Low vacuum (LV) or variable pressure (VP) modes are now standard on most scanning electron microscopes (SEMs). For this reason it has become important to control water evaporation from wet specimens. Cooling such specimens reduces the loss of water by evaporation, or - depending on chamber pressure - can prevent it altogether.
Saturated vapour pressure of water decreases considerably with temperature. At room temperature, water will very quickly evaporate - causing considerable damage to specimen composition and ultra-structure. This is due to high forces of surface tension at the drying front as it passing though the specimen. In most biological systems this will result in distortion and collapse of membranes and other structures.
At 300 Pa, the specimen temperature needs to be less than -9.5°C, and at 85 Pa less than -25°C to stop water evaporation. Therefore, by cooling a specimen to -25°C, chamber pressures up to 85 Pa can be used with little or no water loss by evaporation.
In this way changes in specimen structure can be minimised. In addition, being able to operate at higher vacuum gives a better signal-to-noise ratio and clearer images.
Specimen size. 10 mm Ø (adaptor stub for 12 Hitachi stubs can be supplied on request).
Stage temperature range. Higher vacuum will allow for cooler temperatures, compatible with high vacuum levels to 1 x 10-5 Pa.
Standard Coolstage. -30ºC to +50ºC at 300 Pa with no external cooling water from the SEM (at ambient +20ºC).
Enhanced Coolstage. 30ºC to +160ºC at 300 Pa with no external cooling water from the SEM (at ambient +20ºC).
Ultra Coolstage. -50ºC to +50ºC at 300 Pa with no external cooling water from the SEM (at ambient +20ºC).
Temperature display resolution. 0.1ºC.
Temperature stability. +/- 0.2ºC.
Temperature accuracy. +/- 1.5ºC or 2% (whichever is greater).
Stage movement. Normal x, y and z movements are maintained. Tilt maintained for X-ray analysis (up to 45º). No rotation.
Working distance. As on SEM, Coolstage is set to the SEM eucentric height.
Operating voltage. 100 V or 115 V or 230 V at 100 VA, voltage tolerance +/- 10%.
Size and weight. Operation/display unit: 90 mm L x 112 mm W x 350 mm H, 300 g.
Power supply/cooling unit. 305 mm L x 245 mm W x 330 mm H, 15 kg.
Packed size and weight. 550 mm L x 580 mm W x 400 mm H, 28 kg.
Operating manual, one set of interconnecting cables and mains supply lead, storage block for specimen cooling unit when not in use, specimen holders: 15 x flat 10 mm stubs and 15 x dish-style 10 mm OD stubs.