Patent US4833433A successfully refreshed from Google Patents.
US4833433A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Magnet system for nuclear spin tomography having superconducting coils and a cold shield
Assignee: Siemens AG
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Filing: 1988-04-21
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Granted: 1989-05-23
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Expires: 2008-04-21
Abstract
Abstract A magnet system for a nuclear spin tomography installation contains annular superconducting coils for generating a magnetic background field and nonsuperconducting gradient coils. A hollow cylindrical thermal shield fits between the gradient coils and the superconducting coils. According to the invention, the thermal shield at the front faces is formed from tubular end pieces. The front faces have a greater specific electrical resistance than a tubular intermediate piece of the thermal shield that extends between the end pieces and cover at least the area of the gradient coils.
Inventors
- 👤 Dieter Schmettow
- 👤 Guenter Ries
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-23 13:18
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/28; G01R33/38; G01R33/381; G01R33/3815
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
194 words
A magnet system for a nuclear spin tomography installation, comprising: at least one pair of annular superconducting coils for generating a homogenous background magnetic field; a protective arrangement for bridging each of said pair of superconducting coils at two front faces of said magnetic system in the event that at least one of said coils unintentionally transists to a nonsuperconducting state; gradient coils that are nonsuperconducting for developing magnetic field gradients; a thermal shield formed from a hollow cylinder that axially extends between the gradient coils and the superconducting coils at least to the front faces of the magnet system, the thermal shield having a specific predetermined electrical resistance; tubular end pieces of the thermal shield at the front faces, the end pieces being formed from a material that has a first predetermined specific electrical resistance which is greater than a second prredetermined specific electrical resistance of the thermal shield at its operating temperature; and the thermal shield comprises at least one intermediate piece that is tubular and extends between the end pieces to cover at least the gradient coils said intermediate piece being made of a material having said second specific electrical resistance.
Claim 2
Dependent Claim
194 words
A magnet system for a nuclear spin tomography installation, comprising: at least one pair of annular superconducting coils for generating a homogenous background magnetic field; a protective arrangement for bridging each of said pair of superconducting coils at two front faces of said magnetic system in the event that at least one of said coils unintentionally transists to a nonsuperconducting state; gradient coils that are nonsuperconducting for developing magnetic field gradients; a thermal shield formed from a hollow cylinder that axially extends between the gradient coils and the superconducting coils at least to the front faces of the magnet system, the thermal shield having a specific predetermined electrical resistance; tubular end pieces of the thermal shield at the front faces, the end pieces being formed from a material that has a first predetermined specific electrical resistance which is greater than a second prredetermined specific electrical resistance of the thermal shield at its operating temperature; and the thermal shield comprises at least one intermediate piece that is tubular and extends between the end pieces to cover at least the gradient coils said intermediate piece being made of a material having said second specific electrical resistance.
Claim 3
Dependent Claim
40 words
A magnet system as claimed in claim 1, wherein the first predetermined specific electrical resistance of the material comprising the end pieces is at least five times greater thanthe second specific electrical resistance of the material comprising the intermediate piece.
Claim 4
Dependent Claim
41 words
A magnet system as claimed in claim 1, wherein the first predetermined specific electrical resistance of the material comprising the end pieces is at least ten times greater than the second specific electrical resistance of the material comprising the intermediate piece.
Claim 5
Dependent Claim
35 words
A magnet system as claimed in claim 1, wherein the thermal shield comprises a continuous tube that extends to the front faces of the end pieces, in which the tubular intermediate piece is concentrically arranged.
Claim 6
Dependent Claim
25 words
A magnet system as claimed in claim 1, wherein the intermediate piece comprises aluminum of high purity and the end pieces comprise an aluminum alloy.
Claim 7
Dependent Claim
155 words
A magnet system for a nuclear spin tomography installation, comprising: a least one pair of annular superconducting coils for generating a homogeneous background magnetic field; a protective arrangement for bridging each of said pair of superconducting coils at two front faces of said magnetic system in the event that at least one of said coils unintentionally transits to a nonsuperconducting state; gradient coils that are nonsuperconducting for developing magnetic field gradients; a thermal shield formed from a hollow cylinder that axially extends beween the gradient coils and the superconducting coils at least up to the front faces of the magnet system, the thermal shield being made of a material that is a good electrical conductor; tubular end pieces at the two front faces, the end pieces having slits cut over their entire axial extent; and at least one intermediate piece that is tubular extending between the end pieces and covering at least the gradient coils.
Claim 8
Dependent Claim
155 words
A magnet system for a nuclear spin tomography installation, comprising: a least one pair of annular superconducting coils for generating a homogeneous background magnetic field; a protective arrangement for bridging each of said pair of superconducting coils at two front faces of said magnetic system in the event that at least one of said coils unintentionally transits to a nonsuperconducting state; gradient coils that are nonsuperconducting for developing magnetic field gradients; a thermal shield formed from a hollow cylinder that axially extends beween the gradient coils and the superconducting coils at least up to the front faces of the magnet system, the thermal shield being made of a material that is a good electrical conductor; tubular end pieces at the two front faces, the end pieces having slits cut over their entire axial extent; and at least one intermediate piece that is tubular extending between the end pieces and covering at least the gradient coils.
Claim 9
Dependent Claim
52 words
A magnet system as claimed in claim 6, wherein the slits in the end pieces are of such number and uniformly distributed over a circumference as to form segments having a width remaining in the circumferential direction of the end pieces that is maximally equal to the axial extent of the slits.
Claim 10
Dependent Claim
25 words
A magnet system as claimed in claim 7, wherein the width of the segments is maximally one half of the axial extent of the slits.
Claim 11
Dependent Claim
24 words
A magnet system as claimed in claim 6, wherein the thermal shield has slits worked into it from the direction of the front faces.
Claim 12
Dependent Claim
28 words
A magnet system as claimed in claim 1, wherein the intermediate piece axially extends to a particular region given by the axial extent of the particular superconducting coil.
Claim 13
Dependent Claim
29 words
A magnet system as claimed in claim 1, wherein the intermediate piece extends into the vicinity of the axial center of the particular region at its two axial ends.
Claim 14
Dependent Claim
28 words
A magnet system as claimed in claim 6, wherein the intermediate piece axially extends to a particular region given by the axial extent of the particular superconducting coil.
Claim 15
Dependent Claim
29 words
A magnet system as claimed in claim 12, wherein the intermediate piece extends into the vicinity of the axial center of the particular region at its two axial ends.
Claim 16
Dependent Claim
35 words
A magnet system as claimed in claim 1, wherein the thermal shield comprises a continuous tube that extends to the front faces of the end pieces, around which the tubular intermediate piece is concentrically arranged.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1992-05-22 | 1992-11-21 | 1993-05-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1996-05-22 | 1996-11-21 | 1997-05-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2000-05-22 | 2000-11-21 | 2001-05-23 | $7700.00 | Window Closed / Lapsed |