Author: Hajima, R.
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TUPGW036 1 mA Stable Energy Recovery Beam Operation with Small Beam Emittance 1482
  • T. Obina, D.A. Arakawa, M. Egi, T. Furuya, K. Haga, K. Harada, T. Honda, Y. Honda, T. Honma, E. Kako, R. Kato, H. Kawata, Y. Kobayashi, Y. Kojima, T. Konomi, H. Matsumura, T. Miura, T. Miyajima, S. Nagahashi, H. Nakai, N. Nakamura, K. Nakanishi, K.N. Nigorikawa, T. Nogami, F. Qiu, H. Sagehashi, H. Sakai, S. Sakanaka, M. Shimada, M. Tadano, T. Takahashi, R. Takai, O. A. Tanaka, Y. Tanimoto, T. Uchiyama, K. Umemori, M. Yamamoto
    KEK, Ibaraki, Japan
  • R. Hajima, R. Nagai, M. Sawamura
    QST, Tokai, Japan
  • N. Nishimori
    National Institutes for Quantum and Radiological Science and Technology (QST), Sayo-cho, Japan
  A compact energy-recovery linac (cERL) have been operating since 2013 at KEK to develop critical components for ERL facility. Details of design, construction and the result of initial commissioning are already reported*. This paper will describe the details of further improvements and researches to achieve higher averaged beam current of 1 mA with continuous-wave (CW) beam pattern. At first, to keep the small beam emittance produced by 500 kV DC-photocathode gun, tuning of low-energy beam transport is essential. Also, we found some components degrades the beam quality, i.e., a non-metallic mirror which disturbed the beam orbit. Other important aspects are the measurement and mitigation of the beam losses. Combination of beam collimator and tuning of the beam optics can improve the beam halo enough to operate with 1 mA stably. The cERL has been operated with beam energy at 20 MeV or 17.5 MeV and with beam rep-rate of 1300 MHz or 162.5 MHz depending on the purpose of experiments. In each operation, the efficiency of the energy recovery was confirmed to be better than 99.9 %.
* S. Sakanaka,, Nucl. Instr. and Meth. A 877 (2017)197,
DOI • reference for this paper ※  
About • paper received ※ 14 May 2019       paper accepted ※ 22 May 2019       issue date ※ 21 June 2019  
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TUPRB041 Simulation of Short-Pulse Generation from a Dynamically Detuned IR-FEL Oscillator and Pulse Stacking at an External Cavity 1778
  • Y. Sumitomo, Y. Hayakawa, T. Sakai
    LEBRA, Funabashi, Japan
  • R. Hajima
    QST, Tokai, Japan
  Funding: Q-LEAP program supported by Ministry of Education, Culture, Sports, Science and Technology, Japan
At the LEBRA facility of Nihon U., we have an IR-FEL oscillator to generate radiations in the range of wavelengths 1-6 um for various experiments. A research program has been established to explore the application of the IR-FEL to generate attosecond UV and X-ray pulses through the high harmonic generation (HHG) in noble gases, where the IR-FEL pulses must have a high-peak power and a short-pulse duration. The property of generated FEL pulse is affected by the cavity length detuning of FEL oscillator as well as the small signal gain and the cavity loss. The operation at a small- or zero-detuning length is necessary to generate a FEL pulse shorter than the bunch length, although it requires a long macro-pulse to reach the saturation. For the short FEL pulse generation within a limited macro-pulse length at the LEBRA LINAC, we apply a dynamical modulation to the electron bunch repetition, that is equivalent to a dynamical detuning of the FEL cavity length. We illustrate the potential performance of the IR-FEL with the dynamical detuning by time-dependent 3D FEL simulations. We also evaluate the enhancement of the FEL pulses by an external cavity stacking for the sake of the HHG application.
DOI • reference for this paper ※  
About • paper received ※ 29 April 2019       paper accepted ※ 23 May 2019       issue date ※ 21 June 2019  
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