APPLICATIONS OF CRYOGENICS IN ELECTRON MICROSCOPY.

With the first prototype of a cryoelectron microscope system (i. e. large-scale, 20 watt capacity, Collins closed-cycle superfluid helium refrigerator with 36-foot transfer lines and novel heat exchanger integrated with a modified 200 kV electron microscope), significantly reduced radiation damage, contamination and thermal noise are available in prolonged vibration-free examination of specimens at 1. 8 degree to 4. 2 degree K. Simultaneously, the system provides high penetration power, ultra-high vacuums, decreased spherical and chromatic lens aberrations, and enhanced image contrast. Specially-adapted vacuum-tight microchambers have been used in studies of ice-crystal structure, wet membranes and new types of organometallic superconducting compounds. Consistent resolutions of 8A to 16A are achieved, compared with corresponding low temperature resolutions of about 50A one year ago. Descriptions of these instrumental developments are given together with results of their applications and implications in specific research areas, particularly membrane ultrastructure, cryobiology, microelectronics and general superconducting work.