Hisayuki Toku

Inertial electrostatic confinement fusion device with an ion source using a magnetron discharge

An inertial electrostatic confinement (IEC) fusion device is studied for a compact fusion neutron/proton source using a built-in magnetron ion source. The addition of an ion source to the IEC fusion device enhances fusion reactions by allowing a lower operating gas pressure and by providing a beam-like ion energy distribution. Under lower gas pressures, charge exchange collisions are reduced, resulting in longer ion lifetime and thus enhanced ion re-circulation. The performance characteristics of this IEC fusion device found in the experiments were compared with the numerical calculations and found qualitatively in good agreement. An improvement in normalized neutron yield (defined as neutron yield divided by the product of grid current and operating gas pressure), more than a factor of two, has been observed compared with the conventional glow-discharge driven IEC fusion device.

Simulations of electron backstreaming in a microwave thermionic gun

Abstract Electron trajectories in a 4 + 1 2 RF gun were calculated by a 2-D simulation code newly developed with full Maxwellian equations with space charge effects taken into account self-consistently to evaluate RF gun performance characteristics, in particular, the effects due to backstreaming electrons. The energy spectra, and current profile of the backstreaming electrons were calculated to show appreciable concentration to the limited area of the cathode, and also that the high energy backstreaming electrons are mainly originated in the 4th cavity of the RF gun.

Research and Development of the Humanitarian Landmine Detection System by a Compact Fusion Neutron Source

Results of 5 years task are described on the research and development of the advanced humanitarian landmine detection system by using a compact discharge-type fusion neutron source called IECF(inertial-electrostatic confinement fusion) device and dual sensors made of BGO and Nal. With 107 neutrons/s stably produced in CW mode, 10.8 MeV, gamma rays from (n, gamma) reaction with nitrogen atoms in the explosives (explosive simulant in our study) are measured for two kinds of explosives(TNT, RDX), under the conditions of three different buried depths, and soil moistures. Tentative detection probability for arid soil is found to be in excess of 80%.

Performance Characteristics of an Inertial Electrostatic Confinement Fusion Device with a Triple-Grid System

Abstract 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 in the triple-grid system shows higher value than the conventional single-grid system.

Application of a Hall Accelerator to Diamondlike Carbon Film Coatings

A Hall accelerator-type ion source for low-voltage continuous operation (hereafter called HALOC) without any exhaustible filaments, designed for film coating purposes, has successfully produced a large-area low-energy continuous beam of methane or oxygen. The thin film of carbon uniformly coated on a steel plate by the HALOC has been found to be a typical amorphous hard carbon film with high Vickers hardness, strong adhesion, and strong anticorrosion properties. The causes of strong adhesion of the film have been studied.

Evaluation of thermal effects due to back-streaming electrons in the IAE RF gun

Back-streaming electrons in thermionic RF guns give a serious thermal effect to a cathode. In this study, the back-streaming beam power onto a thermionic cathode of the IAE RF gun was evaluated quantitatively by using an infrared radiation thermometer. Time evolutions of cathode surface temperature during RF macro-pulse were also calculated by using a simple 1-dimensional heat conduction model and results of a 2-dimensional particle simulation for several methods expected to reduce back-bombardment effect.

Strongly Localized Potential Profile Measurements Through Stark Effects in the Central Core Region of an Inertial Electrostatic Fusion Device

Abstract Strongly localized electric fields were measured in the central cathode helium plasma core region of an inertial electrostatic confinement fusion device by using laser-induced fluorescence (LIF) by the degree of polarization and by the longitudinal alignment methods. Both results show double well potential formation with a slight concave at the center in excellent agreement. The decay time of the excited states is found to indicate least effects by the collisions to ensure the LIF method.

Development of an improved two-dimensional finite-element code for cylindrically symmetric eigenmodes

A new two-dimensional finite-element (FE) eigenmode solver has been developed, which is suitable for calculating cylindrically symmetric modes. The quantity H/sub /spl theta///r is used in the code to describe the electromagnetic fields instead of H/sub /spl theta// or rH/sub /spl theta//, which is preferentially used in the existing codes, and the new formulation with H/sub /spl theta///r is found to show higher accuracy and smoother convergence with respect to the number of mesh points. Comparison is also made between linear and quadratic elements, resulting in remarkably higher accuracy by the latter.

Direct energy recovery from helium ion beams by a beam direct converter with secondary electron suppressors

A 5-yr study of beam direct energy conversion was performed at the Kyoto University Institute of Atomic Energy to clarify the essential features of direct energy recovery from monoenergetic ion beams so that the performance characteristics of energy recovery can be predicted reasonably well by numerical calculations. The study used an improved version of an electrostatically electron-suppressed beam direct converter. Secondary electron suppressor grids were added, and a helium ion beam was used with typical parameters of 15.4 keV, 90 mA, and 100 ms. This paper presents a comparison of experimental results with numerical results by the two-dimensional Kyoto University Advanced Dart (KUAD) code, including evaluation of atomic processes.

Research and Development of Landmine Detection System by a Compact Fusion Neutron Source

Abstract Current results are described on the research and development of an advanced anti-personnel landmine detection system by using a compact discharge-type fusion neutron source called IECF (Inertial-Electrostatic Confinement Fusion). Landmines are to be identified through backscattering of neutrons, and specific-energy capture γ-rays by hydrogen and nitrogen atoms in the landmine explosives. For this purpose, improvements in the IECF were made by various methods to achieve a drastic enhancement of neutron yields of more than 108 n/s in pulsed operation. This required R&D on the power source, as well as analysis of envisaged detection systems with multi-sensors. The results suggest promising and practical features for humanitarian landmine detection, particularly, in Afghanistan.