Method for measuring the resistive transition and critical current in superconductors using pulsed current

• US 5,223,798 A
• Filed: 10/31/1990
• Issued: 06/29/1993
• Est. Priority Date: 10/31/1990
• Status: Expired due to Fees

• Current Assignee: the united states of america as represented by the secretary of the navy
• Original Assignee: the united states of america as represented by the secretary of the navy
• Inventors: McGinnis, Wayne C., Jones, Thomas E.
• Primary Examiner(s): Wieder, Kenneth A.
• Assistant Examiner(s): Regan, Maura K.
• Application Number:
  US07/606,396
• Time in Patent Office: 972 Days
• Field of Search: 324/713, 324/715, 324/248, 324/71.6, 361/19, 505/1, 505/843, 505/726
• US Class Current: 324/713
• CPC Class Codes: G01R 27/00 Arrangements for measuring resistance, reactance, impedance, or electric characteristics derived therefrom
• CPC Class Codes: G01R 33/1246 Measuring critical current
• CPC Class Codes: Y10S 505/843 Electrical

Abstract

The present invention provides a method for measuring the intragranular andntergranular critical current of a granular superconductive material, comprising the steps of: 1) conducting a substantially rectangular electronic pulse through the material so as to conduct a current through the material such that when the intergranular critical current of the material is exceeded, any grains present in the material remain in a superconducting state when the current level is below the intragranular critical current; 2) measuring the current through the material while conducting the pulse; 3) measuring a voltage difference across the material while conducting the pulse; 4) determining the intergranular critical current through the material by discerning a non-zero voltage difference across the material and contemporaneously measuring the current; and 5) determining the intragranular critical current through the material by varying the current to discern a current level at which the electrical resistance of the material increases to that of the non-superconducting state as the grains of the material transition from the superconducting to a non-superconducting state. This method may also be used to determine the critical current of a homogeneous superconductive material.

Claims

1. A method for measuring the intragranular critical current of a granular superconductive material, comprising the steps of:

conducting a substantially rectangular electronic pulse through said material so as to conduct a current through said material such that when said intragranular critical current of said material is exceeded, any grains present in said material are in a superconducting state when said current is less than said intragranular critical current, said material having a critical temperature;

measuring said current through said material while conducting said pulse;

measuring a voltage difference across said material while conducting said pulse; and

determining said intragranular critical current through said material by varying said current to discern a current level at which an electrical resistance of said material increases to that of a non-superconducting state as the grains of said material transition from said superconducting to said non-superconducting state.

2. The method of claim 1 wherein:

said step of conducting includes conducting a series of pulses through said material.

3. The method of claim 2 further including the steps of:

repeatedly measuring said voltage difference; and

averaging said voltage differences over a predetermined number of pulses.

4. The method of claims 1 or 2 which further includes the steps of:

allowing said current to vary; and

maintaining the temperature of said material at a constant temperature below said critical temperature.

5. The method of claim 4 further including the steps of:

repeatedly measuring said voltage difference; and

averaging said voltage differences over a predetermined number of pulses.

6. A method for measuring the intragranular and intergranular critical current of a granular superconductive material, comprising the steps of:

conducting a substantially rectangular electronic pulse through said material so as to conduct a current through said material such that when said intergranular critical current of said material is exceeded, any grains present in said material are in a superconducting state when said current level is below said intragranular critical current, said material having a critical temperature;

measuring said current through said material while conducting said pulse;

measuring a voltage difference across said material while conducting said pulse;

determining said intergranular critical current through said material by discerning a non-zero voltage difference across said material and contemporaneously measuring said current; and

determining said intragranular critical current through said material by varying said current to discern a current level at which an electrical resistance of said material increases to that of a non-superconducting state as said grains of said material transition from said superconducting to said non-superconducting state.

7. The method of claim 6 wherein:

said step of conducting includes conducting a series of pulses through said material.

8. The method of claim 7 further including the steps of:

repeatedly measuring said voltage difference; and

averaging said voltage differences over a predetermined number of pulses.

9. The method of claims 6 or 7 which further includes the steps of:

allowing said current to vary; and

maintaining the temperature of said material at a constant temperature below said critical temperature.

10. The method of claim 9 further including the steps of:

repeatedly measuring said voltage difference; and

averaging said voltage differences over a predetermined number of pulses.

11. A method for measuring the intergranular critical current of a granular superconductive material, comprising the steps of:

conducting a substantially rectangular electronic pulse through said material, having a critical temperature, in order to conduct a current through said material such that when said intergranular critical current of said material is exceeded, any grains present in said material are in a superconducting state;

measuring a voltage difference across said material while conducting said pulse;

determining said intergranular critical current through said material by discerning a non-zero voltage difference across said material and contemporaneously measuring said current

allowing said current to vary; and

maintaining the temperature of said material at a constant temperature below said critical temperature.

12. The method of claim 11 which further includes the steps of:

repeatedly measuring said voltage difference; and

averaging said voltage difference over a predetermined number of pulses.

13. A method for measuring the intergranular critical current of a granular superconductive material, comprising the steps of:

conducting a series of substantially rectangular electronic pulses through said material, having a critical temperature, in order to conduct a current through said material such that when said intergranular critical current of said material is exceeded, any grains present in said material are in a superconducting state;

measuring said current through said material while conducting said pulse;

measuring a voltage difference across said material while conducting said pulse;

determining said intergranular critical current through said material by discerning a non-zero voltage difference across said material and contemporaneously measuring said current;

allowing said current to vary; and

maintaining the temperature of said material at a constant temperature below said critical temperature.

14. The method of claim 13 which further includes the steps of:

repeatedly measuring said voltage difference; and

averaging said voltage difference over a predetermined number of pulses.

15. A method for measuring the critical current of a homogeneous superconductive material, comprising the steps of:

conducting a substantially rectangular electronic pulse through said material so as to conduct a current through said material, said material having a critical temperature;

measuring said current through said material while conducting said pulse;

measuring a voltage difference across said material while conducting said pulse;

determining said critical current through said material by discerning a non-zero voltage difference across said material and contemporaneously measuring said current;

allowing said current to vary; and

maintaining the temperature of said material at a constant temperature below said critical temperature.

16. The method of claim 15 further including the steps of:

repeatedly measuring the voltage difference; and

averaging said voltage differences over a predetermined number of pulses.

17. A method for measuring the critical current of a homogeneous superconductive material, comprising the steps of:

conducting a series of substantially rectangular electronic pulses through said material so as to conduct a current through said material, said material having a critical temperature;

measuring said current through said material while conducting said pulse;

measuring a voltage difference across said material while conducting said pulse;

determining said critical current through said material by discerning a non-zero voltage difference across said material and contemporaneously measuring said current;

allowing said current to vary; and

maintaining the temperature of said material at a constant temperature below said critical temperature.

18. The method of claim 17 further including the steps of:

repeatedly measuring said voltage difference; and

averaging said voltage differences over a predetermined number of pulses.