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129610A
Criostato Solartron/Janis Modelo SVT-200T de Janis |
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Sistema de Pruebas Criogénico para Caracterización de
Materiales The Janis
Research Company special model SuperVariTemp (SVT) research cryostat is a versatile research tool
designed to operate between approximately 5 and 600 K with the sample in
static exchange gas. The sample tchamber
can withstand temperatures to 600 K under proper operating conditions. This model
offering quick sample exchange, an operational range of 5-300 K, highly
efficient operation and structural features a Model 10CNDT
dewar with The
special SVT system provides cooling to a sample by
means of helium exchange gas. This gas
is cooled as it comes in contact with the copper wall of the sample support
tube, which is in turn cooled by flowing vapour from the internal cryogen
reservoir. The gas provides a thermal
link between the sample mounting surface and the liquid cryogen. The thermal link must be strong enough to
cool the sample to the cryogen temperature, yet still allow the sample
temperature to be raised when desired.
The strength of the link is a function of the pressure of the exchange
gas within the tube. The sample
temperature is varied by controlling the temperature of the copper sample
tube walls. Descripción The
cryostat consists of a regular SuperVariTemp system
with a static exchange gas insert (or sample tube) inside the SVT sample chamber.
The sample is mounted on a sample positioner
inside the sample tube. By
controlling the temperature of the flowing helium vapor
in which samples are immersed, both the sample and holder are simultaneously
cooled to the same temperature, thereby eliminating the need for thermal
anchoring and sample mount heating. The helium flow rate and heater current
are balanced to provide flowing vapor/sample
temperatures over the range of 5-300 K; automatic temperature controllers
together with application specific thermometry provide accurate and precise
temperature control. The SVT cryostat makes full use of the cooling power of
escaping helium vapour as it exits the sample chamber, resulting in improved
efficiency over exchange gas systems. Operation of the SVT
typically adds about 0.1 L/hr to the total liquid helium evaporation rate of
the dewar. The sample chamber is thermally isolated
from the helium reservoir by the dewar vacuum,
thereby eliminating heat conduction into the reservoir. This provides for low
helium consumption rate even at higher sample temperatures. The SVT's unique design allows for operation below 4.2 K
without wasteful pumping on the main helium reservoir. Operation below lamda is readily achieved with the sample immersed,
either in liquid or vapor, by simply throttling the
rate of helium introduced to the sample chamber while evacuating the sample
tube. Célula de Muestras especial para Espectroscopia de Impedancia. The
system includes a special sample holder for impedance spectroscopy, as shown
in the photograph below. The insulation used for the wiring is suitable for
high temperature use, but is susceptible to fraying. Spare insulation for the
wire has been included with the system so that the insulation near the wire
connections may be replaced as needed.
Célula
de Muestras |
Vista superior del Criostato
Cuerpo del Criostato SVT-200T
Controlador de Temperatura LakeShore 332 de 2 canales
Controlador de Nivel para Líquidos Criogénicos - LM-500 |
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Criostato SVT-200T: Vista en 2D |
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There are several independent
spaces inside the cryostat, which have been colour-coded in the drawing as
follows: 1.
Vacuum space (red). The insulating vacuum space must be kept
evacuated at all times. 2.
Nitrogen space (green). This space is filled with liquid nitrogen
to form a 77 K shield. 3.
Helium space (blue). This is the working space for the cooling cryogen
(which may be liquid helium or liquid nitrogen). The liquid cryogen is collected inside the
helium reservoir. A controlled amount of cryogen flows through the helium
valve to the vaporizer assembly (as described in the standard system
manual). The cryogen then flows
through the annular space outside the sample tube, cooling the sample tube
walls. The cryogen exits the cryostat
through the flow meter. For high
temperature operation, the needle valve is closed and the annular space
outside the sample tube is evacuated. 4.
Sample tube (brown). This space is filled with static exchange
gas and contains the Sample Positioner (black) and sample. |
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Criostato SVT-200T: Vista en 3D
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Foto en Laboratorio
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