IPAC2016 - List of Authors (Terunuma, N.)

Paper	Title	Page
MOPMR040	First Steps Towards a Single-Shot Longitudinal Profile Monitor: Study of the Properties of Coherent Smith-Purcell Radiation Using the Surface Current Model	340
SUPSS069	use link to see paper's listing under its alternate paper code
	H. Harrison, G. Doucas, I.V. Konoplev, A.J. Lancaster JAI, Oxford, United Kingdom A. Aryshev, K. Lekomtsev, M. Shevelev, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	Funding: UK STFC, Leverhulme Trust, Photon and Quantum Basic Research Coordinated Development Program (Ministry of Education, Culture, Sports, Science and Technology, Japan)and JSPS KAKENHI. We propose to use the polarization of coherent Smith-Purcell radiation (cSPr) to separate the signal from background radiation in a single-shot longitudinal bunch profile monitor. We compare simulation and experimental results for the degree of polarization of cSPr generated by a grating with a 1mm periodic structure at the LUCX facility, KEK (Japan). Both experiment and simulation show that the majority of the cSPr signal is polarized in the direction parallel to the grating grooves. The degree of polarization predicted by simulation is higher than the measured result, therefore further investigation is needed to resolve this discrepancy.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPMR040
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MOPOW016	Status of Design and Development of Delhi Light Source at IUAC, Delhi	748
	S. Ghosh, R.K. Bhandari, G.K. Chaudhari, V.J. Joshi, D. Kabiraj, D. Kanjilal, B. Karmakar, J. Karmakar, N. Kumar, P. Patra, B.K. Sahu, A.S. Sharma, A.S. Sthuthikkatt Reghu IUAC, New Delhi, India A. Aryshev, M.K. Fukuda, S. Fukuda, N. Terunuma, J. Urakawa, J. Urakawa KEK, Ibaraki, Japan A. Deshpande SAMEER, Mumbai, India V. Naik, A. Roy VECC, Kolkata, India T. Rao BNL, Upton, Long Island, New York, USA
	Funding: The project is supported jointly by Board of Research in Nuclear Sciences (BRNS) and IUAC The demand for the photon beams for basic research is growing in India. To address the requirements, a project to develop a compact Light Source based on the principle of Free Electron Laser has been initiated at the Inter University Accelerator Centre (IUAC). In the first phase of the project, a normal conducting RF gun will be used to produce electron beam of energy ~ 8 MeV by using copper photocathode and subsequently by Cs2Te photocathode. A high power fiber laser with short pulse length is planned to be used to produce the pre-bunched electron beam by splitting the single laser pulse in to 16 pulses ("comb beam"). The electron beam will be injected in to a compact, variable gap undulator magnet to produce the THz radiation whose frequency can be tuned by varying the undulator field strength and the time separation of the comb beam. In the second and third phases of the project, superconducting RF gun and superconducting accelerating structure will be used to increase the energy of the electron beam up to ~ 40 MeV which will be used to produce IR radiation by using long undulator magnets and to produce X-rays by colliding the electron beam with another high power laser beam.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-MOPOW016
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TUPOW036	Recent Developments and Operational Status of the Compact ERL at KEK	1835
	T. Obina, M. Adachi, S. Adachi, T. Akagi, M. Akemoto, D.A. Arakawa, S. Araki, S. Asaoka, M. Egi, K. Enami, K. Endo, S. Fukuda, T. Furuya, K. Haga, K. Hara, K. Harada, T. Honda, Y. Honda, H. Honma, T. Honma, K. Hosoyama, K. Hozumi, A. Ishii, X.J. Jin, E. Kako, Y. Kamiya, H. Katagiri, R. Kato, H. Kawata, Y. Kobayashi, Y. Kojima, Y. Kondo, T. Konomi, A. Kosuge, T. Kume, T. Matsumoto, H. Matsumura, H. Matsushita, S. Michizono, T. Miura, T. Miyajima, H. Miyauchi, S. Nagahashi, H. Nakai, H. Nakajima, N. Nakamura, K. Nakanishi, K. Nakao, K.N. Nigorikawa, T. Nogami, S. Noguchi, S. Nozawa, T. Ozaki, F. Qiu, H. Sagehashi, H. Sakai, S. Sakanaka, S. Sasaki, K. Satoh, Y. Seimiya, T. Shidara, M. Shimada, K. Shinoe, T. Shioya, T. Shishido, M. Tadano, T. Tahara, T. Takahashi, R. Takai, H. Takaki, T. Takenaka, O. Tanaka, Y. Tanimoto, N. Terunuma, M. Tobiyama, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, J. Urakawa, K. Watanabe, M. Yamamoto, N. Yamamoto, Y. Yamamoto, Y. Yano, M. Yoshida KEK, Ibaraki, Japan R. Hajima, M. Mori, R. Nagai, N. Nishimori, M. Sawamura, T. Shizuma QST, Tokai, Japan M. Kuriki Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan
	The Compact Energy Recovery Linac (cERL) at KEK is a test accelerator in order to develop key components to realize remarkable ERL performance as a future light source. After the beam commissioning in December 2013, the legal current limit has been increased step-by-step like 1 uA, 10 uA, and 100 uA. Survey for the source of beam losses has been conducted in each step, and the study on beam dynamics and tuning has also been carried out. As a next step, 1 mA operation is scheduled in February 2016. In parallel to the increase in beam current, a laser Compton scattering (LCS) system which can provide high-flux X-ray to a beamline has been successfully commissioned. We report recent progress in various kinds of beam tuning: improvement of electron gun performance, high bunch charge operation, mitigation of beam losses, LCS optics tuning and bunch compression for THz radiation.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW036
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TUPOW044	Experimental Investigation of THz Smith-Purcell Radiation From Composite Corrugated Capillary	1861
	K. Lekomtsev, A. Aryshev, M. Shevelev, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan A. Ponomarenko, A.A. Tishchenko MEPhI, Moscow, Russia
	Funding: This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. Terahertz part of electromagnetic spectrum has a variety of potential applications ranging from fundamental to security applications. Further advances in development of a linac based, tunable, and narrow band coherent source of THz radiation are very important. Mechanisms of Cherenkov radiation and Smith-Purcell radiation (SPR) [] may be used for generation of THz radiation via coherent emission [, ]. In this report we will present experimental investigations of the SPR generated from the corrugated capillary with a reflector, using the femtosecond multi-bunch electron beam of LUCX accelerator at KEK, Japan [*]. LUCX is capable to generate a train of 4 bunches each with 200 femtosecond (60 micrometer) duration and 200 micrometer transverse size. We will discuss the composite design of the capillary, measurements of the SPR angular distributions and the comparison of these measurements with PIC simulations. In addition, we will discuss SPR spectral characteristics; bunch energy modulation, introduced by the corrugated capillary; and the way in which the bunch spacing changes the spectrum and angular distributions of SPR. K.Lekomtsev et al., NIMB 355 (2015) 164 A. M. Cook et al., PRL 103, (2009) 095003. S. E. Korbly et al., PRL 94, (2005) 054803. ***A. Aryshev, arXiv:1507.03302 [physics.acc-ph]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW044
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TUPOW045	Pre-bunched Electron Beam Emittance Simulation and Measurement	1864
	Yu.D. Kliuchevskaia, S.M. Polozov MEPhI, Moscow, Russia A. Aryshev, M. Shevelev, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	LUCX facility at KEK is used as the high brightness pre-bunched electron beam source for radiation experiments. Emittance measurement and optimization is one of the important research activities for newly developed operation mode of the facility. Characterization of the pre-bunched beam (THz sequence of a hundred femtosecond bunches) properties opens a possibility to establish detailed simulation of the THz FEL radiation yield and continuously improve pre-bunched beam dynamics insight. Emittance has been measured by the Q-scan method. The measurement results and possible ways of emittance optimization are discussed. The measurement results are compared with beam dynamics simulation done by self-consistent BEAMDULAC-BL code.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW045
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TUPOW046	Development and Upgrade Plan of an X-ray Source Based on Laser Compton Scattering in Laser Undulator Compact X-ray Source(LUCX)	1867
	M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan M. Kageyama, M. Kuribayashi Rigaku Corporation, XG & Core Technology, Tokyo, Japan A. Momose, M.P. Olbinado, Y. Wu Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Sendai, Japan K. Sakaue Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan M. Washio RISE, Tokyo, Japan
	Funding: This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan. We have been developing a compact X-ray source based on Laser Compton scattering(LCS) at Laser Undulator Compact X-ray source(LUCX) accelerator in KEK. Our aim is to obtain a clear X-ray image in a shorter period of times and the target number of X-ray is 1.7x10⁷ photons/pulse with 10% bandwidth. In the accelerator, an electron beam with the energy of 18-24 MeV is generated by an S-band normal conducting accelerator. The beam is collided with a laser pulse stacked in a 4-mirror planar optical cavity and then 6-10 keV X-rays are generated by LCS. Presently, the generation of X-rays with the number of 3x10⁶ photons/pulse at the collision point has been achieved. X-ray imaging test such as refraction contrast images and phase contrast imaging with Talbot interferometer has also started. To increase the intensity of X-rays, we are continuing the tuning of the electron beam and the optical cavity because the exposure time of X-ray imaging is too long now. We are also planning to increase the beam energy by appending the accelerating tube. In this conference, the recent results and upgrade plan in LUCX will be reported.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW046
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WEPMY037	Cold Model Cavity for 20-K Cryocooled C-band Photocathode RF Gun	2635
	T. Tanaka, M. Inagaki, R. Nagashima, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka LEBRA, Funabashi, Japan M.K. Fukuda, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan D. Satoh TIT, Tokyo, Japan
	Funding: Work 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 2.6-cell C-band photocathode RF gun is under development at Nihon University in collaboration with KEK. The RF characteristics of a pillbox-type 2.6-cell C-band RF cavity at 20 K were in agreement with the theoretical predictions. The result of the cold test for a cavity with the input coupler confirmed the same characteristics. Based on these results a refined cold model of the 20-K cryocooled photocathode RF gun has been designed using SUPERFISH and CST-STUDIO. The separation between the TM01 pi and the TM01 half-pi modes has been increased from 20 MHz to 52 MHz by extending the diameter of the cavity iris and reducing the disk thickness. The 2.6-cell structure has been modified from pillbox to ellipsoid-like type. The end-plate of the 0.6-cell cavity has a center hole for bead-pull measurements of the on-axis electric filed through the entire structure. Mounting of a photocathode assembly in the end-plate has not been considered, since the purpose is solely to measure the low-power and low-temperature RF characteristics. A new design for the input coupler has been employed. The cavity will be completed early in 2016.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY037
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WEPMY038	Optimization of C-band RF Input Coupler as a Mode Converter for 20-K Cryocooled Photocathode RF Gun	2638
	T. Tanaka, M. Inagaki, R. Nagashima, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka LEBRA, Funabashi, Japan M.K. Fukuda, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida KEK, Ibaraki, Japan D. Satoh TIT, Tokyo, Japan
	Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT). Development of a cryocooled 2.6-cell C-band photocathode RF gun has been conducted at Nihon University in collaboration with KEK. An RF mode converter from square TE10 to circular TM01 mode has been employed as an RF input coupler that has a coupling coefficient of approximately 20 at 20 K to the 2.6-cell accelerating structure. In the previous design, the circular waveguide in the mode converter formed part of the accelerating cavity. After the cold test of the cavity completed in 2014, the coupler design was modified to work as a pure mode converter with a VSWR of 1 at 5712 MHz. From the design simulation using CST-STUDIO, the insertion loss in the converter is 0.2 %. The TM010 and TM011 modes excited in the circular waveguide were separated by several ten MHz from the accelerating frequency. The simulation has suggested that the amplitude of the transverse electric filed on the axis in the circular waveguide is reduced to approximately 2 % of that in the longitudinal direction.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPMY038
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WEPOR005	Ground Motion Compensation using Feed-forward Control at ATF2	2670
	D.R. Bett, C. Charrondière, M. Patecki, J. Pfingstner, D. Schulte, R. Tomás CERN, Geneva, Switzerland A. Jeremie IN2P3-LAPP, Annecy-le-Vieux, France K. Kubo, S. Kuroda, T. Naito, T. Okugi, T. Tauchi, N. Terunuma KEK, Ibaraki, Japan
	Ground motion compensation using feed-forward control is a novel technique being developed to combat beam imperfections resulting from the vibration-induced misalignment of beamline components. The method is being evaluated experimentally at the KEK Accelerator Test Facility 2 (ATF2). It has already been demonstrated that the beam position correlates with the readings from a set of seismometers located along the beamline. To compensate for this contribution to the beam jitter, the fully operational system will use realtime measurement and processing in order to calculate and apply the feed-forward correction on a useful time scale. The progress towards a working system is presented in this paper.
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-WEPOR005
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THOAA02	The Development of C-Band Cavity Beam Position Monitor with a Position Resolution of Nano Meter	3149
	S.W. Jang, E.-S. Kim Korea University Sejong Campus, Sejong, Republic of Korea P. Bambade, O.R. Blanco-García, S. Wallon LAL, Orsay, France N. Blaskovic Kraljevic, T. Bromwich, P. Burrows JAI, Oxford, United Kingdom T. Tauchi, N. Terunuma KEK, Ibaraki, Japan
	We developed and tested an C-band beam position monitor with position resolution of nano meter in ATF2. The C-band BPM was developed for the fast beam feedback system at the interaction point of ATF in KEK, which C-band beam position monitor called to IPBPM (Interaction Point Beam Position Monitor). The developed IPBPM was measured 26nm with 30% of nominal beam charge of ATF. From the measured beam position resolution, we can expected to 8nm beam position resolution with nominal ATF beam charge condition. In this talk, we will described about the development of IPBPM and the beam test results of nano meter level beam position resolution.
	Slides THOAA02 [4.806 MB]
DOI •	reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THOAA02
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THPMB043	Progress in Ultra-Low β* Study at ATF2	3335
	M. Patecki, D.R. Bett, F. Plassard, R. Tomás CERN, Geneva, Switzerland K. Kubo, S. Kuroda, T. Naito, T. Okugi, T. Tauchi, N. Terunuma KEK, Ibaraki, Japan M. Patecki Warsaw University of Technology, Warsaw, Poland T. Tauchi, N. Terunuma Sokendai, Ibaraki, Japan
	A nanometer beam size in the interaction point (IP) is required in case of future linear colliders for achieving the desired rate of particle collisions. KEK Accelerator Test Facility (ATF2), a scaled down implementation of the beam delivery system (BDS), serves for investigating the limits of electron beam focusing at the interaction point. The goal of the ultra-low beta∗ study is to lower the IP vertical beam size by lowering the beta_y∗ value while keeping the beta_x∗ value unchanged. Good control over the beam optics is therefore required. The first experience with low beta∗ optics revealed a mismatch between the optics designed in the model with respect to the beam parameters observed in the experiment. Additionally, existing methods of beam parameters characterization at the IP were biased with high uncertainties making it difficult to set the desired optics. In this paper we report on the new method introduced in ATF2 for IP beam parameters characterization which gives a good control over the applied optics and makes the ultra-low beta∗ study possible to conduct. It can be also used for verifying the performance of some of the existing beam instrumentation devices.
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THPOR030	Commissioning and First Performance Studies of a Single Vertical Beam Halo Collimation System at ATF2	3844
	N. Fuster-Martínez, A. Faus-Golfe IFIC, Valencia, Spain P. Bambade, A. Faus-Golfe, S. Wallon, R.J. Yang LAL, Orsay, France K. Kubo, T. Okugi, T. Tauchi, N. Terunuma KEK, Ibaraki, Japan I. Podadera, F. Toral CIEMAT, Madrid, Spain T. Tauchi, N. Terunuma Sokendai, Ibaraki, Japan
	A single vertical beam halo collimation system has been installed in the ATF2 beamline to reduce the background that could limit the precision of the diagnostics located in the post-IP beamline. On this paper the commissioning and first performance studies of a single vertical beam halo collimation system are reported. Furthermore realistic efficiency studies have been done using the simulation code BDSIM and compared with the first experimental tests.
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THPOW007	Cs2Te Photocathode Response Time Measurements and Femtosecond Comb Electron Beam Generation as a Milestone Towards Pre-Bunched Thz Fel Realization	3941
	A. Aryshev, Y. Honda, K. Lekomtsev, M. Shevelev, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan
	Funding: Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan and JSPS KAKENHI: 23226020 and 24654076 Currently there is a rapidly growing demand to increase the brightness of electron beams generated by conventional RF guns as well as to decrease the cost of the injector accelerator system for many research facilities worldwide. To address this demand we investigate one of the most important parameter of the high Q.E. conventional semiconductor Cs2Te photocathode, its response time. It sets the principle limitation for generated bunch length and hence maximum achievable beam brightness of electron diffraction and pre-bunched THz FEL facility's injectors. The experimental investigation was done at KEK: LUCX facility. The Cs2Te photocathode response time better than 250 fs was demonstrated. The generation of 4 micro-bunch comb electron beam with variable time separation as a crucial technology for pre-bunched THz FEL realization was achieved.
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Paper

Title

Page

First Steps Towards a Single-Shot Longitudinal Profile Monitor: Study of the Properties of Coherent Smith-Purcell Radiation Using the Surface Current Model

340

SUPSS069

use link to see paper's listing under its alternate paper code

H. Harrison, G. Doucas, I.V. Konoplev, A.J. Lancaster
JAI, Oxford, United Kingdom
A. Aryshev, K. Lekomtsev, M. Shevelev, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

Funding: UK STFC, Leverhulme Trust, Photon and Quantum Basic Research Coordinated Development Program (Ministry of Education, Culture, Sports, Science and Technology, Japan)and JSPS KAKENHI.
We propose to use the polarization of coherent Smith-Purcell radiation (cSPr) to separate the signal from background radiation in a single-shot longitudinal bunch profile monitor. We compare simulation and experimental results for the degree of polarization of cSPr generated by a grating with a 1mm periodic structure at the LUCX facility, KEK (Japan). Both experiment and simulation show that the majority of the cSPr signal is polarized in the direction parallel to the grating grooves. The degree of polarization predicted by simulation is higher than the measured result, therefore further investigation is needed to resolve this discrepancy.

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MOPOW016

Status of Design and Development of Delhi Light Source at IUAC, Delhi

748

S. Ghosh, R.K. Bhandari, G.K. Chaudhari, V.J. Joshi, D. Kabiraj, D. Kanjilal, B. Karmakar, J. Karmakar, N. Kumar, P. Patra, B.K. Sahu, A.S. Sharma, A.S. Sthuthikkatt Reghu
IUAC, New Delhi, India
A. Aryshev, M.K. Fukuda, S. Fukuda, N. Terunuma, J. Urakawa, J. Urakawa
KEK, Ibaraki, Japan
A. Deshpande
SAMEER, Mumbai, India
V. Naik, A. Roy
VECC, Kolkata, India
T. Rao
BNL, Upton, Long Island, New York, USA

Funding: The project is supported jointly by Board of Research in Nuclear Sciences (BRNS) and IUAC
The demand for the photon beams for basic research is growing in India. To address the requirements, a project to develop a compact Light Source based on the principle of Free Electron Laser has been initiated at the Inter University Accelerator Centre (IUAC). In the first phase of the project, a normal conducting RF gun will be used to produce electron beam of energy ~ 8 MeV by using copper photocathode and subsequently by Cs2Te photocathode. A high power fiber laser with short pulse length is planned to be used to produce the pre-bunched electron beam by splitting the single laser pulse in to 16 pulses ("comb beam"). The electron beam will be injected in to a compact, variable gap undulator magnet to produce the THz radiation whose frequency can be tuned by varying the undulator field strength and the time separation of the comb beam. In the second and third phases of the project, superconducting RF gun and superconducting accelerating structure will be used to increase the energy of the electron beam up to ~ 40 MeV which will be used to produce IR radiation by using long undulator magnets and to produce X-rays by colliding the electron beam with another high power laser beam.

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TUPOW036

Recent Developments and Operational Status of the Compact ERL at KEK

1835

T. Obina, M. Adachi, S. Adachi, T. Akagi, M. Akemoto, D.A. Arakawa, S. Araki, S. Asaoka, M. Egi, K. Enami, K. Endo, S. Fukuda, T. Furuya, K. Haga, K. Hara, K. Harada, T. Honda, Y. Honda, H. Honma, T. Honma, K. Hosoyama, K. Hozumi, A. Ishii, X.J. Jin, E. Kako, Y. Kamiya, H. Katagiri, R. Kato, H. Kawata, Y. Kobayashi, Y. Kojima, Y. Kondo, T. Konomi, A. Kosuge, T. Kume, T. Matsumoto, H. Matsumura, H. Matsushita, S. Michizono, T. Miura, T. Miyajima, H. Miyauchi, S. Nagahashi, H. Nakai, H. Nakajima, N. Nakamura, K. Nakanishi, K. Nakao, K.N. Nigorikawa, T. Nogami, S. Noguchi, S. Nozawa, T. Ozaki, F. Qiu, H. Sagehashi, H. Sakai, S. Sakanaka, S. Sasaki, K. Satoh, Y. Seimiya, T. Shidara, M. Shimada, K. Shinoe, T. Shioya, T. Shishido, M. Tadano, T. Tahara, T. Takahashi, R. Takai, H. Takaki, T. Takenaka, O. Tanaka, Y. Tanimoto, N. Terunuma, M. Tobiyama, K. Tsuchiya, T. Uchiyama, A. Ueda, K. Umemori, J. Urakawa, K. Watanabe, M. Yamamoto, N. Yamamoto, Y. Yamamoto, Y. Yano, M. Yoshida
KEK, Ibaraki, Japan
R. Hajima, M. Mori, R. Nagai, N. Nishimori, M. Sawamura, T. Shizuma
QST, Tokai, Japan
M. Kuriki
Hiroshima University, Graduate School of Science, Higashi-Hiroshima, Japan

The Compact Energy Recovery Linac (cERL) at KEK is a test accelerator in order to develop key components to realize remarkable ERL performance as a future light source. After the beam commissioning in December 2013, the legal current limit has been increased step-by-step like 1 uA, 10 uA, and 100 uA. Survey for the source of beam losses has been conducted in each step, and the study on beam dynamics and tuning has also been carried out. As a next step, 1 mA operation is scheduled in February 2016. In parallel to the increase in beam current, a laser Compton scattering (LCS) system which can provide high-flux X-ray to a beamline has been successfully commissioned. We report recent progress in various kinds of beam tuning: improvement of electron gun performance, high bunch charge operation, mitigation of beam losses, LCS optics tuning and bunch compression for THz radiation.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW036

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TUPOW044

Experimental Investigation of THz Smith-Purcell Radiation From Composite Corrugated Capillary

1861

K. Lekomtsev, A. Aryshev, M. Shevelev, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
A. Ponomarenko, A.A. Tishchenko
MEPhI, Moscow, Russia

Funding: This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
Terahertz part of electromagnetic spectrum has a variety of potential applications ranging from fundamental to security applications. Further advances in development of a linac based, tunable, and narrow band coherent source of THz radiation are very important. Mechanisms of Cherenkov radiation and Smith-Purcell radiation (SPR) [*] may be used for generation of THz radiation via coherent emission [**, ***]. In this report we will present experimental investigations of the SPR generated from the corrugated capillary with a reflector, using the femtosecond multi-bunch electron beam of LUCX accelerator at KEK, Japan [****]. LUCX is capable to generate a train of 4 bunches each with 200 femtosecond (60 micrometer) duration and 200 micrometer transverse size. We will discuss the composite design of the capillary, measurements of the SPR angular distributions and the comparison of these measurements with PIC simulations. In addition, we will discuss SPR spectral characteristics; bunch energy modulation, introduced by the corrugated capillary; and the way in which the bunch spacing changes the spectrum and angular distributions of SPR.
*K.Lekomtsev et al., NIMB 355 (2015) 164
**A. M. Cook et al., PRL 103, (2009) 095003.
***S. E. Korbly et al., PRL 94, (2005) 054803.
****A. Aryshev, arXiv:1507.03302 [physics.acc-ph]

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-TUPOW044

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TUPOW045

Pre-bunched Electron Beam Emittance Simulation and Measurement

1864

Yu.D. Kliuchevskaia, S.M. Polozov
MEPhI, Moscow, Russia
A. Aryshev, M. Shevelev, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

LUCX facility at KEK is used as the high brightness pre-bunched electron beam source for radiation experiments. Emittance measurement and optimization is one of the important research activities for newly developed operation mode of the facility. Characterization of the pre-bunched beam (THz sequence of a hundred femtosecond bunches) properties opens a possibility to establish detailed simulation of the THz FEL radiation yield and continuously improve pre-bunched beam dynamics insight. Emittance has been measured by the Q-scan method. The measurement results and possible ways of emittance optimization are discussed. The measurement results are compared with beam dynamics simulation done by self-consistent BEAMDULAC-BL code.

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TUPOW046

Development and Upgrade Plan of an X-ray Source Based on Laser Compton Scattering in Laser Undulator Compact X-ray Source(LUCX)

1867

M.K. Fukuda, S. Araki, Y. Honda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
M. Kageyama, M. Kuribayashi
Rigaku Corporation, XG & Core Technology, Tokyo, Japan
A. Momose, M.P. Olbinado, Y. Wu
Tohoku University, Institute of Multidisciplinary Research for Advanced Materials, Sendai, Japan
K. Sakaue
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
M. Washio
RISE, Tokyo, Japan

Funding: This work was supported by Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan.
We have been developing a compact X-ray source based on Laser Compton scattering(LCS) at Laser Undulator Compact X-ray source(LUCX) accelerator in KEK. Our aim is to obtain a clear X-ray image in a shorter period of times and the target number of X-ray is 1.7x10⁷ photons/pulse with 10% bandwidth. In the accelerator, an electron beam with the energy of 18-24 MeV is generated by an S-band normal conducting accelerator. The beam is collided with a laser pulse stacked in a 4-mirror planar optical cavity and then 6-10 keV X-rays are generated by LCS. Presently, the generation of X-rays with the number of 3x10⁶ photons/pulse at the collision point has been achieved. X-ray imaging test such as refraction contrast images and phase contrast imaging with Talbot interferometer has also started. To increase the intensity of X-rays, we are continuing the tuning of the electron beam and the optical cavity because the exposure time of X-ray imaging is too long now. We are also planning to increase the beam energy by appending the accelerating tube. In this conference, the recent results and upgrade plan in LUCX will be reported.

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WEPMY037

Cold Model Cavity for 20-K Cryocooled C-band Photocathode RF Gun

2635

T. Tanaka, M. Inagaki, R. Nagashima, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka
LEBRA, Funabashi, Japan
M.K. Fukuda, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan

Funding: Work 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 2.6-cell C-band photocathode RF gun is under development at Nihon University in collaboration with KEK. The RF characteristics of a pillbox-type 2.6-cell C-band RF cavity at 20 K were in agreement with the theoretical predictions. The result of the cold test for a cavity with the input coupler confirmed the same characteristics. Based on these results a refined cold model of the 20-K cryocooled photocathode RF gun has been designed using SUPERFISH and CST-STUDIO. The separation between the TM01 pi and the TM01 half-pi modes has been increased from 20 MHz to 52 MHz by extending the diameter of the cavity iris and reducing the disk thickness. The 2.6-cell structure has been modified from pillbox to ellipsoid-like type. The end-plate of the 0.6-cell cavity has a center hole for bead-pull measurements of the on-axis electric filed through the entire structure. Mounting of a photocathode assembly in the end-plate has not been considered, since the purpose is solely to measure the low-power and low-temperature RF characteristics. A new design for the input coupler has been employed. The cavity will be completed early in 2016.

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WEPMY038

Optimization of C-band RF Input Coupler as a Mode Converter for 20-K Cryocooled Photocathode RF Gun

2638

T. Tanaka, M. Inagaki, R. Nagashima, K. Nakao, K. Nogami, T. Sakai, K. Takatsuka
LEBRA, Funabashi, Japan
M.K. Fukuda, T. Takatomi, N. Terunuma, J. Urakawa, M. Yoshida
KEK, Ibaraki, Japan
D. Satoh
TIT, Tokyo, Japan

Funding: Work supported by the Photon and Quantum Basic Research Coordinated Development Program of the Japanese Ministry of Education, Culture, Sports, Science, and Technology (MEXT).
Development of a cryocooled 2.6-cell C-band photocathode RF gun has been conducted at Nihon University in collaboration with KEK. An RF mode converter from square TE10 to circular TM01 mode has been employed as an RF input coupler that has a coupling coefficient of approximately 20 at 20 K to the 2.6-cell accelerating structure. In the previous design, the circular waveguide in the mode converter formed part of the accelerating cavity. After the cold test of the cavity completed in 2014, the coupler design was modified to work as a pure mode converter with a VSWR of 1 at 5712 MHz. From the design simulation using CST-STUDIO, the insertion loss in the converter is 0.2 %. The TM010 and TM011 modes excited in the circular waveguide were separated by several ten MHz from the accelerating frequency. The simulation has suggested that the amplitude of the transverse electric filed on the axis in the circular waveguide is reduced to approximately 2 % of that in the longitudinal direction.

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WEPOR005

Ground Motion Compensation using Feed-forward Control at ATF2

2670

D.R. Bett, C. Charrondière, M. Patecki, J. Pfingstner, D. Schulte, R. Tomás
CERN, Geneva, Switzerland
A. Jeremie
IN2P3-LAPP, Annecy-le-Vieux, France
K. Kubo, S. Kuroda, T. Naito, T. Okugi, T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan

Ground motion compensation using feed-forward control is a novel technique being developed to combat beam imperfections resulting from the vibration-induced misalignment of beamline components. The method is being evaluated experimentally at the KEK Accelerator Test Facility 2 (ATF2). It has already been demonstrated that the beam position correlates with the readings from a set of seismometers located along the beamline. To compensate for this contribution to the beam jitter, the fully operational system will use realtime measurement and processing in order to calculate and apply the feed-forward correction on a useful time scale. The progress towards a working system is presented in this paper.

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THOAA02

The Development of C-Band Cavity Beam Position Monitor with a Position Resolution of Nano Meter

3149

S.W. Jang, E.-S. Kim
Korea University Sejong Campus, Sejong, Republic of Korea
P. Bambade, O.R. Blanco-García, S. Wallon
LAL, Orsay, France
N. Blaskovic Kraljevic, T. Bromwich, P. Burrows
JAI, Oxford, United Kingdom
T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan

We developed and tested an C-band beam position monitor with position resolution of nano meter in ATF2. The C-band BPM was developed for the fast beam feedback system at the interaction point of ATF in KEK, which C-band beam position monitor called to IPBPM (Interaction Point Beam Position Monitor). The developed IPBPM was measured 26nm with 30% of nominal beam charge of ATF. From the measured beam position resolution, we can expected to 8nm beam position resolution with nominal ATF beam charge condition. In this talk, we will described about the development of IPBPM and the beam test results of nano meter level beam position resolution.

Slides THOAA02 [4.806 MB]

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THPMB043

Progress in Ultra-Low β* Study at ATF2

3335

M. Patecki, D.R. Bett, F. Plassard, R. Tomás
CERN, Geneva, Switzerland
K. Kubo, S. Kuroda, T. Naito, T. Okugi, T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan
M. Patecki
Warsaw University of Technology, Warsaw, Poland
T. Tauchi, N. Terunuma
Sokendai, Ibaraki, Japan

A nanometer beam size in the interaction point (IP) is required in case of future linear colliders for achieving the desired rate of particle collisions. KEK Accelerator Test Facility (ATF2), a scaled down implementation of the beam delivery system (BDS), serves for investigating the limits of electron beam focusing at the interaction point. The goal of the ultra-low beta∗ study is to lower the IP vertical beam size by lowering the beta_y∗ value while keeping the beta_x∗ value unchanged. Good control over the beam optics is therefore required. The first experience with low beta∗ optics revealed a mismatch between the optics designed in the model with respect to the beam parameters observed in the experiment. Additionally, existing methods of beam parameters characterization at the IP were biased with high uncertainties making it difficult to set the desired optics. In this paper we report on the new method introduced in ATF2 for IP beam parameters characterization which gives a good control over the applied optics and makes the ultra-low beta∗ study possible to conduct. It can be also used for verifying the performance of some of the existing beam instrumentation devices.

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THPOR030

Commissioning and First Performance Studies of a Single Vertical Beam Halo Collimation System at ATF2

3844

N. Fuster-Martínez, A. Faus-Golfe
IFIC, Valencia, Spain
P. Bambade, A. Faus-Golfe, S. Wallon, R.J. Yang
LAL, Orsay, France
K. Kubo, T. Okugi, T. Tauchi, N. Terunuma
KEK, Ibaraki, Japan
I. Podadera, F. Toral
CIEMAT, Madrid, Spain
T. Tauchi, N. Terunuma
Sokendai, Ibaraki, Japan

A single vertical beam halo collimation system has been installed in the ATF2 beamline to reduce the background that could limit the precision of the diagnostics located in the post-IP beamline. On this paper the commissioning and first performance studies of a single vertical beam halo collimation system are reported. Furthermore realistic efficiency studies have been done using the simulation code BDSIM and compared with the first experimental tests.

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THPOW007

Cs2Te Photocathode Response Time Measurements and Femtosecond Comb Electron Beam Generation as a Milestone Towards Pre-Bunched Thz Fel Realization

3941

A. Aryshev, Y. Honda, K. Lekomtsev, M. Shevelev, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan

Funding: Photon and Quantum Basic Research Coordinated Development Program from the Ministry of Education, Culture, Sports, Science and Technology, Japan and JSPS KAKENHI: 23226020 and 24654076
Currently there is a rapidly growing demand to increase the brightness of electron beams generated by conventional RF guns as well as to decrease the cost of the injector accelerator system for many research facilities worldwide. To address this demand we investigate one of the most important parameter of the high Q.E. conventional semiconductor Cs2Te photocathode, its response time. It sets the principle limitation for generated bunch length and hence maximum achievable beam brightness of electron diffraction and pre-bunched THz FEL facility's injectors. The experimental investigation was done at KEK: LUCX facility. The Cs2Te photocathode response time better than 250 fs was demonstrated. The generation of 4 micro-bunch comb electron beam with variable time separation as a crucial technology for pre-bunched THz FEL realization was achieved.

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reference for this paper ※ DOI:10.18429/JACoW-IPAC2016-THPOW007

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