IPAC2018 - List of Authors (Sakaue, K.)

Paper	Title	Page
THPMK145	Evaluation of Coherent Terahertz Radiation Generated from Tilted Electron Beams Aiming for Higher Light Intensity	4642
	M. Brameld, K. Sakaue, Y. Tadenuma, M. Washio, R. Yanagisawa Waseda University, Tokyo, Japan R. Kuroda, Y. Taira AIST, Tsukuba, Japan
	Funding: This work was supported by a research granted from The Murata Science Foundation and JSPS KAKENHI 26286083. When a target medium is irradiated by electron beams travelling at relativistic speed, terahertz(THz) radiation is produced by Cherenkov radiation. THz radiation is released at an angle to the direction of travel of the electron beams, and the coherence of the radiation can be improved by tilting the electron beams to match this angle, resulting in higher light intensity. The Cherenkov angle differs according to the refraction index of the target medium. At Waseda University, the generation of high-quality electron beams by a Cs-Te Photocathode RF-Gun and its applications are being researched. By utilizing the RF-Deflector, the tilt angle of the electron beam can be controlled to achieve coherent THz radiation. To gain higher light intensity, the use of Silicon and Aerogel as a target medium was challenged and compared to the conventional medium TOPAS. The THz radiation produced from the three target mediums were analyzed by use of the power meter and time domain spectroscopy(TDS). At this conference, the generation of THz Cherenkov radiation from different target mediums and the measurement results will be reported along with future perspectives.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK145
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THPMK009	Study on Improving Durability of Bialkali Photocathode for an RF-Gun with the CsBr Protective Layer	4310
	J. Miyamatsu, H. Ono, M. Washio Waseda University, Tokyo, Japan H. Iijima Tokyo University of Science, Tokyo, Japan K. Sakaue Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
	At Waseda University, we have been studying for high quality electron beam generation and developing variety of application experiments using 1.6 cells photocathode RF-gun. We are using photocathode as the electron source, which can generate high-performance electron beam such as low emittance, short pulse. The performance of photocathodes is evaluated mainly in terms of Quantum Efficiency (Q.E.) and the lifetime. Cs-Te photocathode used in the RF-Gun at Waseda University is known for high Q.E. with UV light and relatively longer lifetime among semiconducting photocathodes. For increasing the charge of electron beam and simplify the laser system, we started introducing CsK2Sb photocathode in the RF-gun which has light sensitivity in UV and visible range, and high Q.E. with green light. However, CsK2Sb photocathode has a difficulty in durability and we observed that it was not enough for long-term operation in the RF-gun. Then we plan to improve lifetime and durability of CsK2Sb photocathode by coating the cathode surface with CsBr thin film. In this conference, we report the result of lifetime measurement of CsK2Sb photocathode with CsBr thin film and future prospects.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK009
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THPMK146	Enhancement of Laser-Compton X-ray by Crab Crossing	4645
	Y. Koshiba, R. Morita, S. Ota, M. Washio Waseda University, Tokyo, Japan T. Higashiguchi Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan K. Sakaue Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan J. Urakawa KEK, Ibaraki, Japan
	Funding: This work is supported by JSPS Research Fellowships for Young Scientists (17J04371). We are going to apply crab crossing of electrons and laser photons for the enhancement of laser-Compton X-ray flux. Crab crossing will enable quasi-head-on collision and increase the luminosity. Therefore, it could be combined with an optical enhancement cavity without the interference of beams and cavity mirrors, leading to the generation of intense X-ray pulses. Calculation show more than fourfold luminosity will be achievable in our system, and could be larger depending on beam parameters. Although crab crossing in laser-Compton scattering has been already proposed, it has not been demonstrated yet anywhere. This will be the proof-of-principle study of the crab crossing laser-Compton scattering. In this conference, we will report our laser system based on thin-disk technology, and results of crab crossing laser-Compton scattering. Variola Alessandro, et al. "Luminosity optimization schemes in Compton experiments based on Fabry-Perot optical resonators." Physical Review Special Topics-Accelerators and Beams 14.3 (2011): 031001.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK146
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THPMK147	Measurement of Slice-Emittance of Electron Bunch Using RF Transverse Deflector	4648
	T. Sasaki, Y. Nakazato, M. Washio Waseda University, Tokyo, Japan Y. Koshiba RISE, Tokyo, Japan K. Sakaue Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
	We have been studying a compact electron accelerator based on an S-band Cs-Te photocathode rf electron gun at Waseda University. We are applying this high quality electron beam to soft X-ray generation, coherent THz wave generation and pulse radiolysis experiment. In these applications, longitudinal parameters of the electron beam are important. Thus, we developed the RF deflecting cavity which can directly convert longitudinal distribution of the beam to transverse with high temporal resolution, and succeeded in measuring longitudinal profile of an electron beam from the RF gun. Encouraged by these successful results, we started to measure slice emittance. Slice emittance would be very useful for improving the RF electron gun cavity. Therefore, we tried to measure the slice emittance of the electron beam by applying the Q-scan method to deflected beam by RF deflecting cavity. In this conference, we will report the principle, experimental results of the slice emittance measurement, and future prospects. C. Vaccarezza et al., "Slice emittance measurements at SPARC photoinjector with a RF deflector", Proc. of EPAC08, Genoa, Italy
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK147
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THPMK148	Design Study on Linac-bsed Laser-cmpton Scattering X-Ray Source	4651
	K. Sakaue Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan M.K. Fukuda, N. Terunuma, J. Urakawa KEK, Ibaraki, Japan Y. Koshiba RISE, Tokyo, Japan M. Washio Waseda University, Tokyo, Japan
	We have been developing a laser-Compton scattering X-ray source using multi-bunch linac and optical enhancement cavity. This combination have a possibility to realize a high brightness compact X-ray source. A key issue of the system is around interaction point. Compatibility of electron focusing, optical cavity and X-ray path is difficult in the current setup. Thus we propose to use rf transverse deflecting cavity for crab crossing of laser and electron. In this conference, design study of the whole laser-Compton X-ray source consist of electron linac and optical enhancement cavity will be reported. The system configuration, resulting flux and brightness, and its applications will be discussed.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK148
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Paper

Title

Page

Evaluation of Coherent Terahertz Radiation Generated from Tilted Electron Beams Aiming for Higher Light Intensity

4642

M. Brameld, K. Sakaue, Y. Tadenuma, M. Washio, R. Yanagisawa
Waseda University, Tokyo, Japan
R. Kuroda, Y. Taira
AIST, Tsukuba, Japan

Funding: This work was supported by a research granted from The Murata Science Foundation and JSPS KAKENHI 26286083.
When a target medium is irradiated by electron beams travelling at relativistic speed, terahertz(THz) radiation is produced by Cherenkov radiation. THz radiation is released at an angle to the direction of travel of the electron beams, and the coherence of the radiation can be improved by tilting the electron beams to match this angle, resulting in higher light intensity. The Cherenkov angle differs according to the refraction index of the target medium. At Waseda University, the generation of high-quality electron beams by a Cs-Te Photocathode RF-Gun and its applications are being researched. By utilizing the RF-Deflector, the tilt angle of the electron beam can be controlled to achieve coherent THz radiation. To gain higher light intensity, the use of Silicon and Aerogel as a target medium was challenged and compared to the conventional medium TOPAS. The THz radiation produced from the three target mediums were analyzed by use of the power meter and time domain spectroscopy(TDS). At this conference, the generation of THz Cherenkov radiation from different target mediums and the measurement results will be reported along with future perspectives.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK145

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMK009

Study on Improving Durability of Bialkali Photocathode for an RF-Gun with the CsBr Protective Layer

4310

J. Miyamatsu, H. Ono, M. Washio
Waseda University, Tokyo, Japan
H. Iijima
Tokyo University of Science, Tokyo, Japan
K. Sakaue
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan

At Waseda University, we have been studying for high quality electron beam generation and developing variety of application experiments using 1.6 cells photocathode RF-gun. We are using photocathode as the electron source, which can generate high-performance electron beam such as low emittance, short pulse. The performance of photocathodes is evaluated mainly in terms of Quantum Efficiency (Q.E.) and the lifetime. Cs-Te photocathode used in the RF-Gun at Waseda University is known for high Q.E. with UV light and relatively longer lifetime among semiconducting photocathodes. For increasing the charge of electron beam and simplify the laser system, we started introducing CsK2Sb photocathode in the RF-gun which has light sensitivity in UV and visible range, and high Q.E. with green light. However, CsK2Sb photocathode has a difficulty in durability and we observed that it was not enough for long-term operation in the RF-gun. Then we plan to improve lifetime and durability of CsK2Sb photocathode by coating the cathode surface with CsBr thin film. In this conference, we report the result of lifetime measurement of CsK2Sb photocathode with CsBr thin film and future prospects.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK009

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMK146

Enhancement of Laser-Compton X-ray by Crab Crossing

4645

Y. Koshiba, R. Morita, S. Ota, M. Washio
Waseda University, Tokyo, Japan
T. Higashiguchi
Center for Optical Research and Education, Utsunomiya University, Utsunomiya, Japan
K. Sakaue
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
J. Urakawa
KEK, Ibaraki, Japan

Funding: This work is supported by JSPS Research Fellowships for Young Scientists (17J04371).
We are going to apply crab crossing of electrons and laser photons for the enhancement of laser-Compton X-ray flux. Crab crossing will enable quasi-head-on collision and increase the luminosity. Therefore, it could be combined with an optical enhancement cavity without the interference of beams and cavity mirrors, leading to the generation of intense X-ray pulses. Calculation show more than fourfold luminosity will be achievable in our system, and could be larger depending on beam parameters. Although crab crossing in laser-Compton scattering has been already proposed*, it has not been demonstrated yet anywhere. This will be the proof-of-principle study of the crab crossing laser-Compton scattering. In this conference, we will report our laser system based on thin-disk technology, and results of crab crossing laser-Compton scattering.
*Variola Alessandro, et al. "Luminosity optimization schemes in Compton experiments based on Fabry-Perot optical resonators." Physical Review Special Topics-Accelerators and Beams 14.3 (2011): 031001.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK146

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMK147

Measurement of Slice-Emittance of Electron Bunch Using RF Transverse Deflector

4648

T. Sasaki, Y. Nakazato, M. Washio
Waseda University, Tokyo, Japan
Y. Koshiba
RISE, Tokyo, Japan
K. Sakaue
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan

We have been studying a compact electron accelerator based on an S-band Cs-Te photocathode rf electron gun at Waseda University. We are applying this high quality electron beam to soft X-ray generation, coherent THz wave generation and pulse radiolysis experiment. In these applications, longitudinal parameters of the electron beam are important. Thus, we developed the RF deflecting cavity which can directly convert longitudinal distribution of the beam to transverse with high temporal resolution, and succeeded in measuring longitudinal profile of an electron beam from the RF gun. Encouraged by these successful results, we started to measure slice emittance. Slice emittance would be very useful for improving the RF electron gun cavity. Therefore, we tried to measure the slice emittance of the electron beam by applying the Q-scan method to deflected beam by RF deflecting cavity. In this conference, we will report the principle, experimental results of the slice emittance measurement, and future prospects.
C. Vaccarezza et al., "Slice emittance measurements at SPARC photoinjector with a RF deflector", Proc. of EPAC08, Genoa, Italy

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK147

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)

THPMK148

Design Study on Linac-bsed Laser-cmpton Scattering X-Ray Source

4651

K. Sakaue
Waseda University, Waseda Institute for Advanced Study, Tokyo, Japan
M.K. Fukuda, N. Terunuma, J. Urakawa
KEK, Ibaraki, Japan
Y. Koshiba
RISE, Tokyo, Japan
M. Washio
Waseda University, Tokyo, Japan

We have been developing a laser-Compton scattering X-ray source using multi-bunch linac and optical enhancement cavity. This combination have a possibility to realize a high brightness compact X-ray source. A key issue of the system is around interaction point. Compatibility of electron focusing, optical cavity and X-ray path is difficult in the current setup. Thus we propose to use rf transverse deflecting cavity for crab crossing of laser and electron. In this conference, design study of the whole laser-Compton X-ray source consist of electron linac and optical enhancement cavity will be reported. The system configuration, resulting flux and brightness, and its applications will be discussed.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2018-THPMK148

Export •

reference for this paper using ※ BibTeX, ※ LaTeX, ※ Text/Word, ※ RIS, ※ EndNote (xml)