DD258867A1

DD258867A1 - POWER SUPPLY FOR CRYOTECHNICAL EQUIPMENT

Info

Publication number: DD258867A1
Application number: DD86291110A
Authority: DD
Inventors: Dieter Eckert; Alexander Gladun; Manfred Knonn
Original assignee: Akad Wissenschaften Ddr
Priority date: 1986-06-09
Filing date: 1986-06-09
Publication date: 1988-08-03

Abstract

Die Erfindung bezieht sich auf den wissenschaftlichen Geraetebau und ist bei Stromzufuehrungen fuer supraleitende, mittels verfluessigtem Gas gekuehlte Einrichtungen, insbesondere fuer supraleitende Spulen, die sich in Kryostatraeumen befinden, anwendbar. Der Erfindung liegt die Aufgabe zugrunde, eine Stromzufuehrung, deren Leiter im aufsteigenden Strom des Kuehlmittelgases angeordnet und mit einem Fuehrungsrohr fuer das Gas umgeben sind, so zu gestalten, dass unter Vermeidung einer Zusatzkuehlung und von aufwendigen konstruktiven Gestaltungsmassnahmen eine ausreichende Kuehlung der Leiter unter allen Betriebsbedingungen erfolgt. Erfindungsgemaess ist der Querschnitt fuer das aufsteigende Kuehlmittelgas im Fuehrungsrohr so gross bemessen, dass bei der dem maximalen Betriebsstrom entsprechenden Gasmenge der Druckabfall 40 Pa pro Meter Rohrlaenge ist. Die Fuehrungsrohre muenden innerhalb des Kryostaten in dessen oberen Bereich in einem Gassammelraum, der ueber Zwischenraeume fuer aufsteigendes Kuehlmittelgas mit dem Raum ueber dem fluessigen Kuehlmittel in Verbindung steht. An den Gassammelraum ist eine von den Stromzufuehrungsleitern raeumlich getrennte Leitung zum Abfuehren des Gases angeschlossen.The invention relates to scientific Geraetebau and is in power supplies for superconducting, cooled by liquefied gas devices, in particular for superconducting coils, which are located in Kryostatraeumen applicable. The invention has for its object to make a power supply, the conductors are arranged in the rising stream of coolant gas and surrounded by a Fuehrungsrohr for the gas so that while avoiding a Zusatzkuehlung and elaborate structural design measures sufficient cooling of the ladder under all operating conditions he follows. According to the invention, the cross-section for the rising coolant gas in the guide tube is dimensioned so large that at the gas flow rate corresponding to the maximum operating flow the pressure drop is 40 Pa per meter of tube length. The guide tubes are located inside the cryostat in its upper part in a gas collection room communicating with the space above the liquid coolant via intermediate spaces for rising coolant gas. Connected to the gas collecting space is a line separated from the power supply conductors for discharging the gas.

Description

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Die erfindungsgemäße Stromzuführung zeichnet sich gegenüber dem Stand der Technik durch ihren einfachen Aufbau und dadurch aus, daß sich der für die Kühlung notwendige Gasstrom bei allen Betriebsbedingungen selbsttätig optimal einstellt, wobei kein zusätzliches Kühlmedium und keine diesbezügliche Regeleinrichtung erforderlich sind. Eine Gefahr des Einfrierens besteht nicht. Außerdem wird die Temperaturwechselbelastung der elektrischen Isolation der Stromzuführungsleiter bei starker Verdampfung des verflüssigten Kühlmittelgases deutlich verkleinert, und die von der elektrischen Durchführung räumlich getrennte Kühlmittelgasabführung ermöglicht eine einfache Gestaltung der elektrischen Isolation.The power supply according to the invention is distinguished from the prior art by its simple structure and the fact that automatically adjusts the necessary for the cooling gas flow under all operating conditions optimally, with no additional cooling medium and no relevant control device are required. There is no danger of freezing. In addition, the thermal cycling of the electrical insulation of the power supply conductors is significantly reduced with strong evaporation of the liquefied coolant gas, and the spatially separated from the electrical feedthrough coolant gas discharge allows a simple design of the electrical insulation.

embodiment

Die Erfindung ist nachstehend an einem Ausführungsbeispiel und einer zugehörigen Zeichnung näher erläutert: In einem Kryostaten 1 befindet sich eine mit flüssigem Helium 2 gekühlte supraleitende Spule 3, die an einem Zentralrohr 4 befestigt ist. Aus parallelgeschalteten Messingdrähten bestehende Leiterelemente 5 der beiden Stromzuführungen befinden sich in Führungsrohren 6 für das aufsteigende Heliumgas, die mit einem schlecht wärmeleitenden Gewebeisolierschlauch 7 thermisch isoliert sind. Die unteren und oberen Enden der Führungsrohre 6 sind so ausgebildet, daß der Strömungswiderstand für das Heliumgas 8 im Führungsrohr 6 nur unwesentlich beeinflußt wird. Eine Wärmeisolation 9 im oberen Teil des Kryostater* 1 ist so ausgebildet, daß auch im Zentralrohr4und an der Innenwand 10 Spalte 11 für Heliumgas 12 bestehen. Oberhalb der Wärmeisolation 9 ist ein Gassammeiraum 13 gebildet. Im Flansch 14 des Kryostaten 1 sind eine Leitung 15 zum Abführen des Heliumgases sowie aus gut leitfähigem Kupfer bestehende Zuführungsteile 16 mit elektrischen Isolationsteilen 17 angeordnet. Den Zuführungsteilen 18 am unteren Ende der Stromzuführungen sind Supraleiterdrähte zur Beseitigung von elektrischen Verlusten parallelgeschaltet. Die thermische Isolation am Umfang der Führungsrohre 6 ermöglicht die Ausbildung eines von den übrigen gasgekühlten Bauteilen unabhängigen Temperaturprofils entlang der Leiterelemente 5. Falls die sich zunächst einstellenden Ströme des Heliumgases zur Kühlung nicht ausreichend sind, erwärmen sich die Leiterelemente 5 durch die in ihnen entstehenden elektrischen Verluste und durch Wärmeleitung von den oberen Enden. Durch den guten Wärmeaustausch erwärmt sich auch das H'eliumgas 8 und verringert damit seine mittlere Dichte. Die Querschnitte der Leiterelemente 5 und der Führungsrohre 6 sind so dimensioniert, daß bei der dem maximalen Betriebsstrom entsprechenden Gasmenge der Druckabfall kleiner.als35Pa pro Meter Rohrlänge bleibt. Damit stellt sich für jeden zulässigen Betriebsstrom ein stabiles Gleichgewicht für die Aufteilung der verdampften Menge des Heliumgases auf die unterschiedlichen Gasströme 8 und 12 ein.The invention is explained in more detail below with reference to an exemplary embodiment and an associated drawing: In a cryostat 1 there is a superconducting coil 3 cooled with liquid helium 2, which is fastened to a central tube 4. From parallel connected brass wires existing conductor elements 5 of the two power supply lines are located in guide tubes 6 for the rising helium gas, which are thermally insulated with a poor heat-conducting Gewebisolierschlauch 7. The lower and upper ends of the guide tubes 6 are formed so that the flow resistance for the helium gas 8 in the guide tube 6 is only insignificantly affected. A heat insulation 9 in the upper part of the cryostat * 1 is formed so that column 11 for helium gas 12 also exist in the central tube 4 and on the inner wall 10. Above the heat insulation 9, a gas collection chamber 13 is formed. In the flange 14 of the cryostat 1, a conduit 15 for discharging the helium gas as well as good conductive copper existing supply members 16 are arranged with electrical insulation parts 17. The supply parts 18 at the lower end of the power supply lines superconducting wires are connected in parallel to eliminate electrical losses. The thermal insulation on the circumference of the guide tubes 6 allows the formation of a temperature profile independent of the other gas-cooled components along the conductor elements 5. If the initially adjusting currents of the helium gas are not sufficient for cooling, the conductor elements 5 are heated by the electrical losses occurring in them and by heat conduction from the upper ends. Due to the good heat exchange, the h'elium gas 8 also heats up, thus reducing its mean density. The cross sections of the conductor elements 5 and the guide tubes 6 are dimensioned so that at the maximum operating current corresponding amount of gas, the pressure drop kleiner.als35Pa per meter tube length remains. This establishes a stable equilibrium for the distribution of the evaporated amount of helium gas to the different gas streams 8 and 12 for each permissible operating current.

Claims

Claim:

Power supply for cryogenic, cooled by means of liquefied gas devices in cryostats, in particular for superconducting coils, which electrical energy for generating and maintaining the operating state is supplied in a time required for this, limited time via power supply conductor, which arranged in the ascending flow of the refrigerant gas and with a guide tube for the coolant gas are surrounded, characterized in that the cross section for the ascending refrigerant gas in the guide tube (6) is dimensioned so large that at the maximum operating current corresponding amount of gas, the pressure drop <40Pa per meter tube length, and that the guide tubes (6) within the cryostat (1) in its upper region in a Gassammeiraum (13) open, which is connected via spaces (11) for rising refrigerant gas with the space above the liquid coolant (2) and to the one of the power supply conductors (5) rä umlich separate line (15) is connected for discharging the gas.

For this 1 page drawing

Field of application of the invention

This invention relates to the field of scientific instrumentation and is applicable to power supplies for cryogenic liquefied gas cooled devices, in particular superconducting coils housed in cryostats.

Characteristic of the known technical solutions

Power supplies for cryogenic equipment located in a liquid helium cryostat are already known. They serve to supply electrical energy for generating and maintaining the operating state in a required for this, limited time via power supply conductor. The conductors are arranged in the rising stream of coolant gas and surrounded by a guide tube for the gas. In one of these known power supply lines, an additional cooling which can be operated during the supply of electrical energy is provided for the power supply conductors. For the power supply includes a plurality of mutually parallel tubes that serve as a conductor, are connected to each other at their low temperature side ends, and form at least one outgoing line and at least one return line for the additional cooling medium. Liquid nitrogen is used as additional cooling medium. To further improve the cooling, the tubes are structured or their surface roughness is increased. The guide tube for the helium gas surrounding the conductor tubes is guided through the flange of the cryostat. Outside the cryostat is located on the guide tube an outlet for the helium gas. Due to the special design of the conductors and the electrical insulation required between the conductor tubes and the guide tube, this known power supply has a relatively complicated construction. With strong evaporation of helium is due to the additional cooling with liquid nitrogen and the risk of freezing. Another disadvantage is the complex operation of this power supply, since an additional coolant must be provided and the coolant flow must be regulated.

Object of the invention

The object of the invention is to create conditions for a simple in construction and operation power supply with high reliability.

Explanation of the essence of the invention

The invention is based on the object for cryogenic, cooled by means of liquefied gas in cryostat devices, a power supply, arranged in the rising current of the refrigerant gas supply lead and surrounded with a guide tube for the refrigerant gas to make such that while avoiding an additional cooling and of costly structural design measures sufficient cooling of the conductor takes place under all operating conditions.

This object is achieved according to the invention in that the cross section for the ascending refrigerant gas in the guide tube is sized so large that at the maximum operating current corresponding amount of gas pressure drop <40Pa per meter tube length. The guide tubes open within the cryostat in its upper region in a Gassammeiraum, which is connected via spaces for rising coolant gas with the space above the liquid coolant. To the Gassammeiraum one of the power supply conductors spatially separated line for discharging the gas is connected.