915 Double Tilt Cryotransfer System

Analysis of frozen-hydrated specimens

The 915 Double Tilt Cryotransfer holder combines many of the analytical features of our ambient temperature double tilt holders with the cryotransfer capabilities of the widely used 626 for examining the crystalline structure of frozen, vitrified samples. The low background design and reduction of contamination and mass loss through maintenance of cryotemperatures facilitates high quality data collection for EDX, PEELS and GIF experiments.

Double tilt capability

The most widely used tilting geometry for specimen holders is achieved with two perpendicular tilt axes built into the holder. This combination is favored since it gives great flexibility in orienting the specimen for imaging, stereo pairs and diffraction studies of crystalline specimens. The ToggleTilt™ drive mechanism used for the second tilt in Gatan holders smoothly operates with low vibration and backlash over the full range of tilt angles and speeds.

Rapid, frost-free transfer

Gatan technology made frost-free transfer possible with the introduction of the cryoshield in 1980, and we have continued to provide new concepts to preserve sample integrity. In the 915 Double Tilt Cryotransfer holder, the one-piece cryoshield slides over the double-tilt cradle and shutter movement is controlled externally by the operator. The shield is retracted during sample loading, closed during transfer, then opened during the imaging session. To protect the cradle mechanism, a special interlock makes it impossible to close the shutter if the cradle is tilted. During specimen loading the holder tip inserts into the Workstation's liquid nitrogen well, surrounding the holder tip and frozen sample grid in a protective dry nitrogen gas atmosphere.

Hexring® System

The Hexring® was developed for easy sample loading without the difficulties associated with spring clips and slotted, threaded rings. This method to secure samples allows easy grid manipulation and ensures specimen clamping control. Hexrings® are fabricated of beryllium for analytical applications since the metal has good mechanical properties, is UHV-compatible and is easy to clean.

Precise temperature control

The specimen holder tip temperature is monitored by a calibrated silicon diode. This type of sensor has the following advantages over a thermocouple: (1) its output is not affected by cold-junction temperature gradients, (2) it is more sensitive, and (3) it has a more linear temperature response. The conductor rod connecting the specimen holder tip to the nitrogen dewar contains an electric heater to control the specimen temperature. Gatan cooling holders are designed so that the whole specimen holder tip is cooled and not just the specimen cradle. This ensures the minimum possible temperature gradient around the specimen.