Author: Fujimoto, M.
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TUP010 Recent Progress in Upgrade of the High-Intensity THz-FEL at Osaka University 354
 
  • G. Isoyama, M. Fujimoto, S. Funakoshi, K. Furukawa, A. Irizawa, R. Kato, K. Kawase, A. Tokuchi, R. Tsutsumi, M. Yaguchi
    ISIR, Osaka, Japan
 
  We are upgrading the THz-FEL at Osaka University for its applications to high intensity THz sciences, which originally generated the high intensity FEL with the macropulse energy up to 3.7 mJ and the micropulse energy up to ~10 uJ at a wavelength around 70 um. To increase the micropulse energy, charge in electron bunches is increased four time higher and the bunch intervals are expanded four times longer to maintain the average current in the linac unchanged. In the new operation mode, the macropulse energy increases up to 26 mJ and the micropulse energy to ~0.2 mJ, which is 20 times higher than the energy previously obtained in the conventional mode. We have developed a solid-state switch for the klystron modulator to highly stabilize the klystron voltage, so that the output power of the FEL becomes stable. We are conducting basic studies on FEL for further improvement of its performance, including measurement of power evolution from start-up to saturation, time structures of FEL micropulses measured with a Michelson interferometer, and time structures of macropulses measured with a Schottky diode detector. We will report results of these studies on the THz-FEL at Osaka University.  
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TUP029 Single Picosecond THz Pulse Extraction from the FEL Macropulse using a Laser Activating Semiconductor Reflective Switch 430
 
  • K. Kawase, M. Fujimoto, K. Furukawa, A. Irizawa, G. Isoyama, R. Kato, K. Kubo
    ISIR, Osaka, Japan
 
  The THz-FEL at the Institute of Scientific and Industrial Research, Osaka University can generate high-intensity THz pulses or FEL macropulses, which comprise approximately 100 micropulses at 37 ns intervals in the 27 MHz mode or 400 micropulses at 9.2 ns intervals in the 108 MHz mode. The maximum macropulse energy in the 27 MHz mode reaches 26 mJ at a frequency of 4.5 THz and the micropulse energy is estimated to be 0.2 mJ. To open new areas of studies with high intensity THz radiation for user experiments, we are developing a single pulse extraction system from the pulse train using a laser activating semiconductor reflective switch. We have succeeded in extracting a single THz pulse, duration of which is estimated to be less than 20 ps, from the FEL macropulse using a gallium arsenide wafer for the switch. We will report on the THz pulse extraction system and its performance.  
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