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The cryostreamer is designed for precise temperature
control near the samples placed in open flow of cool cryogenic gas (nitrogen,
helium) without ice formation. Cryostreamer set consists of storage dewar with
level gauge, gas transport line, gas generator, and nozzle. Cryogenic liquid is
evaporated by a heater mounted at the end of the transfer line that is placed in
the storage dewar. Then the mixture of the liquid and gas moves to the gas
generator. The gas generator produces stable gas flow with a fixed temperature.
In a case of the liquid nitrogen, the gas generator is placed within the dewar.
In a case of the liquid helium, the gas generator is placed directly before the
streamer nozzle. The nozzle forms two concentric gas flows, which differ in
diameter in a laminar region to about 1 - 2 mm. The hot outer gas beam with a
circumference cross-section prevents the ice formation on the sample. The inner
gas beam has a circular cross-section. The inner beam forms the cool cryogen gas
flows to the sample. The temperature of the gas inside of the inner beam depends
on the coordinate across the diameter. The temperature distribution has a
minimum around the center of the beam within a spot with diameter 2 - 3 mm.
Outside of this spot the temperature gradually increases up to room temperature.
In the region of laminar gas flow, the inner and outer beams flow independently.
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The laminar flow region dimension is of about the outer
diameter of nozzle. The sample has to be placed within the laminar zone. The
temperature control system includes two heaters located at the nozzle and within
the gas generator. A tSTAT335i temperature control unit that delivers an optimal
consumption of cryogenic liquids and precise temperature regulation controls the
heating power of heaters. The system can be equipped by a beam adjust set. The
STREAM335 is very good for the X-ray measurements of the small samples. It can
be adapted also for AFM and STM microscopy. The general applications of the
cryostreamer relate to the temperature control in local small regions on the
open air without ice
formation.
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