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Sano, Tomokazu*; Matsuda, Tomoki*; Hirose, Akio*; Terai, Tomoyuki*; Kakeshita, Tomoyuki*; Inubushi, Yuichi*; Sato, Takahiro*; Yabashi, Makina*; Shobu, Takahisa; 22 of others*
Scientific Reports (Internet), 13, p.13796_1 - 13796_10, 2023/08
Times Cited Count：0 Percentile：0(Multidisciplinary Sciences)Minehara, Eisuke
Nuclear Instruments and Methods in Physics Research A, 557(1), p.16 - 22, 2006/02
Times Cited Count：11 Percentile：60.27(Instruments & Instrumentation)The JAERI FEL facility at Tokai, Ibaraki, Japan has been well known one of the two existing and operating superconducting energy recovery linacs together with one more of JLAB (Jefferson national accelerator facility) FEL facility at Newport News, Virginia, U.S.A. We have independently and successfully developed one of the most advanced and newest accelerator technologies named "superconducting energy recovery linacs (ERLs)" and the application technologies using ERLs in future. We plan to report the current high power FEL upgrade program research, stress corrosion cracking prevention technology research, large current and high brightness photoelectron gun research of negative-electron affinity (NEA) photocathode and NEA electron-excitation cathode as the most important elemental technology in realizing many powerful ERLs.
Hajima, Ryoichi
Nuclear Instruments and Methods in Physics Research A, 557(1), p.45 - 50, 2006/02
Times Cited Count：2 Percentile：21.09(Instruments & Instrumentation)no abstracts in English
Kikuzawa, Nobuhiro; Nagai, Ryoji
Proceedings of 2nd Annual Meeting of Particle Accelerator Society of Japan and 30th Linear Accelerator Meeting in Japan, p.430 - 432, 2005/07
no abstracts in English
Iijima, Hokuto; Hajima, Ryoichi; Nagai, Ryoji; Minehara, Eisuke; Yamauchi, Toshihiko
Proceedings of 2nd Annual Meeting of Particle Accelerator Society of Japan and 30th Linear Accelerator Meeting in Japan, p.793 - 795, 2005/07
We report the construction of FEL transport line and the measurement method of chirped FEL pulse. An infrared-chirped pulse is an effective way of dissociating molecules. The chirped FEL pulse oscillator is operated by the JAERI-FEL superconducting accelerator, in which a long pulse of electron beam is produced. Until now, the chirped pulse was measured to be 
= 14.3% with the wavelength of 23.3 
m and the pulse width of 319 fs at FWHM by an autocorrelation. In order to measure the correlation between time and frequency in the chirped pulse directly, the frequency-resolved optical grating (FROG) is developing. Since the measurement is performed in new experimental room, the vacuum transport line guiding the FEL to the room has been constructed.
Iijima, Hokuto; Hajima, Ryoichi; Uesaka, Mitsuru*; Sakumi, Akira*; Sakamoto, Fumito*; Ueda, Toru*
Proceedings of 2nd Annual Meeting of Particle Accelerator Society of Japan and 30th Linear Accelerator Meeting in Japan, p.501 - 503, 2005/07
We report the availability of velocity bunching in an energy recovery linac (ERL) by a numerical analysis, and the plan of precise measurement of bunching emittance via a double-slit-scan method. The simulation performed for eight TESLA-type cavities reveals successful bunch compression from 3.2 ps to 0.17 ps. Since the residual energy spread after velocity bunching is considerably smaller than the correlated energy spread required for magnetic compression through a recirculation loop, velocity bunching is useful to realized short-pulse and high-brightness X-rays by ERL. The emittance of velocity bunching was calculated to be 1.5 
mm.mrad for the bunch charge of 77pC without the emittance compensation by an external solenoid field. Although the emittance growth due to the space-charge effect was small in the simulation, it is necessary to evaluate the emittance-growth mechanism under velocity bunching. Therefore, the emittance measurement via double-slit-scan method is carrying out in the UTNL-18L.
Kikuzawa, Nobuhiro
JAERI-Tech 2005-022, 48 Pages, 2005/03
JAERI-Tech-2005-022.pdf:3.14MB
no abstracts in English
Iijima, Hokuto; Uesaka, Mitsuru*; Sakamoto, Fumito*; Ueda, Toru*; Kumagai, Noritaka*; Serafini, L.*
Japanese Journal of Applied Physics, Part 1, 44(7A), p.5249 - 5253, 2005/01
Times Cited Count：8 Percentile：32.18(Physics, Applied)We represent an experimental verification of a bunch compression method named "velocity bunching". The velocity bunching based on the rectilinear compression uses a traveling wave accelerating tube as a compressor. The experiment was performed by an S-band photoinjector and a linac at Nuclear Engineering Research Laboratory, University of Tokyo. The shot-by-shot bunch length was measured to be 0.5 
0.1 ps (rms) in average by the femtosecond streak camera for a bunch charge of 1 nC. The experimental result is in good agreement with PARMELA simulations.
Minehara, Eisuke; Hajima, Ryoichi; Iijima, Hokuto; Kikuzawa, Nobuhiro; Nagai, Ryoji; Nishimori, Nobuyuki; Nishitani, Tomohiro; Sawamura, Masaru; Yamauchi, Toshihiko
Proceedings of 27th International Free Electron Laser Conference (FEL 2005) (CD-ROM), p.305 - 308, 2005/00
The JAERI high power ERL-FEL has been extended to the more powerful and efficient free-electron laser (FEL) than 10kW for nuclear energy industries, and other heavy industries like defense, shipbuilding, chemical industries, environmental sciences, space-debris, and power beaming and so on. In order to realize such a tunable, highly-efficient, high average power, high peak power and ultra-short pulse FEL, we need the efficient and powerful FEL driven by the JAERI compact, stand-alone and zero boil-off super-conducting RF linac with an energy-recovery geometry. Our discussions on the ERL-FEL will cover the current status of the 10kW upgrading and its applications of non-thermal peeling, cutting, and drilling to decommission the nuclear power plants, and to demonstrate successfully the proof of principle prevention of cold-worked stress-corrosion cracking failures in nuclear power reactors under routine operation using small cubic low-Carbon stainless steel samples.
Yamauchi, Toshihiko
Japanese Journal of Applied Physics, 43(9A), p.6473 - 6474, 2004/09
Times Cited Count：0 Percentile：0(Physics, Applied)The output pattern of He-Ne laser that passes through the optical glass fiber bundle used for free electron laser etc. depends on the weight of load (modulation of transverse mode). The increment of pattern radius exponentially increases with the load. It is considered that the micro bending causes this increment. Next, the estimated delay time also exponentially increases with the weight of load, and the estimated delay time is the extent of pico-second.
Nishimori, Nobuyuki
Nuclear Instruments and Methods in Physics Research A, 528(1-2), p.34 - 38, 2004/08
Times Cited Count：1 Percentile：10.3(Instruments & Instrumentation)The sustained saturation in an FEL oscillator at zero detuning of an optical cavity (
=0) is studied analytically. The FEL field at =0 is characteristic of self-amplified spontaneous emission (SASE) FEL. For both cases, the field is composed of the forward incoherent and subsequent coherent states. The coherent field at =0 evolves with round trips due to the lethargy. The field at saturation is similar to that of the leading edge of SASE FEL with high electron beam density. It is found that the peak intensity and the pulse length of the saturation field scale with fundamental FEL parameter and an optical cavity loss.
Hajima, Ryoichi
Nuclear Instruments and Methods in Physics Research A, 528(1-2), p.335 - 339, 2004/08
Times Cited Count：20 Percentile：76.55(Instruments & Instrumentation)Dilution of electron beam emittance through a return arc is one of critical problems in the design of an energy-recovery linac for high-power FEL and a synchrotron light source. We present that the emittance dilution can be compensated by establishing the matching between the phase ellipse orientation and the CSR kick direction, and the effect of coherent synchrotron radiation on the beam emittance dilution can be estimated from simple calculation of transfer matrices.
Nagai, Ryoji; Hajima, Ryoichi; Sawamura, Masaru; Nishimori, Nobuyuki; Kikuzawa, Nobuhiro; Minehara, Eisuke
Nuclear Instruments and Methods in Physics Research A, 528(1-2), p.231 - 234, 2004/08
Times Cited Count：2 Percentile：18.14(Instruments & Instrumentation)An optical resonator geometry of JAERI ERL-FEL is optimized to ensure the high-power operation. Efficiency of the FEL strongly depends on performance of the optical resonator such as an output efficiency and interaction mode volume. The resonator geometry is optimized by maxmization of the output efficiency and minimization of the interaction mode volume. The output efficiency and the interaction mode volume of the optical resonator is calculated by a simulation code using Fox-Li procedure. To search rapidly with various parameters, the simulation code is improved utilizing Fast-Fourie-Transform.
Nishimori, Nobuyuki
Proceedings of 1st Annual Meeting of Particle Accelerator Society of Japan and 29th Linear Accelerator Meeting in Japan, p.174 - 176, 2004/08
no abstracts in English
Maebara, Sunao; Zheng, X.*; Watanabe, Akihiko*; Kishiro, Junichi*; Takayama, Ken*; Horioka, Kazuhiko*; Ogawa, Masao*; Kawasaki, Sunao*; Shiho, Makoto
JAERI-Research 2004-007, 40 Pages, 2004/03
JAERI-Research-2004-007.pdf:4.48MB
no abstracts in English
Nishimori, Nobuyuki; Hajima, Ryoichi; Nagai, Ryoji
Free Electron lasers 2003, p.II_21 - II_22, 2004/00
Free-Electron Laser (FEL) interaction with unbunched electrons at resonant energy induces a positive phase shift of the FEL field relative to the input phase. The positive phase shift corresponds to giving electrons positive energy detuning, and results in the FEL amplification. The zero small signal gain on resonance in low gain regime is related to the exponential growth in high gain regime by the positive phase shift.
Nishimori, Nobuyuki
Proceedings of 26th International Free Electron Laser Conference (FEL 2004) and 11th FEL Users Workshop (CD-ROM), p.41 - 44, 2004/00
The phase space evolution of electrons in a self-amplified spontaneous emission (SASE) FEL operating in the linear regime before saturation is solved analytically from the one dimensional (1D) FEL equaiton. The analytical solution agrees well with a time-dependent numerical simulation which solves the 1D FEL equation in an exact manner and includes a shot-noise effect. The radiation field reaches saturation when the optimum bunching of the electrons is formed on the scale of the resonant wavelength. The optimum bunching leads to the well known saturation condition 
Nw 1.
Nishimori, Nobuyuki; Hajima, Ryoichi; Kikuzawa, Nobuhiro; Minehara, Eisuke; Nagai, Ryoji; Sawamura, Masaru
Proceedings of 3rd Asian Particle Accelerator Conference (APAC 2004), p.625 - 627, 2004/00
no abstracts in English
Nishimori, Nobuyuki
Dai-14-Kai Kasokuki Kagaku Kenkyu Happyokai Hokokushu, p.108 - 110, 2003/11
The evolution of the field of an FEL oscillator at zero detuning length of an optical cavity (dL = 0) is studied analytically. The field on the leading edge at the first round trip is the same as that of a self-amplified spontaneous emission (SASE) FEL characterized by an FEL parameter. The field evolves with round trips by interaction with electrons. The field in the early stage of the evolution is found to scale with the FEL parameter and the round-trip number, and is similar to that of SASE with high electron beam density.
Kikuzawa, Nobuhiro
Proceedings of 28th Linear Accelerator Meeting in Japan, p.437 - 439, 2003/08
no abstracts in English
