• R. Kato, K. Furuhashi, G. Isoyama, S. Kashiwagi, M. Morio, S. Suemine, N. Sugimoto, Y. Terasawa
  ISIR, Osaka
• K. Tsuchiya, S. Yamamoto
  KEK, Ibaraki

We have been developing a Terahertz free electron laser (FEL) based on the 40 MeV, 1.3 GHz L-band electron linac at the Institute of Scientific and Industrial Research (ISIR), Osaka University. After the FEL lasing at the wavelength of 70 um (4.3 THz)*, next targets of the FEL development are to extend the available laser wavelength, to increase the FEL power, and to evaluate characteristics of FEL. Since the lowest energy of the linac was restricted by a fixed-ratio power divider between the acceleration tube and the buncher, we have prepared the new one with a different ratio to extend the wavelength longer side. As a result, the wavelength region is able to be extended to 25 - 147 um (12.5 - 2 THz). The maximum output energy of the FEL macropulse so far obtained is 3.6 mJ at 66 um. The peak macropulse power available to user experiments is estimated to be 1 kW or less, given that the pulse duration is 3 us. Three users groups have begun experiments using the FEL. We will report these recent activities on the Terahertz FEL.

* G. Isoyama, R. Kato, S. Kashiwagi, T. Igo, Y. Morio, Infrared Physics & Technology 51 (2008) 371-374.

• G. Isoyama, M. Fujimoto, K. Furuhashi, S. Kashiwagi, R. Kato, M. Morio, J. Shen, S. Suemine, N. Sugimoto, Y. Terasawa
  ISIR, Osaka
• S. Hirata
  Hiroshima University, Faculty of Science, Higashi-Hirosima

The 40 MeV L-band electron linac at the Institute of Scientific and Industrial Research, Osaka University is extensively used for various applications on advanced beam sciences including radiation chemistry by means of pulse radiolysis and development of the free electron laser in the THz region. It was constructed in 1975-78 and has been remodeled sometimes for improving its performance. The most recent one was made in 2002-2004 for higher operational stability and reproducibility, resulting in significant advances in the studies. We will report the present status of the linac and results of its performance evaluation.