World’s First Observation of Saturable Absorption of Hard X-rays -Opening a promising path using the world’s most intense X-rays of SACLA- (Press Release)
- Release Date
- 02 Oct, 2014
- SACLA
RIKEN
The University of Electro-Communications
Japan Synchrotron Radiation Research Institute (JASRI)
Osaka University
The University of Tokyo
Kyoto University
Key points
• The transparency of materials increases with increasing X-ray intensity.
• This observation was realized for the first time in the world using the most intense X-rays.
• This finding opens a promising path for future innovations of attosecond X-ray optics.
|
Scientists from RIKEN (President, Ryoji Noyori) and the University of Electro-Communications (President, Takashi Fukuda) succeeded in observing saturable absorption of X-rays*1 using the SPring-8 Angstrom Compact Free Electron Laser (SACLA)*2, an X-ray free electron laser (XFEL) facility. This was achieved by a joint research group led by Hitoki Yoneda (professor) of the University of Electro-Communications; Makina Yabashi (group director) of the Beam Line Research and Development Group of RIKEN SPring-8 Center (Director, Tetsuya Ishikawa). Publication: |
<<Figures>>
Materials that do not allow X-rays with a low intensity to be transmitted become transparent when most electrons absorbing X-rays are ionized using X-rays with a high intensity. Optical waveguides of X-rays and high-speed switching mechanisms using X-rays can be structured because only the regions irradiated with X-rays with a high intensity become transparent.
An iron foil (thickness, 20 µm) is irradiated with X-rays focused to a diameter of 50 nm using a two-stage focusing system. The transmitted X-rays are detected using a spectroscope with a high energy resolution.
The red dots denote experimental values. Blue and green curves denote calculated values obtained by computer simulation assuming that the times required for the holes in the K shell (the electron orbital nearest to the atomic core), emptied after X-ray irradiation, to be occupied again are 0.5 and 2 fs (femtosecond is one-quadrillionth of a second), respectively. As theoretically predicted, the iron foil becomes significantly transparent at X-ray intensities higher than 1019 W/cm2.
《補足説明》
※1 Saturable absorption
Saturable absorption is a phenomenon of decreased absorption and increased transparency in materials when strong absorption is induced in the materials and the elements responsible for absorption (mainly electrons in some level) are depleted. A excitation absorption process sometimes follows after the fundamental absorption.
Thus a simple system is generally considered to be appropriate for saturable absorption.
※2 SPring-8 Angstrom Compact Free Electron Laser (SACLA), an X-ray free electron laser (XFEL) facility
Japan’s first XFEL facility constructed jointly by RIKEN and JASRI. As one of the five national key technologies in the Basic Program for Science and Technology in Japan, the facility was constructed and developed in a five-year project starting from FY 2006. It was completed in March 2011 and named SACLA after the initial letters of SPring-8 Angstrom Compact Free Electron LAser. The first successful generation of an X-ray laser was in June 2011. Public operations started in March 2012. Since then, SACLA has been used in various experiments. Although the facility is smaller than those in other countries, SACLA can produce lasers with the world’s shortest wavelength of 0.1 nm or shorter.
※3 Optical waveguide
When a waveguide with a locally high reflective index is formed in a material, light propagates within the waveguide. An optical fiber is a type of optical waveguide and enables light to propagate for several hundred kilometers within the waveguide with a small diameter.
※4 Two-stage focusing system
To simultaneously realize a small diameter of a focused X-ray laser and a long distance from a focusing optical system to a focal point (working distance), the diameter of the X-ray lasers themselves should be increased and the lasers should be focused using a large mirror. SACLA realizes this goal by adopting a two-stage focusing system with two optical systems in charge of the former and latter roles.
※5 Attosecond X-ray optics
An attosecond is one-quintillionth (10−18) of a second. An attosecond is so short that even electron’s motion in a material are freezed.
※6 Dynamic X-ray optics
In a visible to infrared wavelength region optical constants itself are changed by dynamically with optical wave and applied electric/magnetic field. They change the direction, wavelength, pulse waveform, spectral width and so on. This concept is applied to the light in an X-ray region.
|
For more information, please contact: Group Director Makina Yabashi Professor Kazuto Yamauchi Associate Professor Hidekazu Mimura Assistant Professor Hikaru Kitamura （Press） Public Relations Division, Administration Office,
Public Relations Office, SPring-8 Users Office, JASRI Evaluation/Public Relations Division, Administration Office,
Public Relations Office, Graduate School of Engineering,
Public Relations Division, Kyoto University |
- Previous Article
- Clarification of Mechanism Underlying Destruction of Red Blood Cells by Pathogenic Bacteria (Press Release)
- Current article
- World’s First Observation of Saturable Absorption of Hard X-rays -Opening a promising path using the world’s most intense X-rays of SACLA- (Press Release)