FEL2012 - List of Authors (Isoyama, G.)

Paper	Title	Page
WEPD64	FEL Gain Measurement with a Novel Method	515
	M. Fujimoto, A. Irizawa, G. Isoyama, F. Kamitsukasa, R. Kato, K. Kawase, H. Ohsumi, M. Yaguchi ISIR, Osaka, Japan S. Kashiwagi Tohoku University, Research Center for Electron Photon Science, Sendai, Japan S. Yamamoto KEK, Tsukuba, Japan
	The FEL gain is an important factor characterizing performance of the FEL. We used to derive the gain of the THz-FEL at Osaka University from the macropulse shape measured using a Ge:Ga detector with the time resolution of ~10 ns. The method was recently found faulty because the response of the detector shows strong non-linearity in amplitude at a high intensity level. We, therefore, have developed a new method for the gain measurement using a silicon bolometer, which has a very high linearity over the wide intensity range. The detector has the time resolution of ~1 ms, which is much longer than the FEL macropulse of a few microseconds, so that it measures energy in the macropluse. In order to derive the temporal revolution of FEL power, the number of amplifications is varied by changing the macropulse length of the electron beam. The sensitivity of the detector is also high, so that we could measure the energy development of the FEL over 6~7 orders of magnitude at a wavelength ~100 micrometers in combination with appropriate absorbers. We will report results of the measurement and analysis of the FEL gain.

Paper

Title

Page

FEL Gain Measurement with a Novel Method

515

M. Fujimoto, A. Irizawa, G. Isoyama, F. Kamitsukasa, R. Kato, K. Kawase, H. Ohsumi, M. Yaguchi
ISIR, Osaka, Japan
S. Kashiwagi
Tohoku University, Research Center for Electron Photon Science, Sendai, Japan
S. Yamamoto
KEK, Tsukuba, Japan

The FEL gain is an important factor characterizing performance of the FEL. We used to derive the gain of the THz-FEL at Osaka University from the macropulse shape measured using a Ge:Ga detector with the time resolution of ~10 ns. The method was recently found faulty because the response of the detector shows strong non-linearity in amplitude at a high intensity level. We, therefore, have developed a new method for the gain measurement using a silicon bolometer, which has a very high linearity over the wide intensity range. The detector has the time resolution of ~1 ms, which is much longer than the FEL macropulse of a few microseconds, so that it measures energy in the macropluse. In order to derive the temporal revolution of FEL power, the number of amplifications is varied by changing the macropulse length of the electron beam. The sensitivity of the detector is also high, so that we could measure the energy development of the FEL over 6~7 orders of magnitude at a wavelength ~100 micrometers in combination with appropriate absorbers. We will report results of the measurement and analysis of the FEL gain.