/1.4933213.
@article{osti_22486442,
title = {Fusion energy in an inertial electrostatic confinement device using a magnetically shielded grid},
author = {Hedditch, John, E-mail: john.hedditch@sydney.edu.au and Bowden-Reid, Richard, E-mail: rbow3948@physics.usyd.edu.au and Khachan, Joe, E-mail: joe.khachan@sydney.edu.au},
abstractNote = {Theory for a gridded inertial electrostatic confinement (IEC) fusion system is presented, which shows a net energy gain is possible if the grid is magnetically shielded from ion impact. A simplified grid geometry is studied, consisting of two negatively biased coaxial current-carrying rings, oriented such that their opposing magnetic fields produce a spindle cusp. Our analysis indicates that better than break-even performance is possible even in a deuterium-deuterium system at bench-top scales. The proposed device has the unusual property that it can avoid both the cusp losses of traditional magnetic fusion systems and the grid losses of traditional IEC configurations.},
doi = {10.1063/1.4933213},
journal = {Physics of Plasmas},
number = 10,
volume = 22,
place = {United States},
year = 2015,
month =
}
  • Performance characteristics of an inertial electrostatic confinement fusion triple-grid system are experimentally studied to provide an ample fusion reaction rate under a lower-gas-pressure region to make the operation free from glow discharge restrictions between the discharge voltage, current, and gas pressure. With a filament to provide sufficient electrons, the operating gas pressure is found to reduce down to 1/5 for the same discharge current and voltage. Although the gas pressure region that was achieved still remains the region where the fusion reaction between the ion beam and background gas is dominant, the neutron yield normalized by the gas pressure inmore » the triple-grid system shows higher value than the conventional single-grid system.« less
  • New diagnostics are required to understand the physics operation of an inertial electrostatic confinement (IEC) device. In an attempt to understand the fusion source regimes within the IEC device, a new diagnostic called the eclipse disk has been introduced. This diagnostic was used to exploit the byproduct protons' energy difference between the deuterium-deuterium (D-D) and deuterium--an isotope of helium with two protons and one neutron (D-{sup 3}He) reactions to study the contributions of the protons generated from various source regimes. These source regimes are divided into five categories namely: converged core, embedded, beam background, volume, and wall-surface sources. The eclipsemore » disk diagnostic has provided the first confirmed evidence that D-{sup 3}He reactions are predominantly embedded reactions. It has been observed that at the present operating power levels (6-10 kW) most of the D-D reactions occur in the volume of the chamber caused by the charge exchanged neutrals, and the converged core contribution is significant only for D-D reactions. Since the branching ratio for the proton and neutron generation in a D-D fusion reaction is {approx}50%, it is inferred that the proton to neutron count ratio is a better parameter to monitor than either proton or neutron counts measured alone while studying the source regimes. This parameter may also be used for studying the potential wells within the cathode grid.« less
  • In recent researches, an assisted glow discharge experiment using an external ion source has been tried to reduce operation gas pressure. As results, operating gas pressure has been successfully reduced from 1.5 Pa to 0.3 Pa, and the neutron production rate has increased.These results are considered to be due to an increase of ion energy. However, it is necessary to measure the ion energy distribution of the Cylindrical Inertial Electrostatic Confinement Fusion (C-IECF) device in order to confirm this. To do this, we have measured the distribution of the neutral particle beam energy (relative to ion energy distribution). These experimentalmore » results demonstrate that a decrease of operation gas pressure (from 1.7 Pa to 0.3 Pa) contributes to the increase in ion energy.« less
  • 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 inmore » a high voltage ({approx}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.« less
  • Experiments were performed to understand the dynamics of the ion flow in an inertial electrostatic confinement (IEC) device. This was done by monitoring the fusion rate as the symmetry of the grid was increased starting with a single loop all the way until the entire grid is constructed. The fusion rate was observed to increase with grid symmetry and eventually saturate. A single loop grid was observed to generate a cylindrical ({approx}line) fusion source. The ion flow distribution was measured by introducing fine wires across a single loop of the grid in the form of a chord of a circlemore » (chord wires). This study revealed that with increased symmetry of the cathode grid wires the convergence of the ions improves. The chord wires provided electrons for ionization even at low pressures ({approx}6.67 mPa) and helped sustain the plasma. The impinging ions heat these wires locally and the temperature of the wires was measured using an infrared thermometer that was used to understand the ion flow distribution across the cathode grid. The presence of the grid wires seems to affect the fusion rate more drastically than previously thought (was assumed to be uniform around the central grid). Most of the fusion reactions were observed to occur in the ion microchannels that form in gaps between the cathode wires. This work helps understand the fusion source regimes and calibrate the IEC device.« less