A5104909382- Particle accelerators and beam dynamics
- Particle Accelerators and Free-Electron Lasers
- Superconducting Materials and Applications
- Gyrotron and Vacuum Electronics Research
- Magnetic confinement fusion research
- Semiconductor materials and devices
- Electron and X-Ray Spectroscopy Techniques
- Plasma Diagnostics and Applications
- High voltage insulation and dielectric phenomena
- Metal and Thin Film Mechanics
- Particle Detector Development and Performance
- GaN-based semiconductor devices and materials
- Particle physics theoretical and experimental studies
- Radiation Effects in Electronics
- Muon and positron interactions and applications
- Advanced X-ray Imaging Techniques
- Quantum Chromodynamics and Particle Interactions
- Ion-surface interactions and analysis
- Power Transformer Diagnostics and Insulation
- Diamond and Carbon-based Materials Research
- Ga2O3 and related materials
- Photocathodes and Microchannel Plates
- Superconductivity in MgB2 and Alloys
- Electrostatic Discharge in Electronics
- Advanced ceramic materials synthesis
High Energy Accelerator Research Organization
2014-2024
The Graduate University for Advanced Studies, SOKENDAI
2014-2021
European Organization for Nuclear Research
2017
Japan Aerospace Exploration Agency
2009-2012
Saitama University
2006
The University of Tokyo
1990-1992
Bunkyo University
1990
We report the observation of a narrow charmoniumlike state produced in exclusive decay process B+/--->K+/-pi(+)pi(-)J/psi. This state, which decays into pi(+)pi(-)J/psi, has mass 3872.0+/-0.6(stat)+/-0.5(syst) MeV, value that is very near M(D0)+M(D(*0)) threshold. The results are based on an analysis 152M B-Bmacr; events collected at Upsilon(4S) resonance Belle detector KEKB collider. signal statistical significance excess 10sigma.
The machine commissioning of KEKB started in December 1998 and its operation was terminated at the end June 2010 to upgrade SuperKEKB. In this paper, we summarize history show achievements made there.
The Technical Design Report (TDR) of the ILC mainly concentrates on a baseline machine 500 GeV centre-of-mass with detailed cost and manpower estimates consistent this option. However, discovery Higgs Boson mass 125 opens up possibility reducing by starting at energy 250 future upgrades to or even 1 TeV should physics case for such an upgrade be compelling. rest paper outlines options design "Higgs factory".
The behavior of multipactoring electrons in an S-band pillbox RF window used the KEK electron linac was investigated. electric field distributions were calculated using MAFIA code. trajectory emitted to surface alumina disk simulated. energy deposition distribution impinging on also obtained. results agree well with discoloring patterns observed for disks after operation. This shows that can be explained terms bombardment single-surface electrons. Knowledge concerning and will useful...
We have performed a search for the lepton-flavor-violating decay tau -> mu gamma using data sample of 86.3fb^{-1} accumulated by Belle detector at KEK. No evidence signal is seen, and we set an upper limit branching fraction B(tau gamma) < 3.1 x 10^{-7} 90% confidence level.
Breakdown phenomena on alumina RF windows for S-band high-power use were investigated using a resonant ring. Occasional flashovers observed TiN-coated surfaces, though the multipactor effect is suppressed by coating. The show luminescence with treelike pattern, resulting in limitation of transmittable power through window. This flashover threshold depends dielectric materials; sapphire F-center defects shows lower threshold. For further investigations mechanism under field, situ measurements...
Thin films of TiN having low secondary electron emission (SEE) yields are coated on alumina rf windows in order to suppress the occurrence multipactor. It is necessary form with a proper thickness obtain sufficient reduction SEE as well avoid any excessive ohmic loss conductive films. For an optimization film surface, measurements coefficients, and losses (S-band) field were carried out. High-power examinations also performed. The results show that 0.5 nm or greater ceramics have...
The breakdown of alumina rf windows is mostly caused by multipactor, as well material defects and contamination. Since multipator induces localized surface heating, leading to melting, it necessary observe secondary electron emission (SEE) coefficients ceramics under high temperature conditions. SEE commercial sapphire were measured a scanning microscopy (SEM) with single short-pulsed beam (100 pA, 1 ms) at room 650degC. Additive materials used for sintering alumina, such SiO <sub...
The development of alumina RF windows for use at the output section high-power sources is an important issue accelerators. breakdown caused by 1. multipactor effect (electron multiplication on surface) and/or 2. discharge accumulated charges (due to effect). Measurements secondary electron emission (SEE) and surface charging were carried out determine durability various ceramics in this application. Since excessive heating takes place during discharge, SEE yields high temperature also...
A disturbance observer (DOB)-based control for a digital low-level radio-frequency (LLRF) system in compact energy recovery linac (cERL) at KEK has been developed. The motivation this approach is to compensate or suppress the signal rf such as beam loading, power supply ripples, and microphonics. Disturbance signals specified frequency ranges were observed reconstructed accurately field-programmable gate array then removed feedforward model real time. key component DOB controller observer,...
An 8-km long MgB <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> wire for a prototype klystron magnet was made and evaluated. The by typical in situ method; it has 10 filaments 0.67 mm outer diameter. homogeneity of I xmlns:xlink="http://www.w3.org/1999/xlink">c</sub> this evaluated several methods. Deviation values short sample wires very small. In addition, the current sharing temperature (made two reels 2.9 km each) agreed well with...
The effect of surface roughness insulator on the secondary electron emission (SEE) coefficients was investigated with changing incident angle primary electrons. SEE were measured using a scanning microscope single-pulse beam (100 pA, 1 ms). As result, increased for smooth surface, while those rough almost did not change angle. commercial alumina ceramics three different finishes, i.e. as-sintered, as-ground and mirror-finished samples, also before after annealing treatments. This treatment...
The KEKB electron/positron injector linac is under the upgrade for SuperKEKB. A new positron source with a target, beam spoiler, flux-concentrator and large-aperture S-band accelerating structures inside DC solenoids an separator have been installed. Preliminary commissioning has started. first observed after upgrade. construction status of recent performance are reported.
Abstract We present the cost-effective production of superconducting radio frequency (SRF) cavities made medium grain (MG) niobium (Nb) discs directly sliced from forged and annealed billet. This method provides clean surface conditions reliable mechanical characteristics with sub-millimeter average size resulting in stable SRF cavity production. propose to apply this material particle accelerator science industrial applications. The applications require high field gradients(≥ 30 MV/m)...
A Low-level radio-frequency (LLRF) control systems is required to regulate the rf field in cavity used for beam acceleration. As LLRF system usually complex, testing of basic functions or algorithms this real time and advance commissioning strongly recommended. However, equipment necessary test system, such as superconducting cavities high-power sources, very expensive; therefore, we have developed a field-programmable gate array (FPGA)-based simulator substitute cavities. Digital models...
We evaluate the neutron and muon fluxes produced in ILC beam dumps by Monte Carlo simulations discuss their potential use irradiation fields. show that can provide high-intensity with spectra quite similar to secondary cosmic rays, which are suitable for soft error studies. The deliver neutrons about $10^{11}$ times rays on spaces perpendicular axis muons $10^8$ downstream of initial phase ILC. Large-area 1\,m$^2$ or more is possible. Differences energy distribution electron positron also...