Crystat Operation
Manipulator can be cooled down using either liquid nitrogen or helium.
When the temperature of the manipulator goes down it absorbs residual moisture and other gasses. Therefore, we remove the sample from the manipulator and transferred back after the manipulator is reached its lowest temperature.
Conversely, when the manipulator starts warming up, it releases the absorbed gasses, therefore the chamber pressure worsens. You might consider transferring out the sample to preserve its surface.
First insert the transfer line in the cryogenic dewar, keep the needle valve closed. Once the pressure of the dewar grows up to 0.5 bar, takes about 10-20 minutes, then open the needle valve 2-3 full turns. The cold finger reaches to 77 K in about 10-15 minutes once the liquid starts collecting in the manipulator cryostat.
Once the cold finger reaches the lowest temperature, we need the needle valve less than a quarter of a turn to maintain the temperature.
The sample stage requires longer time to stabilize. After about 2 hrs, the sample stage temperature reaches about 85 K while using liquid nitrogen.
We have only one heating channel (loop 1). In order to set temperature, press
key 5 or 6 (for loop 1 or loop 2, respectively), if the section is not
set point, use up/down arrow keys to select set point, entered desired number,
press Enter. Go back to main screen by pressing Home.
You can also access set point by Set Pt key, select the loop by up/down arrow
keys, enter desired number and press Enter.
In order to start the heating press Control, and stop press Stop.
Once experiment is done, close the needle valve, open the venting/ pressure release valve in the dewar, and remove the transfer line from the cryogenic dewar.
Make sure that the cryogen flow is optimal. If there is excessive flow, it will cause condensation at the manipulator head. Later when it melts, water could fall over motors and other sensitive electrical/ mechanical components.
The pressure in the dewar must not exceed 0.5 bar. The dewar used for liquid nitrogen has pressure release valve to maintain 0.5 bar. However, always keep an eye on the meter, in case there is blockade due to icing.