IPAC2017 - List of Authors (Ohgaki, H.)

Paper	Title	Page
MOPAB073	Measurement of Electron-Bunch Length Using Coherent Radiation in Infrared Free-Electron Laser Facilities	288
	N. Sei, H. Ogawa AIST, Tsukuba, Ibaraki, Japan K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, T. Tanaka LEBRA, Funabashi, Japan H. Ohgaki, H. Zen Kyoto University, Kyoto, Japan
	Funding: This study was financially supported by JSPS KAKENHI Grant Number JP16H03912. We have studied techniques evaluating bunch length of micropulses in an electron beam. The bunch length of the electron beam is an important parameter for free-electron laser (FEL) facilities with linear accelerators. In order to obtain high FEL gain at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University and at Kyoto University Free Electron Laser (KU-FEL), the electron-bunch length is compressed to less than 1 ps in their undulator sections. Using the compressed electron beams, intense terahertz lights were generated by coherent radiation. The power of the coherent radiation was more than 50 micro-joule per electron-beam macropulse. We can extract the information of the bunch length of the electron-beam micropulse from the intense coherent radiation by using narrow-band diode detectors. In this presentation, experimental results of the measurements of the root-mean-square electron-bunch length using the coherent radiation at LEBRA* and KU-FEL** will be reported. : N. Sei et al., J. Opt. Soc. Am. B, 31, 2150 (2014). *: N. Sei et al., Nucl. Instrum. Methods Phys. Res., Sect. A, 832, 208 (2016).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB073
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THPAB023	The Influence of Initial Current Density Distribution on the Emittance Reduction	3744
SUSPSIK062	use link to see paper's listing under its alternate paper code
	H. Yamashita, T. Kii, K. Masuda, K. Nagasaki, T. Nogi, H. Ohgaki, K. Torgasin, H. Zen Kyoto University, Kyoto, Japan
	In this study, the influence of current density distribu-tion on the cathode surface on the beam emittance evolution was investigated. The emittance evolution with different beam profiles (flat-top, peak and hollow distribution) have been compared. The modification of the current profile was shown to affect the axial distance of the point of minimal emittance over wide range. The hollow profile allows extending the axial distance of the point of emittance minimum keeping its value extremely low. Further the parameters of a peak profile, which give the smallest emittance were determined. This work demonstrates the significance of initial current density distribution for the emittance evolution.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB023
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Paper

Title

Page

Measurement of Electron-Bunch Length Using Coherent Radiation in Infrared Free-Electron Laser Facilities

288

N. Sei, H. Ogawa
AIST, Tsukuba, Ibaraki, Japan
K. Hayakawa, Y. Hayakawa, K. Nogami, T. Sakai, T. Tanaka
LEBRA, Funabashi, Japan
H. Ohgaki, H. Zen
Kyoto University, Kyoto, Japan

Funding: This study was financially supported by JSPS KAKENHI Grant Number JP16H03912.
We have studied techniques evaluating bunch length of micropulses in an electron beam. The bunch length of the electron beam is an important parameter for free-electron laser (FEL) facilities with linear accelerators. In order to obtain high FEL gain at Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University and at Kyoto University Free Electron Laser (KU-FEL), the electron-bunch length is compressed to less than 1 ps in their undulator sections. Using the compressed electron beams, intense terahertz lights were generated by coherent radiation. The power of the coherent radiation was more than 50 micro-joule per electron-beam macropulse. We can extract the information of the bunch length of the electron-beam micropulse from the intense coherent radiation by using narrow-band diode detectors. In this presentation, experimental results of the measurements of the root-mean-square electron-bunch length using the coherent radiation at LEBRA* and KU-FEL** will be reported.
*: N. Sei et al., J. Opt. Soc. Am. B, 31, 2150 (2014).
**: N. Sei et al., Nucl. Instrum. Methods Phys. Res., Sect. A, 832, 208 (2016).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-MOPAB073

Export •

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

THPAB023

The Influence of Initial Current Density Distribution on the Emittance Reduction

3744

SUSPSIK062

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

H. Yamashita, T. Kii, K. Masuda, K. Nagasaki, T. Nogi, H. Ohgaki, K. Torgasin, H. Zen
Kyoto University, Kyoto, Japan

In this study, the influence of current density distribu-tion on the cathode surface on the beam emittance evolution was investigated. The emittance evolution with different beam profiles (flat-top, peak and hollow distribution) have been compared. The modification of the current profile was shown to affect the axial distance of the point of minimal emittance over wide range. The hollow profile allows extending the axial distance of the point of emittance minimum keeping its value extremely low. Further the parameters of a peak profile, which give the smallest emittance were determined. This work demonstrates the significance of initial current density distribution for the emittance evolution.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-IPAC2017-THPAB023

Export •

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