24P144P
Research on Compact Inertial Electrostatic Confinement Fusion Device
放電型プラズマ中性子源の小型化に関する研究
Hodaka Osawa, Yukari Nakajima, Yuta Nakagawa and Masami Ohnishi
大澤穂高, 中島由加里，中川裕太，大西正視
Kansai Univ. 3-3-35, Yamate-cho, Suita-shi, Osaka 564-8680, Japan
関西大学 〒564-8680 大阪府吹田市山手町3-3-35
Inertial Electrostatic Confinement Fusion (IECF) device is a neutron source which is portable, small andeasy-structured. IECF researchers have been studied to get more neutron production rate, using more
expensive and powerful power supply and larger vacuum chamber. The research of downsizing about IECF
device has not been studied. The discharge characteristic of minimized IECF device is investigated by theparticle simulations. As the results, compact IECF device can be operated with much cheaper power supply.
The parallel running of small IECF devices with one power supply probably make more neutrons.

Discharge Voltage (kV)

1. Introduction
The schematic view of the inertial electrostatic Deuterium Gas
confinement fusion device as a neutron source inKansai University is shown in Fig.1. It consists of AnodeAppearance
the cylindrical stainless steel vacuum chamber,the spherical mesh anode (300mm in diameter), Cathode(Mo 6-rings)
the hollow cathode of the molybdenum, thepower sources of DC and pulse, the gas feeding
system, and the pumps. The cathode made ofDC (or Pulse)
Discharge photocombined six rings to form a spherical shape is voltage supply
set in the center of the anode. The current (80kV, 50mA)
feed-through terminal made of stainless steel isconnected with the cathode. The set of a turbo
molecular pump and a rotary pump achieves theCathodegas pressure less than 10-3 Pa in the chamber. The
Fig.1. Sketch of Inertial Electrostatic
deuterium gas is supplied at the steady pressure
Confinement Fusion Deviceof 0.6 – 6.0 Pa in the chamber. The D.C. power
supply is used for stationary mode operation and
2. Characteristics of IECF device
applies up to the potential of 80 kV and theFigure 2 shows the experimental discharge
maximum current in 50 mA. The glow discharge
characteristics of IECF device which is comparing
occurs between the anode and the cathode, andthe diameters of mesh anodes (150mm and 300mm).
the deuterium ions and the electrons are produced.
It is difficult to discharge with smaller anode
The electrons move towards the anode and hit thebecause that there is not enough length and pass foranode surface. On the other hand, the ions are
the avalanche phenomenon.
accelerated to the cathode. Some of them collidewith the cathode and lost, but most of them gothrough the cathode and traverse through thecathode many times. During the round-trips, theФ150mmions sometimes get the high velocity from thepotential energy and make nuclear fusions withthe other ions or the background molecules. As
Ф300mmthe result of the deuterium- deuterium fusion, theneutrons come out through the chamber. The
neutrons production rate measured by 3He counteris 107-108 (1/sec).
Gas pressure (Pa)Fig.2. Experimental discharge characteristics of
150mm anode and 300mm anode (Ic=40mA)

Фc70mmDischarge Voltage (kV)

Neutron production rate(1/sec)

Figure 3 shows the neutron production rate v.s.
applied voltage characteristics with two different
diameters of anodes at 40mA of discharge current.
Although there is some difference on the discharge
characteristics, almost same neutron production rate
is obtained. This is very important characteristicthat the operation of the same discharge current
produces almost same neutrons.

Фc7mm

Фa15mm
Фa30mmФa400mmФa300mmФa200mm

Фa150mm

Ф300mm

Ф150mmApplied voltage (kV)Fig.3. Experimental data of neutron production rate
v.s. applied voltage with 150mm anode and 300mm
anode (Ic=40mA)

3. Simulation model
The three-dimensional Monte Carlo particle incell code [1] including the atomic processes is used
for investigation of the discharge. The full three
dimensional potential are calculated containing thepotential effect of the feed-through and the spatial
structure of the cathode. The finite difference
method with the 1 mm spatial mesh is used for thecalculation. Deuterium ions (D+, D2+, D3+), fastneutrals (D0, D20) and electrons (e-) are taken as
tracking particles. The initially 1000 particles ofeach kind of ion species and 3000 electrons aredistributed uniformly between the space of theanode and the cathode. The trajectory of eachparticle is followed by the Runge-Kutta method.
The time step is 10 -12 sec. After pushing eachparticle, the atomic and molecular collisions and theelastic collisions are taken into account by Monte
Carlo method. When the total number of ionsbecomes more than 60000, it is recognized that‘discharge’ is occurred in this discharge simulation.
4. Simulation Results
Figure 4 shows the calculation results ondischarge characteristics compare of device’s anode
diameters. The anode diameters of 400mm, 300mm,200mm and 150mm is calculated with the large
cathode (70mm in diameter). The anode diameter of
30mm and 15mm with small cathode (7mm indiameter) is used in this particle simulation.

Gas pressure (Pa)Fig.4. the calculated comparison discharge characteristics
of different size of electrodes (400mm, 300mm,200mmand 150mm anodes with 70mm cathode, 30mm and15mm anodes with 7mm cathode)

These simulation results of discharge characteristics
mean that the operation with smaller anode needs
more gas pressure, that the 60kV will be appliedeven in using 15mm anode’s device.
4. Conclusions
IECF device is a neutron source with simple
structure. The neutron production rate is almost
same at same discharge current. The particle
simulation shows that the 60kV of discharge
probably applied with small 15mm anode.
IECF researchers have been studied for moreneutron production rate, using more expensive andpowerful power supply (e.g.100kV, 100mA) andlarger vacuum chamber (e.g. 600mm anode indiameter). Some researchers are thinking that thebeam- beam fusion will occur in low gas pressure.
Those attempts’ neutron production rates are notmuch the price of expensive power supplies andequipments.
Smaller IECF device does not need the expensive
equipments. It is easy to make the set up of theparallel running of 2 or more small IECF devices.
The series connection of the IECF devices with onepower supply is possible. It is obvious that 2 IECF
devices produce 2 times of neutrons. The stabilityof the discharge with smaller anode should be
investigated in detail.
References[1] H. Osawa, T. Tabata, M. Ohnishi: Fusion Sci.
Technol.47(2005) p.1270-1273[2] H. Osawa, T. Ishibashi, M. Ohnishi, K. Yoshikawa :Fusion Sci. Technol.47(2005) p. 1265-1269[3] K. Kamakura, Y. Ishikura, K. Fukuta, N. Yamashita,H. Osawa, M. Ohnishi: 24P145P[4] T. Yoshida, T. Kajiwara, K. Takaoka, K. Kamakura,
H. Osawa, K. Masuda, M. Ohnishi: 24P146P