Satoshi Kurashima

Japan Atomic Energy Agency, Muramatsu, Niigata, Japan

Are you Satoshi Kurashima?

Claim your profile

Publications (46)27.19 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: We have developed a system for measuring the temporal profiles of scintillation at high linear energy transfer (LET) by using pulsed ion beams from a cyclotron. The half width at half maximum time resolution was estimated to be 1.5-2.2 ns, which we attributed mainly to the duration of the pulsed ion beam and timing jitter between the trigger signal and the arrival of the ion pulse. The temporal profiles of scintillation of BaF2 at different LETs were successfully observed. These results indicate that the proposed system is a powerful tool for analyzing the LET effects in temporal profiles of scintillation.
    Review of Scientific Instruments 01/2015; 86(1):013101. DOI:10.1063/1.4904872 · 1.58 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A new technique for evaluating the phase bunching performance in the central region of a cyclotron was developed. A newly-developed radial probe with a 6-mm-wide, 5-mm-height plastic scintillator was applied to analysis of the correlation between the internal beam phase distribution and the initial beam phase, defined by adjusting the relative RF phase of the beam buncher. The phase distribution measurement system, comprising the radial probe equipped with a plastic scintillator and the signal-processing modules, had a sufficiently good time resolution of 45 ps full-width at half-maximum for the phase bunching evaluation. The correlations between the buncher phase and the measured phase distribution for the acceleration harmonic number h=1 and 2 were consistent with the calculation result of the geometric trajectory analysis. For h=1 case of a 107 MeV 4He2+ beam, the internal beam phase region spread over 71 RF degrees full-width at quarter-maximum (FWQM) for the acceptable buncher phase region of 48 RF degrees, and no evidence of the phase bunching effect was observed. For h=2 case of a 260 MeV 20Ne7+ beam, the internal beam phase region for the acceptable buncher phase region of 59 RF degrees was compressed into 21 RF degrees FWQM. The phase bunching effect was sharply evident for h=2, and contributed to increase of the acceptable beam phase region and the beam intensity per phase width.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 11/2014; 767:372–378. DOI:10.1016/j.nima.2014.09.006 · 1.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The JAEA AVF cyclotron accelerates various kinds of high-energy ion beams for research in biotechnology and materials science. Beam intensities of an ion species of the order of 10(-9)-10(-6) ampere are often required for various experiments performed sequentially over a day. To provide ion beams with sufficient intensity and stability, an operator has to retune an ion source in a short time. However, the beam intensity downstream of the cyclotron rarely increases in proportion to the intensity at the ion source. To understand the cause of this beam behavior, transmission efficiencies of a (12)C(5+) beam from an electron cyclotron resonance ion source to the cyclotron were measured for various conditions of the ion source. Moreover, a feasible region for acceleration in the emittance of the injection beam was clarified using a transverse-acceptance measuring system. We confirmed that the beam emittance and profile were changed depending on the condition of the ion source and that matching between the beam emittance and the acceptance of the cyclotron was degraded. However, after fine-tuning to improve the matching, beam intensity downstream of the cyclotron increased.
    The Review of scientific instruments 02/2014; 85(2):02A725. DOI:10.1063/1.4824749 · 1.58 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A transverse beam emittance and acceptance measurement system has been developed to visualize the relationship between the injected beam emittance and the acceptance of a cyclotron. The system is composed of a steering magnet, two pairs of slits to limit the horizontal and vertical phase-space, a beam intensity detector just behind the slits for the emittance measurement, and a beam intensity detector in the cyclotron for the acceptance measurement. The emittance is obtained by scanning the slits and measuring the beam intensity distribution. The acceptance is obtained by measuring the distribution of relative beam transmission by injecting small emittance beams at various positions in a transverse phase-space using the slits. In the acceptance measurement, the beam from an ion source is deflected to the defined region by the slits using the steering magnet so that measurable acceptance area covers a region outside the injection beam emittance. Measurement tests were carried out under the condition of accelerating a beam of (16)O(6+) from 50.2 keV to 160 MeV. The emittance of the injected beam and the acceptance for accelerating and transporting the beam to the entrance of the extraction deflector were successfully measured. The relationship between the emittance and acceptance is visualized by displaying the results in the same phase-plane.
    The Review of scientific instruments 02/2014; 85(2):02A735. DOI:10.1063/1.4858175 · 1.58 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: An optimum condition for realizing phase bunching in the central region of a cyclotron was quantitatively clarified by a simplified geometric trajectory analysis of charged particles from the first to the second acceleration gap. The phase bunching performance was evaluated for a general case of a cyclotron. The phase difference of incident particles at the second acceleration gap depends on the combination of four parameters: the acceleration harmonic number h, the span angle θD of the dee electrode, the span angle θF from the first to the second acceleration gap, the ratio RV of the peak acceleration voltage between the cyclotron and ion source. Optimum values of θF for phase bunching were limited by the relationship between h and θD, which is 90°/h+θD/2≤θF≤180°/h+θD/2, and sin θF>0. The phase difference with respect to the reference particle at the second acceleration gap is minimized for voltage-ratios between two and four for an initial phase difference within 40 RF degrees. Although the slope of the first acceleration gap contributes to the RF phase at which the particles reach the second acceleration gap, phase bunching was not affected. An orbit simulation of the AVF cyclotron at the Japan Atomic Energy Agency verifies the evaluation based on geometric analysis.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 07/2013; 715:126–131. DOI:10.1016/j.nima.2013.03.033 · 1.32 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: The JAEA AVF cyclotron provides heavy-ion beams covering a wide range of linear-energy-transfers for microbeam formation. Two types of microbeam formation systems, one using a micro-aperture and the other focusing lenses, are installed on two vertical beam lines of the cyclotron. The average beam time for an experiment using the former system is usually less than 3 h, that is comparable to the time for cyclotron tuning. The time ratio between experiment and tuning determines the usage efficiency of the facility. In order to reduce the tuning time, a scaling method has been introduced to change the ion species with various mass to charge ratios (M/Q) in a shorter total time. The principle of the scaling method is to keep the magnetic rigidity of ion beams constant. This requirement is easily achieved by adjusting the extraction voltage of an ion source proportionally to the M/Q in the beam injection line. Although some cyclotron adjustments, other than the magnetic field strength at the extraction radius, are required, the tuning can be completed within 20 min, and no change is basically required in the beam transport line downstream of the cyclotron. Using the scaling method, 255 MeV 20Ne7+, 335 MeV 20Ne8+, and 440 MeV 40Ar13+ beams were extracted from the cyclotron in sequence after the usual tuning of a 220 MeV 12C5+. As a result, we have succeeded in changing the ion species of the heavy-ion microbeam within a total of 30 min.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 07/2013; 306:40–43. DOI:10.1016/j.nimb.2012.11.040 · 1.19 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A new diagnosis method for high energy ions utilizing a single CR-39 detector mounted on plastic plates is demonstrated to identify the presence of the high energy component beyond the CR-39’s detection threshold limit. On irradiation of the CR-39 detector unit with a 25 MeV per nucleon He ion beam from conventional rf-accelerators, a large number of etch pits having elliptical openings are observed on the rear surface of the CR-39. Detailed investigations reveal that these etch pits are created by heavy ions inelastically backscattered from the plastic plates. This ion detection method is applied to laser-driven ion acceleration experiments using cluster-gas targets, and ion signals with energies up to 50 MeV per nucleon are identified.
    Radiation Measurements 05/2013; 50:92. DOI:10.1016/j.radmeas.2012.10.010 · 1.14 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: We demonstrate a new ion diagnosis method for high energy ions by utilizing a combination of a single CR-39 detector and plastic plates, which enables to detect high energy ions beyond the detection threshold limit of the CR-39. This detection method coupled with a magnetic spectrometer is applied to identify high energy ions of 50 MeV per nucleon in laser-driven ion acceleration experiments using cluster-gas targets.
    Proceedings of SPIE - The International Society for Optical Engineering 05/2013; DOI:10.1117/12.2018479 · 0.20 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A new diagnosis method has been developed utilizing back scattered particles for high energy intense ion beams. The CR-39 detector mounted on the uniform back-scatterer was irradiated with {sup 4}He{sup 2+} ions with an energy 25 MeV/n, which is never recorded as etchable track in CR-39. We found that it is possible to diagnose by analyzing the etch pits on the rear surface of CR-39 that directly contacted on the back-scatterers. It turns out that most of etch pits in the rear surface are made by the backscattered particles by investigating the growth pattern of each etch pit with multi-step etching technique. This method allows simple diagnosis of the ion beam profile and intensity distribution in mixed radiation field such as laser-driven ion acceleration experiments.
    07/2012; 1465(1). DOI:10.1063/1.4737553
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A single CR-39 detector mounted on plastic plates is irradiated with a 100 MeV He ion beam. Although the beam energy is much greater than the detection threshold limit of the CR-39 detector, a large number of etch pits having elliptical openings are observed on the rear surface. Detailed investigations reveal that these etch pits are created by heavy ions inelastically backscattered from the plastic plates. This method allows a simple diagnosis of the ion beam profile and the presence of the high-energy component beyond the detection threshold limit of the CR-39 detector, especially in mixed-radiation fields such as laser-driven ion acceleration experiments. # 2012 The Japan Society of Applied Physics
    Japanese Journal of Applied Physics 04/2012; DOI:10.1143/JJAP.51.056401 · 1.06 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A phase bunching effect has been achieved for the first time using a rising slope of the dee voltage waveform produced at the first acceleration gap between the RF shielding cover of the inflector and the puller in the new central region of the JAEA AVF cyclotron. The feasibility of the phase bunching effect in the central region for a two-dee system with a span angle of 86° in three acceleration harmonic modes was assessed by a simple geometrical analysis of particle trajectories and a three-dimensional beam orbit simulation using the calculated electric field and a measured magnetic field. The simulation indicated that the initial beam phase width of 40 RF degrees is compressed to 11 RF degrees (about 28% of the initial phase width) in the second harmonic mode. A phase width of 1.5 RF degrees FWHM for a 260MeV 20Ne7+ beam accelerated in the second harmonic mode was observed when using a 4mm phase slit gap. The phase width reduction was considerably enhanced by the bunching effect, compared with the beam phase width of 7.3 RF degrees FWHM in the same harmonic mode for a 10MeV H+ beam accelerated in the original central region. The ratio of the beam current for the 1.5 RF degrees FWHM phase width with 4mm phase slit gap restriction to the full beam current without the phase slit was drastically improved to 80%, while the beam current was less than 1% of the full beam when narrowing the phase slit gap to obtain the 7.3 RF degrees FWHM phase width in the original central region.
    Nuclear Instruments and Methods in Physics Research Section A Accelerators Spectrometers Detectors and Associated Equipment 04/2011; 636(1):41-47. DOI:10.1016/j.nima.2011.01.174 · 1.32 Impact Factor
  • Source
    01/2011; 36(3):329-332. DOI:10.14723/tmrsj.36.329
  • [Show abstract] [Hide abstract]
    ABSTRACT: We have developed a new technique for analysis and control of the acceleration beam phase in the cyclotron. In this technique, the beam current pattern at a fixed radius r is measured by slightly scanning the acceleration frequency in the cyclotron. The acceleration beam phase is obtained by analyzing symmetry of the current pattern. Simple procedure to control the acceleration beam phase by changing coil currents of a few trim coils was established. The beam phase width is also obtained by analyzing gradient of the decreasing part of the current pattern. We verified reliability of this technique with 260 MeV (20)Ne(7+) beams which were accelerated on different tuning condition of the cyclotron. When the acceleration beam phase was around 0 degrees, top of the energy gain of cosine wave, and the beam phase width was about 6 degrees in full width at half maximum, a clear turn pattern of the beam was observed with a differential beam probe in the extraction region. Beam phase widths of ion beams at acceleration harmonics of h=1 and h=2 were estimated without beam cutting by phase-defining slits. We also calculated the beam phase widths roughly from the beam current ratio between the injected beam and the accelerated beam in the cyclotron without operating the beam buncher. Both beam phase widths were almost the same for h=1, while phase compressions by a factor of about 3 were confirmed for h=2.
    The Review of scientific instruments 03/2010; 81(3):033306. DOI:10.1063/1.3354981 · 1.58 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This article reports a highly sensitive transient absorbance measurement system using pulsed energetic ions. The ions were pulsed by a beam chopper, which was synchronized with the cyclotron, and accelerated to the desired energy around 18MeV/u. H, He, C and Ne ions can be used for the transient absorption measurement. The optical system can measure an absorbance smaller than 1.0×10−4 in the wavelength range of 400–740nm.
    Radiation Physics and Chemistry 12/2009; 78(12):1169-1174. DOI:10.1016/j.radphyschem.2009.05.019 · 1.19 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A heavy-ion microbeam with hundreds of MeV energy is utilized for research in biotechnology and materials science at the JAEA AVF cyclotron facility. Beam users need microbeams providing a wide range of the LET. We have to change ion species and/or energy in order to vary the LET widely. However, it takes much time to develop a new microbeam of different ion species step by step using a flat-top acceleration system. A cocktail beam acceleration technique is frequently used to change the ion species and energy quickly. The cocktail beam acceleration has been first applied to the microbeam formation for quick change of the ion species. As a result, we have succeeded to reduce considerably microbeam changing time to within 30min between a 520MeV 40Ar14+ and a 260MeV 20Ne7+. No deterioration of the microbeam spot size has been confirmed using a SE image of a copper grid.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 06/2009; 267(12):2024-2027. DOI:10.1016/j.nimb.2009.03.083 · 1.19 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Single-turn extraction from the Japan Atomic Energy Agency AVF cyclotron with a K number of 110 using a flat-top (FT) acceleration system has been achieved to reduce the energy spread of an ion beam for microbeam formation with energy up to hundreds of MeV and to increase extraction efficiency from the cyclotron. In order to generate a FT waveform voltage using the fifth-harmonic frequency on a dee electrode, a FT resonator was designed using MAFIA code to achieve downsizing and low power consumption. The FT resonator, coupled to the main resonator through a coupling capacitor, covered the full range of the fifth harmonic frequency from 55 to 110 MHz. Various ion beams, accelerated using different acceleration harmonic modes of h=1 and 2, such as 220 MeV (12)C(5+) (h=2), 260 MeV (20)Ne(7+) (h=2), and 45 MeV H(+) (h=1), were developed by FT acceleration. A clear turn separation of the beam bunches was successfully observed at the extraction region of the large-scale AVF cyclotron with number of revolutions greater than 200. As a result, high extraction efficiency (over 95%) from the cyclotron was achieved. Single-turn extraction was confirmed by counting the number of beam bunches out of the cyclotron for an injected beam pulsed by a beam chopping system in the injection line. The energy spread of the 260 MeV (20)Ne(7+) beam was measured using an analyzing magnet, and we verified a reduction in the energy spread from DeltaE/E=0.1% to 0.05% by single-turn extraction after FT acceleration.
    The Review of scientific instruments 04/2009; 80(3):033302. DOI:10.1063/1.3093810 · 1.58 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Ion optical analysis was made for a new focusing high-energy heavy ion microbeam system connected to the AVF cyclotron (K=110) at the accelerator facility, TIARA of JAEA Takasaki. The focusing performance of the microbeam system was estimated from both the calculation up to third-order term using TRANSPORT code and the measurement of beam resolution with the secondary electron imaging. As a result, a minimum beam size was evaluated at 0.56 and 0.62 microm in FWHM for the X and Y directions, respectively. The high-energy heavy ion microbeam system seemed to have been established as designed by the calculation with the TRANSPORT code, because it was confirmed that the calculation results was fairly reproduced by the measurement result.
    Applied radiation and isotopes: including data, instrumentation and methods for use in agriculture, industry and medicine 07/2008; 67(3):484-7. DOI:10.1016/j.apradiso.2008.06.025 · 1.06 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: In order to achieve a heavy-ion microbeam with an energy of hundreds of MeV applied to the research fields of biotechnology and materials science, the JAEA AVF cyclotron (K = 110) has been upgraded to provide a high quality beam with a smaller energy spread and a higher current stability. A flat-top (FT) acceleration system of the cyclotron, designed to produce ion beams with an energy spread of ΔE/E ⩽ 0.02%, has been developed to reduce chromatic aberrations in the lenses of the focusing microbeam system. The FT acceleration system provides uniform energy gain of the beam by superimposing a fifth-harmonic voltage on the fundamental one. In addition, stabilization of the acceleration rf voltage and the phase were achieved to accelerate the high quality beam and to provide it stably to the microbeam system connected to a cyclotron beam line. In the latest experiment, we have succeeded to accelerate 260 MeV 20Ne7+ with an energy spread of 0.05% in FWHM using the FT acceleration system.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 07/2007; DOI:10.1016/j.nimb.2007.01.278 · 1.19 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Performance of a focusing high-energy heavy ion microbeam system in TIARA facility of JAEA Takasaki was tested for the spatial resolution and for the hitting accuracy at a target. A 260MeV 20Ne7+ ion beam was successfully extracted from the JAEA AVF cyclotron (K=110) with the smallest momentum spread (ΔP/P=δ) at present. The beam was focused by the microbeam lens system, and a spatial resolution of 260MeV 20Ne7+ microbeam was measured from a secondary electron image of a Cu grid which had sharp edges, and the hitting accuracy was estimated using single ion hitting onto a CR-39 film. From those two methods of measurement, both the spatial resolution and the hitting accuracy were evaluated at less than 1μm.
    Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 07/2007; 260(1):85-90. DOI:10.1016/j.nimb.2007.01.280 · 1.19 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A time-of-flight system for determining the absolute energy of ion beams has been developed for the azimuthally varying field (AVF) cyclotron at Japan Atomic Energy Agency (JAEA). Ion detectors, a microchannel-plate detector and a plastic scintillation detector, were applied to the system in order to achieve high time resolution measurement of the flight time and to cover a wide range of beam intensity in combination with a beam attenuator. The change of the flight length, performed by moving the plastic scintillation detector with flexible bellows, allows determination of the mean beam energy only from the relative measurement of the flight time and the flight length without knowing their absolute values. A maximum movable distance of 2 m yields the difference in the time of flight from 16 to 94 ns for the energy range of ion beams accelerated by the JAEA AVF cyclotron. The time-of-flight system even with the 2 m change in the flight length achieves accurate energy determination of the order of 0.1%, since the relative measurement has an advantage of elimination of the uncertainties in determination of the time zero and the length zero. The time-of-flight measurement with the relative measurement also allows estimation of the beam energy spread without conventional expensive systems such as a magnetic spectrometer. By comparing the widths of the time-of-flight spectra of ions accumulated at different flight lengths, we have estimated the energy spread. In order to reduce the labor process of the coincidence detection of ions in the time-of-flight measurement, we have also accomplished a simple estimation method for mean beam energy determination with a beam bunch, naturally modulated with the acceleration RF of the cyclotron. The mean beam energy has been obtained from the shift of the beam bunch centroids at different flight lengths in the time-of-flight spectrum.
    Review of Scientific Instruments 11/2005; 76(11):113106-113106-6. DOI:10.1063/1.2135285 · 1.58 Impact Factor