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Journal Articles

Demonstration of laser Compton-scattered photon source at the cERL

Nagai, Ryoji; Hajima, Ryoichi; Shizuma, Toshiyuki; Mori, Michiaki; Akagi, Tomoya*; Kosuge, Atsushi*; Honda, Yosuke*; Araki, Sakae*; Terunuma, Nobuhiro*; Urakawa, Junji*

Proceedings of 12th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1328 - 1330, 2015/09

Accelerator and laser technologies required for laser Compton scattering (LCS) photon source based on an energy-recovery linac (ERL) have been developed at the Compact ERL (cERL) facility. A high-flux, energy tunable, and monochromatic photon source such as the ERL-based LCS photon source is necessary for nondestructive assay of nuclear materials. For the demonstration of the ERL-based LCS photon generation, a laser enhancement cavity was installed at the recirculation loop of the cERL. The electron beam energy, the laser wavelength, and the collision angle are 20 MeV, 1064 nm, and 18 $$^{circ}$$, respectively. The calculated maximum energy of the LCS photons is about 7 keV. A silicon drift detector (SDD) with active area of 17 mm$$^{2}$$ placed 16.6 m from the collision point was used for observation of the LCS photons. As a result of the measurement, the flux on the detector, central energy, and energy width of the LCS photons were obtained as 1200/s, 6.91 keV, and 81 eV, respectively.

Journal Articles

Demonstration of high-flux photon generation from an ERL-based laser Compton photon source

Nagai, Ryoji; Hajima, Ryoichi; Mori, Michiaki; Shizuma, Toshiyuki; Akagi, Tomoya*; Araki, Sakae*; Honda, Yosuke*; Kosuge, Atsushi*; Terunuma, Nobuhiro*; Urakawa, Junji*

Proceedings of 6th International Particle Accelerator Conference (IPAC '15) (Internet), p.1607 - 1609, 2015/06

Accelerator and laser technologies required for laser Compton scattering (LCS) photon source based on an energy-recovery linac (ERL) have been developed at the Compact ERL (cERL) facility. A high-flux, energy tunable, and monochromatic photon source such as the ERL-based LCS photon source is necessary for nondestructive assay of nuclear materials. For the demonstration of the ERL-based LCS photon generation, a laser enhancement cavity was installed at the recirculation loop of the cERL. The electron beam energy, the laser wavelength, and the collision angle are 20 MeV, 1064 nm, and 18 deg., respectively. The calculated maximum energy of the LCS photons is about 7 keV. A silicon drift detector (SDD) with active area of 17 mm$$^{2}$$ placed 16.6 m from the collision point was used for observation of the LCS photons. As a result of the measurement, the flux on the detector, central energy, and energy width of the LCS photons were obtained as 1200 /s, 6.91 keV, and 81 eV, respectively.

Journal Articles

Construction of the equipment for a demonstration of laser Compton-scattered photon source at the cERL

Nagai, Ryoji; Hajima, Ryoichi; Mori, Michiaki; Shizuma, Toshiyuki; Akagi, Tomoya*; Kosuge, Atsushi*; Honda, Yosuke*; Urakawa, Junji*

Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.1328 - 1331, 2014/10

A high intensity $$gamma$$-ray source from the laser Compton scattering (LCS) by an electron beam in an energy-recovery linac (ERL) is a key technology for a nondestructive assay system to identify nuclear materials. In order to demonstrate accelerator and laser technologies required for a LCS photon generation, a LCS photon source is under construction at the Compact ERL (cERL). The LCS photon source consists of a mode-locked fiber laser and a laser enhancement cavity. A beamline and an experimental hatch are also under construction. The commissioning of the LCS photon source will be started in February 2015 and LCS photon generation is scheduled in March 2015.

Journal Articles

Development of the beamline flux monitor for the laser Compton-scattered photon source

Nagai, Ryoji; Hajima, Ryoichi; Mori, Michiaki; Shizuma, Toshiyuki; Akagi, Tomoya*; Kosuge, Atsushi*; Honda, Yosuke*; Urakawa, Junji*

Proceedings of 11th Annual Meeting of Particle Accelerator Society of Japan (Internet), p.839 - 842, 2014/10

In order to demonstrate accelerator and laser technologies required for a laser Compton scattering (LCS) photon generation, a LCS photon source is under construction at the Compact ERL (cERL). We considered the flux monitors for the adjustment LCS photon source. A thin scintillator detector and a silicon drift detector are employed as flux monitors and are installed at the upstream part of the LCS beamline. The background signal level due to the bremsstrahlung of the electron beam was measured by a CsI(pure) scintillator. In the result of the measurement, the background signal is acceptable level for the flux monitors.

Journal Articles

Construction of a laser Compton scattered photon source at cERL

Nagai, Ryoji; Hajima, Ryoichi; Mori, Michiaki; Shizuma, Toshiyuki; Akagi, Tomoya*; Honda, Yosuke*; Kosuge, Atsushi*; Urakawa, Junji*

Proceedings of 5th International Particle Accelerator Conference (IPAC '14) (Internet), p.1940 - 1942, 2014/07

In order to demonstrate required accelerator and laser technologies for a high intensity $$gamma$$-ray source from the laser Compton scattering (LCS), an LCS photon source and the peripheral equipment are under construction at the Compact ERL (cERL) at High Energy Accelerator Research Organization (KEK). The LCS photon source by an electron beam in the energy-recovery linac (ERL) is a key technology for a nondestructive assay system to identify nuclear species. The LCS photon source and the peripheral equipment consist of a mode-locked fiber laser, laser enhancement cavity, beamline, and experimental hatch. The commissioning of the LCS photon source will be started in February 2015.

Journal Articles

Separation of ionization and subsequent electronic excitation for formation of electronically excited ethanol cation in intense laser fields

Ikuta, Tomoya*; Hosaka, Koichi*; Akagi, Hiroshi; Yokoyama, Atsushi; Yamanouchi, Kaoru*; Kannari, Fumihiko*; Itakura, Ryuji

Journal of Physics B; Atomic, Molecular and Optical Physics, 44(19), p.191002_1 - 191002_5, 2011/10

 Times Cited Count:8 Percentile:39.78(Optics)

Ionization and subsequent electronic excitation occurring within the same laser pulse (400 nm, 96 fs, 1.3$$sim$$18 TW/cm$$^{-2}$$) are separately investigated by measuring in coincidence an electron and a product ion produced from C$$_{2}$$H$$_{5}$$OH. We reveal that the nascent population in the electronically excited C$$_{2}$$H$$_{5}$$OH$$^{+}$$ prepared by the ionization decreases as the laser intensity increases, while the subsequent electronic excitation is enhanced through the resonant electronic transitions. Ionization and electronic excitation mechanisms are described based on the electronic state distributions of C$$_{2}$$H$$_{5}$$OH$$^{+}$$.

Oral presentation

Photoelectron-photoion coincidence imaging for dissociative ionization of ethanol in intense UV laser fields

Ikuta, Tomoya; Hosaka, Koichi; Itakura, Ryuji; Akagi, Hiroshi; Yamanouchi, Kaoru*; Kannari, Fumihiko*; Yokoyama, Atsushi

no journal, , 

Recently, using a photoelectron-photoion coincidence momentum imaging apparatus, we found two possible pathways for the dissociative ionization of ethanol in intense NIR laser fields: one pathway is the direct access to the electronically excited states leading to the dissociation, the other is the stepwise excitation through the ionization to the electronic ground state. In this study, we investigate the dissociative ionization in intense UV laser with the same technique and compare the results with those with the NIR pulses.

Oral presentation

Dissociative ionization of ethanol in intense UV laser fields studied by photoelectron-photoion coincidence momentum imaging

Itakura, Ryuji; Ikuta, Tomoya*; Hosaka, Koichi*; Akagi, Hiroshi; Yamanouchi, Kaoru*; Yokoyama, Atsushi; Kannari, Fumihiko*

no journal, , 

When ethanol molecules are irradiated with an intense UV pulse (400 nm,100 fs, I = 10 TW/cm$$^{2}$$), channel-specific photoelectron momentum images correlated with C$$_{2}$$H$$_{5}$$OH$$^{+}$$, C$$_{2}$$H$$_{4}$$OH$$^{+}$$, CH$$_{2}$$OH$$^{+}$$, and C$$_{2}$$H$$_{5}$$$$^{+}$$ show different features, suggesting that different electronic and vibrational state distributions are prepared upon the ionization for the respective product ion channels.

Oral presentation

Dissociative ionization of ethanol in intense UV laser fields observed by photoelectron-photoion coincidence momentum imaging

Ikuta, Tomoya; Itakura, Ryuji; Hosaka, Koichi*; Akagi, Hiroshi; Yamanouchi, Kaoru*; Kannari, Fumihiko*; Yokoyama, Atsushi

no journal, , 

When ethanol molecules are irradiated with an intense UV pulse (400 nm, 100 fs, 15$$sim$$33 TW/cm$$^{2}$$), channel-specific photoelectron momentum images correlated with C$$_{2}$$H$$_{5}$$OH$$^{+}$$, C$$_{2}$$H$$_{4}$$OH$$^{+}$$, CH$$_{2}$$OH$$^{+}$$, and C$$_{2}$$H$$_{5}$$$$^{+}$$ show different features, suggesting that different electronic and vibrational state distributions are prepared upon the ionization for the respective product ion channels. Basically, the electronic ground state and the first electronically excited state are prepared upon the ionization, and then the subsequent interaction between the ion and the laser field takes place, leading to the respective reaction channels.

Oral presentation

Dissociative ionization of ethanol in intense UV laser fields studied by photoelectron-photoion coincidence momentum imaging

Ikuta, Tomoya; Itakura, Ryuji; Hosaka, Koichi*; Akagi, Hiroshi; Yamanouchi, Kaoru*; Kannari, Fumihiko*; Yokoyama, Atsushi

no journal, , 

Dissociative ionization of ethanol is more efficiently induced by intense ultraviolet laser fields than by intense near-infrared laser fields. In this study, our concern are focused on the electronic excitation dynamics in dissociative ionization of ethanol in intense ultraviolet laser fields. Photoelectron-photoion coincidence measurement allows us to understand the dissociation mechanism in terms of electronic excitation.

Oral presentation

Ionization of ethanol and subsequent electronic excitation in ethanol cation in intense laser fields

Itakura, Ryuji; Ikuta, Tomoya*; Hosaka, Koichi*; Akagi, Hiroshi; Yokoyama, Atsushi; Yamanouchi, Kaoru*; Kannari, Fumihiko*

no journal, , 

Using photoelectron-photoion coincidence technique, we identify two ionization routes of ethanol to the electronic ground state and the electronically excited state of ethanol cation in intense ultraviolet (UV) laser fields (400 nm, 96 fs). The population ratio of the electronically excited state with respect to the electronic ground state of C$$_{2}$$H$$_{5}$$OH$$^{+}$$ at the instant of the ionization decreases significantly as the laser intensity increases from 1.3 to 18.1 TW/cm$$^{2}$$. It is also revealed that the probability of the subsequent electronic excitation of C$$_{2}$$H$$_{5}$$OH$$^{+}$$ within the same pulse is enhanced as the laser intensity increases.

Oral presentation

Dissociative ionization dynamics of ethanol in intense laser fields; Energy correlation between photoelectron and fragment ion

Itakura, Ryuji; Ikuta, Tomoya*; Hosaka, Koichi*; Akagi, Hiroshi; Yokoyama, Atsushi; Yamanouchi, Kaoru*; Kannari, Fumihiko*

no journal, , 

We investigate dissociative ionization of ethanol induced by intense laser fields using photoelectron-photo ion coincidence momentum imaging. Our attentions are focused on the energy correlation between an electron and a fragment ion produced from an identical ethanol molecule. We reveal that the internal energy gained from laser fields depends on the ionization and fragmentation pathways. We discuss the ionization and dissociation mechanism based on the experimental results depending on the laser characteristics.

Oral presentation

Response characterization of ZnS(Ag) screen for on-line imaging diagnosis of laser-accelerated ion beams

Kanasaki, Masato; Sakaki, Hironao; Fukuda, Yuji; Yogo, Akifumi; Jinno, Satoshi; Kondo, Kiminori; Akagi, Takashi*; Hattori, Atsuto*; Matsukawa, Kenya*; Oda, Keiji*; et al.

no journal, , 

In the laser-driven ion acceleration experiment, fast electrons and X-rays also generated and these particles could cause significant contaminants to the ion detectors an a background noise. In the present study, to minimize the noise signals, we have optimized thickness of ZnS(Ag) fluorescent screen, which is much sensitive for ions, through Monte Carlo particle transport code PHITS. And we have also evaluate the response of the fluorescent screen as a function of fluence using rf-accelerator.

Oral presentation

Energy correlation of photoelectron and fragment ion in dissociative ionization of ethanol in intense laser fields

Itakura, Ryuji; Ikuta, Tomoya*; Hosaka, Koichi*; Akagi, Hiroshi; Yokoyama, Atsushi; Yamanouchi, Kaoru*; Kannari, Fumihiko*

no journal, , 

We investigate dissociative ionization of ethanol induced by intense laser fields using photoelectron-photo ion coincidence momentum imaging. Our attention is focused on the correlation between (1) photoelectron energy reflecting the state of ethanol cation at ionization and (2) kinetic energy of a fragment ion. From the observed correlation maps, we clarified that the internal energy gained from the laser field strongly depends on the ionization and dissociation pathways.

Oral presentation

Diagnostics of laser-accelerated ion beams using CR-39 and ZnS(Ag) fluorescent screen

Kanasaki, Masato; Fukuda, Yuji; Sakaki, Hironao; Yogo, Akifumi; Jinno, Satoshi; Nishiuchi, Mamiko; Ogura, Koichi; Akagi, Takashi*; Kondo, Kiminori; Oda, Keiji*; et al.

no journal, , 

Recently, high energy protons with a maximum energy of 40 MeV have been generated by laser-driven ion acceleration experiment with solid target. Although, the CR-39 detectors have been widely utilized in the laser-driven ion acceleration experiments, it has not been carried out the precise analysis for each etch pit. In the present study, we have applied the multi-step etching technique to stacked CR-39 detector unit which is irradiated by laser-accelerated protons. This method allows us to measure the maximum energy of proton precisely, which can obtain high energy resolution with uncertainty $$Delta$$E = 0.1 MeV. And also we have carried out the on-line measurement using ZnS(Ag) fluorescent screen for laser-accelerated ion beams.

Oral presentation

Overview of the equipment for a demonstration of laser Compton-scattered photon source at the cERL

Nagai, Ryoji; Hajima, Ryoichi; Kosuge, Atsushi; Mori, Michiaki; Shizuma, Toshiyuki; Nishimori, Nobuyuki; Akagi, Tomoya*; Honda, Yosuke*; Urakawa, Junji*

no journal, , 

A nondestructive assay system of isotopes by quasi-monochromatic $$gamma$$-rays and nuclear resonance fluorescence is under development in JAEA. The quasi-monochromatic $$gamma$$-rays are generated by laser Compton scattering (LCS) based on energy recovery linac accelerator and laser technologies. In order to demonstrate the accelerator and laser performance required for the $$gamma$$-ray source, an LCS experiment is planned at Compact ERL (cERL) at KEK. A mode-locked fiber laser, laser enhancement cavity, beamline, and experimental hatch are under construction for the LCS experiment. Up-to-date construction status is presented in detail.

Oral presentation

Plan of the laser Compton scattering experiment at the compact ERL

Nagai, Ryoji; Hajima, Ryoichi; Shizuma, Toshiyuki; Mori, Michiaki; Akagi, Tomoya*; Kosuge, Atsushi*; Honda, Yosuke*; Urakawa, Junji*

no journal, , 

no abstracts in English

Oral presentation

Development of the beamline flux monitor for the laser Compton-scattered photon source in the cERL

Nagai, Ryoji; Hajima, Ryoichi; Mori, Michiaki; Shizuma, Toshiyuki; Akagi, Tomoya*; Kosuge, Atsushi*; Honda, Yosuke*; Urakawa, Junji*

no journal, , 

no abstracts in English

Oral presentation

Generation of laser Compton $$gamma$$-rays using cERL and its application

Shizuma, Toshiyuki; Hajima, Ryoichi; Nagai, Ryoji; Mori, Michiaki; Akagi, Tomoya*; Kosuge, Atsushi*; Honda, Yosuke*; Terunuma, Nobuhiro*

no journal, , 

We have developed a non-destructive assay system based on nuclear resonance fluorescence (NRF). In the proposed detection system, an energy-tunable and mono-energetic $$gamma$$-rays generated by Compton scattering of laser light (laser Compton scattering; LCS) with high-energy electrons are used. We have demonstrated the generation of LCS $$gamma$$-rays from Compact energy recovery linac (ERL) at KEK and X-ray fluorescence for elements around iron as an application study. The results on the demonstration of the LCS photon generation as well as the X-ray fluorescence measurement will be reported.

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