Akira Tonegawa

Misting-free diamond surface created by sheet electron beam irradiation

We developed a diamond surface that does not mist near the room temperature under a saturated humidity atmosphere, by sheet electron beam irradiation (SEBI) treatment. SEBI treatment decreased the time to clear vision of the diamond surface. Following SEBI treatment for 1.91 s (= 0.72 MGy) to a diamond surface, the time to clear vision was less than 2 s. The effective duration time was a few hours. Based on the results of the size distribution of the drops on the misting-free diamond surface following blowing for 3 s, we proposed an explanation for the short time to clear vision of the diamond surface treated by SEBI.

Effects of electron beam irradiation on time to clear vision of misted dental mirror glass

A misting free dental mirror is obtained near the human temperature under the saturated humidity atmosphere by use of the sheet electron beam irradiation treatment. It is shown that electron beam irradiation treatment decreases the time to clear vision in a misted mirror. This effect is due to an enhancement of the interfacial energy between the dental mirror glass and water.

High fracture resistance of carbon fiber treated by electron beam irradiation

A crack reduction by electron beam (EB) irradiation treatment for carbon fiber, used without the traditional method of accompanying heat, was developed to modify the mechanical properties at lower temperature. The EB treatment improved the resistance to fracture. Namely, the maximum ratio of fractured samples ( max R f ) and the minimum bending strain on fracture ( min e f ) were defined as simple indicators of fracture resistance and became smaller by the EB treatment. Furthermore, a critical density of dangling bonds for a fracture was suggested and determined for carbon fiber treated by EB irradiation. The EB irradiation to reduce cracking and the determination of the critical density of dangling bonds are new concepts that can be broadly applied in the fields of aerospace and rapid-transit production engineering.

Effects of EB irradiation on spring constant of C/C composite coil

In order to enhance a spring constant of C/C composite coil spring, the electron beam irradiation was homogeneously performed. The EB irradiation largely enhanced initial spring constants, which were higher than that before EB irradiation. The constant spring constant was also obtained by 150 Mrad-irradiation for the C/C composite coil spring.

Effects of sheet electron beam irradiation on aircraft design stress of carbon fiber

Using sheet electron beam (EB) irradiation, reinforcement for carbon fiber was achieved. In order to annihilate twisting strain in carbon fiber, the fracture stress was precisely obtained by means of a twisting free tensile test developed. The EB treatment enhanced the fracture stress at different integrated fracture rates (Rf) and increased Weibull modulus. It also enhanced design stress, when the integrated fracture probability (Pf) is 10−5 for aircraft materials. The aircraft design stress (5 GPa) was approximately 4 GPa larger than that (1 GPa) before EB treatment.

Effect of electron-beam irradiation on water wettability of hydroxy apatites for artificial bone

The influence of electron-beam irradiation on the wettability of hydroxy apatites (HAP) has been investigated. The wettability was evaluated from the interfacial energy between HAP and water. It was measured by the contact angle of distilled water on HAP. Electron-beam irradiation increases the wettability. Based on the rate process, the influence of electron-beam irradiation on wettability is discussed. Using electron-beam irradiation, we can precisely control the surface condition of HAP.

Observation of molecular assisted recombination via negative ions formation in a divertor plasma simulator, TPDSHEET-IV

Abstract Molecular assisted recombination (MAR) via negative ions formation has been observed in a linear plasma simulator. A small amount of hydrogen gas puffed into a hydrogen plasma strongly reduced the heat flux to the target and rapidly increased the density of negative ions of hydrogen atom, n H − , in the circumference of the plasma, while the conventional radiative and three-body recombination processes disappeared. n H − is localized in the outer region where electrons exist ( n e ∼5×10 17 m −3 , T e =3–5 eV). The peak value of n H − is 1.2×10 17 m −3 and the ratio of n H − / n e in the outer region goes up to over 20%. These results can be well explained by taking the mutual neutralization between the negative and positive ions of MAR in the detached plasma into account.

Plasma filament ion source

Abstract This paper reports the use of a plasma filament instead of a heated solid filament in the Freeman ion source to make a new ion source which has a very long lifetime and especially enables the steady supply of a high intensity oxygen ion beam. The plasma filament is a highly ionized and high density plasma ( n e >10 13 cm −3 ), and composed of ions, high temperature electrons ( T e =3–9 eV ) and metastable atoms. It has been recognized that the O + ion beams are obtained using an argon or a neon plasma filament. The lifetime of this ion source is longer than that of the Freeman ion source.

Plasma compression type hollow cathode ion source

Abstract In general, a hollow cathode ion source (HCIS) for implantation industries has the fatal demerit of low gas efficiency. This paper reports that this disadvantage of HCIS is solved by inserting insulated narrow slits between the anode and the cathode in order to compress the cross section of the discharge path. As a result, the large pressure differences between outer and inner regions of the ion source can be held and the gas efficiency is increased.

Influences of Electron Beam Irradaiton on Misting and Related Surface Condition on Sapphire Lens

In order to explain the misting-free treatment by sheet electron beam irradiation (SEBI) for sapphire lens setting on endoscope top, influences of SEBI on surface energy are investigated. The SEBI increases surface energy, resulting in force-distance curve used for atomic force microscope. Based on the results of X-ray photoelectron spectroscopy, the SEBI enhances the bonding rates of -C-O- and -C-O-O- and decreases -C-C- bonding rate. On the other hand, influences of SEBI on surface water wettability are investigated. The SEBI enhances the wettability of the sapphire surface for water, n-hexadecan, and 1-bromonaphthalene. Since the adhesion molecular change coincides with the surface energy change, the dipole of adhesion molecular is the dominant factor to control the surface energy. In order to explain to the dipole factor change, the electron charge is measured, too. From the results, the surface energy change can be explained by the adhesion molecular change and electron charging.