• K. Nakao, K. Hayakawa, Y. Hayakawa, M. Inagaki, K. Nogami, T. Sakai, I. Sato, T. Tanaka
  LEBRA, Funabashi

The near-infrared free electron laser (FEL) has been provided for scientific studies in various fields since 2003 at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. The behaviour of the LEBRA electron linac system has been monitored using various diagnostic devices such as beam position monitors, vacuum gauges, thermocouples, optical power monitors and so on. The results obtained during operation of the linac have been routinely stored in databases or files. This paper discusses about the analysis on the factors of fluctuation for the electron beam energy/position and the FEL optical power on the basis of the linac diagnostic results. Intentional change in the linac cooling water temperature, introduced periodically with 0.1°C peak-to-peak, has resulted in negligibly small fluctuation of the FEL output power. This suggests that the LEBRA linac cooling water system offering the temperature regulation within 0.02°C has sufficient performance for stable FEL lasing.

• F. Shishikura, K. Ishikawa
  Nihon University School of Medicine, Tokyo
• K. Hayakawa, Y. Hayakawa, T. Kuwada, K. Nakao, K. Nogami, T. Tanaka
  LEBRA, Funabashi
• M. Inagaki, T. Sakai, I. Sato
  Nihon University, Advanced Research Institute for the Sciences and Humanities, Funabashi

The Free-Electron Laser (FEL) of LEBRA[1] produces near infrared FELs (IR FELs) including tunable wavelength from 1 to 6 microns. The higher harmonics generated by means of the nonlinear optical crystals are also available with output energy of about 0.5 mJ/micro-pulse. The IR FELs of LEBRA are of significant interest because these tunable wavelengths covered with visible and near infrared regions (350 nm-6000 nm) expect to unveil photochemical reactions of bio-macromolecules even in living organisms. We use LEBRA IR FELs for macromolecules such as caronmonoxy hemoglobin (COHb), whose maximum absorption spectra are known as Soret band (418 nm) and two weaker bands (538 nm and 568 nm). We first selected three of the visible wavelengths. After irradiation (up to about 10 J), the each effect of three wavelengths on COHb was separately investigated by several methods icluding visible scanning absorption spectroscopy and Raman microscopy. We report the present results on the mesurements.

[1] Laboratory for Electron Beam Research and Application, Institute of Quantum Science, Nihon University.