K. Hayakawa

Tunable Monochromatic X‐ray Source Based on Parametric X‐ray Radiation at LEBRA, Nihon University

The monochromatic X‐ray source based on parametric X‐ray radiation (PXR) was developed by using the electron beam from the 125‐MeV linac at Nihon University. The X‐ray generating system consists of two silicon perfect‐crystal plates to offer a wide tunability. The system has actually been providing the energy dispersive monochromatic X‐ray beam in the region of 6 to 20 keV, using Si(111)‐plane for the target and the second crystals. Since the X‐ray beam from the PXR generator has rather high energy resolution and coherency, X‐ray absorption fine structure (XAFS) measurement and phase‐contrast imaging are possible applications of PXR. Actually, preliminary experiments on energy dispersive XAFS measurement and refraction‐contrast imaging have been successfully carried out using the PXR beam.

Status of Infrared Free Electron Laser at Nihon University

A free electron laser (FEL) system has been developed for the experiments of material, life, resource sciences and others at the Laboratory for Electron Beam Research and Application (LEBRA) in Nihon University. The beam from a 125MeV electron linac was first introduced to the FEL system in 1998. We had encountered several difficulties especially in the electron beam stability for the long pulse operation of the linac which was required for a relatively short wavelength FEL system. In 2001 the first lasing of 1.5µm FEL was achieved at the electron energy of 86MeV using an undulator designed for the near infrared FEL. We could suppress the beam current fluctuations quite effectively by improving the stability of the phase of the klystron output RF and have succeeded in lasing. The current important subject is to improve the stability of the FEL lasing for the applications of the LEBRA FEL to various studies.