Closed-cycle refrigerating system for superconductive magnet and maser is operated in vacuum environment. Each wire leading from external power source passes through cooling station which blocks heat conduction. In connection with these stations, switch with small incandescent light bulb, which generates heat, is used to stop superconduction

Wiebe, E. R.

English

NASA Technical Reports Server

September 1974	 B74-10158 
NASA TECH BRIEF 
•	 NASA Pasadena Office
	
A 
NASA Tech Briefs announce new technology derived from the U.S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Improved Thermal Isolation for Superconducting Magnet Systems 
From To Compressor 
Compressor Intermediate 
High Pressure Pressure 
Drive Motor 
To Compressor 
Low Pressure I Valve 
From Power Supply I	 Drive 
I 300K  
- - ----- 
I 
Exhaust Valve 
First Heat Inlet Valve 
..	 UadH 
I Exchanger Displacer- 
Regenerator 
Assembly 
70-K Station 
Second Heat 
Exchanger
_ 15-K
Third Heat 
Exchanger 
-,	 Ground Lead 
4.5-K Station .
______	 X3 Valve 
y	 ,
j. 
Light
Switch Bulb •TA'i Tl 
Shield Over	 Magnet Coil 
Light Bulb 
Cooling System for Superconductive Magnet To Be Used in a Maser 
The problem:	 utilized, two problems must be resolved. First, the 
Masers designed for operation above S-band fre- 	 magnets operate in the temperature range between 4.5 
quencies require large magnetic fields which can be 	 and 5 K, depending on conductor composition; they are 
generated using superconductive magnets. These fields	 cooled by direct contact with cryogenic fluids. Cooling 
must be constant to maintain uniform gain and frequency	 by conduction is necessary because a high vacuum must 
qt,ihilitv However hpfnre sunprcnndiictive m—et are 	 he retained within the maser Second once the maonef is 
•	 .,--.-._-.J •	 0 
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cooled to a superconductive state, the current flow in 
the magnet coil is initiated by an external power source. 
Wires leading from this source conduct heat from the 
external environment. This heat often reverts the magnet 
to the nonsuperconducting state. 
The solution: 
A closed-cycle refrigerating system for the super-
conductive magnet and maser is operated in a vacuum 
environment. In addition, each wire leading from the 
external power source passes through a cooling station 
which blocks heat conduction. In connection with these 
stations, a switch with a small incandescent light bulb, 
which generates heat, is used to stop the supercon-
duction. 
How it's done: 
The system includes three stations, as shown in the 
figure, to progressively cool helium from gas to liquid 
state. The station temperatures are maintained at 78 K, 
15 K, and 4.5 K, respectively. An additional or fourth 
station is used which maintains helium at 4.5 K. 
Each of the two 4.5-K stations is connected in series 
by resistive stainless steel tubes and is used in con-
nection with a wire leading from the external power,
 
source. These stations remove the heat from the wires 
generated by the current flow and any additional heat
picked up from surrounding environment. Both of these 
stations are made from copper, forming plenums within 
which liquid helium flows. 
Superconduction is interrupted by a switch which 
operates with a tiny incandescent light bulb connected 
to the external power supply. When the bulb is turned 
on, it radiates heat which raises the temperature of the 
switch wire above the critical point, reverting the 
magnet coil to the nonsuperconductive state. The bulb 
is shielded from the magnet coil by a copper housing 
which is cooled by one 4.5-K station. 
Note: 
Requests for further information may be directed to: 
Technology Utilization Officer 
NASA Pasadena Office 
4800 Oak Grove Drive 
Pasadena, California 91103 
Reference: TSP74-101 58 
Patent status: 
NASA has decided not to apply for a patent. 
Source: Ervin R. Wiebe of

Caltech/JPL
under contract to

NASA Pasadena Office

(NPO-1 1875) 
B74-10158	 Category O2,03,06
	
S


Improved thermal isolation for superconducting magnet systems

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