US4851762A
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Novel technique using magnetic field dependent phase detection for detection of superconductivity
Assignee: Johns Hopkins University
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Filing: 1988-08-31
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Granted: 1989-07-25
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Expires: 2008-08-31
Abstract
Abstract The invention relates to a method and apparatus to detect the superconductive state by measuring the change in the resistance of a sample. A dc magnetic field is imposed on the sample while the temperature is swept. The strength of the magnetic field is held below the critical value and is frequency modulated by the application of an ac field in such a way that total magnetic field is always positive. The resistance of the sample is measured incrementally as the temperature is swept and is phase detected at the modulation frequency. According to this embodiment, only magnetic field dependent changes demonstrating a precipitous drop in resistance identify a composition as superconductive.
Inventors
- 👤 Boris F. Kim
- 👤 Joseph Bohandy
- 👤 Kishin Moorjani
- 👤 Frank J. Adrain
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-08 22:57
CPC Classifications
G; G01; G01N; G01N27/00; G01N27/02; G01N27/04; G01N27/041; Y; Y10; Y10S; Y10S505/00; Y10S505/825; Y10S505/842; Y10S505/843
Claims Analysis
Total Claims: 41
Claim 1
Independent Claim
112 words
A method for detecting superconductivity and the superconductive phase transition comprising: providing a resistance measuring device; placing a sample within a device; imposing a magnetic field on the sample; sequentially changing one of the temperature of the sample and the magnetic field while maintaining the other below its critical value and while modulating one of said temperature and magnetic field at a known frequency in such a fashion that the total magnetic field is always positive; and measuring the resistance of the sample by phase detection at said modulating frequency; wherein only changes in resistance occuring at the modulating frequency and demonstrating a precipitous drop in resistance indicate the presence of superconductivity.
Claim 2
Independent Claim
112 words
A method for detecting superconductivity and the superconductive phase transition comprising: providing a resistance measuring device; placing a sample within a device; imposing a magnetic field on the sample; sequentially changing one of the temperature of the sample and the magnetic field while maintaining the other below its critical value and while modulating one of said temperature and magnetic field at a known frequency in such a fashion that the total magnetic field is always positive; and measuring the resistance of the sample by phase detection at said modulating frequency; wherein only changes in resistance occuring at the modulating frequency and demonstrating a precipitous drop in resistance indicate the presence of superconductivity.
Claim 3
Dependent Claim
18 words
A method according to claim 1, wherein the temperature is sequentially changed while the magnetic field is modulated.
Claim 4
Dependent Claim
23 words
A method according to claim 2, wherein the resistance measuring device is a resonant cavity and microwave power is imposed on the sample.
Claim 5
Dependent Claim
76 words
A method according to claim 3, wherein the measuring step comprises: recording the temperature at each change and producing first signals; measuring the amount of microwave power reflected from the cavity at each temperature change and producing second signals; comparing the second signals to the modulation frequency by phase detection and producing third signals; and plotting a series of coordinate points wherein one axis represents said first signals and the other axis represents said third signals.
Claim 6
Dependent Claim
29 words
A method according to claim 4, wherein the temperature is recorded and the reflected microwave power is measured only at equal preselected temperature increments in a linear temperature progression.
Claim 7
Dependent Claim
50 words
A method according to claim 5, wherein the imposed magnetic field is in the range of 30-5000 gauss, the modulation frequency is in the range of 1 Hertz-100 Kilo Hertz, the microwave power is in the range of 1-200 milliwatts and temperature increment is on the order of 0.2° C.
Claim 8
Dependent Claim
32 words
A method according to claim 4, wherein said first signal is the temperature and said third signal is a derivative of said phase detected reflected microwave power with respect to the temperature.
Claim 9
Dependent Claim
21 words
A method according to claim 7, wherein the precipitous drop resistance is expressed by a peak formed by the series of
Claim 10
Dependent Claim
17 words
A method according to claim 1, wherein the temperature is sequentially changed while the temperature is modulated.
Claim 11
Independent Claim
81 words
A method according to claims 2 or 9, wherein the temperature is sequentially changed and wherein the measuring step comprises: recording the temperature at each change and producing first signals; measuring the resistance of the sample at each temperature change and producing second signals; comparing the second signals to the modulation frequency by phase detection and producing third signals; and plotting a series of coordinate points wherein one axis represents said first signals and the other axis represents said third signals.
Claim 12
Dependent Claim
27 words
A method according to claim 10, wherein the temperature is recorded and the resistance is measured only at equal preselected temperature increments in a linear temperature progression.
Claim 13
Dependent Claim
30 words
A method according to claim 10, wherein said first signal is the temperature and said third signal is a derivative of said phase detected resistance with respect to the temperature.
Claim 14
Dependent Claim
46 words
A method according to claim 10, wherein the precipitous drop in resistance is expressed by a peak formed by the series of coordinate points and wherein T c is identified by the location of the peak in reference to said one axis representing said first signals
Claim 15
Dependent Claim
19 words
A method according to claim 1, wherein the magnetic field is sequentially changed while the magnetic field is modulated.
Claim 16
Dependent Claim
18 words
A method according to claim 1, wherein the magnetic field is sequentially changed while the temperature is modulated.
Claim 17
Independent Claim
87 words
A method according to claims 14 or 15, wherein the magnetic field is sequentially changed and wherein the measuring step comprises: recording the strength of the magnetic field at each change and producing first signals; measuring the resistance of the sample at each magnetic field change and producing second signals; comparing the second signals to the modulation frequency by phase detection and producing third signals; and plotting a series of coordinate points where one axis represents said first signals and the other axis represents said third signals.
Claim 18
Dependent Claim
31 words
A method according to claim 16, wherein the strength of the magnetic field is recorded and the resistance is measured only at equal preselected magnetic field increments in a linear progression.
Claim 19
Dependent Claim
35 words
A method according to claim 16, wherein said first signal is the strength of the magnetic field and said third signal is a derivative of said phase detected resistance with respect to the magnetic field.
Claim 20
Dependent Claim
24 words
A method according to claim 16, wherein the precipitous drop in resistance is expressed by a peak formed by the series of coordinate points.
Claim 21
Dependent Claim
29 words
A method according to claim 1, wherein the resistance measuring device is one of a resonant cavity, a resonant circuit, a two point probe and a four point probe.
Claim 22
Independent Claim
123 words
An apparatus for detecting superconductivity and the superconductive phase transition comprising: a resistance measuring device; means imposing a magnetic field on a sample within the device; means sequentially changing one of the temperature of the sample and the magnetic field while maintaining the other below its critical value; means modulating one of said temperature and magnetic field at a known frequency while one of said temperature and magnetic field is sequentially changed and in such a way that the total magnetic field is always positive; and means measuring the resistance of the sample by phase detection at said modulating frequency; wherein only changes in the resistance occurring at the modulating frequency and demonstrating a precipitous drop in resistance indicate the presence of superconductivity.
Claim 23
Independent Claim
123 words
An apparatus for detecting superconductivity and the superconductive phase transition comprising: a resistance measuring device; means imposing a magnetic field on a sample within the device; means sequentially changing one of the temperature of the sample and the magnetic field while maintaining the other below its critical value; means modulating one of said temperature and magnetic field at a known frequency while one of said temperature and magnetic field is sequentially changed and in such a way that the total magnetic field is always positive; and means measuring the resistance of the sample by phase detection at said modulating frequency; wherein only changes in the resistance occurring at the modulating frequency and demonstrating a precipitous drop in resistance indicate the presence of superconductivity.
Claim 24
Dependent Claim
18 words
An apparatus according to claim 20, wherein the temperature is sequentially changed while the magnetic field is modulated.
Claim 25
Dependent Claim
27 words
An apparatus according to claim 22, wherein the resistance measuring device is one of a resonant cavity, a resonant circuit, a two-point probe and a four-point probe.
Claim 26
Dependent Claim
27 words
An apparatus according to claim 23, wherein the resistance measuring device is a resonant cavity, wherein the apparatus includes means to impose microwave power on the sample.
Claim 27
Dependent Claim
103 words
An apparatus according to claim 24, wherein the means measuring comprises: means measuring the temperature of the sample; means to record the temperature at each change and produce first signals; a microwave detector measuring microwave power reflected from the cavity at each temperature change and producing second signals; a phase detector comparing the second signals to the modulation frequency by phase detection and producing third signals; an x-y recorder; and means combining said first and third signals to plot a series of coordinate points on the x-y recorder wherein one axis represents said first signals and the other axis represents said third signals.
Claim 28
Dependent Claim
32 words
An apparatus according to claim 25, wherein the means measuring the temperature is recorded and the reflected microwave power is measured only at equal preselected temperature increments in a linear temperature progression.
Claim 29
Dependent Claim
31 words
An apparatus according to claim 25, wherein the said first signal is a derivative of the temperature and said third signal is a derivative of said phase detected reflected microwave power.
Claim 30
Dependent Claim
46 words
An apparatus according to claim 27, wherein the precipitous drop in resistance is expressed by a peak formed by the series of coordinate points and wherein T c is identified by the location of the peak in reference to said one axis representing said first signals.
Claim 31
Dependent Claim
17 words
An apparatus according to claim 21, wherein the temperature is sequentially changed while the temperature is modulated.
Claim 32
Independent Claim
112 words
An apparatus according to claims 22 or 29, wherein the temperature is sequentially changed and wherein the means measuring comprises: means measuring the temperature of the sample; means to record the temperature at each change and produce first signals; a resistance measuring device measuring the resistance of the sample at each temperature change and producing second signals; a phase detector comparing the second signals to the modulation frequency by phase detection and producing third signals; an x-y recorder; and means combining said first and third signals to plot a series of coordinate points on the x-y recorder wherein one axis represents said first signals and the other axis represents said third signals.
Claim 33
Dependent Claim
30 words
An apparatus according to claim 30, wherein the means measuring the temperature is recorded and the resistance is measured only at equal preselected temperature increments in a linear temperature progression.
Claim 34
Dependent Claim
31 words
An apparatus according to claim 30, wherein the said first signal is the temperature and said third signal is a derivative of said phase detected resistance with respect to the temperature.
Claim 35
Dependent Claim
46 words
An apparatus according to claim 30, wherein the precipitous drop in resistance is expressed by a peak formed by the series of coordinate points and wherein T c is identified by the location of the peak in reference to said one axis representing said first signals.
Claim 36
Dependent Claim
19 words
An apparatus according to claim 21, wherein the magnetic field is sequentially changed while the magnetic field is modulated.
Claim 37
Dependent Claim
18 words
An apparatus according to claim 21, wherein the magnetic field is sequentially changed while the temperature is modulated.
Claim 38
Independent Claim
121 words
An apparatus according to claims 34 or 35, wherein the magnetic field is sequentially changed and the means measuring comprises: means measuring the strength or the magnetic field of the sample; means to record strength of the magnetic field at each change and produce first signals; a resistance measuring device measuring resistance of the sample at each change of the magnetic field and producing second signals; a phase detector comparing the second signals to the modulation frequency by phase detection and producing third signals; an x-y recorder; and means combining said first and third signals to plot a series of coordinate points on the x-y recorder wherein one axis represents said first signals and the other axis represents said third signals.
Claim 39
Dependent Claim
31 words
An apparatus according to claim 36, wherein the strength of the magnetic field is recorded and the resistance is measured only at equal preselected magnetic field increments in a linear progression.
Claim 40
Dependent Claim
35 words
An apparatus according to claim 36, wherein said first signal is the strength of the magnetic field and said third signal is a derivative of said phase detected resistance with respect to the magnetic field.
Claim 41
Dependent Claim
24 words
An apparatus according to claim 36, wherein the precipitous drop in resistance is expressed by a peak formed by the series of coordinate points.
References Cited (Backward Citations)
US4185237A
Cited
US4674513A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-07-24 | 1993-01-23 | 1993-07-25 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-07-24 | 1997-01-23 | 1997-07-25 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-07-24 | 2001-01-23 | 2001-07-25 | $7700.00 | Window Closed / Lapsed |