Two Developments - A Superconducting Microscope Conversion and A Precision High Voltage Divider

1970 ◽  
Vol 28 ◽  
pp. 354-355
Author(s):  
R. E. Worsham ◽  
J. E. Mann ◽  
E. G. Richardson ◽  
N. F. Ziegler
Keyword(s):  
High Resolution ◽  
Liquid Helium ◽  
High Voltage ◽  
Experimental Evaluation ◽  
Voltage Divider ◽  
Bottom Plate ◽  
Objective Lens ◽  
Optical Bench ◽  
Radiation Shields ◽  
Helium Vapor

Two elements in the chain of development for a 500 kV high resolution microscope have been completed for initial experimental evaluation. They are a conversion of a Siemens Elmiskop I to use a superconducting objective lens and a 150 kV precisely regulated accelerating supply.The superconducting microscope, shown in Fig. 2 is designed as an optical bench for proving the cryostat, lenses, stage mechanism, and other parts prior to the design of a superconducting column for 500 keV. The lens as shown in Figs. 1 and 2 mounts on the removable bottom plate of the 7-liter helium vessel. The vessel is supported and can be clamped rigidly by the four sets of G-10 epoxy-glass posts. Radiation Shields I and II are concentric with the helium vessel. They are cooled by the boil-off helium vapor to about 30 and 130°K, respectively. All electrical leads are carried into the helium vessel through the four symmetrically located vents. Cooldowns from 77°K requires about 30 liters of liquid helium and the boil-off rate is 0.3-0.5 1/HR at either 4.2 or ∼ 1.8°K.

A Superconducting Microscope

1971 ◽  
Vol 29 ◽  
pp. 10-11 ◽  
Author(s):  
R. E. Worsham ◽  
J. E. Mann ◽  
E. G. Richardson
Keyword(s):  
Liquid Helium ◽  
Focal Length ◽  
Vacuum System ◽  
Objective Lens ◽  
Electrical Instability ◽  
Radiation Shields ◽  
And Control ◽  
Thermal Oscillations ◽  
Flux Pump

This superconducting microscope, Figure 1, was first operated in May, 1970. The column, which started life as a Siemens Elmiskop I, was modified by removing the objective and intermediate lenses, the specimen chamber, and the complete vacuum system. The large cryostat contains the objective lens and stage. They are attached to the bottom of the 7-liter helium vessel and are surrounded by two vapor-cooled radiation shields.In the initial operational period 5-mm and 2-mm focal length objective lens pole pieces were used giving magnification up to 45000X. Without a stigmator and precision ground pole pieces, a resolution of about 50-100Å was achieved. The boil-off rate of the liquid helium was reduced to 0.2-0.3ℓ/hour after elimination of thermal oscillations in the cryostat. The calculated boil-off was 0.2ℓ/hour. No effect caused by mechanical or electrical instability was found. Both 4.2°K and 1.7-1.9°K operation were routine. Flux pump excitation and control of the lens were quite smooth, simple, and, apparently highly stable. Alignment of the objective lens proved quite awkward, however, with the long-thin epoxy glass posts used for supporting the lens.

100 KV Scanning Microscope

1972 ◽  
Vol 30 ◽  
pp. 472-473 ◽  
Author(s):  
A. V. Crewe ◽  
M. W. Retsky
Keyword(s):  
High Voltage ◽  
Voltage Divider ◽  
Electron Gun ◽  
Objective Lens ◽  
Parallel Beam ◽  
Emission Point ◽  
Error Amplifier ◽  
External Reference ◽  
Scanning Transmission ◽  
Transmission Microscope

A 100 kv scanning transmission microscope has been built. Briefly, the design is as follows: The electron gun consists of a field emission point and a 3 cm Butler gun. The beam has a crossover outside the gun and is collimated by a condenser lens.The parallel beam passes through a defining aperture and is focused by the objective lens onto the specimen. The elastic electrons are detected by two annular detectors, each subtending a different angle, and the unscattered and inelastic electrons are collected by a third detector. The spectrometer that will separate the inelastic and unscattered electrons has not yet been built.The lens current supplies are stable to within one part per million per hour and have been described elsewhere.The high voltage is also stable to 1 ppm/hr. It consists of the raw supply from a 100 kv Spellman power supply controlled by an external reference voltage, high voltage divider, and error amplifier.

A Liquid Helium Cryostat for a Superconducting Objective and Cold Stage

1976 ◽  
Vol 34 ◽  
pp. 532-533
Author(s):  
R. E. Worsham ◽  
J. E. Mann
Keyword(s):  
Liquid Helium ◽  
High Vacuum ◽  
Strong Support ◽  
Liquid Helium Temperature ◽  
Ultra High Vacuum ◽  
Objective Lens ◽  
Helium Temperature ◽  
Different Temperatures ◽  
Radiation Shields ◽  
High Coherence

In the design of the 150 kV High-Coherence Column, it was considered essential that the specimen be in ultra-high vacuum at liquid helium temperature for minimum radiation damage. It followed that the simplest solution was to make the entire region about the specimen at liquid helium temperature and to make the objective lens with a superconducting winding.For mechanical rigidity, two things were considered essential. First, a strong support structure for the liquid helium vessel and the objective lens. Second, the use of no liquid nitrogen but rather the use of helium vapor cooling for the radiation shields, leads and supports. The drawing, fig. 1, shows the helium vessel, 9-1/2-inches diameter by 5-inches tall, surrounded by two concentric radiation shields. The entire assembly is rigidly supported on four posts one of which is shown. These posts consist of cylinders of epoxyglass (G-10) spacing the components between their different temperatures.

Development of ultra high resolution analytical electron microscope ISI-EM-002A

1983 ◽  
Vol 41 ◽  
pp. 312-313 ◽  
Author(s):  
T. Yanaka ◽  
A. Yonezawa ◽  
K. Oosawa ◽  
T. Iwaki ◽  
S. Suzuki ◽  
...  
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
High Voltage ◽  
Electron Gun ◽  
Objective Lens ◽  
Magnetic Circuits ◽  
Analytical Electron ◽  
Analytical Electron Microscope ◽  
Mode 3 ◽  
High Voltage Generator

Total design concept of EM-002A is to realize the following essential performance, that is, 1) attainment to ultimate high resolution as the conventional electron microscope, 2) complete compatibility of the high resolution mode and the analytical mode, 3) identification of the analyzed region and the observed image with atomic-level resolution, 4) observation of ultra fine structure of the biological specimen with maximum high contrast and so on.[Electron source] Accelerating voltage ranges from 20kV to 120kV in 6 steps Double Cockroft-Walton circuit is used as the high voltage generator and the high frequency ripple voltage is reduced to 0.1V. Electron gun assembly is composed of high voltage alumina insulator, whose shape is so well designed as to suppress micro-discharge to the negligible order.[Objective lens and specimen chamber] The objective lens is a strong symmetrical lens where the specimen chamber is located between the symmetrical upper and lower objective lens magnetic circuits. The objective lens has two powerful pole pieces, one being used for the ultra high resolution mode and the other for the standard mode.

Development Program for a 500-kV High Resolution Microscope

1969 ◽  
Vol 27 ◽  
pp. 184-185
Author(s):  
R. E. Worsham ◽  
J. E. Mann ◽  
E. G. Richardson ◽  
G. G. Slaughter ◽  
N. F. Ziegler
Keyword(s):  
High Resolution ◽  
Liquid Helium ◽  
Spherical Aberration ◽  
National Laboratory ◽  
Development Program ◽  
Objective Lens ◽  
Helium Temperature ◽  
Oak Ridge ◽  
Point To Point ◽  
High Resolution Microscopy

The goal of the development program for high resolution microscopy at Oak Ridge National Laboratory is a 100-500 kV instrument with a point-to-point resolution of at least 1Å. As reported previously, this microscope is intended for biological specimens to be observed at liquid helium temperature. This resolution is to be achieved principally by reduction of the primary spherical aberration for the objective lens with a quadrupole-octupole system of lenses.

A Liquid Nitrogen Cooled Stage for STEM

1974 ◽  
Vol 32 ◽  
pp. 444-445
Author(s):  
Louis T. Germinario
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Liquid Nitrogen ◽  
Room Temperature ◽  
Objective Lens ◽  
Thermal Drift ◽  
Specimen Holder ◽  
Resolution Capability ◽  
Focal Position

A liquid nitrogen stage has been developed for the JEOL JEM-100B electron microscope equipped with a scanning attachment. The design is a modification of the standard JEM-100B SEM specimen holder with specimen cooling to any temperatures In the range ~ 55°K to room temperature. Since the specimen plane is maintained at the ‘high resolution’ focal position of the objective lens and ‘bumping’ and thermal drift la minimized by supercooling the liquid nitrogen, the high resolution capability of the microscope is maintained (Fig.4).

High Resolution Specimen Area Imaged Under Negligible Field Aberrations

1970 ◽  
Vol 28 ◽  
pp. 540-541 ◽  
Author(s):  
T. Yanaka ◽  
K. Shirota
Keyword(s):  
High Resolution ◽  
Field Distribution ◽  
Image Space ◽  
Beam Deflection ◽  
Objective Lens ◽  
Resolution Limit ◽  
Leakage Flux ◽  
Specimen Area ◽  
Points Of View ◽  
Aberration Theory

It is significant to note field aberrations (chromatic field aberration, coma, astigmatism and blurring due to curvature of field, defined by Glaser's aberration theory relative to the Blenden Freien System) of the objective lens in connection with the following three points of view; field aberrations increase as the resolution of the axial point improves by increasing the lens excitation (k2) and decreasing the half width value (d) of the axial lens field distribution; when one or all of the imaging lenses have axial imperfections such as beam deflection in image space by the asymmetrical magnetic leakage flux, the apparent axial point has field aberrations which prevent the theoretical resolution limit from being obtained.

The Reduction of Chromatic Aberrations Due to Instrumental Instabilities

1971 ◽  
Vol 29 ◽  
pp. 14-15
Author(s):  
J. S. Lally ◽  
R. Evans
Keyword(s):  
Electron Microscope ◽  
High Voltage ◽  
Focal Length ◽  
Chromatic Aberration ◽  
Objective Lens ◽  
Usual Practice ◽  
Voltage Electron ◽  
Short Focal Length ◽  
Chromatic Aberrations ◽  
Electron Microscopes

One of the instrumental factors often limiting the resolution of the electron microscope is image defocussing due to changes in accelerating voltage or objective lens current. This factor is particularly important in high voltage electron microscopes both because of the higher voltages and lens currents required but also because of the inherently longer focal lengths, i.e. 6 mm in contrast to 1.5-2.2 mm for modern short focal length objectives.The usual practice in commercial electron microscopes is to design separately stabilized accelerating voltage and lens supplies. In this case chromatic aberration in the image is caused by the random and independent fluctuations of both the high voltage and objective lens current.

A New High Resolution Transmission Electron Microscope with Second-Zone Objective Lens

1969 ◽  
Vol 27 ◽  
pp. 176-177 ◽  
Author(s):  
H. Tochigi ◽  
H. Uchida ◽  
S. Shirai ◽  
K. Akashi ◽  
D. J. Evins ◽  
...  
Keyword(s):  
Electron Microscope ◽  
High Resolution ◽  
Transmission Electron Microscope ◽  
Objective Lens ◽  
High Excitation ◽  
Transmission Electron ◽  
New Instrument

A New High Excitation Objective Lens (Second-Zone Objective Lens) was discussed at Twenty-Sixth Annual EMSA Meeting. A new commercially available Transmission Electron Microscope incorporating this new lens has been completed.Major advantages of the new instrument allow an extremely small beam to be produced on the specimen plane which minimizes specimen beam damages, reduces contamination and drift.

Description of a New High Resolution Scanning Transmission EM

1972 ◽  
Vol 30 ◽  
pp. 418-419
Author(s):  
Michael Beer ◽  
J. W. Wiggins ◽  
David Woodruff ◽  
Jon Zubin
Keyword(s):  
High Resolution ◽  
Field Emission ◽  
Energy Dispersive Spectrometer ◽  
Scanning Transmission Electron Microscope ◽  
Objective Lens ◽  
Condenser Lens ◽  
Transmission Electron ◽  
Pattern Size ◽  
Scanning Transmission ◽  
Under Construction

A high resolution scanning transmission electron microscope of the type developed by A. V. Crewe is under construction in this laboratory. The basic design is completed and construction is under way with completion expected by the end of this year.The optical column of the microscope will consist of a field emission electron source, an accelerating lens, condenser lens, objective lens, diffraction lens, an energy dispersive spectrometer, and three electron detectors. For any accelerating voltage the condenser lens function to provide a parallel beam at the entrance of the objective lens. The diffraction lens is weak and its current will be controlled by the objective lens current to give an electron diffraction pattern size which is independent of small changes in the objective lens current made to achieve focus at the specimen. The objective lens demagnifies the image of the field emission source so that its Gaussian size is small compared to the aberration limit.

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