FEL2017 - List of Authors (Ohgaki, H.)

Paper	Title	Page
MOP049	Development of Compact THz Coherent Undulator Radiation Source at Kyoto University	158
	S. Krainara, T. Kii, H. Ohgaki, H. Zen Kyoto University, Kyoto, Japan S. Suphakul Chiang Mai University, Chiang Mai, Thailand
	A new THz Coherent Undulator Radiation (THz-CUR) source has been developed to generate intense quasi-monochromatic THz radiation at the Institute of Advanced Energy, Kyoto University. The system consists of a photocathode RF gun, bunch compression chicane, quadrupole magnets, and short planar undulator. The total length of this system is around 5 meters. At present, this compact accelerator has successfully started giving the THz-CUR in the frequency range of 0.16 - 0.65 THz. To investigate the performance of the source, the relationship between the total radiation energy, peak power and power spectrum as a function of bunch charge at the different undulator gaps were measured. The results are reported in the paper.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP049
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MOP050	Present Status of Infrared FEL Facility at Kyoto University	162
	H. Zen, T. Kii, S. Krainara, K. Masuda, H. Ohgaki, J. Okumura, S. Suphakul, S. Tagiri, K. Torgasin Kyoto University, Kyoto, Japan
	A mid-infrared free electron laser (FEL) named KU-FEL has been developed for promoting energy-related research at the Institute of Advanced Energy, Kyoto University.* KU-FEL can cover the wavelength range from 3.6 to 23 micrometers and is routinely operated for internal and external user experiments. Recently a THz Coherent Undulator Radiation (CUR) source using a photocathode RF gun has been developed as an extension of the facility.* As the result of commissioning the experiment, it was confirmed that the CUR source can cover the frequency range from 160 to 550 GHz. Present status of these infrared light sources will be presented. * H. Zen et al., Physics Procedia 84, pp.47-53 (2016).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP050
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TUP070	Development of Mid-Infrared Photoacoustic Spectroscopy System for Solid Samples at Kyoto University Free Electron Laser Facility	378
	J. Okumura, T. Kii, H. Ohgaki, H. Zen Kyoto University, Kyoto, Japan
	Photoacoustic Spectroscopy (PAS) enables IR absorption spectrum measurements of solid samples without preprocessing of samples. Its sensitivity and resolution depend on the intensity and spectral width of the infrared light, respectively. Mid-infrared free electron laser (MIR-FEL) is an intense, quasi-monochromatic and tunable laser in MIR region, so the method of PAS with FEL (FEL-PAS) was proposed.,* However, the resolution was not so good since they used the direct FEL beam which has the spectral width of 1%. We considered that the resolution can be significantly increased by inserting a high-resolution grating monochromator before the PAS cell. Based on this consideration, a PAS system using an MIR-FEL with the monochromator is under development. We have already conducted preliminary experiments using a PAS cell which has been used in previous studies and successfully measured quite high PAS signals with this setup.,* A demonstration of experiments to check the spectral resolution will be conducted soon. In this presentation, the progress of the development including the result of demonstration experiments will be reported. * M. Yasumoto et al., Proceedings of the 2004 FEL Conference, 703-705 (2004). ** M. Yasumoto et al., Eur. Phys. J. Special Topics, 153, 37-40 (2008).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP070
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TUP071	Study on Second Harmonic Generation in SiC Using Infrared FEL	382
	S. Tagiri Kyoto Univeristy, Kyoto, Japan T. Kii, H. Ohgaki, H. Zen Kyoto University, Kyoto, Japan
	Mode-selective phonon excitation (MSPE) is an attractive method for studying the lattice dynamics (e.g. electron-phonon interaction and phonon-phonon interaction). In addition, MSPE can control electronic, magnetic, and structural phases of materials. In 2013, we have directly demonstrated MSPE of a bulk material (6H-SiC) with MIR-FEL (KU-FEL) by anti-Stokes (AS) Raman-scattering spectroscopy. Recently, we have certified that the Sum Frequency Generation (SFG) also occurs with AS Raman scattering. For distinguishing between the AS Raman scattering and SFG, we need to know the nonlinear susceptibility and transmittance. The coefficients can be measured by the Second Harmonic Generation (SHG) spectroscopy. In this paper, the outline of the measurement system and the preliminary results with a 6H-SiC sample are reported.
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP071
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WEP014	Pulse Duration Measurement of Pico-second DUV Photocathode Driving Laser by Autocorrelation Technique Using Two-Photon Absorption in Bulk Material	447
	H. Zen, T. Kii, K. Masuda, T. Nakajima, H. Ohgaki Kyoto University, Kyoto, Japan
	A multi-bunch, pico-second DUV photocathode drive laser system has been developed for photocathode operation of mid-infrared free electron laser facility, KU-FEL.* By using the laser, KU-FEL has already succeeded in first lasing under the photocathode operation. The pulse duration of the photocathode driving laser is a quite important parameter because it determines the initial electron pulse duration on the cathode surface. However, the pulse duration of the photocathode driving laser had not been characterized. A very convenient pulse duration measurement method utilizing two-photon absorption in bulk material, which can be used for DUV laser pulses, has been proposed and demonstrated so far.* In this study, a DUV nonlinear autocorrelator based on the proposed method was developed to measure the pulse duration of the DUV photocathode driving laser. As the result of measurement, the pulse duration was evaluated as 5.8±0.2 ps (FWHM). The principle of this method, experimental setup and measured results will be presented. * H. Zen et al., Proc. of FEL2014, pp.828-831 (2015). H. Zen et al., Proc. of IPAC2016, pp.754-756 (2016). * C. Homann et al., Applied Physics B 104, 783 (2011).
DOI •	reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP014
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Paper

Title

Page

Development of Compact THz Coherent Undulator Radiation Source at Kyoto University

158

S. Krainara, T. Kii, H. Ohgaki, H. Zen
Kyoto University, Kyoto, Japan
S. Suphakul
Chiang Mai University, Chiang Mai, Thailand

A new THz Coherent Undulator Radiation (THz-CUR) source has been developed to generate intense quasi-monochromatic THz radiation at the Institute of Advanced Energy, Kyoto University. The system consists of a photocathode RF gun, bunch compression chicane, quadrupole magnets, and short planar undulator. The total length of this system is around 5 meters. At present, this compact accelerator has successfully started giving the THz-CUR in the frequency range of 0.16 - 0.65 THz. To investigate the performance of the source, the relationship between the total radiation energy, peak power and power spectrum as a function of bunch charge at the different undulator gaps were measured. The results are reported in the paper.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP049

Export •

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

MOP050

Present Status of Infrared FEL Facility at Kyoto University

162

H. Zen, T. Kii, S. Krainara, K. Masuda, H. Ohgaki, J. Okumura, S. Suphakul, S. Tagiri, K. Torgasin
Kyoto University, Kyoto, Japan

A mid-infrared free electron laser (FEL) named KU-FEL has been developed for promoting energy-related research at the Institute of Advanced Energy, Kyoto University.* KU-FEL can cover the wavelength range from 3.6 to 23 micrometers and is routinely operated for internal and external user experiments. Recently a THz Coherent Undulator Radiation (CUR) source using a photocathode RF gun has been developed as an extension of the facility.* As the result of commissioning the experiment, it was confirmed that the CUR source can cover the frequency range from 160 to 550 GHz. Present status of these infrared light sources will be presented.
* H. Zen et al., Physics Procedia 84, pp.47-53 (2016).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-MOP050

Export •

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

TUP070

Development of Mid-Infrared Photoacoustic Spectroscopy System for Solid Samples at Kyoto University Free Electron Laser Facility

378

J. Okumura, T. Kii, H. Ohgaki, H. Zen
Kyoto University, Kyoto, Japan

Photoacoustic Spectroscopy (PAS) enables IR absorption spectrum measurements of solid samples without preprocessing of samples. Its sensitivity and resolution depend on the intensity and spectral width of the infrared light, respectively. Mid-infrared free electron laser (MIR-FEL) is an intense, quasi-monochromatic and tunable laser in MIR region, so the method of PAS with FEL (FEL-PAS) was proposed.*,** However, the resolution was not so good since they used the direct FEL beam which has the spectral width of 1%. We considered that the resolution can be significantly increased by inserting a high-resolution grating monochromator before the PAS cell. Based on this consideration, a PAS system using an MIR-FEL with the monochromator is under development. We have already conducted preliminary experiments using a PAS cell which has been used in previous studies and successfully measured quite high PAS signals with this setup.*,** A demonstration of experiments to check the spectral resolution will be conducted soon. In this presentation, the progress of the development including the result of demonstration experiments will be reported.
* M. Yasumoto et al., Proceedings of the 2004 FEL Conference, 703-705 (2004).
** M. Yasumoto et al., Eur. Phys. J. Special Topics, 153, 37-40 (2008).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP070

Export •

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

TUP071

Study on Second Harmonic Generation in SiC Using Infrared FEL

382

S. Tagiri
Kyoto Univeristy, Kyoto, Japan
T. Kii, H. Ohgaki, H. Zen
Kyoto University, Kyoto, Japan

Mode-selective phonon excitation (MSPE) is an attractive method for studying the lattice dynamics (e.g. electron-phonon interaction and phonon-phonon interaction). In addition, MSPE can control electronic, magnetic, and structural phases of materials. In 2013, we have directly demonstrated MSPE of a bulk material (6H-SiC) with MIR-FEL (KU-FEL) by anti-Stokes (AS) Raman-scattering spectroscopy. Recently, we have certified that the Sum Frequency Generation (SFG) also occurs with AS Raman scattering. For distinguishing between the AS Raman scattering and SFG, we need to know the nonlinear susceptibility and transmittance. The coefficients can be measured by the Second Harmonic Generation (SHG) spectroscopy. In this paper, the outline of the measurement system and the preliminary results with a 6H-SiC sample are reported.

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-TUP071

Export •

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

WEP014

Pulse Duration Measurement of Pico-second DUV Photocathode Driving Laser by Autocorrelation Technique Using Two-Photon Absorption in Bulk Material

447

H. Zen, T. Kii, K. Masuda, T. Nakajima, H. Ohgaki
Kyoto University, Kyoto, Japan

A multi-bunch, pico-second DUV photocathode drive laser system has been developed for photocathode operation of mid-infrared free electron laser facility, KU-FEL.* By using the laser, KU-FEL has already succeeded in first lasing under the photocathode operation.** The pulse duration of the photocathode driving laser is a quite important parameter because it determines the initial electron pulse duration on the cathode surface. However, the pulse duration of the photocathode driving laser had not been characterized. A very convenient pulse duration measurement method utilizing two-photon absorption in bulk material, which can be used for DUV laser pulses, has been proposed and demonstrated so far.*** In this study, a DUV nonlinear autocorrelator based on the proposed method was developed to measure the pulse duration of the DUV photocathode driving laser. As the result of measurement, the pulse duration was evaluated as 5.8±0.2 ps (FWHM). The principle of this method, experimental setup and measured results will be presented.
* H. Zen et al., Proc. of FEL2014, pp.828-831 (2015).
** H. Zen et al., Proc. of IPAC2016, pp.754-756 (2016).
*** C. Homann et al., Applied Physics B 104, 783 (2011).

DOI •

reference for this paper ※ https://doi.org/10.18429/JACoW-FEL2017-WEP014

Export •

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