Water accumulation as a function of temperature on specimens in an electron microscope cold stage

Last year we reported1 that there is a striking reduction in the rate of mass loss when a specimen is observed at liquid helium temperature. It is important to determine whether liquid helium temperature is significantly better than liquid nitrogen temperature. This requires a good understanding of mass loss effects in cold stages around 100K.

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Irradiation-induced mass loss effects at low temperature are dependent on specimen material

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100105242 ◽

1988 ◽

Vol 46 ◽

pp. 636-637

Author(s):

M.K. Lamvik ◽

S.D. Davilla

Keyword(s):

Mass Loss ◽

Liquid Helium ◽

Substantial Reduction ◽

Adsorbed Water ◽

Liquid Nitrogen Temperature ◽

Liquid Helium Temperature ◽

Helium Temperature ◽

Qualitative And Quantitative ◽

Specimen Material ◽

Electron Microscopes

Low temperatures reduce the rate at which total mass or specific elements are lost from specimens during irradiation in electron microscopes. Many studies have shown such reductions when liquid nitrogen temperature was compared with room temperature. Some studies suggested an even greater benefit at liquid helium temperature. We recently found that there was a substantial reduction in the rate of mass loss from collodion when specimens were held at liquid helium temperature. The need for additional studies is illustrated by a comparison of collodion with albumin, which shows qualitative and quantitative differences in the response of these two materials to electron irradiation at liquid helium temperature.Collodion had distinct advantages as an initial specimen: There have been previous measurements, thus allowing comparison. Collodion is sensitive to radiation, so experiments could be completed efficiently. Most important was that collodion films could be made of uniform thickness, thus allowing the inital thickness to be used to monitor for accidental pre-exposure or unwanted material (like adsorbed water).

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Colder specimens give a sharper impression: Prospects for higher resolution Electron Microscopy at liquid helium temperature

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100156055 ◽

1989 ◽

Vol 47 ◽

pp. 816-817

Author(s):

M.K. Lamvik

Keyword(s):

Electron Microscopy ◽

Mass Loss ◽

Liquid Helium ◽

Liquid Helium Temperature ◽

Persistent Current ◽

Helium Temperature ◽

Electron Microscopes ◽

Diffraction Patterns ◽

Current Flows ◽

The Stability

Designers of electron microscopes started putting liquid helium into their plans with the hopes of improving instrumental resolution. Liquid helium can be used to cool specimen stages within conventional lenses, but it can also be used to make some materials superconducting. Once started, current flows continuously in a superconducting coil because it faces negligible electrical resistance. Superconducting lenses were introduced in electron microscopy to take advantage of the high magnetic field strengths that could be generated as well as the stability of the persistent current in the superconducting coils. As time passed, it became clear that electronic regulation of power supplies could produce more than adequate current regulation to supercede the need for the persistent current maintained in a superconducting lens. Meanwhile, the realization grew that low temperatures might give another kind of advantage to electron microscopy of radiation-sensitive materials. The very low temperature might help protect sensitive specimens from damage.Several methods are available for detecting damage to specimens in electron microscopes. The loss of mass from specimens is one sign of radiation damage. A mass loss measurement with a liquid helium cooled stage seemed to show a significant reduction in mass loss; a different measurement that included a superconducting lens also indicated reduced damage. Another indicator of damage is the rate of fading of diffraction patterns of ordered specimens, and in this case it has been established that liquid helium temperature causes a moderate reduction of damage.

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Radiation-Induced Movement of a Mercury Stain at Room Temperature and Liquid Helium Temperature

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100054509 ◽

1982 ◽

Vol 40 ◽

pp. 376-377

Author(s):

M. K. Lamvik ◽

K. -H. Müller ◽

K. Weiss

Keyword(s):

Electron Microscope ◽

Radiation Damage ◽

Liquid Helium ◽

Heavy Element ◽

Room Temperature ◽

Liquid Helium Temperature ◽

Helium Temperature ◽

Radiation Induced ◽

Preliminary Study ◽

Effects Of Radiation

Cryomicroscopy at liquid helium temperature has shown promise in protecting organic materials from the effects of radiation damage, and it might be expected that sensitive heavy-element stains would be similarly protected. We have made a preliminary study of a positively-stained protein specimen using the superconducting-objective electron microscope at Berlin. We have used the mercury stain TAMM, solubilized with penicillamine (TAMM-pen3), which is known to be radiation-sensitive, on tropomyosin paracrystals of the type made by Ohtsuki. Specimens were treated with 10μM TAMM-pen3 on the grid for times ranging from 15 min to 11 hr, then were washed with 1 ml water, blotted and dried. Staining time had little effect on our results. Here we are not studying the protein or stain specificity; our interest is in the movement of the stain, which we can clearly demonstrate.

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Mass Loss is Reduced at Liquid Helium Temperature

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100119181 ◽

1985 ◽

Vol 43 ◽

pp. 472-473

Author(s):

M.K. Lamvik ◽

L.L. Klatt ◽

S.D. Davilla

Keyword(s):

Energy Loss ◽

Mass Loss ◽

Liquid Helium ◽

Electron Energy ◽

Liquid Helium Temperature ◽

Helium Temperature ◽

Duke University ◽

Electron Energy Loss ◽

Electron Energy Loss Spectra ◽

Fundamental Limitation

Since mass loss is a fundamental limitation in electron microscopy and microanalysis of biological materials it is very valuable to understand the effect of specimen temperature on the mass loss process. An electron energy loss spectrometer has been added to the Duke University Cryomicroscope (fig. 1) to allow a general study of radiation damage effects in specimens held at liquid helium temperature.The reduction of specimen mass is measured by recording a long series of electron energy loss spectra with a Tracor-Northern TN-5400 analyzer, using the region integration feature of the analyzer to report the number of counts in the zero-loss and inelastic scattering regions of the spectrum.

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