The pump is responsible for the gas flow from an unpressurised Dewar, through the flexible vacuum insulated transfer line, into the Cryostream coldhead. The liquid nitrogen passes through a heater, which evaporates most of the liquid into gas. This gas then flows outward along one path of the heat exchanger, through the temperature and flow controller, to arrive at the pump.This gas flows back into the Cryostream coldhead where it is re-cooled along the second path of the heat exchanger. The gas temperature is regulated by a heater and sensor before entering the nozzle of the Cryostream, flowing along the isothermal nozzle and out over the sample.
The temperature indicated on the Controller is a mapped temperature for the crystal position. The default Cryostream gas flow rate is 5 L /minute, which equates to roughly 0.6 L of liquid nitrogen per hour. This means that a 60 litre Dewar will last for up to 4 days so can easily be run over a weekend without refilling. Turbo mode gives an increased flow rate of 10 L/minute if required.