Sho Kumakura

New tandem type ion source based on electron cyclotron resonance for universal source of synthesized ion beams.

A new tandem type source has been constructed on the basis of electron cyclotron resonance (ECR) plasma for producing synthesized ion beams. We investigate feasibility and hope to realize the device which has wide range operation window in a single device to produce many kinds of ion beams based on ECR ion source (ECRIS). It is considered that ECR plasmas are necessary to be available to individual operations with different plasma parameters. Both of analysis of ion beams and investigation of plasma parameters are conducted on produced plasmas. We describe construction of the new tandem type ion source based on ECRIS with wide operation window for aiming at producing synthesized ion beams as this new source can be a universal source.

Electron energy distribution function by using probe method in electron cyclotron resonance multicharged ion source.

We are constructing a tandem type electron cyclotron resonance (ECR) ion source (ECRIS). High-energy electrons in ECRIS plasma affect electron energy distribution and generate multicharged ion. In this study, we measure electron energy distribution function (EEDF) of low energy region (≦100 eV) in ECRIS plasma at extremely low pressures (10(-3)-10(-5) Pa) by using cylindrical Langmuir probe. From the result, it is found that the EEDF correlates with the electron density and the temperature from the conventional probe analysis. In addition, we confirm that the tail of EEDF spreads to high energy region as the pressure rises and that there are electrons with high energy in ECR multicharged ion source plasma. The effective temperature estimated from the experimentally obtained EEDF is larger than the electron temperature obtained from the conventional method.

Controlling precise magnetic field configuration around electron cyclotron resonance zone for enhancing plasma parameters and beam current.

Multi-charged ion source which has wide operating conditions is required in various application fields. We have constructed tandem type ECR ion source (ECRIS); one of the features of its main stage is an additional coil for controlling magnetic field distribution around the mirror bottom precisely. Here the effect of magnetic field variation caused by the additional coil is experimentally considered in terms of plasma parameters and beam current as the first investigation of the main stage plasma. Furthermore, behavior of magnetic lines of force flowing from the ECR zone is calculated, and is compared with measurement results aiming for better understanding of interrelationship between plasma production and ion beam generation on the ECRIS.

Formation of multi-charged ion beams by focusing effect of mid-electrode on electron cyclotron resonance ion source

We are constructing a tandem type electron cyclotron resonance ion source (ECRIS) and a beam line for extracting ion beams. The ion beam is extracted from the second stage by an accel-decel extraction system with a single-hole and the ion beam current on each electrode is measured. The total ion beam current is measured by a faraday cup downstream the extraction electrodes. We measure these currents as a function of the mid-electrode potential. We also change the gap length between electrodes and perform similar measurement. The behaviors of these currents obtained experimentally against the mid-electrode potential show qualitatively good agreement with a simple theoretical consideration including sheath potential effects. The effect of mid-electrode potential is very useful for decreasing the beam loss for enhancing ion beam current extracted from ECRIS.

Enhanced production of electron cyclotron resonance plasma by exciting selective microwave mode on a large-bore electron cyclotron resonance ion source with permanent magnet.

We are constructing a tandem type ECRIS. The first stage is large-bore with cylindrically comb-shaped magnet. We optimize the ion beam current and ion saturation current by a mobile plate tuner. They change by the position of the plate tuner for 2.45 GHz, 11-13 GHz, and multi-frequencies. The peak positions of them are close to the position where the microwave mode forms standing wave between the plate tuner and the extractor. The absorbed powers are estimated for each mode. We show a new guiding principle, which the number of efficient microwave mode should be selected to fit to that of multipole of the comb-shaped magnets. We obtained the excitation of the selective modes using new mobile plate tuner to enhance ECR efficiency.

Accessibility condition of wave propagation and multicharged ion production in electron cyclotron resonance ion source plasma

A new tandem type source of electron cyclotron resonance (ECR) plasmas has been constructing for producing synthesized ion beams in Osaka University. Magnetic mirror field configuration with octupole magnets can be controlled to various shape of ECR zones, namely, in the 2nd stage plasma to be available by a pair mirror and a supplemental coil. Noteworthy correlations between these magnetic configurations and production of multicharged ions are investigated in detail, as well as their optimum conditions. We have been considering accessibility condition of electromagnetic and electrostatic waves propagating in ECR ion source plasma, and then investigated their correspondence relationships with production of multicharged ions. It has been clarified that there exits efficient configuration of ECR zones for producing multicharged ion beams experimentally, and then has been suggested from detail accessibility conditions on the ECR plasma that new resonance, i.e., upper hybrid resonance, must have occurred.

Plasma potential measurement on ECRIS by using extracted ion beam

With the miniaturization of semiconductors, the technology of shallow junctions becomes important. As shallow junctions advance, ion implantation by using ion beams at low energy with good control is needed. An electron cyclotron resonance ion source (ECRIS) can efficiently generate a high-density plasma at low pressure and a high intensity ion beam. In our ECRIS, the wide operation of various ion beam is available from deeper implantation of multi-charged ions at high energy to shallow junction at very low energy. However, a potential and a sheath near the wall are formed with an ECR plasma, because ECRIS is a volume source. Therefore, the potential affects the control of the ion beam at very low energy. In this study, we measure the potential by using the ion beam extracted from the ECRIS. In addition, we confirm that the potential by using the ion beam method correlates with electron temperature when microwave power and pressure change in ECRIS.

First operation and effect of a new tandem-type ion source based on electron cyclotron resonance

A new tandem type source has been constructed on the basis of electron cyclotron resonance plasma for producing synthesized ion beams in Osaka University. Magnetic field in the first stage consists of all permanent magnets, i.e., cylindrically comb shaped one, and that of the second stage consists of a pair of mirror coil, a supplemental coil and the octupole magnets. Both stage plasmas can be individually operated, and produced ions in which is energy controlled by large bore extractor also can be transported from the first to the second stage. We investigate the basic operation and effects of the tandem type electron cyclotron resonance ion source (ECRIS). Analysis of ion beams and investigation of plasma parameters are conducted on produced plasmas in dual plasmas operation as well as each single operation. We describe construction and initial experimental results of the new tandem type ion source based on ECRIS with wide operation window for aiming at producing synthesized ion beams as this new source can be a universal source in future.

Effect of mid-electrode potential on multi-charged ion beam extracted from electron cyclotron resonance ion source

We are constructing a tandem type electron cyclotron resonance ion source (ECRIS) and a beam line for extracting, analyzing ion beams, and their applications. The ion beam is extracted from the second stage by an accel-decel extraction system with single-holes and the ion beam current on each electrode is measured. The total ion beam current is measured by a faraday cup installed at downstream from the extraction electrodes. The ion beam current of each charge state is measured by the faraday cup beyond the sector magnet. The most of the total ion beam is consisted of mainly Ar+ ~ 4+ and we can measure up to Ar9+. We measure the total ion beam current and the currents of each charge state as a function of the mid-electrode potential. It is found that the ion current of each charge state depends on the same manner to the mid-electrode potential as similar to the total ion beam currents. The results obtained experimentally against the mid-electrode potential show qualitatively good agreement with a simple theoretical consideration including sheath potential effects for formation of ion beams. The beam loss is estimated by comparing the total ion beam currents with the sum of the currents after mass/charge analysis. The effect of mid-electrode potential is very useful for decreasing the beam loss and then optimizing beam transport for enhancing ion beam current extracted from tandem type ECRIS with many ion sources.

Improved ion production and extraction on tandem type ECRIS with low magnetic mirror field

A tandem-type electron cyclotron resonance (ECR) ion source (ECRIS) has been constructed for synthesizing, extracting, and analyzing ions. The feasibility and realization of the device which has rangy operation window in a single device are investigated to produce many kinds of ion beams like universal source based on ECRIS. The ECR plasmas are considered to be necessary to be available to coexist and to be operated individually with different plasma parameters. Both of analysis of ion beams and investigation of plasma parameters will be conducted on produced plasmas. In this article the experimental study concentrates on improvement of producing and extracting multicharged ion beams from the second stage of the tandem-type ECRIS under lower magnetic mirror field with octupole magnets. The assembly of the extractor is modified and their positions, gap, and potentials are investigated against each ion spices. We succeeded in producing, extracting multicharged ion currents and improving ion extraction, while the magnetic field is about 60% of the previous magnetic field strength. We will present obtained evidences experimentally in detail.