Development of a new multi-anvil apparatus for in situ X-ray diffraction, "SPEED-Mk.II"
Difficulty of V measurement by in situ X-ray diffraction using MA
- Limited number of grains
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- Due to the limited diffraction V
- Particularly, the number of grains largely decreases at high T due to grain growth
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- Diffraction peaks disappear at high T
- Limited pressure range
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- Only 30 GPa can be generated by a usual multi-anvil apparatus with tungsten carbite anvils
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- Not enough to investigate pressure dependence of α of Pv
- Practical use of sintered-diamond anvils is necessary in order to generate higher pressure than 30 GPa
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- However, it is difficult!
A new HP apparatus for in situ X-ray diffraction
- Development of a new Kawai-type high pressure apparatus, SPEED-Mk.II
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- Installed at the bending magnet white X-ray beam line, BL04B1 at SPring-8 in 2001.
- Constructed by the group grant for the HP geoscience community of Japan, represented by Prof. Eiji Ohtani
Basic design of SPEED-Mk.II
- Followed the basic design of SPEED-1500
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- Installed at the bending magnet white X-ray beam line, BL04B1 at SPring-8
- Kawai-type multi-anvil apparatus with a DIA-type guide block system
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- Maximum Load: 15 MN
- Energy dispersive X-ray diffraction system with a horizontal goniometer
- CCD camera for radiography
- Two major improvements from SPEED-1500
Improvement 1.
- Oscillation system
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- The whole press can rotate in the 20°range
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- Press weight: 20 tons.
- Shift of the sample by oscillation is suppressed to less than 50μm
- Renders it possible to take high-quality diffraction patterns against grain growth
Left: 0-degree, Right: 20-degrees
Example: MgO
- Without oscillation, all peaks but (311) and (422) disappeared
- With oscillation, all peaks but (331) appeared
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- Intensity ratios are largely deviated from the crystal structure
- 20°oscillation is useful but not perfect
- Sufficiently high-quality diffractions determine volumes
Improvement of precision in pressure determination
Improvement 2.
- Adjustable guide block system
- In the DIA-type guide block system, compressions in the horizontal and vertical directions are not equivalent
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- Break brittle sintered diamond anvils
- cause blow out
- The top and bottom first-stage anvils are placed on the supporting columns that are separated from the guide block
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- The strength of the supporting columns can be adjusted by try-and-error
Guide block adjustment
Progress in pressure generation
- Max pressure was 45 GPa before introducing SPEED-Mk.II
- The pressure record has been renewed by 10 GPa every 2 years
- In Feb. 2008, the max. P has exceeded 90 GPa.
