Hiroshi Mase

Capacity-coupled multidischarge for atmospheric plasma production

We propose a method of plasma production by capacity-coupled multidischarge (CCMD) at atmospheric pressure. The discharge gaps in the CCMD consist of a common electrode and a number of compact electrodes (CCE) which are directly coupled with small capacitors for quenching the discharge. A simple CCE structure is provided by a cylindrical capacitor, the inner conductor of which is used as a gap electrode. A short pulse discharge is observed to appear homogeneously at each CCE. A charge transfer for the single-pulsed discharge is 10–100 times as large as that of the conventional dielectric barrier discharge. A high efficiency of ozone production has been confirmed in the CCMD using O2 gas. A device configuration of the CCMD is quite flexible with respect to its geometrical shape and size. The CCMD could be used to produce plasmas for various kinds of industrial applications at atmospheric pressure.

Sheath formation and ion flux distribution inside the trench in plasma-based ion implantation

Abstract Geometrical effects of a three-dimensional workpiece on the plasma-based ion implantation have been studied using trench-shape and L-shape workpieces. Temporal and spatial evolution of the sheath and the ion flux on the workpiece are measured for a negative voltage pulse of −1.8 to −7.0 kV, 40 μs: (1) The trench is occupied by the ion sheath quickly due to the sheath overlapping from both side walls; this effect is not seen in the L-shape workpiece with only one side wall. (2) Electrons are detected inside the trench even after the ion sheath fills the trench, which is attributed to secondary electrons emitted from the surface of the workpiece by ion impact and trapped electrostatically between the side walls. (3) The ion flux incident upon the inner surface of the trench is strongly enhanced because trapped secondary electrons ionize the filling gas as in the hollow-cathode discharge. The enhanced ionization is therefore not seen in L-shape and planar workpieces.

Capacity-coupled multidischarge at atmospheric pressure

A new method of plasma production at atmospheric pressure, capacity-coupled multidischarge (CCMD), is proposed. The discharge gaps in the CCMD consist of a common electrode and a number of compact electrodes (CCE) which are directly coupled with small capacitors for quenching the discharge. A simple CCE structure is provided by a cylindrical capacitor, the inner conductor of which is used as a gap electrode. A short pulse discharge is observed to appear homogeneously at each CCE. A charge transfer for the single pulsed discharge is 10-100 times as large as that of the conventional dielectric barrier discharge. In the CCMD using O/sub 2/ gas, a high efficiency of ozone production has been obtained. A device configuration of the CCMD is quite flexible with respect to its geometrical shape and size. The CCMD could be used to produce plasmas for various kinds of industrial applications at atmospheric pressure.

Performance of the undulator for JAERI FEL project

Abstract A newly designed hybrid undulator (DFTH-1), whose field termination parts are a novel implementation of the displacement-free termination scheme, has been constructed for the JAERI FEL project. The field termination part of the undulator was designed to minimize the electron trajectory walkoff by using the 3D magnetic field computational code named ELF/Magic. The DFTH-1 undulator could reduce the walkoff by one third of that of the conventional hybrid undulator with non-steering termination.

Positive pulse bias method in plasma-based ion implantation

A novel scheme of the plasma-based ion implantation (PBII), the positive pulse bias (PPB) method has been proposed, in which a workpiece to be treated is at the ground potential while the plasma surrounding it is biased to a positive high voltage; thus the ion sheath same as the one in the conventional negative pulse bias (NPB) method is formed on the workpiece. Principal merit of the PPB method over the NPB method is that it possesses a mechanism of suppressing X-rays from the wall by impact of secondary electrons and it enables to manipulate the workpiece during PBII processing. The latter merit will serve to realize an efficient continuous processing system. The principle of the PPB method is discussed based on the asymmetric double probe theory and results of the proof-of-principle experiment are presented.

Si-Fullerene Compounds Produced by Controlling Spatial Structure of an Arc-Discharge Plasma.

Silicon-fullerene compounds are produced in a modified fullerene generator, where a direct-current (DC) or a radio-frequency (RF) discharge is superimposed in the periphery region of an arc-discharge plasma. The soot mass analysis gives spectrum peaks corresponding to silicon-endohedral fullerenes Si@Cn (n=74, 86, etc.). The soot structure analyses with X-ray diffraction (XRD) and high-resolution electron microscopy (HREM) demonstrate that there exist nanoparticles with the fullerene size, which are considered to be Si@Cn, and carbon nanocapsules filled with SiC.

Gap structure multilayer piezoelectric actuator

A new multilayer piezoelectric actuator (MPA), in which gaps were formed at the ends of the internal electrodes, was manufactured by a cofiring method. Its high endurance has been confirmed both by a 500-million-pulse driving test and by 120 VDC voltage-applying life test for 500 hours under high humidity. Large displacement was achieved in a wide temperature range up to 135°C by using newly developed piezoelectric ceramics.

Control of Ion Energy for Low-Damage Plasma Processing in RF Discharge

A new control technique for ion energy is based on the external electron injection into the capacitively coupled rf plasma using an auxiliary plasma source. The externally injected electrons replace the plasma electrons carrying the rf current and then reconstruct the rf sheath in which ions are accelerated. The experiment is carried out by using a parallel-plate rf plasma device with a magnetron discharge plasma source mounted behind the mesh grounded electrode. The experimental results show that the energies of ions are continuously controlled by varying the amount of injected electrons in a wide range from ≃(1 /2)eV rf to ≃T e ; and this result agrees with that derived from our simple model.

Scaling Relations for the Production and Acceleration of a J × B Driven Rotating Plasma

The density and velocities (rotational and axial) of a rotating plasma driven by the J ×B Lorentz force and their parametric dependence on radial current I and axial magnetic field Bz are investigated in ranges of 3–11 kA and 0–3.6 kG, respectively. Results are compared with those from a simplified single-fluid model that describes the motion of an incompressible plasma with uniform density under the existence of ion production by electron-impact ionization and ion loss by convection to electrodes. In the experiment, argon plasmas are produced by the pulsed discharge (28 µs) of a coaxial plasma gun and are accelerated in both the azimuthal and axial directions by J ×Bz and J ×Bθ forces, respectively, where Bθ is induced by I. Typical values of the plasma density n, the rotational frequency ω and the axial velocity vz are ~1021 m-3, 1 ×106 rad/s and 2 ×104 m/s, respectively, at I=9 kA and Bz=3.6 kG. Scaling laws derived from the experiment: n ∝I2Bz0, ω∝I1Bz1n-1 and vz ∝I2Bz0n-1, are found to agree well with predictions of the model. As a result, plasma production and acceleration are found to be strongly related to each other.

A novel laser technique for constructing a plasma micro-undulator and a compact X-ray source

Abstract A plasma micro-undulator has been previously proposed for a compact, short-wavelength free electron laser in which a relativistic electron beam is forced to oscillate transversely in the near-sinusoidal electric field of the rippled ion-space-charge. This paper proposes a new scheme to create a plasma density ripple for the plasma micro-undulator: the laser-interference, resonance-ionization-scheme, where the pitch and density of ripple can be controlled independently by adjustment of the wavelength, intersection angle and intensity of two laser beams. A preliminary design of an undulator with a pitch of 10–100 μm, a number of pitches of 100–1000 and an undulator constant of 0.1–1.0 is discussed and concluded to be attainable by present-day technology.