IPAC2017 - List of Authors (Yoshida, M.)

Paper	Title	Page
MOPIK009	Characterization of Cold Model Cavity for Cryocooled C-Band 2.6-Cell Photocathode RF Gun at 20 K	518
	T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka LEBRA, Funabashi, Japan M.K. Fukuda, D. Satoh, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan
	Funding: This work was partly supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). A cryocooled C-band 2.6-cell photocathode RF electron gun has been studied at Nihon University in cooperation with KEK. The cold model cavity with an input coupler was completed in spring 2016. The RF characteristics measured at room temperature were in agreement with the prediction by the CST Studio simulation. The RF characteristics at 20 K have been measured using a rather simple cavity-cooling vacuum system that was built by using existing components for tentative experiments. A thin-wall stainless-steel R48 waveguide with copper-plated inner walls has been used for the RF power transmission from the room-temperature input port to the 20-K cooled coupler waveguide. The unloaded Q-value of 73000 has been obtained by the reflection coefficient measurement at 20 K, which is in agreement with the result of the CST Studio simulation using the cavity surface resistance predicted by the theory of the anomalous skin effect.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK009
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TUPAB004	Progress of 7-GeV SuperKEKB Injector Linac Upgrade and Commissioning	1300
	K. Furukawa, M. Akemoto, D.A. Arakawa, Y. Arakida, H. Ego, A. Enomoto, Y. Enomoto, S. Fukuda, Y. Funahashi, T. Higo, H. Honma, N. Iida, M. Ikeda, H. Kaji, K. Kakihara, T. Kamitani, H. Katagiri, M. Kawamura, M. Kurashina, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, T. Miura, F. Miyahara, H. Nakajima, K. Nakao, T. Natsui, M. Nishida, Y. Ogawa, Y. Ohnishi, S. Ohsawa, F. Qiu, I. Satake, D. Satoh, M. Satoh, Y. Seimiya, A. Shirakawa, H. Sugimoto, H. Sugimura, T. Suwada, T. Takatomi, T. Takenaka, M. Tanaka, N. Toge, Y. Yano, K. Yokoyama, M. Yoshida, R. Zhang, X. Zhou KEK, Ibaraki, Japan
	KEK injector linac has delivered electrons and positrons for particle physics and photon science experiments for more than 30 years. It is being upgraded for the SuperKEKB project, which aims at a 40-fold increase in luminosity over the previous project KEKB, in order to increase our understanding of new physics beyond the standard model of elementary particle physics. SuperKEKB asymmetric electron and positron collider with its extremely high luminosity requires a high current, low emittance and low energy spread injection beam from the injector. Electron beams will be generated by a new type of RF gun, that will provide a much higher beam current to correspond to a large stored beam current and a short lifetime in the ring. The positron source is another major challenge that enhances the positron bunch intensity from 1 to 4 nC by increasing the positron capture efficiency, and the positron beam emittance is reduced from 2000 micron to 20 micron in the vertical plane by introducing a damping ring, followed by the bunch compressor and energy compressor. The recent status of the upgrade and beam commissioning is reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB004
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TUPAB056	New Achievements of the Laser System for RF-Gun at SuperKEKB Injector	1452
	R. Zhang, T. Natsui, Y. Ogawa, M. Yoshida, X. Zhou KEK, Ibaraki, Japan
	For realizing high charge and low emittance electron and positron beams in SuperKEKB, we have been making improvements in current laser system for RF-gun. In order to realize more excellent thermal management in current laser system at high repetition rate operation, novel soldering Yb:YAG thin disk and copper tungsten heat sink laser head is manufactured via gold tin solder. Comparing with old design, less residual stress is introduced and more efficient thermal removal can be obtained. These new soldering laser heads are placed into a compact vacuum chamber and cooled by Peltier plates directly. This design can realize higher gain and amplification factor in regenerative amplifier and multi-pass amplifier. In addition, the compact and simple cooling method can achieve excellent thermal management for the purpose of realize laser operation at high repetition rate for following phases of SuperKEKB project. A perspective towards the next step experiment is also presented in this paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB056
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TUPVA094	Beam Dynamics Design of the Muon Linac High-Beta Section	2304
	Y. Kondo, K. Hasegawa JAEA/J-PARC, Tokai-mura, Japan R. Kitamura University of Tokyo, Tokyo, Japan T. Mibe, M. Otani, M. Yoshida KEK, Ibaraki, Japan
	Funding: This work was supported by JSPS KAKENHI Grant Number 16H03987. A muon linac development for a new muon g-2 experiment is now going on at J-PARC. Muons from the muon beam line (H-line) at the J-PARC MLF are once stopped in an silica aerojel target and room temperature muoniums are evaporated from the aerogel. They are dissociated with laser (ultra slow muons), then accelerated up to 212 MeV using a linear accelerator. For the accelerating structure from 40 MeV, disk-loaded traveling-wave structure is applicable because the particle beta is more than 0.7. The structure itself is similar to that for electron linacs, however, the cell length should be harmonic to the increase of the particle velocity. In this paper, the beam dynamics design of this muon linac using the disk-loaded structure is described.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA094
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WEPAB044	Construction and Commissioning of Direct Beam Transport Line for PF-AR	2678
	N. Higashi, S. Asaoka, K. Furukawa, K. Haga, K. Harada, T. Higo, T. Honda, H. Honma, N. Iida, H. Iwase, K. Kakihara, T. Kamitani, M. Kikuchi, Y. Kishimoto, Y. Kobayashi, K. Kodama, K. Kudo, T. Kume, K. Mikawa, T. Mimashi, F. Miyahara, H. Miyauchi, S. Nagahashi, H. Nakamura, N. Nakamura, T. Natsui, K.N. Nigorikawa, Y. Niwa, T. Nogami, T. Obina, Y. Ogawa, M. Ono, T. Ozaki, H. Sagehashi, T. Sanami, M. Sato, M. Satoh, T. Suwada, M. Tadano, T. Tahara, R. Takai, H. Takaki, S. Takasaki, M. Tanaka, Y. Tanimoto, M. Tawada, N. Toge, T. Uchiyama, A. Ueda, Y. Yamada, M. Yamamoto, M. Yoshida KEK, Ibaraki, Japan
	PF-AR was constructed as an accumulator ring for TRISTAN, and in the KEKB era it has been revitalized as a 6.5 GeV synchrotron radiation source. The injection energy was 3 GeV and the beam was accelerated to 6.5 GeV prior to the user run. The original beam transport line (BT) from the LINAC to the PF-AR shared its upstream part with the the BT line of KEKB High Energy Ring (HER). The injection-mode change from PF-AR to HER or vice versa needs about 10 minutes for the magnet cycling procedure of the shared part. In SuperKEKB, the upgrade of KEKB, the lifetime of HER is about 10 minutes. The mode-switch operation of the BT is, therefore, not allowed for maintaining the highest luminosity of the SuperKEKB. In order to avoid this problem, a new 6.5 GeV BT line dedicated to PF-AR has been constructed. This also enables the top-up injection for the user run. The commissioning of the new BT line has been completed in this March, and now the first user run has been operated successfully.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB044
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WEPVA011	Development of a Laser Driven Dielectric Accelerator for Radiobiology Research	3272
	K. Koyama, M. Yoshida KEK, Ibaraki, Japan Z. Chen, H. Okamoto The University of Tokyo, Tokyo, Japan M. Uesaka The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan
	Funding: This work was supported by KAKENHI, (Grant-in-Aid for Scientific Research) Grant Number 15H03595 and partly supported by NIMS Nanofabrication Platform in Nanotechnology Platform Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan. A laser-driven dielectric accelerator below 1 MeV is under development for applying a sub-micron size electron-beam to radiobiological research. Simulations of the electric field and electron trajectories in the proximity of the dielectric structure (transmission grating) were performed in order to fix parameters of the demonstration experiment. Serious deflection of electron beam towards the grating limited the injection phase as well as the height from the structure. The energy gain of 50-keV electron was estimated to be 1 keV in 30-micron length at the optimum condition. Transmission gratings for the experiment were fabricated by using facilities of the NIMS Nanofabrication Platform. In addition to the acceleration experiment using the simple grating, a resonator type accelerator structure was designed for exciting the acceleration field by a moderately small laser.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA011
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THPVA047	Developing an Yb/Nd Doped Hybrid Solid Laser of RF Gun for SuperKEKB Phase II Commissioning	4540
	X. Zhou, T. Natsui, Y. Ogawa, M. Yoshida, R. Zhang KEK, Ibaraki, Japan
	The electron beams with a charge of several nC and a normalized emittance of less than 10 'm are expected to be generated in the photocathode RF gun for injector linac of SuperKEKB accelerator project. By development of the Yb-doped laser system, more than 1.0 nC electron has been obtained in 25 Hz. The laser system is already for commissioning phase I. But, the 30 ps pulse width stretch limit the pulse energy of the amplifier laser system. As well-established laser material, Nd:YAG rods with high optical homogeneity and high damage threshold, simplify the design of high-pulse-energy amplifier. Therefore, a new Nd/Yb hybrid laser system is development to increase the pulse energy of the laser source. For phase II commissioning, more than 3 nC electron beam is expected. Also, a chirped pulse amplification (CPA) laser system is prepared for the phase III commissioning, both pulse energy and pulse shaping controller are expected.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA047
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Paper

Title

Page

Characterization of Cold Model Cavity for Cryocooled C-Band 2.6-Cell Photocathode RF Gun at 20 K

518

T. Tanaka, K. Hayakawa, Y. Hayakawa, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka
LEBRA, Funabashi, Japan
M.K. Fukuda, D. Satoh, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan

Funding: This work was partly supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
A cryocooled C-band 2.6-cell photocathode RF electron gun has been studied at Nihon University in cooperation with KEK. The cold model cavity with an input coupler was completed in spring 2016. The RF characteristics measured at room temperature were in agreement with the prediction by the CST Studio simulation. The RF characteristics at 20 K have been measured using a rather simple cavity-cooling vacuum system that was built by using existing components for tentative experiments. A thin-wall stainless-steel R48 waveguide with copper-plated inner walls has been used for the RF power transmission from the room-temperature input port to the 20-K cooled coupler waveguide. The unloaded Q-value of 73000 has been obtained by the reflection coefficient measurement at 20 K, which is in agreement with the result of the CST Studio simulation using the cavity surface resistance predicted by the theory of the anomalous skin effect.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPIK009

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TUPAB004

Progress of 7-GeV SuperKEKB Injector Linac Upgrade and Commissioning

1300

K. Furukawa, M. Akemoto, D.A. Arakawa, Y. Arakida, H. Ego, A. Enomoto, Y. Enomoto, S. Fukuda, Y. Funahashi, T. Higo, H. Honma, N. Iida, M. Ikeda, H. Kaji, K. Kakihara, T. Kamitani, H. Katagiri, M. Kawamura, M. Kurashina, S. Matsumoto, T. Matsumoto, H. Matsushita, S. Michizono, K. Mikawa, T. Miura, F. Miyahara, H. Nakajima, K. Nakao, T. Natsui, M. Nishida, Y. Ogawa, Y. Ohnishi, S. Ohsawa, F. Qiu, I. Satake, D. Satoh, M. Satoh, Y. Seimiya, A. Shirakawa, H. Sugimoto, H. Sugimura, T. Suwada, T. Takatomi, T. Takenaka, M. Tanaka, N. Toge, Y. Yano, K. Yokoyama, M. Yoshida, R. Zhang, X. Zhou
KEK, Ibaraki, Japan

KEK injector linac has delivered electrons and positrons for particle physics and photon science experiments for more than 30 years. It is being upgraded for the SuperKEKB project, which aims at a 40-fold increase in luminosity over the previous project KEKB, in order to increase our understanding of new physics beyond the standard model of elementary particle physics. SuperKEKB asymmetric electron and positron collider with its extremely high luminosity requires a high current, low emittance and low energy spread injection beam from the injector. Electron beams will be generated by a new type of RF gun, that will provide a much higher beam current to correspond to a large stored beam current and a short lifetime in the ring. The positron source is another major challenge that enhances the positron bunch intensity from 1 to 4 nC by increasing the positron capture efficiency, and the positron beam emittance is reduced from 2000 micron to 20 micron in the vertical plane by introducing a damping ring, followed by the bunch compressor and energy compressor. The recent status of the upgrade and beam commissioning is reported.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB004

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TUPAB056

New Achievements of the Laser System for RF-Gun at SuperKEKB Injector

1452

R. Zhang, T. Natsui, Y. Ogawa, M. Yoshida, X. Zhou
KEK, Ibaraki, Japan

For realizing high charge and low emittance electron and positron beams in SuperKEKB, we have been making improvements in current laser system for RF-gun. In order to realize more excellent thermal management in current laser system at high repetition rate operation, novel soldering Yb:YAG thin disk and copper tungsten heat sink laser head is manufactured via gold tin solder. Comparing with old design, less residual stress is introduced and more efficient thermal removal can be obtained. These new soldering laser heads are placed into a compact vacuum chamber and cooled by Peltier plates directly. This design can realize higher gain and amplification factor in regenerative amplifier and multi-pass amplifier. In addition, the compact and simple cooling method can achieve excellent thermal management for the purpose of realize laser operation at high repetition rate for following phases of SuperKEKB project. A perspective towards the next step experiment is also presented in this paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPAB056

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TUPVA094

Beam Dynamics Design of the Muon Linac High-Beta Section

2304

Y. Kondo, K. Hasegawa
JAEA/J-PARC, Tokai-mura, Japan
R. Kitamura
University of Tokyo, Tokyo, Japan
T. Mibe, M. Otani, M. Yoshida
KEK, Ibaraki, Japan

Funding: This work was supported by JSPS KAKENHI Grant Number 16H03987.
A muon linac development for a new muon g-2 experiment is now going on at J-PARC. Muons from the muon beam line (H-line) at the J-PARC MLF are once stopped in an silica aerojel target and room temperature muoniums are evaporated from the aerogel. They are dissociated with laser (ultra slow muons), then accelerated up to 212 MeV using a linear accelerator. For the accelerating structure from 40 MeV, disk-loaded traveling-wave structure is applicable because the particle beta is more than 0.7. The structure itself is similar to that for electron linacs, however, the cell length should be harmonic to the increase of the particle velocity. In this paper, the beam dynamics design of this muon linac using the disk-loaded structure is described.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-TUPVA094

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WEPAB044

Construction and Commissioning of Direct Beam Transport Line for PF-AR

2678

N. Higashi, S. Asaoka, K. Furukawa, K. Haga, K. Harada, T. Higo, T. Honda, H. Honma, N. Iida, H. Iwase, K. Kakihara, T. Kamitani, M. Kikuchi, Y. Kishimoto, Y. Kobayashi, K. Kodama, K. Kudo, T. Kume, K. Mikawa, T. Mimashi, F. Miyahara, H. Miyauchi, S. Nagahashi, H. Nakamura, N. Nakamura, T. Natsui, K.N. Nigorikawa, Y. Niwa, T. Nogami, T. Obina, Y. Ogawa, M. Ono, T. Ozaki, H. Sagehashi, T. Sanami, M. Sato, M. Satoh, T. Suwada, M. Tadano, T. Tahara, R. Takai, H. Takaki, S. Takasaki, M. Tanaka, Y. Tanimoto, M. Tawada, N. Toge, T. Uchiyama, A. Ueda, Y. Yamada, M. Yamamoto, M. Yoshida
KEK, Ibaraki, Japan

PF-AR was constructed as an accumulator ring for TRISTAN, and in the KEKB era it has been revitalized as a 6.5 GeV synchrotron radiation source. The injection energy was 3 GeV and the beam was accelerated to 6.5 GeV prior to the user run. The original beam transport line (BT) from the LINAC to the PF-AR shared its upstream part with the the BT line of KEKB High Energy Ring (HER). The injection-mode change from PF-AR to HER or vice versa needs about 10 minutes for the magnet cycling procedure of the shared part. In SuperKEKB, the upgrade of KEKB, the lifetime of HER is about 10 minutes. The mode-switch operation of the BT is, therefore, not allowed for maintaining the highest luminosity of the SuperKEKB. In order to avoid this problem, a new 6.5 GeV BT line dedicated to PF-AR has been constructed. This also enables the top-up injection for the user run. The commissioning of the new BT line has been completed in this March, and now the first user run has been operated successfully.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPAB044

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WEPVA011

Development of a Laser Driven Dielectric Accelerator for Radiobiology Research

3272

K. Koyama, M. Yoshida
KEK, Ibaraki, Japan
Z. Chen, H. Okamoto
The University of Tokyo, Tokyo, Japan
M. Uesaka
The University of Tokyo, Nuclear Professional School, Ibaraki-ken, Japan

Funding: This work was supported by KAKENHI, (Grant-in-Aid for Scientific Research) Grant Number 15H03595 and partly supported by NIMS Nanofabrication Platform in Nanotechnology Platform Project sponsored by the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.
A laser-driven dielectric accelerator below 1 MeV is under development for applying a sub-micron size electron-beam to radiobiological research. Simulations of the electric field and electron trajectories in the proximity of the dielectric structure (transmission grating) were performed in order to fix parameters of the demonstration experiment. Serious deflection of electron beam towards the grating limited the injection phase as well as the height from the structure. The energy gain of 50-keV electron was estimated to be 1 keV in 30-micron length at the optimum condition. Transmission gratings for the experiment were fabricated by using facilities of the NIMS Nanofabrication Platform. In addition to the acceleration experiment using the simple grating, a resonator type accelerator structure was designed for exciting the acceleration field by a moderately small laser.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-WEPVA011

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THPVA047

Developing an Yb/Nd Doped Hybrid Solid Laser of RF Gun for SuperKEKB Phase II Commissioning

4540

X. Zhou, T. Natsui, Y. Ogawa, M. Yoshida, R. Zhang
KEK, Ibaraki, Japan

The electron beams with a charge of several nC and a normalized emittance of less than 10 'm are expected to be generated in the photocathode RF gun for injector linac of SuperKEKB accelerator project. By development of the Yb-doped laser system, more than 1.0 nC electron has been obtained in 25 Hz. The laser system is already for commissioning phase I. But, the 30 ps pulse width stretch limit the pulse energy of the amplifier laser system. As well-established laser material, Nd:YAG rods with high optical homogeneity and high damage threshold, simplify the design of high-pulse-energy amplifier. Therefore, a new Nd/Yb hybrid laser system is development to increase the pulse energy of the laser source. For phase II commissioning, more than 3 nC electron beam is expected. Also, a chirped pulse amplification (CPA) laser system is prepared for the phase III commissioning, both pulse energy and pulse shaping controller are expected.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPVA047

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