Toyohisa Asaji

Production of multicharged ions in a 2.45 GHz electron cyclotron resonance source directly excited in a circular TE01 mode cavity resonator

In order to study the upgrading feasibility of the low frequency electron cyclotron resonance (ECR) plasma by using 2.45 GHz microwaves for multicharged ion sources, we have conducted various experiments in the TAIKO device (Toyama Pref. University). In this article the experimental study concentrates on the production of multicharged ions with respect to a microwave mode, especially, a circular TE01 mode, which is expected to enhance the efficiency of electron cyclotron resonance. The electric field of the circular TE01 mode has only a circumferential component in the same direction as electron cyclotron motion, perpendicular to the magnetic mirror field. We can assign the peak position of the electric field of the standing waves to the ECR zone in the cavity resonator, i.e., the vacuum chamber. We investigated the features of the plasma source in the cavity resonator of the circular TE01 mode microwave directly excited. We described the results of the simulation experimentally, and the design of the new...

Bio-Nano ECRIS: an electron cyclotron resonance ion source for new materials production.

We developed an electron cyclotron resonance ion source (ECRIS) for new materials production on nanoscale. Our main target is the endohedral fullerenes, which have potential in medical care, biotechnology, and nanotechnology. In particular, iron-encapsulated fullerene can be applied as a contrast material for magnetic resonance imaging or microwave heat therapy. Thus, our new ECRIS is named the Bio-Nano ECRIS. In this article, the recent progress of the development of the Bio-Nano ECRIS is reported: (i) iron ion beam production using induction heating oven and (ii) optimization of singly charged C(60) ion beam production.

11–13GHz electron cyclotron resonance plasma source using cylindrically comb-shaped magnetic-field configuration for broad ion-beam processing

An electron cyclotron resonance (ECR) plasma source for broad ion-beam processing has been upgraded by a cylindrically comb-shaped magnetic-field configuration and 11–13GHz frequency microwaves. A pair of comb-shaped magnets surrounds a large-bore discharge chamber. The magnetic field well confines plasmas with suppressing diffusion toward the axial direction of the cylindrical chamber. The magnetic field is constructed with a multipole and two quasiring permanent magnets. The plasma density clearly increases as compared with that in a simple multipole magnetic-field configuration. The frequency of microwaves output from the traveling-wave tube amplifier can be easily changed with an input signal source. The plasma density for 13GHz is higher than that for 11GHz. The maximum plasma density has reached approximately 1018m−3 at a microwave power of only 350W and a pressure of 1.0Pa. The enhancement of plasma generation by second-harmonic resonance and microwave modes has been investigated. The plasma densit...

Effects of fundamental and second harmonic electron cyclotron resonances on ECRISa)

A new concept on magnetic field of plasma production and confinement has been proposed to enhance efficiency of an electron cyclotron resonance (ECR) plasma for broad and dense ion beam source under the low pressure. The magnetic field configuration is constructed by a pair of comb-shaped magnet which has opposite polarity to each other, and which cylindrically surrounds the plasma chamber. This magnetic configuration suppresses the loss due to E x B drift, and then plasma confinement is enhanced. The profiles of the electron temperature and density are measured around the ECR zones of the fundamentals and the second harmonics for 2.45 GHz and 11-13 GHz microwaves by using Langmuir probe. Their characteristics and effects are clarified under various operating conditions in both of simple multipole and comb-shaped magnetic configurations.

Production of multicharged ions and behavior of microwave modes in an electron cyclotron resonance ion source directly excited in a circular cavity resonator

Electron cyclotron resonance ion sources (ECRIS) have been widely used for production of high-intensity multicharged ion beams. Making good use of microwave modes is proposed for enhancing the efficiency of ECR for production of multicharged ions (TAIKO II). We can assign the peak position of the electric field of the standing waves to the ECR zone in the directly excited cavity resonator, i.e., the vacuum chamber with the fixed and the mobile plates for selecting and tuning the modes. Periodicity of the extracted multicharged ion currents and plasma parameters is observed as the position of the mobile plate moves. We measure the intensity of the electric field in the ECR plasma by using the insulated semidipole probe and the standing waves are observed. The correlation between the production of multicharged ions and the microwave modes is clarified by measuring the electric field and plasma parameters in the circular cavity resonator.

Production of multicharged iron ions with inductively heated vapor source

Multiply charged Fe ions are produced from solid material in a 2.45GHz electron cyclotron resonance (ECR) ion source. We develop an evaporator by induction heating with an induction coil covered by ceramics in vacuum and surrounding the pure Fe rod with noncontact. The typical power and the frequency of the induction currents range from 300to800W and from 30to40kHz, respectively. The evaporator is inserted into the ECR plasma from the mirror endplate along the geometrical axis of the mirror field. Argon gas is usually chosen for supporting gas, and the working pressure is about 10−4–10−3Pa. The multicharged Fe ions are extracted from the opposite side of mirror and against the evaporator, and then multicharged Fe ion beam is formed. We compare the production of multicharged iron ions by using this source with our previous methods.

Low energy Fe+ beam irradiation to C60 thin film

We have developed an electron cyclotron resonance ion source apparatus, which is designed for the production of endohedral fullerene. In this study, we irradiated the Fe(+) beam to the C(60) thin film. We changed the experimental condition of the dose and the ion energy. We could observe the Fe + C(60) peak by analysis of the time-of-flight mass spectrometry. The highest intensity of the Fe + C(60) peak was observed at the ion energy of 200 eV. The Fe + C(60) peak intensity tended to become high in the case of long irradiation time and large dose.

Multicharged iron ions produced by using induction heating vapor source.

Multiply charged Fe ions are produced from solid pure material in an electron cyclotron resonance (ECR) ion source. We develop an evaporator by using induction heating with an induction coil which is made of bare molybdenum wire partially covered by ceramic beads in vacuum and surrounding and heating directly the pure Fe rod. Heated material has no contact with insulators, so that outgas is minimized. The evaporator is installed around the mirror end plate outside of the ECR plasma with its hole grazing the ECR zone. Helium or argon gas is usually chosen for supporting gas. The multicharged Fe ions up to Fe(13+) are extracted from the opposite side of mirror and against the evaporator, and then multicharged Fe ion beam is formed. We compare production of multicharged iron ions by using this new source with our previous methods.

An Electron Cyclotron Resonance Ion Source with Cylindrically Comb‐Shaped Magnetic Field Configuration

A new concept on magnetic field of plasma production and confinement has been proposed to enhance efficiency of an electron cyclotron resonance (ECR) plasma for broad and dense ion beam source under the low pressure. The magnetic field configuration is constructed by a pair of comb‐shaped magnet which has opposite polarity each other, and which cylindrically surrounds the plasma chamber. This magnetic configuration suppresses the loss due to ExB drift, and then plasma confinement is enhanced. The resonance zones of the fundamental and the second harmonics for 2.45GHz microwaves detach from the wall of the chamber. The connection length of the magnetic field lines through the resonance zone is elongated, and the confinement is better than that of the simple multipole magnetic field. The 2.45 GHz microwaves are fed from the side wall by the rod antenna. The electron density attained to about four times cutoff density for the 2.45GHz microwave at the low Ar pressure below 0.08Pa and also the low microwave power below 300W. We compare profiles of the electron density and temperature in the comb‐shaped magnetic field configuration with those in the simple multipole magnetic field.

Synthesis of Endohedral Fullerene Using ECR Ion Source

We are developing an ECRIS apparatus which is designed for the production of endohedral fullerenes. Our promising approaches to produce the endohedral fullerenes using the ECRIS are the ion‐ion collision reaction of fullerenes and the other atom in their mixture plasma and simple ion implantation of atom into fullerene layer. In this study, we tried to synthesize the endohedral nitrogen‐fullerenes by ion implantation. N+ beam was irradiated to a fullerene target with a specific energy and dose. As a result, we could observe the peak of N+C60 from targets after N+ beam irradiation with TOF‐SIMS and LDI‐TOF‐MS.