EP0140535A2
Expired / Lapsed
EP
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Apparatus for measuring the magnitude of a magnetic field
Assignee: Texas Instruments Inc
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Filing: 1984-08-30
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Granted: —
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Expires: 2004-08-30
Abstract
Abstract @ An apparatus for measuring the magnitude of a magnetic field in one embodiment includes a 3 He cell 16 having an oscillator 18 connected thereto for producing an electrical discharge for metastable 3 He atoms, a "He lamp 22 having a lamp oscillator 26 connected thereto for producing 4 He radiation and an optical path to the 3 He cell including a lens 28 for collimating the 4 He radiation and a circular polarizer 30. The imaged 3 He atoms and 4 He radiation interact to magnetize a portion of the 3 He atoms in a direction parallel to the direction of the ambient magnetic field. After the cell magnetization, an oscillatory magnetic field normal to the ambient field is established by coils 32 and 34 connected to a frequency synthesizer 42 which is scanned over a frequency interval including the free precession (Larmor) frequency. This action rotates the direction of magnetization of the 3 He cell atoms from parallel to the ambient magnetic field to approximately perpendicular to the ambient magnetic field. The cell 16 then is allowed to precess freely and an a.c. is induced in a pick up coil 44 during precession. The a.c. is connected to a frequency discriminator 50 which may be a digital type to digitize the voltage representative of the frequency of the a.c.. A very narrow band digital filter 54 filters the digitized output of the discriminator 50 and a digital to analog converter 56 produces a voltage from the digital filter output for a charge recorder 58 for charting.
Inventors
- 👤 Douglas D. Mcgregor
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-10 01:46
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/24; G01R33/26
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
99 words
Apparatus for rotating nuclear magnetization comprising a sensor means for sensing the ambient magnetic field and a signal processing means operatively connected to the sensor means for producing signals representative of changes thereto, the sensor means including a cell means containing a working substance, a discharge and radiation means operatively connected to the cell means for establishing a magnetization in a first direction, a moment rotation producing means operatively connected to the cell for a preselected time for making the magnetization a precessing magnetization having a second direction, and magnetic pickup means for sensing precessing magnetization of the cell.
Claim 2
Dependent Claim
99 words
Apparatus for rotating nuclear magnetization comprising a sensor means for sensing the ambient magnetic field and a signal processing means operatively connected to the sensor means for producing signals representative of changes thereto, the sensor means including a cell means containing a working substance, a discharge and radiation means operatively connected to the cell means for establishing a magnetization in a first direction, a moment rotation producing means operatively connected to the cell for a preselected time for making the magnetization a precessing magnetization having a second direction, and magnetic pickup means for sensing precessing magnetization of the cell.
Claim 3
Independent Claim
105 words
An apparatus for measuring the magnitude of a magnetic field comprising: sensor means for sensing the ambient magnetic field and a signal processing means operatively connected to the sensor means for producing signals representative of changes in the ambient magnetic field, the sensor means including a cell means having a cell containing a working substance, means for establishing a magnetization in the working substance parallel to the ambient magnetic field, a moment rotation means operatively connected to the cell a preselected time for making the magnetization a precessing magnetization having a second direction, and a magnetic pickup means for sensing precessing magnetization of the cell.
Claim 4
Independent Claim
105 words
An apparatus for measuring the magnitude of a magnetic field comprising: sensor means for sensing the ambient magnetic field and a signal processing means operatively connected to the sensor means for producing signals representative of changes in the ambient magnetic field, the sensor means including a cell means having a cell containing a working substance, means for establishing a magnetization in the working substance parallel to the ambient magnetic field, a moment rotation means operatively connected to the cell a preselected time for making the magnetization a precessing magnetization having a second direction, and a magnetic pickup means for sensing precessing magnetization of the cell.
Claim 5
Dependent Claim
119 words
An apparatus according to Claim 2 wherein the cell and working substance in the cell are, respectively, a glass cell and 3He gas under a preselected pressure and the means for establishing the magnetization in the cell comprises an oscillator operatively connected to the glass cell for producing metastable 3He atoms, a 4He lamp, an oscillator operatively connected to the 4He lamp and an optical path from the 4He lamp to the cell including a circular polarizer optically connected to the glass cell for producing 4He radiation whereby the interaction of the 4He light and the 3 He atoms magnetizes at least a portion of the 3He atoms in a direction parallel to the direction of the ambient field.
Claim 6
Dependent Claim
73 words
An apparatus according to Claim 2 wherein the moment rotation means comprises a plurality of coils circumscribing the cell and a scanning frequency synthesizer operatively connected to the coils whereby the coils are driven by the scanned frequency of the frequency synthesizer through a frequency range containing the 3He free precession frequency and rotates the cell magnetization from a direction substantially parallel to the ambient magnetic field into a plane substantially normal thereto.
Claim 7
Dependent Claim
52 words
An apparatus according to Claim 2 wherein the signal producing means comprises a frequency discriminator for producing a signal corresponding to the output signal of the sensor means, a filter means operatively connected to the frequency discriminator for providing a filtered time signal, and a chart recorder operatively connected to the filter.
Claim 8
Independent Claim
103 words
A method for measuring the magnitude of a magnetic field consisting of the steps of: a) magnetizing the atoms of a working substance in a direction substantially parallel to the direction of the ambient magnetic field; b) inducing an oscillatory magnetic field substantially normal to the ambient magnetic field; c) thereafter permitting free precession of the cell magnetization; d) inducing signals representative of the oscillatory magnetic field during free precession; and e) producing an output voltage proportional to the frequency deviation of the induced signals from a reference frequency, which is usually chosen as the Larmor frequency of the average ambient magnetic field.
Claim 9
Independent Claim
103 words
A method for measuring the magnitude of a magnetic field consisting of the steps of: a) magnetizing the atoms of a working substance in a direction substantially parallel to the direction of the ambient magnetic field; b) inducing an oscillatory magnetic field substantially normal to the ambient magnetic field; c) thereafter permitting free precession of the cell magnetization; d) inducing signals representative of the oscillatory magnetic field during free precession; and e) producing an output voltage proportional to the frequency deviation of the induced signals from a reference frequency, which is usually chosen as the Larmor frequency of the average ambient magnetic field.
Claim 10
Dependent Claim
55 words
An apparatus according to Claim 6 wherein the step of inducing an oscillatory magnetic field substantially normal to the ambient magnetic field consists of applying a scanning frequency including the free precession frequency of the working substance to an induction coil for rotating the magnetized atoms substantially normal to the direction of the ambient field.
References Cited (Backward Citations)
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