JPS5913308A - Cooling device of superconductive magnet - Google Patents

Abstract

PURPOSE:To supply liquid helium in simple work and good efficiency, by a method wherein gas helium in heat exchange to a refrigerator circuit is supplied while a superconductive coil is excited or demagnetized. CONSTITUTION:A heat exchanger 6 of a refrigerator comprises two systems, high-pressure forward system and low-pressure return system, added by a low- pressure supply line 12 thus three systems. Cold connecting portion of the low- pressure supply line 12 is provided with a reducing valve 8, and the line 12 passing through the lowest-temperature stage of the heat exchanger is opened to a liquid helium tank member 3. Parts to be connected to the cold side use a pure helium gas supply source such as a high-pressure helium gas bomb 9. Helium gas supplied from the pure helium gas supply source is fed through the reducing valve 8 to the refrigerator low-pressure line 12. Pressure at low-pressure side of the reducing valve is set to pressure slightly higher than internal pressure of the liquid helium tank during the refrigerator steady operation. When the internal pressure of the helium tank is reduced by the cooling at the condensation heat exchanger 4, helium gas is supplied from outside corresponding to the pressure reduction.

Description

Detailed Description of the Invention ((1) Description of the Technical Field The present invention relates to a helium cooler for cooling superconducting magnets.

(2) Explanation of the prior art When a superconducting coil is excited or demagnetized, the current leads generate a lot of heat and the persistent current switch generates a lot of heat, making it impossible to use liquid helium without sealing it off. (It cannot be condensed in the exchanger, so it has to be discharged to the outside.) In order to make up for the lack of liquid helium, conventional methods have been used to replenish liquid helium from outside.However, with this method, When replenishing liquid helium, the helium is heated and a large amount of liquid helium evaporates at the beginning of replenishment.

In addition, another method is being considered in which gas from room temperature is condensed using the excess bonding power of a helium cooler.

Although this method is easy to operate, it has the disadvantage that since it involves cooling from room temperature, there is little liquefied acid and it is difficult to replenish it in a short period of time. Although it is possible to compensate for this drawback by supplying helium gas pre-cooled to the nitrogen temperature, this level of pre-cooling is still insufficient.

(C) Object of the Invention An object of the present invention is to provide a method for replenishing liquid helium that is simple and efficient.

Mountain c Structure of the Invention A flow diagram of the structure of the invention is shown in FIG. In addition to the conventional two systems for high pressure going and low pressure return, the heat exchanger 6 of the refrigerator is expanded to three systems by adding 42 low pressure supply lines 12 (indicated by dotted lines). A pressure reducing valve 8 is provided at the normal temperature connection of the low pressure supply line 12.

The line 12 exiting the lowest temperature stage of the heat exchanger is opened to the liquid helium tank section 3. For those connected to room temperature, a pure helium gas supply source such as a high pressure helium gas cylinder 9 is used.

Helium gas supplied from the pure helium gas supply source is sent to the refrigerator low pressure line 12 through the pressure reducing valve 8. The pressure on the low pressure side of the pressure reducing valve is set to a pressure that is very slightly higher than the pressure inside the liquid helium tank during steady operation of the refrigerator. Helium gas can be supplied from the outside by the amount that is reduced by the pressure inside the helium tank cooled by the condensing heat exchanger 4.

(e) Effect of the invention The refrigerating capacity of the helium cooler is designed to be slightly larger than the amount of heat entering the liquid helium tank.

When excitation and demagnetization of a superconducting coil is performed, a large amount of heat is generated, albeit for a short period of time, and in this case, the refrigeration capacity of the refrigerator cannot cover it, and the evaporated helium gas must be released to the outside.

Therefore, the amount released into the atmosphere needs to be replenished every time the magnet is excitation and demagnetized.

In this method, this replenishment is performed by supplying gas helium that has undergone heat exchange with the refrigerator circuit.

Pure helium gas supplied from the outside flows into the refrigerator through a pressure reducing valve. IO from room temperature using the refrigerator heat exchanger
Two people were pre-cooled to about K and partially exposed to liquid helium tank gas. This gas is condensed by a condensing heat exchanger inside the liquid helium tank and stored in the helium tank in the form of liquid helium. When the amount of liquid released into the atmosphere during excitation and demagnetization is stored, the closing pulp is closed and the supply side is disconnected.

(f) Other Examples (1) Heat exchange between the supply gas circuit and the refrigerator circuit is considered to be a three-fluid heat exchanger, but if the required amount of liquid helium (condensation amount) is small, the heat exchange of the refrigerator circuit For example, a gas supply circuit in which a pipe is wound around an exchanger (two fluids) may be considered.

(2) The shutoff valve position may be at either the normal temperature or low temperature side.

(3) Although the supply gas is provided in the low pressure circuit, it is also possible to provide it in the high pressure circuit. In this case, the position of the pressure reducing valve will be changed.

Provisional) Overall Effects According to the present invention, replenishment of liquid helium can be performed easily and efficiently.

[Brief explanation of drawings]

FIG. 1 is a refrigeration flow diagram according to the present invention.

Claims (1)

[Claims] In a superconducting magnet system consisting of a superconducting coil, a tank containing liquid helium to house and cool it, and a helium cooler with a condensing heat exchanger, one end is connected to a helium gas supply source via a pressure reducing valve, and the other end is connected to a helium gas supply source through a pressure reducing valve. A cooling device for a superconducting magnet, characterized in that a low-pressure helium gas supply circuit connected to a liquid helium tank is provided in parallel to a heat exchanger of a helium cooler.