System and method for controlling helium pressure during superconducting test piece testing

Abstract

The invention provides a system and method for controlling helium pressure in a Dewar during superconducting test piece testing. The Dewar comprises an inner cavity for accommodating liquid helium, and the inner cavity is provided with a liquid helium gasification area. The control system comprises a pressure sensor, a controller, a first pressure release valve and a second pressure release valve,wherein the pressure sensor detects helium pressure in the gasification area in the Dewar, and the first pressure release valve and the second pressure release valve are communicated with the gasification area through pressure release pipelines; the controller controls the first pressure release valve or the second pressure release valve to be opened and closed according to a pressure signal sentby the pressure sensor; and the aperture of the first pressure release valve is larger than that of the second pressure release valve. The two pressure release valves with different apertures are adopted, the pressure release valves with the corresponding apertures are opened according to the current helium pressure value, when the current helium pressure is large, the large-aperture pressure release valve is opened, pressure is released quickly, after the helium pressure is reduced to a certain degree, the small-aperture pressure release valve is adopted for pressure release, the small-aperture pressure release valve is more beneficial to control over the pressure release speed, and helium pressure precision is controlled conveniently.

Description

technical field [0001] The invention relates to the field of superconductor equipment testing, in particular to a helium pressure control system and control method for superconducting specimen testing. Background technique [0002] Superconducting magnets and superconducting cavities need to be tested for their performance before they are installed. They need to be tested at low temperature, and the working temperature is about -269°C. [0003] The saturation temperature of liquid helium at standard pressure is about -269°C, so liquid helium is selected as the ideal medium for testing superconducting devices at low temperatures. Since liquid helium has a small latent heat of vaporization and is easy to vaporize, a special container is required to hold liquid helium. At present, Dewar is generally used as a container for holding liquid helium. The equipment is placed vertically on the ground, and the size of the top opening should be larger than that of the superconducting e...

AI Technical Summary

Problems solved by technology

[0005] 1. The exhaust valve is in a normally open state, so that the Dewar inner cavity is connected with the atmosphere, and the helium pressure in the Dewar cavity is maintained at 1.0 bara (here refers to the ambient atmospheric pressure); this method causes a large amount of helium waste and a large cost waste , and the temperature of liquid helium cannot be adjusted, the test environment is single, and the adaptability is poor;

[0006] 2. Using a safety valve, when the pressure reaches a certain value, the safety valve will automatically open to release the pressure. This method can only achieve a single temperature, the test environment is single, and the adaptability is poor; passive adjustment, no active control; especially when the superconducting magnet is in the There is a quench phenomenon during the test, and a large amount of heat will be released when the superconducting magnet is quenched. If the passive displacement is insufficient, the helium pressure in the Dewar chamber will rise instantaneously. If the pressure rises to the level that the equipment can withstand At the maximum value, it will cause great harm to surrounding people, the environment, and equipment, and there is a great potential safety hazard;

[0007] 3. The control valve is used. Since the gasification amount is related to the heat source, the tested piece can be considered as a heat source with variable power. When the power of the tested piece is high, the gasification amount of liquid helium is very large, and the pressure relief of the small-caliber control valve The amount of gas can not be matched with the amount of vaporization, resulting in untimely pressure release; if a large-diameter control valve is selected, although the pressure can be released in time, the pressure cannot be accurately controlled, and it cannot meet the requirements of a certain test helium pressure accuracy control

This method has the problems of 2 and 3 above. More importantly, the composite tank is only a storage tank and cannot be applied in a complex environment where the gasification amount of liquid helium changes sharply due to the positive change in temperature during the test of the superconducting specimen.

[0009] To sum up, different Dewars and different superconducting equipment have different heat leakage, so the gasification amount of liquid helium is also different, which brings a lot of inconvenience to the control of helium pressure.

It is impossible to adjust the helium pressure within a certain range by using a single passive air pressure adjustment, and the test adaptability is poor

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