US4757261A
Expired / Lapsed
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Magnetic field homogeneity
Assignee: Varian Inc
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Filing: 1987-04-30
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Granted: 1988-07-12
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Expires: 2007-04-30
Abstract
Abstract An NMR instrument incorporating a cryogenic magnet includes a constant pressure device to maintain the pressure of cryogenic vapors at a constant value whereby a stable magnetic environment is maintained.
Inventors
- 👤 George D. Kneip, Jr.
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 20:51
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/38; G01R33/381; G01R33/3815; F; F17; F17C; F17C13/00; F17C13/02; F17C13/025; F17C2205/00; F17C2205/03; F17C2205/0302; F17C2205/0323; F17C2205/0326; F17C2205/0338; F17C2221/00; F17C2221/01; F17C2221/016; F17C2221/017; F17C2223/00; F17C2223/01; F17C2223/0146; F17C2223/0153; F17C2223/0161; F17C2223/03; F17C2223/033; F17C2250/00; F17C2250/04; F17C2250/0404; F17C2250/043; F17C2270/00; F17C2270/05; F17C2270/0527
Claims Analysis
Total Claims: 5
Claim 1
Independent Claim
77 words
NMR apparatus comprising: cryogenic-cooled magnet means for establishing a controlled magnetic field; RF excitation means to excite nuclear magnetic resonance in a sample subject to said magnetic field; detection means to detect a nuclear resonance signal from said sample; said cryogenic-cooled magnet means further comprising: a cryostat for maintaining a cryogen therewithin; vent means for exhausting cryogen vapor therefrom; and constant pressure means for maintaining the pressure of cryogen vapor within said cryostat at a selected value.
Claim 2
Dependent Claim
77 words
NMR apparatus comprising: cryogenic-cooled magnet means for establishing a controlled magnetic field; RF excitation means to excite nuclear magnetic resonance in a sample subject to said magnetic field; detection means to detect a nuclear resonance signal from said sample; said cryogenic-cooled magnet means further comprising: a cryostat for maintaining a cryogen therewithin; vent means for exhausting cryogen vapor therefrom; and constant pressure means for maintaining the pressure of cryogen vapor within said cryostat at a selected value.
Claim 3
Dependent Claim
19 words
The NMR apparatus of claim 1 wherein said constant pressure means comprises a differential pressure valve referenced to vacuum.
Claim 4
Dependent Claim
23 words
The NMR apparatus of claim 1 wherein said constant pressure means comprises a differential pressure valve referenced to a substantially thermally isolated spring.
Claim 5
Dependent Claim
69 words
The NMR apparatus of claim 1 wherein said constant pressure means comprises sensing means for ascertaining the pressure of said cryogen vapor and developing a pressure signal, comparator means for comparing said pressure signal to a reference whereby an error signal is generated and valve means cooperating with said vent means and responsive to said error signal to increase or decrease the gas flow impedance of said vent means.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1991-07-12 | 1992-01-11 | 1992-07-12 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1995-07-12 | 1996-01-11 | 1996-07-12 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1999-07-12 | 2000-01-11 | 2000-07-12 | $7700.00 | Window Closed / Lapsed |