Method for determining the granular nature of superconductors using pulsed current

• US 5,339,025 A
• Filed: 01/28/1993
• Issued: 08/16/1994
• Est. Priority Date: 01/28/1993
• 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): TOBIN, C
• Application Number:
  US08/010,685
• Time in Patent Office: 565 Days
• Field of Search: 324/71.6, 324/248, 324/713, 324/715, 324/717, 324/719, 505/726, 505/843
• US Class Current: 324/71.6
• CPC Class Codes: G01N 27/041 of a solid body
• CPC Class Codes: G01R 33/1238 Measuring superconductive properties
• CPC Class Codes: Y10S 505/843 Electrical

Abstract

The present invention provides a method for determining the granular nature of superconductive materials and devices which includes the steps of: conducting a substantially rectangular current pulse through the superconductive material, maintaining the temperature of the superconductive material at a substantially constant temperature which does not exceed the critical temperature of the superconductive material; determining the amplitude of the current pulse; determining the electrical resistance, R, of the superconductive material resulting from conducting current pulse through the superconductive material; increasing the current until the electrical resistance of the superconductive material becomes saturated; determining the electrical resistance difference, δ, between the electrical resistance, R, of the saturated superconductive material and a total normal state electrical resistance of the superconductive material; generating a first output signal if |δ|≦ε, where ε represents a predetermined limit, where the first output signal corresponds to the superconductive material having a homogenous microscopic morphology; and generating a second output signal if |δ|>ε, where the second output signal corresponds to the superconductive material having a granular morphology. The method may also be used to determine the saturated electrical resistances of the superconductive sample.

Claims

1. A method for determining the granular nature of a superconductive material, comprising the steps of:

conducting a substantially rectangular current pulse having an amplitude through said superconductive material, said superconductive material having a critical temperature;

maintaining the temperature of said superconductive material at a substantially constant temperature which does not exceed said critical temperature of said superconductive material;

determining said amplitude of said current pulse;

determining the electrical resistance, R, of said superconductive material resulting from conducting said current pulse through said superconductive material;

increasing said amplitude of said current pulse until said electrical resistance of said superconductive material becomes saturated;

determining an electrical resistance difference, δ

, between a saturated electrical resistance, R₁, of said saturated superconductive material and a total normal state electrical resistance of said superconductive material;

generating a first output signal if |δ

|≦

ε

, where ε

represents a predetermined limit, where said first output signal corresponds to said superconductive material having a homogeneous microscopic morphology; and

generating a second output signal if |δ

|>

ε

, where said second output signal corresponds to said superconductive material having a granular microscopic morphology.

2. The method of claim 1 wherein:

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

3. The method of claim 2 further including the step of averaging said electrical resistance differences over a predetermined number of said current pulses.

4. The method of claim 1 further including the step of determining said total normal state resistance of said superconductive material at said constant temperature.

5. The method of claim 4 wherein said step of conducting includes conducting a series of current pulses through said superconductive material.

6. The method of claim 5 further including the step of averaging said electrical resistance difference over a predetermined number of said current pulses.

7. A method for determining the granular nature of a superconductive material, comprising the steps of:

conducting a substantially rectangular current pulse through said superconductive material, said superconductive material having a critical temperature;

maintaining the temperature of said superconductive material at a substantially constant temperature which does not exceed said critical temperature of said superconductive material;

determining said amplitude of said current pulse;

determining the electrical resistance of said superconductive material resulting from conducting said current pulse through said superconductive material;

increasing said amplitude of said current pulse until said electrical resistance of said superconductive material becomes saturated at a first saturated electrical resistance, R₁ ;

further increasing said amplitude of said current pulse until said electrical resistance of said superconductive material increases from said first saturated electrical resistance, R₁, to a second saturated electrical resistance, R₂, said second saturation electrical resistance being equal to the total normal state electrical resistance of said superconductive sample;

determining an electrical resistance difference, δ

, between R₁ and R₂ ;

generating a first output signal if |δ

|≦

ε

, where ε

represents a predetermined limit, where said first output signal corresponds to said superconductive material having a homogeneous morphology; and

generating a second output signal if |δ

|>

ε

, where said second output signal corresponds to said superconductive material having a granular morphology.

8. The method of claim 7 wherein said step of conducting includes conducting a series of current pulses through said superconductive material.

9. The method of claim 8 further including the step of averaging said electrical resistance differences over a predetermined number of said pulses.