Experimental Techniques

• Soft X-ray absorption spectroscopy (XAS)
• Soft X-ray magnetic circular dichroism spectroscopy (XMCD)
• Soft X-ray Imaging SXM, STXM　(Advanced Measurement)

Overview

BL14U is a beamline that utilizes soft X-rays in the energy range of 200 to 1400 eV. Its twin helical undulators enables switching between left and right circularly polarized light in less than one minute. The monochromator employs a constant deviation type that combines a cylindrical mirror and a varied line-spacing plane grating, allowing for a nanofocused beam with a size of Φ100 nm or less using a Fresnel zone plate optics system.
As experimental equipment, a Soft X-ray Imaging (SXM) system equipped with Soft X-ray Magnetic Circular Dichroism (XMCD) measurement capabilities is installed. The SXM measurement methods support both transmission and total electron yield modes. Pre-treatment such as metal thin film deposition and surface cleaning by ion milling is also possible. By using this SXM, the elemental and chemical state distributions of various materials can be visualized at the sub-micron scale. Furthermore, combining it with XMCD measurements allows for the investigation of the magnetic properties of materials with high sensitivity.

Beam Characteristics

Energy

◆For non-focused beam: 200 – 1400 eV
◆For focused beam: 600 – 1400 eV
Note: Measurements may be possible below 400 eV, but the incident soft X-ray intensity decreases significantly, especially near the Carbon K-edge, due to reasons such as contamination of optical elements.
Note: While it is possible to attempt measurements below 300 eV, please be aware of the situation regarding soft X-ray intensity as described above before using the equipment.

Flux

For non-focused beam conditions: >3 x 10¹² photons/s
For focused beam conditions: >3 x 10⁹ photons/s
(Both are calculated values and depend on the energy and experimental conditions.)

Beam size

For non-focused beam conditions: Φ several 100 µm (depends on the slit aperture settings)
For focused beam conditions: Φ 100 nm or less

Light Source and Optics

A soft X-ray beam monochromatized by a grating spectrometer is available, using twin helical undulators with 33 poles and a period length of 56 mm in a tandem arrangement as the light source.
Slits are located upstream and downstream of the monochromator, which can be used to adjust the energy resolution and as a virtual point source in scanning imaging. 　

Experimental Station

Methods:

Transmission and Total Electron Yield

Sample Size:

Max. 10 mm x 10 mm (thickness: a few mm)

About Samples:

Transmission Method:
Thin film samples that are transmissive to soft X-rays
(approximately 1 µm or less. Please contact staff for details)

Total Electron Yield Method:
· Conductive solids where the observation target exists within 5 nm from the surface.
· For non-conductive samples, data acquisition is possible by depositing a metal thin film of several    Å thickness on the sample surface.
· The sample temperature is room temperature for both measurement methods.

Magnetic Field Environment:

Maximum 8T parallel to the beam axis.

Layout

Measurement Examples of Magnetic Imaging using BL14U

[Soft X-ray Imaging of Permanent Magnets]

Soft X-ray Fe Absorption Contrast Image	Sample: Commercially available neodymium magnet Treatment: Thermal demagnetization Measurement Time: ~5 min. X-ray Energy: 708 eV Observation Range: 60 μm × 60 μm
XMCD Contrast (Magnetic Domain Image)	Sample: Commercially available neodymium magnet Treatment: Thermal demagnetization Measurement Time: ~12 min. X-ray Energy: ：708 eV Observation Range: 60 μm × 60 μm

[Soft X-ray Imaging of Meteorite]

XMCD Contrast (Magnetic Domain Image)

Sample: Gibeon meteorite Treatment: Thermal demagnetization Measurement Time: 10 min. X-ray Energy: ：708 eV Observation Range: 60 μm × 60 μm

[Transmission Imaging]

Sample: Colias erate (Yellow butterfly) scale Measurement Time: 25 min. (5 min. × 5) X-ray Energy: ：708 eV Photo of a Yellow butterfly with scales collected Optical microscope image of scales

[Element-Specific Imaging]

Elemental maps can be obtained by acquiring images at the characteristic X-ray absorption edge energy of each element and at an energy just before it, and then calculating the difference between these images.

	Sample: Coin Measurement Time: ~12 min. X-ray Energy: ：931 eV Observation Range: 60 μm × 60 μm Coin references can be found here
Elemental Map (Cu)	Sample: Coin Measurement Time: ~12 min. X-ray absorption edge energy: ：931 eV Observation Range: 60 μm × 60 μm
Elemental Map (Fe)	Sample: Coin Measurement Time: ~12 min. X-ray absorption edge energy: ：708 eV Observation Range: 60 μm × 60 μm

[Soft X-ray Imaging of Biological Samples]

	Sample: Mouse sperm X-ray Energy: ：1028 eV Observation Range: 60 μm × 60 μm
	Sample: Escherichia coli (E. coli) X-ray Energy: ：708 eV Observation Range: 60 μm × 60 μm
	Sample: Cultured cells X-ray Energy: ：708 eV Observation Range: 60 μm × 60 μm
Stereomicroscopic Image of Sperm Sample	Stereomicroscopic Image of Sperm Sample - Chemically fixed biological sample was dropped (approx. 5 μL) onto a SiN membrane and air-dried. - A 3 mm square, 100 nm thick SiN membrane was used. - To prevent damage to the window due to sample dropping, the droplet was placed near the corners of the membrane. - The sample condition was observed with a visible light microscope, and the coordinates of the measurement candidate region were set (reference image). - The SiN membrane was mounted on a sample carrier and introduced into the instrument.

[Imaging of Diatom Fossils]

Sample Information
Sample: Diatom fossil, Stephanodiscus sp.(tentative identification)
Locality: Hiruzen, Maniwa City, Okayama Prefecture, Japan
Age: Quaternary, Pleistocene Epoch (approx. 500,000 years ago)

Sample Preparation
1. After washing with water, the supernatant was collected by gravity sedimentation.
2. Washed with anhydrous ethanol.
3. Dropped onto a SiN membrane.
4. Air-dried, then evacuated in vacuum.

Overall view of diatom fossils. The diatoms in the upper and right positions are presumed to be single diatoms where the epitheca (upper valve) and hypotheca (lower valve) have separated.	Sample: Diatom fossil, Stephanodiscus sp.
Central areolae of the diatom fossil	Sample: Diatom fossil, Stephanodiscus sp.
Marginal areolae of the diatom fossil	Sample: Diatom fossil, Stephanodiscus sp.

Measurement Examples of Spectrum Measurement using BL14U

[MCD Spectrum]

Sample: Commercially available neodymium magnet Measurement Time: Approx. 40 minutes (1 set of 4 measurements: polarization switching + magnetic field reversal) X-ray Energy: Range of approx. 690 eV to 770 eV

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