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Toshikazu Takatomi

Bio: Toshikazu Takatomi is an academic researcher from KEK. The author has contributed to research in topics: Electron gun & Photocathode. The author has an hindex of 9, co-authored 45 publications receiving 335 citations.

Papers
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Proceedings ArticleDOI
16 May 2005
TL;DR: A 60 cm-long traveling-wave structure with low group velocity and 150 degree per cell phase advance is proposed in this paper, which has an average iris size that produces an acceptable short-range wakefield, and dipole mode damping and detuning that adequately suppresses the long range wakefield.
Abstract: During the past five years, there has been an concerted program at SLAC and KEK to develop accelerator structures that meet the high gradient (65 MV/m) performance requirements for the Next Linear Collider (NLC) and Global Linear Collider (GLC) initiatives. The design that resulted is a 60-cm-long, traveling-wave structure with low group velocity and 150 degree per cell phase advance. It has an average iris size that produces an acceptable short-range wakefield, and dipole mode damping and detuning that adequately suppresses the long-range wakefield. More than eight such structures have operated at a 60 Hz repetition rate over 1000 hours at 65 MV/m with 400 ns long pulses, and have reached breakdown rate levels below the limit for the linear collider. Moreover, the structures are robust in that the rates continue to decrease over time, and if the structures are briefly exposed to air, the rates recover to their low levels within a few days. This paper presents a summary of the results from this program, which effectively ended last August with the selection of ‘cold’ technology for an International Linear Collider (ILC).

51 citations

Journal ArticleDOI
TL;DR: In this paper, a high-resolution cavity-beam position monitor (BPM) was used at the focal point of the ATF2, which is a test beam line that is now being built to demonstrate stable orbit control at 8.7 nm resolution.
Abstract: We have developed a high-resolution cavity-beam position monitor (BPM) to be used at the focal point of the ATF2, which is a test beam line that is now being built to demonstrate stable orbit control at $\ensuremath{\sim}\mathrm{\text{nanometer}}$ resolution. The design of the cavity structure was optimized for the Accelerator Test Facility (ATF) beam in various ways. For example, the cavity has a rectangular shape in order to isolate two dipole modes in orthogonal directions, and a relatively thin gap that is less sensitive to trajectory inclination. A two stage homodyne mixer with highly sensitive electronics and phase-sensitive detection was also developed. Two BPM blocks, each containing two cavity BPMs, were installed in the existing ATF beam line using a rigid support frame. After testing the basic characteristics, we measured the resolution using three BPMs. The system demonstrated 8.7 nm position resolution over a dynamic range of $5\text{ }\text{ }\ensuremath{\mu}\mathrm{m}$.

45 citations

Journal ArticleDOI
TL;DR: A laser-driven RF gun with a Cs 2 Te photocathode, a device modeled after the BNL-IV RF gun, has been in development at KEK since 2002 as discussed by the authors.
Abstract: A laser-driven RF gun with a Cs 2 Te photocathode, a device modeled after the BNL-IV RF gun, has been in development at KEK since 2002. This gun has been operated as an electron source for the Accelerator Test Facility (ATF) and generates a beam with an operational intensity of up to 3.2 nC per bunch. Based on successful results at the ATF, this gun has been applied several times for new research at universities. From 2002 onwards, successive improvements have been incorporated into newer models of the RF gun. Most recently, in 2008, a new gun incorporating all of the earlier modifications was produced for the ATF. Tests have confirmed a significant improvement of the Q-value of the latest model. A typical transverse emittance of 1.3 π mm mrad has been obtained under the following conditions: solenoid field of 0.18 T, beam intensity of 1.6 nC per bunch, and RF power of 9 MW. This RF gun equipped with the Cs 2 Te photocathode is being used for the advanced research programs at the ATF. A survey of its performance has recently been completed.

36 citations

01 Jan 2010
TL;DR: A CERN-SLAC-KEK collaboration on high gradient X-band structure research has been established in order to demonstrate the feasibility of the CLIC baseline design for the main linac stably operating at more than 100 MV/m loaded accelerating gradient as mentioned in this paper.
Abstract: A CERN-SLAC-KEK collaboration on high gradient X-band structure research has been established in order to demonstrate the feasibility of the CLIC baseline design for the main linac stably operating at more than 100 MV/m loaded accelerating gradient. Several prototype CLIC structures were successfully fabricated and high power tested. They operated at 105 MV/m with a breakdown rate that meets the CLIC linear collider specifications of < 5 x 10{sup -7}/pulse/m. This paper summarizes the fabrication technologies including the mechanical design, precision machining, chemical cleaning, diffusion bonding as well as vacuum baking and all related assembly technologies. Also, the tolerances control, tuning and RF characterization will be discussed.

32 citations

Proceedings ArticleDOI
27 Mar 1999
TL;DR: In this article, a new type of damped detuned structure with optimized round-shaped cavities (RDDS) was proposed for X-band accelerator structures for the JLC/NLC linear collider.
Abstract: For more than ten years, we have been working on R&D for X-band accelerator structures for the JLC/NLC linear collider. Several types of Detuned (DS) and Damped Detuned Structures (DDS) have been successfully designed and fabricated. They have been experimentally tested at both low power and high power to characterize their mechanical and electrical properties. Recently we started developing a new type of damped detuned structure with optimized round-shaped cavities (RDDS). This paper discusses the special specifications, design methods, fabrication procedures, measurement technologies, and anticipated future improvements for all these structures.

27 citations


Cited by
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Journal ArticleDOI
01 Aug 1952-Nature
TL;DR: Lang as discussed by the authors reviewed Lang's work in the Journal of Scientific Instruments (JSI) and Supplement No 1, 1951 Pp xvi + 388 + iii + 80 (London: Institute of Physics, 1951).
Abstract: Journal of Scientific Instruments Editor: Dr H R Lang Vol 28 and Supplement No 1, 1951 Pp xvi + 388 + iii + 80 (London: Institute of Physics, 1951) Bound, £3 12s; unbound, £3

725 citations

Journal ArticleDOI
TL;DR: In this article, the authors summarize the theoretical properties of the Standard Model Higgs boson and the Higgs sector of the minimal super-symmetric extension of the standard model (MSSM).

455 citations

Journal ArticleDOI
TL;DR: The STEAM device demonstrates the feasibility of terahertz-based electron accelerators, manipulators and diagnostic tools, enabling science beyond current resolution frontiers with transformative impact.
Abstract: Acceleration and manipulation of electron bunches underlie most electron and X-ray devices used for ultrafast imaging and spectroscopy. New terahertz-driven concepts offer orders-of-magnitude improvements in field strengths, field gradients, laser synchronization and compactness relative to conventional radiofrequency devices, enabling shorter electron bunches and higher resolution with less infrastructure while maintaining high charge capacities (pC), repetition rates (kHz) and stability. We present a segmented terahertz electron accelerator and manipulator (STEAM) capable of performing multiple high-field operations on the six-dimensional phase space of ultrashort electron bunches. With this single device, powered by few-microjoule, single-cycle, 0.3 THz pulses, we demonstrate record terahertz acceleration of >30 keV, streaking with 2 kT m–1 strength, compression to ~100 fs as well as real-time switching between these modes of operation. The STEAM device demonstrates the feasibility of terahertz-based electron accelerators, manipulators and diagnostic tools, enabling science beyond current resolution frontiers with transformative impact.

236 citations

Journal ArticleDOI
TL;DR: SuperKEKB as discussed by the authors, a 7 GeV electron - 4 GeV positron double-ring collider, is constructed by upgrading KEKB in order to seek new physics beyond the Standard Model.
Abstract: SuperKEKB, a 7 GeV electron - 4 GeV positron double-ring collider, is constructed by upgrading KEKB in order to seek new physics beyond the Standard Model. The design luminosity of SuperKEKB is 8 x 10^35 /cm^2 /s - 40 times higher than that achieved by KEKB. The greater part of the gain comes from significantly decreasing the beam sizes at the interaction point based on the nanobeam collision scheme; the design beam currents in both rings are double those achieved in KEKB. Large-scale construction to upgrade both the collider rings and the injector was conducted, and beam commissioning without the Belle II detector and final-focus magnets was successfully carried out from February to June in 2016. Subsequently, renovation of the interaction region, including the installation of the final-focus magnets and Belle II, and construction in the final stage of a new positron damping ring were conducted. Having completed the interaction region, beam collision tuning is scheduled from March till July in 2018. This paper reviews the design, construction, and beam commissioning of SuperKEKB.

124 citations

Proceedings Article
01 Oct 1986

86 citations