Publications by authors named "Fuminobu Sato"

31 Publications

Development of epi-thermal neutron beam intensity detector with Ga(n,γ)Ga reaction for boron neutron capture therapy.

Appl Radiat Isot 2019 Sep 23;151:145-149. Epub 2019 May 23.

Division of Sustainable Energy and Environmental Engineering, Graduate School of Engineering, Osaka University, Japan.

Based on the activation method using Ga(n,γ)Ga reaction, a cubic neutron flux intensity detector for epi-thermal neutrons was designed for boron neutron capture therapy (BNCT), and experimentally tested with a prototype detector in a neutron field produced at OKTAVIAN facility of Osaka University, Japan. The experimental test results and related analysis indicated that the performance of the detector was confirmed to be acceptable in the neutron field of BNCT. Practically, the neutron flux intensity mainly covering from 0.5 eV to 10 keV can be measured within 3% by the present detector.
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http://dx.doi.org/10.1016/j.apradiso.2019.05.005DOI Listing
September 2019

DESIGN IMPROVEMENT OF A LIQUID-MODERATOR-BASED NEUTRON SPECTROMETER FOR BNCT.

Radiat Prot Dosimetry 2018 Aug;180(1-4):300-303

Graduate School of Engineering, Osaka University, Yamada-oka, Suita, Osaka, Japan.

Boron neutron capture therapy is known to be an effective radiation cancer therapy that requires neutron irradiation. A neutron field generated by an accelerator-based neutron source has various energy spectra, and it is necessary to evaluate the neutron spectrum in the treatment field. However, the method used to measure the neutron spectrum in the treatment field is not well established. Many researchers are making efforts to improve the spectrometers. To solve this problem, we are developing a liquid-moderator-based neutron spectrometer that is based on the same theory as that of the Bonner sphere spectrometer. The spectrometer uses a liquid moderator and absorber. In the present study, we performed a design study to improve the previously developed liquid-moderator-based neutron spectrometer. By carrying out a numerical simulation of the designed new spectrometer, we finally assessed and confirmed the validity of this spectrometer numerically.
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http://dx.doi.org/10.1093/rpd/ncx237DOI Listing
August 2018

DEVELOPMENT OF ISOTOPICALLY ENRICHED BORON-DOPED ALUMINA DOSIMETER FOR THERMAL NEUTRONS.

Radiat Prot Dosimetry 2017 Dec;177(4):475-480

Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.

A novel optically stimulated luminescence (OSL) detector containing isotopically enriched boron was developed for thermal neutron dosimetry. Alumina containing isotopically enriched boron (Al2O3:B) was synthesised by the sol-gel method. The Al2O3:B was annealed up to ~1800 K. For X-ray diffractometer (XRD) analysis, the diffraction pattern of the Al2O3:B had reflex peaks corresponding to α-Al2O3. The sensitivity of Al2O3:B to photons was slightly 2% of that of a commercial Al2O3:C. The Al2O3:B detector had satisfactory linearity in X-ray dose measurement. A thermal neutron field was constructed using a 241Am-Be neutron source and graphite blocks. A pair of Al2O3:10B and Al2O3:11B detectors were set in the thermal neutron field. The response of Al2O3:10B was larger than that of Al2O3:11B owing to the 10B(n,α)7Li reactions. The sensitivity of Al2O3:10B to thermal neutrons was estimated to be two orders less than the photon sensitivity. Therefore, the pair of Al2O3:10B and Al2O3:11B detectors were useful for thermal neutron dosimetry.
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http://dx.doi.org/10.1093/rpd/ncx066DOI Listing
December 2017

Performance testing of the neutron flux monitors from 10keV to 1MeV developed for BNCT: A preliminary study.

Appl Radiat Isot 2017 Jul 12;125:119-123. Epub 2017 Apr 12.

School of Nuclear Science and Technology, Lanzhou University, Tianshui South Road 222, Lanzhou, Gansu Province 730000, PR China.

The neutron flux monitors from 10keV to 1MeV designed for boron neutron capture therapy (BNCT) were experimentally tested with prototype monitors in an appropriate neutron field produced at the intense deuterium-tritium neutron source facility OKTAVIAN of Osaka University, Japan. The experimental test results and related analysis indicated that the performance of the monitors was good and the neutron fluxes from 10keV to 1MeV of practical BNCT neutron sources can be measured within 10% by the monitors.
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http://dx.doi.org/10.1016/j.apradiso.2017.04.014DOI Listing
July 2017

Experimental study on the performance of an epithermal neutron flux monitor for BNCT.

Appl Radiat Isot 2016 07 8;113:28-32. Epub 2016 Apr 8.

School of Nuclear Science and Technology, Lanzhou University, Tianshui South Road 222, Lanzhou, Gansu Province 730000, PR China.

The performance of an epithermal neutron (0.5eV
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http://dx.doi.org/10.1016/j.apradiso.2016.04.003DOI Listing
July 2016

Producing multicharged fullerene ion beam extracted from the second stage of tandem-type ECRIS.

Rev Sci Instrum 2016 Feb;87(2):02A723

Graduate School of Interdisciplinary New Science, Toyo University, 2100, Kujirai, Kawagoe-shi, Saitama 350-8585, Japan.

We have been constructing the tandem-type electron cyclotron resonance ion source (ECRIS). Two ion sources of the tandem-type ECRIS are possible to generate plasma individually, and they also confined individual ion species by each different plasma parameter. Hence, it is considered to be suitable for new materials production. As the first step, we try to produce and extract multicharged C60 ions by supplying pure C60 vapor in the second stage plasma because our main target is producing the endohedral fullerenes. We developed a new evaporator to supply fullerene vapor, and we succeeded in observation about multicharged C60 ion beam in tandem-type ECRIS for the first time.
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http://dx.doi.org/10.1063/1.4934644DOI Listing
February 2016

Production of multicharged metal ion beams on the first stage of tandem-type ECRIS.

Rev Sci Instrum 2016 Feb;87(2):02A721

Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

Multicharged metal ion beams are required to be applied in a wide range of fields. We aim at synthesizing iron-endohedral fullerene by transporting iron ion beams from the first stage into the fullerene plasma in the second stage of the tandem-type electron cyclotron resonance ion source (ECRIS). We developed new evaporators by using a direct ohmic heating method and a radiation heating method from solid state pure metal materials. We investigate their properties in the test chamber and produce iron ions on the first stage of the tandem-type ECRIS. As a result, we were successful in extracting Fe(+) ion beams from the first stage and introducing Fe(+) ion beams to the second stage. We will try synthesizing iron-endohedral fullerene on the tandem-type ECRIS by using these evaporators.
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http://dx.doi.org/10.1063/1.4934579DOI Listing
February 2016

Experimental results of superimposing 9.9 GHz extraordinary mode microwaves on 2.45 GHz ECRIS plasma.

Rev Sci Instrum 2016 Feb;87(2):02A714

Division of Electrical, Electronic, and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

Efficient production of multicharged ions has been investigated on the tandem-type ECRIS in Osaka University. According to the consideration of the accessibility conditions of microwaves to resonance and cutoff regions, it was suggested that the upper hybrid resonance (UHR) heating contributed to enhancement of ion beam intensity. In order to enhance multicharged ion beams efficiently, injecting higher frequency microwave with extraordinary (X-mode) toward UHR region has been tried. In this study, 2.45 GHz frequency microwaves are used for conventional ECR discharge, and 9.9 GHz frequency microwaves with X-mode are superimposed for UHR heating. The effects of additive microwave injection are investigated experimentally in terms of plasma parameters and electron energy distribution function (EEDF) measured by Langmuir probe and ion beam current. As the results show, it is confirmed that the electrons in the high energy region are affected by 9.9 GHz X-mode microwave injection from the detailed analysis of EEDF.
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http://dx.doi.org/10.1063/1.4934212DOI Listing
February 2016

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

Rev Sci Instrum 2016 Feb;87(2):02A711

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

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.
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http://dx.doi.org/10.1063/1.4933122DOI Listing
February 2016

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

Rev Sci Instrum 2016 Feb;87(2):02A710

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

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.
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http://dx.doi.org/10.1063/1.4933031DOI Listing
February 2016

Basic detection property of an array-type CdTe detector for BNCT-SPECT - Measurement and analysis of anti-coincidence events.

Appl Radiat Isot 2016 Dec 5;118:389-394. Epub 2015 Nov 5.

Division of Sustainable Energy and Environmental Engineering, Graduate School of Engineering, Osaka University, Yamada-oka 2-1 Suita, Osaka, 565-0871 Japan.

Our research group is now investigating a BNCT-SPECT system with cadmium tellurite (CdTe) detectors, which can obtain a three-dimensional image of the BNCT treatment effect by measuring the 478keV gamma-rays emitted from an excited state of the Li nucleus generated by the B(n,α) reaction. The BNCT-SPECT system is composed of a collimator and an array-type CdTe detector. In this study, we produced an array detector with two CdTe elements to test the basic detection property for anti-coincidence events. Our investigation confirmed that the detector offers an improved S/N ratio by the anti-coincidence detection. We also proposed an estimation method using the MCNP5 to analyze coincidence events in the detector.
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http://dx.doi.org/10.1016/j.apradiso.2015.11.003DOI Listing
December 2016

Neutron intensity monitor with activation foil for p-Li neutron source for BNCT--Feasibility test of the concept.

Appl Radiat Isot 2015 Dec 28;106:75-7. Epub 2015 Jul 28.

Graduate School of Engineering, Osaka University, Yamada-oka 2-1, Suita, Osaka 565-0871, Japan.

Proton-lithium (p-Li) reaction is being examined worldwide as a candidate nuclear production reaction for accelerator based neutron source (ABNS) for BNCT. In this reaction, the emitted neutron energy is not so high, below 1 MeV, and especially in backward angles the energy is as low as about 100 keV. The intensity measurement was thus known to be difficult so far. In the present study, a simple method was investigated to monitor the absolute neutron intensity of the p-Li neutron source by employing the foil activation method based on isomer production reactions in order to cover around several hundreds keV. As a result of numerical examination, it was found that (107)Ag, (115)In and (189)Os would be feasible. Their features found out are summarized as follows: (107)Ag: The most convenient foil, since the half life is short. (115)In: The accuracy is the best at 0°, though it cannot be used for backward angles. And (189)Os: Suitable nuclide which can be used in backward angles, though the gamma-ray energy is a little too low. These would be used for p-Li source monitoring depending on measuring purposes in real BNCT scenes.
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http://dx.doi.org/10.1016/j.apradiso.2015.07.034DOI Listing
December 2015

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

Rev Sci Instrum 2014 Feb;85(2):02A955

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

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.
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http://dx.doi.org/10.1063/1.4861401DOI Listing
February 2014

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

Rev Sci Instrum 2014 Feb;85(2):02A950

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

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.
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http://dx.doi.org/10.1063/1.4857975DOI Listing
February 2014

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

Rev Sci Instrum 2014 Feb;85(2):02A938

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

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.
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http://dx.doi.org/10.1063/1.4832068DOI Listing
February 2014

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

Rev Sci Instrum 2014 Feb;85(2):02A937

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

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.
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http://dx.doi.org/10.1063/1.4827424DOI Listing
February 2014

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

Rev Sci Instrum 2014 Feb;85(2):02A925

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, Osaka, Japan.

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.
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http://dx.doi.org/10.1063/1.4829738DOI Listing
February 2014

Electron cyclotron resonance plasma production by using pulse mode microwaves and dependences of ion beam current and plasma parameters on the pulse condition.

Rev Sci Instrum 2012 Feb;83(2):02A324

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

We measure the ion beam current and the plasma parameters by using the pulse mode microwave operation in the first stage of a tandem type ECRIS. The time averaged extracted ion beam current in the pulse mode operation is larger than that of the cw mode operation with the same averaged microwave power. The electron density n(e) in the pulse mode is higher and the electron temperature T(e) is lower than those of the cw mode operation. These plasma parameters are considered to cause in the increase of the ion beam current and are suitable to produce molecular or cluster ions.
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http://dx.doi.org/10.1063/1.3669792DOI Listing
February 2012

Profiles of ion beams and plasma parameters on a multi-frequencies microwaves large bore electron cyclotron resonance ion source with permanent magnets.

Rev Sci Instrum 2012 Feb;83(2):02A317

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

In order to contribute to various applications of plasma and beams based on an electron cyclotron resonance, a new concept on magnetic field with all magnets on plasma production and confinement has been proposed with enhanced efficiency for broad and dense ion beam. The magnetic field configuration consists of a pair of comb-shaped magnet surrounding plasma chamber cylindrically. Resonance zones corresponding for 2.45 GHz and 11-13 GHz frequencies are positioned at spatially different positions. We launch simultaneously multiplex frequencies microwaves operated individually, try to control profiles of the plasma parameters and the extracted ion beams, and to measure them in detail.
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http://dx.doi.org/10.1063/1.3666184DOI Listing
February 2012

Dependence of ion beam current on position of mobile plate tuner in multi-frequencies microwaves electron cyclotron resonance ion source.

Rev Sci Instrum 2012 Feb;83(2):02A310

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.

We are constructing a tandem-type electron cyclotron resonance ion source (ECRIS). The first stage of this can supply 2.45 GHz and 11-13 GHz microwaves to plasma chamber individually and simultaneously. We optimize the beam current I(FC) by the mobile plate tuner. The I(FC) is affected by the position of the mobile plate tuner in the chamber as like a circular cavity resonator. We aim to clarify the relation between the I(FC) and the ion saturation current in the ECRIS against the position of the mobile plate tuner. We obtained the result that the variation of the plasma density contributes largely to the variation of the I(FC) when we change the position of the mobile plate tuner.
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http://dx.doi.org/10.1063/1.3662016DOI Listing
February 2012

Development of thermal neutron-sensitive glass dosemeter containing lithium.

Radiat Prot Dosimetry 2011 Mar 10;144(1-4):226-30. Epub 2011 Jan 10.

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.

New radiophotoluminescence (RPL) phosphate glass containing (6)Li was successfully made from the powder of NaPO(3), Al(PO(3))(3), LiOH, HPO(3) and AgCl. The ternary diagram of NaPO(3)-Al(PO(3))(3)-LiPO(3) has clarified the region where satisfactory RPL characteristics of the glass are kept up. The synthesised phosphate glass indicated good RPL characteristics on the condition that the content of LiPO(3) was below 10 wt%. Gamma-ray irradiation experiments showed that the newly synthesised phosphate glass had satisfactory linearity and wide dynamic range in dose measurement and low variation in sensitivity. It was confirmed from thermal neutron irradiation experiments that a pair of the newly synthesised phosphate glass containing enriched (6)Li and (7)Li, or (n)Li and enriched (7)Li could be effectively used for the evaluation of thermal neutron dosimetry.
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http://dx.doi.org/10.1093/rpd/ncq552DOI Listing
March 2011

Development of confocal laser microscope system for examination of microscopic characteristics of radiophotoluminescence glass dosemeters.

Radiat Prot Dosimetry 2011 Mar 6;144(1-4):222-5. Epub 2011 Jan 6.

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamadaoka, Suita, Osaka 565-0871, Japan.

A confocal laser microscope system was developed for the measurement of radiophotoluminescence (RPL) photons emitted from a minute alpha-ray-irradiated area in an RPL glass dosemeter. The system was composed mainly of an inverted-type microscope, an ultraviolet laser, an XY movable stage and photon-counting circuits. The photon-counting circuits were effective in the reduction of the background noise level in the measurement of RPL photons. The performance of this microscope system was examined by the observation of standard RPL glass samples irradiated using (241)Am alpha rays. The spatial resolution of this system was ∼ 3 μm, and with regard to the sensitivity of this system, a hit of more than four to five alpha rays in unit area produced enough amount of RPL photons to construct the image.
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http://dx.doi.org/10.1093/rpd/ncq563DOI Listing
March 2011

Pulse modulated microwave operation on large bore electron cyclotron resonance ion source with cylindrically comb-shaped magnetic fields configuration.

Rev Sci Instrum 2010 Feb;81(2):02A325

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

In order 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. By using the pulse microwave mode operation, we aim at generation of plasma with parameters that cannot be achieved at the continuous microwave (cw) mode. The maximum beam current is obtained in the experimental condition of the pulse width 100-200 micros at the duty ratio 40%-50%. According to probe measurements of the ECR plasma, it is found the electron density in the pulse mode is larger than that in the cw mode, while the electron temperatures in the pulse mode were lower than that in the cw mode. These indirect evidences cause to enhance ion beams in the pulse mode operation, and then suggest a spread of operation windows for plasma parameters suitable to production of molecular or cluster ions.
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http://dx.doi.org/10.1063/1.3267847DOI Listing
February 2010

Induction heating pure vapor source of high temperature melting point materials on electron cyclotron resonance ion source.

Rev Sci Instrum 2010 Feb;81(2):02A322

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

Multicharged ions that are needed are produced from solid pure material with high melting point in an electron cyclotron resonance ion source. We develop an evaporator by using induction heating (IH) with multilayer induction coil, which is made from bare molybdenum or tungsten wire without water cooling and surrounding the pure vaporized material. We optimize the shapes of induction coil and vaporized materials and operation of rf power supply. We conduct experiment to investigate the reproducibility and stability in the operation and heating efficiency. IH evaporator produces pure material vapor because materials directly heated by eddy currents have no contact with insulated materials, which are usually impurity gas sources. The power and the frequency of the induction currents range from 100 to 900 W and from 48 to 23 kHz, respectively. The working pressure is about 10(-4)-10(-3) Pa. We measure the temperature of the vaporized materials with different shapes, and compare them with the result of modeling. We estimate the efficiency of the IH vapor source. We are aiming at the evaporator's higher melting point material than that of iron.
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http://dx.doi.org/10.1063/1.3272830DOI Listing
February 2010

Production of electron cyclotron resonance plasma by using multifrequencies microwaves and active beam profile control on a large bore electron cyclotron resonance ion source with permanent magnets.

Rev Sci Instrum 2010 Feb;81(2):02A313

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, 2-1 Yamada-oka, Suita-shi, Osaka 565-0871, Japan.

A new concept on magnetic field with all magnets on 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 magnets assembly, i.e., comb-shaped magnet which cylindrically surrounds the plasma chamber. The resonance zones corresponding to the fundamental ECR for 2.45 GHz and 11-13 GHz frequencies are constructed at different positions. The profiles of the plasma parameters in the ECR ion source are different from each frequency of microwave. Large bore extractor is set at the opposite side against the microwave feeds. It is found that differences of their profiles also appear at those of ion beam profiles. We conducted to launch simultaneously multiplex frequencies microwaves controlled individually, and tried to control the profiles of the plasma parameters and then those of extracted ion beam.
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http://dx.doi.org/10.1063/1.3277195DOI Listing
February 2010

Micro/nanopatterning of single-walled carbon nanotube-organic semiconductor composites.

Nanotechnology 2009 Feb 2;20(8):085301. Epub 2009 Feb 2.

Center for Transdisciplinary Research, Niigata University, 8050 Ikarashi 2-nocho, Nishi-ku, Niigata 950-2181, Japan.

In this study, micro/nanopatterning and assembly of single-walled carbon nanotube-organic semiconductor composites using dip-pen nanolithography, microcontact printing and fountain-pen nanolithography techniques are described. First, the solubilization abilities of carbon nanotubes with Alcian blue-tetrakis(methyl pyridium) chloride (AB) are investigated by UV-visible spectroscopy. The assembly of the composites obtained by microcontact printing technique shows well-ordered monolayers of 1 microm linewidth pattern. Dip-pen nanolithography shows that 11 nm height and 100 nm linewidth can be obtained on silicon wafer substrates. Finally, fountain-pen nanolithography is shown as a possible large-scale carbon nanotube assembly technique.
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http://dx.doi.org/10.1088/0957-4484/20/8/085301DOI Listing
February 2009

Microchamber arrays for the identification of individual cells exposed to an X-ray microbeam.

Radiat Environ Biophys 2008 Nov 27;47(4):535-40. Epub 2008 Jun 27.

Division of Electric, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, Suita, Osaka 567-0871, Japan.

To identify individual cells exposed to a X-ray microbeam in a cell population, we developed a biocompatible microchamber-array chip using UV lithography of photopolymer SU-8. The center-to-center distance between microchambers is 50 mum including a wall of 15 mum height. Using the microchamber-array chip, we performed tracking of individual exposed cells. Sample cells loaded in a microchamber array were selectively irradiated with the X-ray microbeam under microscopic observation. All the irradiated cells were indexed by the array arrangement of the microchambers. For about 24 h of post-irradiation incubation, the irradiated cells were identified successfully by time-lapse observation. In addition, the induction of radiation effects was observed in identified cells using immunofluorescence.
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http://dx.doi.org/10.1007/s00411-008-0180-1DOI Listing
November 2008

Effects of fundamental and second harmonic electron cyclotron resonances on ECRIS.

Rev Sci Instrum 2008 Feb;79(2 Pt 2):02A323

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, Suita-Shi, Osaka, Japan.

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.
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http://dx.doi.org/10.1063/1.2816759DOI Listing
February 2008

Multicharged iron ions produced by using induction heating vapor source.

Rev Sci Instrum 2008 Feb;79(2 Pt 2):02A312

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, Suita-Shi, Osaka, Japan.

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.
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http://dx.doi.org/10.1063/1.2816708DOI Listing
February 2008

Hydrated thymine cluster in the supersonic gas jet.

Radiat Prot Dosimetry 2006 24;122(1-4):95-9. Epub 2007 Jan 24.

Division of Electrical, Electronic and Information Engineering, Graduate School of Engineering, Osaka University, Suita, Osaka, Japan.

Fragmentation of hydrated thymine clusters in the gas phase induced by UV laser pulse at 266 nm was studied by means of time-of-flight (TOF) mass spectrometry. Hydrated thymine clusters were produced by supersonic expansion in the gas jet in a high vacuum region. The range of laser intensity for ionisation of the gaseous targets was from 10(6) to 10(9) W cm(-2). In the condition of low laser intensity, the peaks corresponding to hydrated thymine clusters [(C(5)H(6)N(2)O(2))(m)(H(2)O)(n)] and large mass fragments from them were obtained mainly. In the laser intensity region from 10(7) to 10(8) W cm(-2), the fragment ions released from thymine such as HCNH(+), HNCO(+), CH(2)CCHNH(+), CH(3)CCHNH(+), C(3)H(4)O(+), etc. were mainly detected due to C-C and C-N bond breaks in a ring structure of thymine.
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http://dx.doi.org/10.1093/rpd/ncl403DOI Listing
July 2007
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