LINAC2012 - List of Authors (Tomizawa, H.)

Paper

Title

Page

First Observation of Photoemission Enhancement from Copper Cathode Illuminated by Z-Polarized Laser Pulse

996

H. Tomizawa, H. Dewa, A. Mizuno, T. Taniuchi
JASRI/SPring-8, Hyogo-ken, Japan

Since 2006, we have developed a novel photocathode gun gated by laser-induced Schottky-effect. This new type of gun utilizes a laser’s coherency to aim at a compact femtosecond laser oscillator as an IR laser source using Z-polarization on the photocathode. This Z-polarization scheme reduces the laser photon energy (making it possible to excite the cathode with a longer wavelength) by reducing the work function of cathode due to Schottky effect. A hollow laser incidence is applied with a hollow convex lens in a vacuum that is focused after passing the laser beam through a radial polarizer. According to our calculations (convex lens: NA=0.15), a Z-field of 1 GV/m needs 1.26 MW at peak power for the fundamental wavelength (792 nm). In the first demonstration of Z-field emission, enhancement was done with a copper cathode at THG (264 nm). Consequently, we observed 1.4 times enhancement of photoemission at 1.6 GV/m of an averaged laser Z-field on the cathode surface. We report the first observation and analysis of the emission enhancements with this laser-induced Schottky-effect on metal copper photocathodes by comparing radial and azimuthal polarizations of the incident laser pulses.

THPB092

Recent Improvements in SPring-8 Linac for Early Recovery from Beam Interruption

1035

S. Suzuki, T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, T. Magome, A. Mizuno, T. Taniuchi, H. Tomizawa, K. Yanagida
JASRI/SPring-8, Hyogo-ken, Japan

The 1GeV SPring-8 linac is an injector for the SPring-8 synchrotron radiation storage ring with 8GeV booster synchrotron. In recent years, backup systems were installed to eliminate long-time interruption of the beam injections: The main gun system is usually operated, and the second gun is always pre-heated and can inject electron beams into a buncher section with an interval of several minutes in case the main gun failed. The first klystron, that feeds RF powers to the buncher system and the downstream klystrons, can be relieved by the next klystron with an interval of about 20 minutes by switching the waveguide circuit. When one of the eleven working klystrons faults, one of standby klystrons, which are kept for hot spares on line, is automatically activated to accelerate beams instead of the failed one without beam interruption. The total downtime in FY2012 was 0.12% in top-up operation user time. The averaged fault frequency was 0.2 times per day.

TUPLB10

Non-destructive Real-time Monitor to Measure 3D-bunch Charge Distribution with Arrival Timing to Maximize 3D Overlapping for HHG-seeded EUV-FEL

467

H. Tomizawa, K. Ogawa, T. Sato, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
M. Aoyama
JAEA/Kansai, Kyoto, Japan
A. Iwasaki, S. Owada
The University of Tokyo, Tokyo, Japan
S. Matsubara, Y. Okayasu, T. Togashi
JASRI/SPring-8, Hyogo, Japan
T. Matsukawa, H. Minamide
RIKEN ASI, Sendai, Miyagi, Japan
E. Takahashi
RIKEN, Saitama, Japan

Non-destructive, shot-by-shot real-time monitors have been developed to measure 3D bunch charge distribution (BCD). This 3D monitor has been developed to monitor 3-D overlapping electron bunches and higher harmonic generation (HHG) pulses in a seeded VUV-FEL. This ambitious monitor is based on an Electro-Optic (EO) multiple sampling technique in a manner of spectral decoding that is non-destructive and enables real-time measurements of the longitudinal and transverse BCD. This monitor was materialized in simultaneously probing eight EO crystals that surround the electron beam axis with a radial polarized and hollow EO-probe laser pulse. In 2009, the concept of 3D-BCD monitor was verified through electron bunch measurements at SPring-8. The further target of the temporal resolution is ~30 fs (FWHM), utilizing an organic EO crystal (DAST) instead of conventional inorganic EO crystals (ZnTe, GaP, etc.) The EO-sampling with DAST crystal is expected to measure a bunch length less than 30 fs (FWHM). In 2011, the first bunch measurement with an organic EO crystal (DAST) was successfully demonstrated in the VUV-FEL accelerator at SPring-8.

Slides TUPLB10 [2.713 MB]

TUPB080

Non-destructive Real-time Monitor to Measure 3D Bunch Charge Distribution with Arrival Timing to Maximize 3D Overlapping for HHG-Seeded EUV-FEL

657

H. Tomizawa, K. Ogawa, T. Sato, M. Yabashi
RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan
M. Aoyama
JAEA/Kansai, Kyoto, Japan
A. Iwasaki, S. Owada
The University of Tokyo, Tokyo, Japan
S. Matsubara, Y. Okayasu, T. Togashi
JASRI/SPring-8, Hyogo, Japan
T. Matsukawa, H. Minamide
RIKEN ASI, Sendai, Miyagi, Japan
E. Takahashi
RIKEN, Saitama, Japan

Non-destructive, shot-by-shot real-time monitors have been developed to measure 3D bunch charge distribution (BCD). This 3D monitor has been developed to monitor 3D overlapping electron bunches and higher harmonic generation (HH) pulses in a seeded VUV-FEL. This ambitious monitor is based on an Electro-Optic (EO) multiple sampling technique in a manner of spectral decoding that is non-destructive and enables real-time measurements of the longitudinal and transverse BCD. This monitor was materialized in simultaneously probing eight EO crystals that surround the electron beam axis with a radial polarized and hollow EO-probe laser pulse. In 2009, the concept of 3D-BCD monitor was verified through electron bunch measurements at SPring-8. The further target of the temporal resolution is ~30 fs (FWHM), utilizing an organic EO crystal (DAST) instead of conventional inorganic EO crystals (ZnTe, GaP, etc.) The EO-sampling with DAST crystal is expected to measure a bunch length less than 30 fs (FWHM). In 2011, the first bunch measurement with an organic EO crystal (DAST) was successfully demonstrated in the VUV-FEL accelerator at SPring-8.

Paper	Title	Page
THPB068	First Observation of Photoemission Enhancement from Copper Cathode Illuminated by Z-Polarized Laser Pulse	996
	H. Tomizawa, H. Dewa, A. Mizuno, T. Taniuchi JASRI/SPring-8, Hyogo-ken, Japan
	Since 2006, we have developed a novel photocathode gun gated by laser-induced Schottky-effect. This new type of gun utilizes a laser’s coherency to aim at a compact femtosecond laser oscillator as an IR laser source using Z-polarization on the photocathode. This Z-polarization scheme reduces the laser photon energy (making it possible to excite the cathode with a longer wavelength) by reducing the work function of cathode due to Schottky effect. A hollow laser incidence is applied with a hollow convex lens in a vacuum that is focused after passing the laser beam through a radial polarizer. According to our calculations (convex lens: NA=0.15), a Z-field of 1 GV/m needs 1.26 MW at peak power for the fundamental wavelength (792 nm). In the first demonstration of Z-field emission, enhancement was done with a copper cathode at THG (264 nm). Consequently, we observed 1.4 times enhancement of photoemission at 1.6 GV/m of an averaged laser Z-field on the cathode surface. We report the first observation and analysis of the emission enhancements with this laser-induced Schottky-effect on metal copper photocathodes by comparing radial and azimuthal polarizations of the incident laser pulses.

THPB092	Recent Improvements in SPring-8 Linac for Early Recovery from Beam Interruption	1035
	S. Suzuki, T. Asaka, H. Dewa, H. Hanaki, T. Kobayashi, T. Magome, A. Mizuno, T. Taniuchi, H. Tomizawa, K. Yanagida JASRI/SPring-8, Hyogo-ken, Japan
	The 1GeV SPring-8 linac is an injector for the SPring-8 synchrotron radiation storage ring with 8GeV booster synchrotron. In recent years, backup systems were installed to eliminate long-time interruption of the beam injections: The main gun system is usually operated, and the second gun is always pre-heated and can inject electron beams into a buncher section with an interval of several minutes in case the main gun failed. The first klystron, that feeds RF powers to the buncher system and the downstream klystrons, can be relieved by the next klystron with an interval of about 20 minutes by switching the waveguide circuit. When one of the eleven working klystrons faults, one of standby klystrons, which are kept for hot spares on line, is automatically activated to accelerate beams instead of the failed one without beam interruption. The total downtime in FY2012 was 0.12% in top-up operation user time. The averaged fault frequency was 0.2 times per day.

TUPLB10	Non-destructive Real-time Monitor to Measure 3D-bunch Charge Distribution with Arrival Timing to Maximize 3D Overlapping for HHG-seeded EUV-FEL	467
	H. Tomizawa, K. Ogawa, T. Sato, M. Yabashi RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan M. Aoyama JAEA/Kansai, Kyoto, Japan A. Iwasaki, S. Owada The University of Tokyo, Tokyo, Japan S. Matsubara, Y. Okayasu, T. Togashi JASRI/SPring-8, Hyogo, Japan T. Matsukawa, H. Minamide RIKEN ASI, Sendai, Miyagi, Japan E. Takahashi RIKEN, Saitama, Japan
	Non-destructive, shot-by-shot real-time monitors have been developed to measure 3D bunch charge distribution (BCD). This 3D monitor has been developed to monitor 3-D overlapping electron bunches and higher harmonic generation (HHG) pulses in a seeded VUV-FEL. This ambitious monitor is based on an Electro-Optic (EO) multiple sampling technique in a manner of spectral decoding that is non-destructive and enables real-time measurements of the longitudinal and transverse BCD. This monitor was materialized in simultaneously probing eight EO crystals that surround the electron beam axis with a radial polarized and hollow EO-probe laser pulse. In 2009, the concept of 3D-BCD monitor was verified through electron bunch measurements at SPring-8. The further target of the temporal resolution is ~30 fs (FWHM), utilizing an organic EO crystal (DAST) instead of conventional inorganic EO crystals (ZnTe, GaP, etc.) The EO-sampling with DAST crystal is expected to measure a bunch length less than 30 fs (FWHM). In 2011, the first bunch measurement with an organic EO crystal (DAST) was successfully demonstrated in the VUV-FEL accelerator at SPring-8.
	Slides TUPLB10 [2.713 MB]

TUPB080	Non-destructive Real-time Monitor to Measure 3D Bunch Charge Distribution with Arrival Timing to Maximize 3D Overlapping for HHG-Seeded EUV-FEL	657
	H. Tomizawa, K. Ogawa, T. Sato, M. Yabashi RIKEN SPring-8 Center, Sayo-cho, Sayo-gun, Hyogo, Japan M. Aoyama JAEA/Kansai, Kyoto, Japan A. Iwasaki, S. Owada The University of Tokyo, Tokyo, Japan S. Matsubara, Y. Okayasu, T. Togashi JASRI/SPring-8, Hyogo, Japan T. Matsukawa, H. Minamide RIKEN ASI, Sendai, Miyagi, Japan E. Takahashi RIKEN, Saitama, Japan
	Non-destructive, shot-by-shot real-time monitors have been developed to measure 3D bunch charge distribution (BCD). This 3D monitor has been developed to monitor 3D overlapping electron bunches and higher harmonic generation (HH) pulses in a seeded VUV-FEL. This ambitious monitor is based on an Electro-Optic (EO) multiple sampling technique in a manner of spectral decoding that is non-destructive and enables real-time measurements of the longitudinal and transverse BCD. This monitor was materialized in simultaneously probing eight EO crystals that surround the electron beam axis with a radial polarized and hollow EO-probe laser pulse. In 2009, the concept of 3D-BCD monitor was verified through electron bunch measurements at SPring-8. The further target of the temporal resolution is ~30 fs (FWHM), utilizing an organic EO crystal (DAST) instead of conventional inorganic EO crystals (ZnTe, GaP, etc.) The EO-sampling with DAST crystal is expected to measure a bunch length less than 30 fs (FWHM). In 2011, the first bunch measurement with an organic EO crystal (DAST) was successfully demonstrated in the VUV-FEL accelerator at SPring-8.