Hodaka Osawa

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%.

Particle-in-Cell Simulation of Inertial Electrostatic Confinement Fusion Plasma

Abstract A particle-in-cell calculation code was made to simulate the operation of an inertial electrostatic confinement (IEC) fusion device. The computation includes the effects of ionization by electron impact. Several techniques to save computational time are introduced in this program code. One of them is time-dependent fine space meshes used in the regions where the particles concentrate. Several superparticles that have similar radial position as well as similar energy are merged, while one superparticle is divided into several particles with a somewhat different velocity when the total number of superparticles decreases. The methods enable more precise determination of the characteristics of an IEC device in a shorter time than by previous methods.

Shape of Electrodes for High Performance of Inertial Electrostatic Confinement Fusion

Inertial electrostatic confinement (IEC) fusion is a scheme of producing deuterium, tritium, and helium-3 ions between the anode and the hollow cathode in the concentric sphere by glow discharge, accelerating the ions into the spherical center and giving rise to the fusion reactions between the accelerated ions or between the accelerated ions and the background neutrals. The current feed-through is connected to the cathode through the anode in order to apply the negative high potential. Some of accelerated ions directly bombard the feed-through as well as the cathode, and the ions, the orbits of which are deformed by lack of symmetry, hit the cathode after several bounce motions through it. The existence of the feed-through breaks the spherical symmetry of the device and shortens the lifetime of the accelerated ions. The hollow cathode also distorts a spherical potential near it. First, the effects of the structure of the spherical hollow cathode on the life are studied at various birth positions of the ions by numerically tracking the trajectory of ions in three dimensional spaces. Second, the effects of the shapes of the cathode and the anode on the life are investigated. The shapes of the cathode and the anode that assure a longer life are examined, and the virtual transparency of the cathode is numerically derived from the time dependent reduction of ions. It is revealed that the lifetime of accelerated ions becomes three times longer by deforming a hemisphere of the anode pierced by the feed-through into a hemi-ellipsoid. The results are useful in designing an anode and cathode to achieve high performance of an IEC fusion neutron source.

Numerical Study on Glow Discharge of IEC Fusion

Abstract An inertial electrostatic confinement (IEC) fusion device is possibly used for the neutron source that has the ability to produce the neutrons of 105-108/s by the glow discharge. It works more efficiently at the condition of the high voltage and the low pressure. It, however, is difficult to keep the continuous operation at the low-pressure because the glow discharge is apt to be unstable. We have made the three-dimensional Monte Carlo PIC code including atomic processes to investigate the glow discharge. The study reveals the spatial position where the ionization occurs and numerically reproduces the discharge called ’star mode’.

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.

Research and Development on Humanitarian Landmine Detection System by Use of a Compact D-D Fusion Neutron Source

Abstract Current results 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) devices. With a 50 mm-thick water-jacketed IEC device (IEC20C) of 200 mm inner diameter can have produced 107 neutrons/s stably in CW mode for 80 kV and 80 mA. Ample 10.8 MeV σ-rays produced through (n,σ) reaction with nitrogen atoms in the melamine (C3H6N6) powder (explosive simulant) are clearly measured by a BGO-NaI-combined scintillation sensor with distinct difference in case of with/without melamine, indicating identification of the buried landmines feasible.

Optimal Position of Ion Source for High Performance of IEC

Abstract An inertial electrostatic confinement (IEC) fusion device is possibly used for portable neutron sources. R. L. Hirsh reported that D-D the neutrons of 1.8 × 108 n/s were produced. Recently, the similar amounts of fusion reactions are observed to occur in IEC devices In the most of IEC devices, since gas pressure is so high that the ions lose their energy by the frequent collisions with the neutral gas. The conditions of the high voltage and the low pressure are preferable because the energy of beam ions is kept very high and used for the fusion reaction more efficiently. It, however, is difficult to produce enough amounts of ions through a glow discharge at the low pressure. One of the solutions is to equip the ion source such as a magnetron near the anode. We have made three-dimensional orbit following code to evaluate the life of the ions produced near the anode surface. The code includes atomic collisions with background neutral gas and indicates the optimal positions to equip ion source which gives longer life of accelerated ions.

Directional Detection of Nitrogen and Hydrogen in Explosives by Use of a DD-Fusion-Driven Thermal Neutron Source

Results of 5-year task are described on the research and development of the advanced explosive detection system by using a compact discharge-type fusion neutron source called Inertial-Electrostatic Confinement fusion (IECF) device and directional γ-ray detectors made of BGO and NaI. With >107 neutrons/s stably produced in CW operation, 10.8 and 2.22 MeV γ-rays from neutron-capture reactions with nitrogen and hydrogen atoms in explosives (TNT, RDX) are detected well, showing promising features for bulk explosive detections.

Research and development of the humanitarian landmine detection system by a compact fusion neutron source

A 5 year task is 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 3 dual sensors made of BGO and NaI. With 107 D-D neutrons/s stably produced in steady-state mode, H-2.2 MeV, N-5.3, 10.8 MeV, gamma rays from (n, gamma) reaction with nitrogen atoms in the explosives are measured for two kinds of explosives (TNT, RDX), under the conditions of three different buried depths, and soil moistures. Final detection probabilities for arid soil are found to be 100 % in the present tests, i.e., depths not exceeding 15 cm, moisture content of 18.5 % or less, and 20-minute measurements. The neutron backscattering method is found also excellent.

Development of a High-performance Landmine Detection System Through Gamma-ray Detection by Using a Compact Fusion Neutron Source and Dual-sensors

An anti-personnel landmine detection system using an inertial-electrostatic confinement fusion (IECF) neutron source and dual sensors showed excellent performance, particularly, for humanitarian landmine detection. Averaged probability of detection (POD) in this test was found to be 100% for arid soil, and 99% for other conditions including very wet soil moisture of 18.5wt%. Further improvements in reliability by making use of neutron backscattering are found to be efficient.