sshade:databases:ghosst:closed_cells_for_crystal_growth [SSHADE]

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==== Closed cells for crystal ====

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This technique allows crystals to be grown from the liquid in a closed cryogenic cell. A schematic view is shown in the Figure.

Reference: {{ :sshade:databases:ghosst:quirico97a-icarus-127-354_nir-hydrocarbons-co-co2-in-n2.pdf |Quirico and Schmitt 1997a}}

**Cell description**: The cell (1) has two windows (2) sealed with indium gaskets, and is connected to the finger of the cryostat with a copper handle (3). The temperature at the top and at the middle of the cell are respectively measured with the silicon diodes (4) and (5) (at least one of them is calibrated +/- 0.05 K). Heater (7) heats the whole cell, whereas heater (6) establishes a vertical thermal gradient in the cell. The first heater is controlled by a PID controller; the second is connected to a stabilized power supply.

{{:sshade:databases:ghosst:closed-cell_drawing.png?400|Closed-cell drawing}}

**Picture**: Closed cell for in-situ crystal growth from liquid or gas phase

Crystal growth: Crystals are grown as follows. The cell is cooled down to a temperature slightly greater than the melting point and the thermal gradient is established using heater (6). The cell is filled with gas (which condenses immediately to liquid) via the gas inlet (8). When the chamber is full of liquid, the cell is slowly cooled down via the temperature controller and heater (7). The crystal grows from the bottom to the top. The temperature is stabilized when a crystal is obtained, and it is annealed for about 12 hr. Finally, the thermal gradient is set to zero and the study can begin.