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BL40XU OUTLINE

問い合わせ番号

INS-0000000353

ABSTRACT

  The basic design concept of BL40XU is to use the fundamental peak of undulator radiation as a quasi-monochromatic x-ray beam. This eliminates the use of a crystal monochromator which has a band-pass of the order of 10-4, unnecessarily narrow in some experiments. The fundamental undulator radiation has an energy peak-width of 2% and thus the flux is 100 times higher than that obtained with a crystal monochromator.

AREA OF RESEARCH

  • Fast time-resolved x-ray diffraction and scattering
  • X-ray photon correlation spectroscopy
  • Fluorescence analysis
  • Microbeam X-ray diffraction and scattering
  • Time-resolved quick XAFS

KEYWORDS

  • Scientific field
    High flux, Structural biology, Small-angle X-ray scattering/diffraction, Time-resolved experiments, X-ray fluorescence analysis
  • Equipment
    X-ray shutters, Fast CMOS camera, X-ray image intensifier, YAG laser, Vacuum path for small angle X-ray scattering

SOURCE AND OPTICS

Schematic View of Beamline

Schematic View of Beamline

  • Light source

      The X-ray source of BL40XU is a helical undulator, whose period length is 36 mm and the number of period is 125. Helical undulators were originally used to generate circularly polarized X-rays. One of the specific features of this type of undulator is that the energy of the fundamental radiation is concentrated in the core of the radiation. On the other hand, most of the higher harmonics are emitted off-axis. So, by extracting the central part of the radiation, the fundamental radiation with narrow peak-energy-width, which is treated as a quasi-monochromatic X-ray, can be used without loss of its flux. The undulator gap can be varied so that the fundamental radiation is altered between 8 and 17 keV. Simultaneously, the elimination of higher harmonics helps to reduce the heat load on the optics. In order to use the quasi-monochromatic X-ray, the front end slits are used with an aperture of less than 15 µrad (horizontal) × 5 µrad (vertical) in most experiments. However, it was designed that the aperture can be opened up to 50 × 50 µrad2 for experiments which require quasi-white radiation.

  • X-rays at Sample

      The focusing optics consists of horizontally and vertically focusing mirrors that are made of silicon and coated with rhodium. Both mirrors are water-cooled. The glancing angle of the first (horizontally focusing) mirror is set to 3 mrad and the second mirror to 4 mrad to eliminate higher harmonics.
      The mirrors are located about 4:1 position between the undulator source and the focus of the beam. Thus the beam size at the focus is demagnified to about 1/4 of the source. By tuning the front end XY slits and the two mirrors, X-ray beam size can be altered to suit different experiments. In the case of most experiments, it is expected that the front end XY slits are used with an aperture of 15 µrad (horizontal) × 5 µrad (vertical). The X-ray focus size was observed to be as small as 250 µm (horizontal) × 40 µm (vertical) (FWHM) by bending two focusing mirrors optimally (Fig. 2). The flux, when the ring current was 100 mA, was estimated to be 7 × 1014 photons/sec at 8 keV, 9 × 1014 photons/sec at 10 keV, 1 × 1015 photons/sec at 12 keV and 6×1014 photons/sec at 15 keV, respectively (Table 1). These values were measured with an ion chamber at 1 mA of the ring current and calculated by extrapolation to 100 mA. Using these values, the flux density was calculated to be on the order of 1017 photons/sec/mm2. The energy spectrum showed a sharp peak and its peak width was about 1.8% (FWHM). The higher harmonics were not observed. The peak width of the fundamental energy was observed to be 1.8% at 10 keV, 1.7% at 12.4 keV and 2.0% at 15 keV, respectively (Fig. 2).

  • Table 1. Photon flux

    Energy (keV) Flux (photons/sec)
    8 7 × 1014
    10 9 × 1014
    12 1 × 1015
    15 6 × 1014

Fig. 1. Forcused direct beam

Fig. 1. Forcused direct beam

Fig. 2. Energy spectrum

Fig. 2. Energy spectrum

  • X-rays at Sample

     

    Energy range 8 ~ 17 keV
    Energy resolution 0.02
    Photon flux 1015 (12 keV) photons/s
    Beam Size 0.25(H) × 0.04(V)
    (with focusing mirrors)

EXPERIMENTAL STATIONS

  The experimental hutch 1 is about 6 m long × 4 m wide × 3 m high. Users can freely arrange and set up a detector and other experimental apparatuses in the experimental hutch to suit their experiments. For small angle scattering experiments, a 3 m-long vacuum pipe can be used (Fig. 3). There are, moreover, two kinds of shutters in the experimental hutch (Fig. 4). One is driven by a galvanometric motor operating within 1.5 msec after a trigger pulse. The other is a rotating-aperture type shutter. By synchronizing the two shutters, pulsed X-rays with different pulse widths can be generated. The shortest pulse width is 6 μsec. As detectors, we have a flat-panel detector, PILATUS 100K, a cooled CCD camera and a fast CMOS camera with a framing rate of 6,400 per sec (1024 × 1024 pixels, 12 bits). The latter two are used in combination with an image intensifier (4 in. or 6 in.) with a short-decay phosphor. For the fast CMOS camera, faster framing rates are achievable by reducing the size of the frame. A YAG laser is also installed in the hutch for experiments that requires quick trigger of events (Fig.6).

Fig. 3. Vacuum path for small-angle X-ray scattering

Fig. 3. Vacuum path for small-angle X-ray scattering

Fig. 4. X-ray shutters

Fig. 4. X-ray shutters

Fig. 5. An X-ray image intensifier

Fig. 5. An X-ray image intensifier

Fig. 6. YAG laser

Fig. 6. YAG laser

  The experimental hutch 2 is about 5 m long × 4 m wide × 3.3 m high. Since experimental hutch 2 is downstream of BL40XU beamline, 4 m-long vacuum or helium path is installed in upstream experimental hutch to avoid the decay of X-ray beam.There are X-ray pulse selector (XPS, Fig.7), Si(111) channel-cut monochromator (Fig.8), high-precision diffractometer (Fig.9), low temperature equipment and femto-second laser (800 nm). XPS can generate X-ray pulse with variable intervals (100~1000 Hz). The laser pulse can be synchronized with X-ray pulse. These systems enable time-resolved pump and probe experiment.

Fig. 7. X-ray pulse selector (XPS)

Fig. 7. X-ray pulse selector (XPS)

Fig. 8. Si(111) channel-cut monochromator

Fig. 8. Si(111) channel-cut monochromator

Fig. 9. high-precision diffractometer

Fig. 9. high-precision diffractometer


PUBLICATION SEARCH

* Sorry, Some parts of results are displayed in Japanese.

BL40XU PUBLICATION SEARCH

 

CONTACT INFORMATION

Please note that each e-mail address is followed by "@spring8.or.jp."

Hiroshi SEKIGUCHI
SPring-8 / JASRI
1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198
Phone : +81-(0)791-58-0833
Fax : +81-(0)791-58-0830
e-mail : sekiguchi

Nobuhiro YASUDA
SPring-8 / JASRI
1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198
Phone : +81-(0)791-58-0833
Fax : +81-(0)791-58-0830
e-mail : nyasuda

Koki AOYAMA
SPring-8 / JASRI
1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198
Phone : +81-(0)791-58-0833
Fax : +81-(0)791-58-0830
e-mail : kaia

Hiroyuki IWAMOTO
SPring-8 / JASRI
1-1-1 Kouto, Sayo-cho, Sayo-gun, Hyogo 679-5198
Phone : +81-(0)791-58-0833
Fax : +81-(0)791-58-0830
e-mail : iwamoto

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