A5037312241- Particle accelerators and beam dynamics
- Plasma Diagnostics and Applications
- Magnetic confinement fusion research
- Soil and Unsaturated Flow
- Radioactive contamination and transfer
- Particle Accelerators and Free-Electron Lasers
- Plant Water Relations and Carbon Dynamics
- Irrigation Practices and Water Management
- Rice Cultivation and Yield Improvement
- Plant responses to water stress
- Nuclear and radioactivity studies
- Climate change impacts on agriculture
- Superconducting Materials and Applications
- Nuclear Physics and Applications
- Dust and Plasma Wave Phenomena
- Hydrology and Watershed Management Studies
- Greenhouse Technology and Climate Control
- Image Processing and 3D Reconstruction
- Gyrotron and Vacuum Electronics Research
- Ionosphere and magnetosphere dynamics
- Radioactive element chemistry and processing
- Plant nutrient uptake and metabolism
- Environmental and Agricultural Sciences
- Atomic and Molecular Physics
- Plant Stress Responses and Tolerance
The University of Tokyo
2010-2024
National Agriculture and Food Research Organization
2022
Institute for Rural Engineering
2020-2022
Keio University
2013-2018
University of Jyväskylä
2017
Tokyo University of Science
2011
Kyushu University
2006
J-Power (Japan)
1994
We present a fully-implicit electromagnetic Particle-In-Cell Monte Carlo collision code, called NINJA, written for the simulation of inductively coupled plasmas. NINJA employs kinetic enslaved Jacobian-Free Newton Krylov method to solve self-consistently interaction between field generated by radio-frequency coil and plasma response. The simulated includes description charged neutral species as well processes them. algorithm allows simulations with cell sizes much larger than Debye length...
CERN's Linac4 45 kV H− ion sources prototypes are installed at a dedicated source test stand and in the tunnel. The operation of pulsed hydrogen injection, RF sustained plasma, high voltages described. first experimental results two relying on 2 MHz RF-plasma heating presented. plasma is ignited via capacitive coupling, by inductive coupling. light emitted from collected viewports pointing to chamber wall middle solenoid axis. Preliminary measurements optical emission spectroscopy photometry...
CERN’s 160 MeV H− linear accelerator (Linac4) is a key constituent of the injector chain upgrade Large Hadron Collider that being installed and commissioned. A cesiated surface ion source prototype tested has delivered beam intensity 45 mA within an emittance 0.3 π ⋅ mm mrad. The optimum ratio co-extracted electron- to ion-current below 1 best production efficiency, defined as current 2 MHz RF-power transmitted plasma, reached 1.1 mA/kW. first tests new optics, electron-dump, front end...
福島第一原子力発電所事故で放射性物質が多量に降下してから約2か月後に,耕起されていない水田の深さ15cmまでの表土を厚さ1~5cmの6層に分割してサンプリングし,放射性セシウム(134Csと137Cs)の鉛直濃度分布を求めた結果,放射性Csの88%が0~3cmに,96%が0~5cmに止まっていた。しかし,量的に大半は表面付近に存在するものの,15~20cmの層まで新たに降下した放射性Csの影響が及んでいた。濃度分布から求めた放射性Csの平均移動距離は約1.7cmで,70日間の雨量(148mm)から蒸発散量を引いて体積含水率で割った水分子の平均移動距離は約20cmと推定され,土壌への収着により,Csの移流速度は水の移流速度に比べて1/10であった。しかし,文献にみられる実験室で測定した収着平衡時の土壌固相と土壌水との間の分配係数から計算される移流速度よりは2~3桁大きく,現場の移動現象が収着平衡からほど遠いことを示している。一方,耕起された水田では,表層の高濃度の放射性セシウムが0~15cmの作土層内に混合されて平均値(約4000Bq/kg)となっていた。
Two volume sources equipped with DESY and CERN plasma generators a low voltage electron dump were operated at 45 kV in the Linac4 tunnel on dedicated test stand. These delivered approximately 20 mA ensured commissioning of Radio Frequency Quadrupole accelerator first section Drift Tube Linac. CERN's prototype cesiated surface source this was continuously from November 2013 to April 2014 ion stand is being commissioned tunnel. Before cesiation, conditioned mode provided up 30 H− beam. Short...
The present status of kinetic modeling particle dynamics in hydrogen negative ion (H−) source plasmas and their comparisons with experiments are reviewed discussed some new results. main focus is placed on the following topics, which important for research development H− sources intense high-quality beams: (i) effects non-equilibrium features electron energy distribution function volume surface production, (ii) origin spatial non-uniformity giant multi-cusp arc-discharge sources, (iii)...
Abstract We investigated the effects of continuous salt accumulation in root zone wheat. Leaf water potential and transpiration rate were measured plants grown an experimental pot system. Plants a controlled-environment glasshouse sand-filled pots, which groundwater table was maintained at desired depth. Saline recharged from base, providing constant content unsaturated zone. At 52 days after sowing, set depth 47 cm soil surface. Groundwater initial replaced with saline electrical...
A novel 2D ion temperature measurement for toroidal plasmas has been developed by use of cost-effective discrete tomography reconstruction Doppler spectroscopy composed a polychromator with an ICCD camera and optical fibres. The projection the line spectrum collected 35 (7 × 5) fibres is transformed into r–z profile local means Abel inversion at each wavelength finally (r–z) temperature. Numerical tests its algorithm indicate that error peaked smaller than 15% if chord-integrated signals...
Radio Frequency (RF) Inductively Coupled Plasmas (ICPs) are widely known for their two discharge modes, i.e., H-mode and E-mode, where the dynamics of plasmas completely different from each other. We have performed a kinetic simulation hydrogen plasma in order to clarify mechanism E-to-H transition RF ICPs. The numerical results, such as time variations spatial distribution electron density power dissipated plasma, show characteristic changes due mode transition. Especially, drastic change...
We investigated salt accumulation processes induced by root water uptake above the groundwater table. compared experimentally determined results from a pot experiment with those predicted numerical simulation. Spring wheat ( Triticum aestivum L.) was grown in sand‐filled pots, and constant table of saline maintained. measured physiological factors such as daily transpiration rate, leaf potential, length distribution. Water content distribution pots were determined. developed model for that...
Linac4 cesiated surface H− sources are routinely operated for the commissioning of CERN's and on an ion source test stand. Stable current 40-50 mA achieved but transmission through LEBT 80% was below expectations triggered additional beam simulation characterization. The profile is not Gaussian emittance measurements larger than simulation. status ongoing development work described; 36 20 D− beams were produced with a 5.5 mm aperture source. emittances measured at stand presented. During...
Inductively Coupled Plasmas (ICP) are well known to exhibit two modes of operation: a low density capacitive E-mode and high inductive H-mode.In this study we investigate the E-H transition in cylindrical ICP, show e↵ect an external magnetic cusp field on dynamics.The plasma is simulated by Electro-Magnetic Particle-In-Cell Monte Carlo Collision code order take into account spatio-temporal variations dynamics as kinetic e↵ects.Simulations compared photometry measurements Linac4 H ion source...
Time structure of Balmer Hα line intensity in Linac4 RF plasma has been analyzed by the combined simulation model atomic transport and Collisional-Radiative models. As a preliminary result, time variation ignition phase is calculated compared with experimental results photometry. For comparison, spatial distribution local photon emission rate at each from numerical model. The contribution rates to observed via optical viewing port also investigated application mock-up known light source. It...
In order to evaluate Electron Energy Distribution Function (EEDF) more correctly for radio frequency inductively coupled plasma (RF-ICP) in hydrogen negative ion sources, the Electromagnetic Particle-In-Cell (EM-PIC) simulation code has been improved by taking into account electron-electron Coulomb collision. Binary collision model is employed process and we have successfully modeled it. The preliminary calculation including done it shown that doesn't significant effects under condition:...
Progress in the kinetic modeling of particle dynamics H(-) negative ion source plasmas and their comparisons with experiments are reviewed, discussed some new results. Main focus is placed on following two topics, which important for research development large sources high power beams: (i) Effects non-equilibrium features EEDF (electron energy distribution function) production, (ii) extraction physics ions beam optics.
The power requirements of RF heated sources for negative hydrogen ions in fusion are substantial, which poses strong demands on the generators and components circuit. Consequently, an increase coupling efficiency would be highly beneficial. Fundamental investigations inductively coupled deuterium discharges cylindrical symmetry conducted at lab experiment CHARLIE. is equipped with several diagnostics including optical emission spectroscopy a movable floating double probe to monitor plasma...
To control the H0 atom production profile in H− ion sources is one of important issues for efficient and uniform surface production. The purpose this study to construct a collisional radiative (CR) model calculate effective rate atoms from H2 molecules geometry radio-frequency (RF) source Linac4 accelerator. In order validate CR by comparison with experimental results optical emission spectroscopy, it also necessary Balmer photon source. As basic test model, time evolutions Hα are calculated...
The ratio of the diffusion coefficient a solute in soil to bulk water ( D r ) has been shown be proportional volumetric content (θ) power n , and studies dependency on θ have that is approximately 2. This value can explained physically using simple tortuosity model. However, values 4 found two soils (sandy loamy) with low contents, these high attributed an electrically diffuse double layer formed near charged solid surfaces, restricting ion within it. We examined effect electrical charge...
To understand the Electron Energy Distribution Function (EEDF) in Radio Frequency Inductively Coupled Plasmas (RF-ICPs) hydrogen negative ion sources, detailed analysis of EEDFs using numerical simulation and theoretical approach based on Boltzmann equation has been performed. It is shown that EEDF RF-ICPs consists two parts, one low energy part which obeys Maxwellian distribution other high deviated from distribution. These results have confirmed to be reasonable by analytical approach. The...
Abstract Water management methods regulate water temperature in paddy fields, which affects rice growth and the environment. To understand effect of irrigation conditions on a field, distribution under 42 different models including use ICT management, enables remote automatic irrigation, was simulated using physical model heat balance. The following results were obtained: (1) Irrigation had more significant close to inlet. As distance from inlet increased, converged an equilibrium,...
Abstract Large clods (centimetres in size) can be formed by tillage clayey paddy fields where upland crops are planted. These cause early water depletion near the soil surface, which decreases crop germination and emergence rates. Because of difficulty reducing clod size, desiccation damage to seeds avoided adjusting seeding depth based on size‐dependent moisture profile. This study aimed clarify effect size (1) evaporation rate ( E ) profile (2) mobility during drying process. Evaporation...
Abstract The occurrence of water ponding on soil surfaces during and after heavy rainfall produces surface run‐off or accumulation in low‐lying areas, which might reduce the supply to soils result a reduction that plants can use, especially arid climates. On Mongolian rangeland, we observed ponded specific condition subjected 30 mm/hr. By contrast, was not for same type where livestock grazing had been removed 6–8 years via fence nearby containing less clay. We measured infiltration rate...