High Voltage Electron Microscopy†
Features of the ultra-high voltage electron microscope (H-3000)†
Figure 1
Ultra-High Voltage Electron Microscope - Hitachi H-3000 in Osaka University
The 3 MV ultra-high voltage electron microscope (Hitachi H-3000) was developed based on various advanced technologies, such as the high stability of the high voltage generating circuit, the reduction of power losses, the improvement of the response speed of the objective lens, negative ion removal equipment, a remote control system, and an online image enhancement system. The ultra-high voltage electron microscope is widely used by researchers in many fields, including materials science, nanotechnology, biology, and medical science. The particular advantages of the H-3000 can be summarized as follows:
- Remarkable increases in the maximum observable thickness of a specimen.
- Various types of in-situ observations made possible by the very large specimen space.
- Lattice defect introduction and/or non-equilibrium phase formation through the interaction between high energy electrons and constituent elements in materials.
Main specifications
- High voltage generator
- Symmetrical Cockcroft–Walton circuit: 35-stage
- Electricity consumption in high voltage tank: under 1 kW
- Acceleration voltage:
- Normal: 3.0 MV (3000 kV)
- Medium: 0.5, 1.0, 1.5, 2.0, 2.5 MV
- Maximum: 3.5 MV
- Stability of high voltage: less than 2.0×10-6/min
- Electron gun and acceleration tube
- Cathode: LaB6 single crystal (thermal type)
- Beam current: maximum 20 mA
- Acceleration tube: 22 kV/step × 138 steps (3 MV)
- Insulating gas: SF6 (4 atom)
- Irradiation lens system
- Ion trapping system: electron beam shift by polarization coil
- Lens constitution: double-condenser lens
- Beam angle: less than 10-3
- Imaging lens system
- Lens configuration: six-step lens system (no image rotation)
- Magnification: 200 to 1,000,000 (30-step switching)
- Camera length at electron diffraction: maximum 14 m (six-step switching)
- Resolution: less than 10 nm
- Objective lens
- Magnetomotive force: maximum 23 A/V1/2 (3 MV)
- Focusing length: less than 11 mm
- Spherical aberration coefficient: less than 10 mm
- Chromatic aberration coefficient: less than 10 nm
- Defocused point: minimum 5 nm
- Specimen space
- Holder: Top-entry type and side-entry type
- Orientation angle of top-entry type: ±30 degrees (double-tile type)
- Orientation angle of side-entry type: ±45 degrees (double-tile type)
- Specimen motion: ±1 mm (mechanical system), ±1.5 mm (electrical system)
- Vacuum: 5×10-6 Pa (oil-free vacuum system)
- Camera room and operation room
- Photo system: imaging plate (32 sheets × 2), film (50 sheets × 2)
- Fluorescent substance: P22, YAG
- Fluorescent screen: maximum 60 × 80 mm
- TV camera
- High resolution type: 1125-line HARP camera
- High sensitivity type: slow-scan CCD camera with cooling
- Video recording: NTSC mode HARP camera
- Remote control system
- Operation system: Console panel for remote operation
- Controlling system: main control workstation system and decentralized data processing system
- Monitoring system: X-ray, oxygen deficiency, beam position, specimen holder
Review papers for High Voltage Electron Microscopy (Materials Science)†
REFERENCES
[1] H. Fujita: J. of Electron Micro. Tech. 3, 243–304 (1986).
[2] H. Fujita.: J. of Electron Micro. Tech. 12, 201–218 (1989).
[3] A. Seeger: J. of Electron Micro. 48, 301-305 (1999).
[4] H. Fujita: Proc. Jpn. Acad., Ser. B, Vol. 81, 141-155 (2005).
[5] H. Mori: J. of Electron Micro., 60, S189-S197 (2001).
[6] H. Yasuda: Kenbikyo, 46, 160-164 (2011). (in Japanese)
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