K. Nomaru

Optical beam transport system at FEL-SUT

Abstract Kawasaki Heavy Industries Ltd. has installed an FEL beam transport system at the IR FEL Research Center of the Science University of Tokyo (FEL-SUT). This system transports the FEL output beam from the FEL machine room to the optical diagnostic room through a vacuum tube. The in-vacuum multi-mirror synchronized system operated from the FEL control room enables the operator to control the multiple mirrors simultaneously on or off axis of the FEL beam and to distribute the FEL output to one of the laboratories. The essential component of the transport system is the passive control optics that is composed of an elliptical and parabolic mirror couple. Once the control optics is aligned, a parallel FEL beam with a good pointing stability is obtained without any active operation to tune the optical system for different wavelengths.

Performance of the KHI FEL device at FEL-SUT

FEL lasing with the saturated power in the wavelength of 4–16mm was achieved by using the KHI (Kawasaki Heavy Industries, Ltd.) FEL device. The macro-pulse length of the electron beam was improved by using the LaB6 cathode instead of the dispenser cathode as a cathode of the OCS RF-gun. The improvement yielded the saturated FEL power with the macro-pulse length of 0.5–1.5ms. The FEL energy was 2–40 mJ. The measured FEL output powers were in agreement with the values which were taken into account Piovella’s theory. r 2002 Elsevier Science B.V. All rights reserved. PACS: 41.60.C

Improvement of KHI FEL device at FEL-SUT

FEL lasing with the saturated power in the wavelength of 4-16 µm was achieved by using the KHI (Kawasaki Heavy Industries, ltd.) FEL device. The macro-pulse length of the electron beam was improved by using the LaB6 cathode instead of the dispenser cathode as a cathode of the OCS RF-gun. The improvement yielded to obtain the saturated FEL power. The FEL energy was 2-40mJ. In addition to it, the vertical position (the same direction as the electron beam from the cathode) of the RF-gun cathode was tuned. As a result, the FEL energy was increased to 2-65mJ. The FEL output powers estimated from the FEL energy and the macro-pulse shape were in agreement with the values which were taken into account Piovellas theory.

Gas-Flow Circulation Apparatus Coupled with TEA-CO2 Laser for Free Electron Laser Isotope Separation

A gas-flow circulation apparatus coupled with a TEA-CO2 laser has been developed for the purpose of the isotope separation experiments using a free electron laser (FEL). The working gaseous mixture filled in the reaction chamber was smoothly circulated by the ventilation fan. Using the reaction chamber with the large volume, the multi-photon dissociation of a SiF3I molecule was successfully demonstrated. The change of IR spectrum monitored on-line by a FT-IR spectrometer showed that the TEA-CO2 laser effectively assisted the multi-photon dissociation of the molecules by the FEL.

A device for the enhancement of the micro-pulse peak power and the shortening of the macro-pulse duration

Abstract We have developed a cavity dumping device for increasing the micro-pulse peak power to about one hundred times and for shortening the macro-pulse duration for the mid-infrared FEL apparatus (MIR-FEL) operating in the IR FEL Research Center of the Tokyo University of Science (FEL-SUT). The device is composed of a Pockels cell with a CdTe crystal and a couple of Brewster windows made of germanium, and they are installed into the optical resonance cavity of MIR-FEL. By operating this device, the micro-pulse peak power is expected to be a few hundreds of megawatts with the macro-pulse duration of 23 ns, within an operating wavelength range of 5—8 μm. PACS codes: 41.60. Cr; 42.60. Gd

Status of FEL-SUT

Abstract In the IR FEL Research Center of the Tokyo University of Science (FEL-SUT), a mid-infrared free electron laser (MIR-FEL) is in full operation and a variety of application experiments are going on by use of light beams from MIR-FEL. A far-infrared FEL covering the wavelength of 300—1000μm is now under construction. The status of those FEL machines and that of experimental facilities for application will be reported. PACS codes: 41.60. Cr, 29.17.+w,42.72. Ai

Infrared Multi-Photon Dissociation of SiF3I by Co-Irradiation with FEL and TEA-CO2 Laser

IR multi-photon dissociation of SiF3I in gaseous phase (pure SiF3I at 5 torr with natural abundance of Si isotopes) was studied by use of the mid-infrared free electron laser (MIR-FEL) of the IR FEL Research Center of the Tokyo University of Science. The following three kinds of experiment were carried out: irradiation with FEL only, irradiation with TEA-CO2 laser and co-irradiation with FEL and TEA-CO2 laser. Upon irradiating SiF3I with a strong light in the 10 µm spectral region, SiF3I was partially dissociated. The dissociation rate was found to be markedly enhanced by the co-irradiation with TEA-CO2 laser and FEL. The experimental results showed that the dissociation reaction SiF3I →SiF3 + I was induced by the multi-photon process, but isotope selectivity could not be found because SiF3 radical thus formed further reacted to form SiF4, SiF3I and SiF2I2.