Working Principle

X-Temp 2 cools a crystalline sample embedded in inert-oil under a microscope by a cold nitrogen gas-stream, the temperature of which is adjustable from -160°C to room temperature. At the same time, the gas-stream surrounds the microscope slide with an inert gas atmosphere such that the formation of ice due to humidity is prevented.

Stalke's DM800
Fig. 2: The liquid nitrogen evaporator.

Liquid nitrogen stored in the thermo-insulation container fills the evaporator tube. The main heater causes the liquid nitrogen to boil, and the nitrogen gas generated is lead through a copper tube into the liquid nitrogen level where it is recooled to approximately -195°C. The glass tubes direct the cold gas-stream outside the insulation-container. The nitrogen gas-stream reaches the microscope slide with the sample via the fan-shaped gas-stream teflon nozzle.

The gas-stream flow rate depends on the adjustable power supply of the main heater while the variable power setting of a stream heater is used to warm the gas-stream to achieve the desired temperature. A nozzle heater prevents the formation of ice at the outlet of the gas-stream teflon nozzle. The main heater and the nozzle heater are electrically connected in series such that the nozzle heater power supply and the gas-stream flow rate are increased or decreased simultaneously.

The adjustment of the sample temperature by regulating the gas-stream flow rate and the gas-stream heating is aided and monitored by an internal thermocouple and an external thermocouple. If during operation the liquid nitrogen level drops below the upper level sensor, an optical and a switchable acoustic alarm goes off.

In case the liquid nitrogen level drops below the lower level sensor, all heating circuits will be switched off automatically and can be reactivated only after refilling. Through the LN2-refill tube, the thermo-insulation container can be refilled with liquid nitrogen without interrupting operation, i.e. the running time of the device is virtually unlimited.