SU436334A1 - HEAT-REGULATED CRYOSTATIC DEVICE - Google Patents

Description

one

The invention relates to the field of physical testing and material research and is intended to automatically stabilize an object's temperature in the range of 4.2-350 ° K with an accuracy of + 0.02 ° K.

In the existing temperature-controlled cryostat systems, which use the pumping of vapor of a cryogenic liquid from a thermostatically controlled chamber, it is necessary to have permanently operating withdrawable pumping equipment, which complicates the design of this device and its exploitation. In these devices, n-evaporating the sample without disturbing the thermostating mode is possible or is possible only with full warming of the sampling device.

In the device, in which the electric heating device is used to regulate the intensity of the boiling cryogenic liquid, a high consumption of the latter is observed.

The purpose of the invention is to simplify the cryostat device by replacing the pumping equipment with a constant pressure valve installed on the tank with a refrigerant. Thanks to this, the pressure in the thermostatting chamber becomes excessive and therefore there is no need to seal it, which leads to additional simplification of the cryostat node.

In addition, functional OPPORTUNITIES are expanded; devices:

the possibility of replacing the thermostating object, and introducing various manipulators and probes from the outside into the thermostatically controlled chamber to retrieve information without disturbing the operating modes of the cryostat device in general and the thermostatic mode of the 1st I camera in particular;

ensuring high accuracy of temperature control, constant pressure in a thermostatically controlled chamber and a wide range of temperatures in it, without having to replace the cryogenic liquid used as a refrigerant.

The goals are achieved by the following means:

1. The cryostat supply tank, which contains the cryogenic liquid, is equipped with a constant pressure valve designed to maintain both the reservoir and the thermostatted chamber with a constant overpressure and to induce the cryogenic liquid to flow through the cryostat. the system.

2. In the cavity of the reservoir-feeder, a switching valve is installed, having a lower

and the upper intake ports intended to be taken from the feed tank or cryogenic liquid through the lower intake port (or its vapors through the upper intake port).

3. The valve seat of the flow regulator installed on the line for exhaust refrigerant vapor discharge from the thermostatic chamber has a variable cross section and is intended to optimize the thermostatic system.

FIG. 1 is a schematic diagram of the device; in fig. 2 - vertical section of the cryostat; in fig. 3 is a vertical section of the flow regulator.

The cryogenic liquid or its vapors, located in tank I (Fig. 1) under pressure, maintained by constant pressure valve 2, flows through a heat exchange prechamber 3 into a thermostatically controlled chamber 4, in which the cryostatting of the object or device under study is carried out by a gas flow, having a temperature close to the task. This flow is controlled by a flow controller 5, which is the actuator of the thermal control and temperature stabilization system. This system consists of a temperature sensor 6 (for example, an Au thermometer + 0.02 Fe; Cu), a reference voltage adjuster 7 (for example, a potentiometer), an unbalance amplifier 8 (for example, a photocompensation amplifier), and a two-position electronic potentiometer 9 with two contact in groups, one of which, with an imbalance corresponding to the temperature in the working chamber, gives a current pulse necessary to increase the flow area of the valve of the regulator 5, and the other with an imbalance corresponding to a decrease in the temperature. It includes an electric heater mounted on a heat exchange fork on meter 3. A valve 10 allows the refrigerant to be removed in the form of steam (with the upper intake opening open) or in the form of a liquid (with the lower opening intake opening).

The cryostat (Fig. 2) consists of an outer casing And, the cavity of which is evacuated, a reservoir of liquid nitrogen 12 with suspended radiation screens 13, covering the tank-feeder with a cryogenic liquid and other parts cooled to the lowest temperature level. Part of the pipeline coming out of the switching valve is also surrounded by a radiation shield 14. The heat exchange chamber is divided into two sections: the first is filled with a massive nozzle 15 and is equipped with a heater 16, and the second with a small nozzle 17 that cuts and mixes the gas flow. The thermostatted chamber is suspended from a thin-walled suspension tube 18 made of stainless steel. In its upper part, there is a sluice chamber 19, which makes it possible to change the sample, enter the manipulators and other things without disturbing the operation of the thermal control system. The sample or device is introduced into the thermostatically controlled chamber with the help of a rod made in the form of a particularly thin-walled tube made of a material with low thermal conductivity. Stock missed

through the cap 20 installed on the upper cut pipe-suspension.

The level of cryogenic fluid in the feeder tank is determined visually using a float level indicator 21.

The sensor 22 of the thermal control system is either inserted into the heat exchange prechamber by means of low-temperature electrical leads through its wall from the side of the evacuated 10 space, or is inserted into the thermostatically controlled chamber together with the rod.

In the case 23 of the flow control valve (Fig. 3), needle valve 24 is mounted, which regulates the flow area of the valve blocked by the striker 25 and the solenoid 26. The flow section of the bypass channel 27 is adjusted by the needle 28.

The temperature of the chamber is controlled by the continuous supply of gaseous or liquid refrigerant to it. At the same time, already at the exit from the first section of the heat exchange pre-chamber refrigerant, it has a temperature slightly lower than the set one, since the amount of refrigerant entering the heat exchange prechamber 25 RU is determined by the temperature level of the thermostatting and heat losses of the cryostatted system elements.

This balance is achieved by adjusting the flow area of the bypass channel 27 of the flow controller.

After the predetermined temperature has been established in the temperature-controlled chamber, an automatic temperature stabilization system is activated. A potentiometer 7 (FIG. 1) creates

5 is the reference voltage that corresponds to thermo-e. d. thermocouples at a given chamber temperature. In this thermo-e. d. is compensated by the reference voltage, and the signal at the input and output of amplifier 8 is zero; The self-recording adjustment potentiometer 9 slide motor is located in the control zone and both of its contact groups are turned on, i.e. the electric heater 16 is turned off, and the solenoid valve blocks the passage under the needle of the needle valve 24.

When the temperature in the thermostated chamber at the input of the amplifier 8 decreases, a voltage of a certain polarity appears and an amplified unbalance signal arrives

on the adjusting potentiometer 9 and actuates the slide motor, bringing it out of the control zone. This closes the electrical heater circuit, which raises the temperature of the refrigerant.

When an excessive temperature rises in the temperature-controlled chamber at the input of the amplifier 8, the imbalance signal also appears, as well as when the temperature in the temperature-controlled chamber decreases, but the opposite polarity

0 and the regulating potentiometer control slide motor rotates in the opposite direction, thereby closing the solenoid circuit. The passage under the needle of the valve 24 opens, which entails a pulsed increase in the flow of refrigerant through the heat exchange prechamber and thermostatically controlled chamber and a decrease in the temperature in this chamber. Manual adjustment of the flow area under the solenoid valve with the help of the needle 28 allows to select the optimum amplitude of the temperature yaw in the heat exchange chamber and significantly affects the accuracy of temperature stabilization in the cryostat chamber. The subject of the invention 1. A thermostatically controlled cryostat device containing a crank out switch and thermostatic control systems, characterized in that, in order to simplify the device, increase and expand its functionality, the refrigerant tank is equipped with a constant pressure valve. 2. The device according to claim 1, characterized in that, in order to ensure a wide range of operating temperatures of the thermostatted cryostat chamber, its reservoir with a refrigerant is equipped with a switching valve. 3. The device according to claim 1, characterized in that, in order to increase the accuracy of thermostating, the valve seat of the flow control valve, installed on the suction line of the refrigerant exhaust vapor from the cryostat and included in the automatic control system, has a variable cross-section.

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