31 results about "Saddle coil" patented technology

The invention relates to a radio frequency coil design method for transmitting array space coding imaging, and belongs to the technical field of magnetic resonance imaging. Aiming at the problems of low single-dimensional coding efficiency, strong coupling interference among coils and nonlinear phase gradient in the traditional TRASE technology, axial and radial coding coils are designed based on a target field method and a magnetic dipole method, two-dimensional radio frequency phase coding is realized through reverse current solenoid decoupling combination, and excitation and signal receiving are realized in combination with a saddle-shaped coil. According to the technical scheme, by optimizing the coil structure and the decoupling design, multi-dimensional efficient coding, high-precision phase gradient, strong anti-interference and light system weight are achieved, and the method is suitable for portable and dynamic monitoring scenes of low-field magnetic resonance.

The invention relates to the technical field of particle acceleration, in particular to a dipolar magnet, a combined magnet and a particle accelerator. The two-pole magnet comprises a first saddle-shaped winding and a second saddle-shaped winding which are oppositely arranged along the direction of a central ion beam current to form a main magnetic field structure; the pole head areas of the first saddle-shaped winding and the second saddle-shaped winding respectively extend towards the outer side far away from the central ion beam current direction to form an arch-shaped cavity penetrating through the two ends of the dipolar magnet; the runway-shaped coil comprises a first runway-shaped winding and a second runway-shaped winding, the first runway-shaped winding and the second runway-shaped winding are located in the arch-shaped cavity and correspond to the first saddle-shaped winding and the second saddle-shaped winding respectively, and the pole head area of the first runway-shaped winding and the pole head area of the second runway-shaped winding are adjacent to the pole head area of the saddle-shaped coil. While the contribution of the pole head position to the magnetic field of the good field area of the coil is ensured, the wire turn number density of the deflection section is obviously improved, thereby enhancing the magnetic field intensity.

The invention relates to the technical field of magnetic resonance, in particular to a multi-nuclear magnetic resonance coil device for small animals and a magnetic resonance system.The multi-nuclear magnetic resonance coil device comprises a first coil assembly, a second coil assembly, a third coil assembly and a fourth coil assembly, the resonant frequencies of the first saddle-shaped coil and the first solenoid coil correspond to a first atomic nucleus; the second coil group comprises a second saddle-shaped coil and a second solenoid coil which extend on a second cylindrical surface, and the resonant frequencies of the second saddle-shaped coil and the second solenoid coil correspond to second atomic nucleuses different from the first atomic nucleuses; the second cylindrical surface is coaxially positioned on the inner circumferential side of the first cylindrical surface; and the examination cavity is configured on the inner peripheral side of the second cylindrical surface and is used for accommodating the small animal.

Techniques and apparatus for determining quadrant-based locations of casing defects based on multi-frequency, non-collocated, induction measurements are described. An electromagnetic (EM) inspection tool is operated inside of a well including multiple casings. The EM inspection tool includes a triaxial transmitter and multiple triaxial receivers, each being located at a different spacing from the triaxial transmitter. The triaxial transmitter is configured to emit primary time-varying magnetic field signals in a radial direction, a tangential direction, and an axial direction. Each respective primary time-varying magnetic field signal induces corresponding secondary time-varying magnetic field signal(s) in the radial direction, the tangential direction, and the axial direction that are detected by one or more of the triaxial receivers. Induction measurements of the casings are obtained using the EM inspection tool, and a quadrant of a casing in which a defect of the casing is located is determined based on the induction measurements.

The invention discloses aerospace-grade vanadium-aluminum intermediate alloy material smelting equipment and a using method thereof.The aerospace-grade vanadium-aluminum intermediate alloy material smelting equipment comprises a hot melting furnace body, the top port of the hot melting furnace body is fixedly in butt joint with a deslagging assembly, the top port of the deslagging assembly is covered with a sealing cover, a magnetic pole array rotor assembly is installed below the sealing cover, and the bottom of the hot melting furnace body is a hemispherical shell; a plurality of saddle-shaped coils which are arranged in an annular array are embedded in the hemispherical shell; and a liftable liquid level adjusting block is mounted below the magnetic pole array rotor assembly. The invention relates to the technical field of smelting equipment. According to the method, the problems that in an existing vanadium-aluminum smelting technology, stirring dead angles are generated due to insufficient stirring capacity, so that macroscopic segregation and microcosmic segregation of alloy components are caused, and the requirement of aerospace-level materials for extreme uniformity cannot be met are solved.

The invention consists of a magnetic-inductive flowmeter (1) for determining a flow velocity-dependent measured quantity of a flowable medium, comprising: - a measuring tube (2) for guiding the medium; - two measuring electrodes (11, 12), - a coil system (3) for generating a magnetic field penetrating the measuring tube (2) at least section by section, wherein the coil system comprises at least one saddle coil (4a), wherein the at least one saddle coil (4a) has a saddle coil interior (5a), - a magnetic field guide (6) for guiding magnetic field lines outside the measuring tube (2), wherein the magnetic field guide (6) consists of a first field guide part (7a) and a second field guide part (7b) arranged opposite the first field guide part (7a), wherein the first field guidance part (7a) extends at least section by section into the saddle coil interior (5a), wherein the first field guidance part (7a) has an end section (EA) which is located in the saddle coil interior (5a) and which rests on the outer surface (MF) of the measuring tube (2), in particular directly, wherein in a cross-section (QS) through the at least one saddle coil (4a), the first field guidance part (7a) and the at least two measuring electrodes (11, 12) each point P located on a cross-sectional area (QS1) of the first field guidance part (7a) in the end section (EA) and each point Q located on a cross-sectional area (QS2) of the saddle coil (4a) spans a central angle δ which is greater than 12°, in particular greater than 17° and preferably greater than 22°, and less than 35°, in particular less than 32° and preferably less than 27°.

The invention provides a circularly polarized coil and a probe for a low-field magnetic resonance spectrometer, and relates to the field of magnetic resonance spectrums, and the circularly polarized coil comprises a group of orthogonal saddle-shaped coils and Helmholtz coils. The supporting structure and size of a single-turn coil are determined according to structural parameters of a detection target area, the optimal number of turns of the circularly polarized coil is determined by using Ansys Maxwell magnetic field simulation software, a CuSO4 solution is tested by using a self-developed circularly polarized probe in combination with a peripheral radio frequency circuit, and the performance of the circularly polarized coil is evaluated according to the test result. Experimental results show that compared with a single-channel saddle-shaped coil and a Helmholtz coil, the SNR of the combined circularly polarized coil is respectively improved by 28.78% and 29.21%, the transmitting power is saved by about 37.5%, and it is proved that the circularly polarized coil can effectively improve the performance of the desktop magnetic resonance spectrometer probe.

The application relates to a radio frequency coil design method for transmit array spatial encoding imaging, and belongs to the technical field of magnetic resonance imaging. In view of the problems of low single-dimension coding efficiency, strong coupling interference between coils and nonlinear phase gradient of a traditional TRASE technology, axial and radial coding coils are designed based on a target field method and a magnetic dipole method, two-dimensional radio frequency phase coding is realized through reverse current solenoid decoupling combination, and excitation and signal receiving are realized in combination with a saddle coil. Through optimization of the coil structure and decoupling design, the technical scheme achieves multi-dimensional efficient coding, high-precision phase gradient, strong anti-interference and system light weight, and is suitable for the portability and dynamic monitoring scene of low-field magnetic resonance.

The invention discloses a production process of a saddle type inductance coil, which comprises the following steps of: S1, winding a wire into a rectangular frame body structure through a winding unit, and then binding a plurality of positions of the frame body structure by adopting a high-temperature adhesive tape to obtain a flat shaping coil; s2, the flat shaping coil is conveyed to a workbench and arranged; s3, the flat shaping coil is heated and shaped into a saddle-shaped coil through a forming die of the forming unit; and S4, detecting and packaging the saddle-shaped coil. A flat shaping coil can be wound through the winding unit, then the flat shaping coil is shaped into a saddle-shaped coil through the forming die, pressing is convenient, and efficiency is high. The high-temperature adhesive tape is adopted to perform rubberizing protection on the easy-to-damage position of the coil, so that friction is reduced, and the damage risk of the wire is reduced, thereby protecting the insulating layer from being damaged. The mode that the coil is heated while constant-pressure downward pressing is adopted, the situation that an insulating layer is damaged due to the fact that contact pressure is too large is reduced, the contact pressure is more uniform, and the arc precision is higher.

The present application discloses a magnetic control coil, comprising: a coil support structure and N pairs of coil assemblies, wherein the coil assemblies are arranged in a planar manner along the surface of the coil support structure; N is an integer not less than 1. The present application employs a plurality of surface-type coils to replace conventional rectangular cross-section circular, racetrack-shaped, or saddle-shaped coils, which can enhance the generation efficiency of transverse magnetic fields, thereby effectively suppressing the introduction of impurities and the generation of defects during crystal manufacturing processes and improving the efficiency and quality of crystal manufacturing.

The invention relates to saddle coil winding apparatus, methods of manufacturing saddle coils, and saddle coils produced using the winding apparatus and / or manufacturing methods. The saddle coil winding apparatus and methods of manufacturing beneficially reduce or eliminate the stretching of electrical wires, and do not cause the electrical wires to slide past each other. The saddle coils produced using the winding apparatus and / or manufacturing methods may have electrical leads provided on the outside of the coil.

The utility model discloses a saddle-shaped coil winding device which comprises a winding framework, a saddle-shaped wire groove is formed in the peripheral wall of the winding framework, an inner ring framework is arranged in the middle of the saddle-shaped wire groove, the saddle-shaped wire groove comprises a plurality of groove sections which are sequentially connected in the circumferential direction of the saddle-shaped wire groove, and a plurality of pressing assemblies are arranged in the circumferential direction of each groove section. Each pressing assembly can move perpendicular to the peripheral edge of the corresponding groove section and press the superconducting wire entering the groove section to be attached to the groove bottom of the groove section. When the saddle-shaped coil is wound by the device, the compressing assembly arranged in the circumferential direction of the groove section moves and directly presses the superconducting wire in the groove section, so that the superconducting wire is tightly attached to the groove bottom of the groove section, the superconducting wire is fixedly arranged and limited in the groove section to be attached to the groove bottom, and the phenomenon that the superconducting wire rebounds or twists or the like is avoided; the superconducting wire is ensured to be stably located at the preset position in the groove section, and the winding success rate of the saddle-shaped coil is improved.

The invention relates to a method for manufacturing a saddle coil for a gradient coil unit comprising the process steps: - providing a stabilizing pad, a planar and at least partially spiral conductor structure unit and a room temperature curing adhesive, - applying the adhesive to a first side of the conductor structure unit and / or to a first surface of the stabilizing pad according to a defined pattern, - pressing the stabilizing pad with the conductor structure unit, wherein the first side of the conductor structure unit faces the first surface of the stabilizing pad.

The invention relates to a magnetic-inductive flow meter (1) for determining a flow velocity-dependent measured quantity of a flowable medium, comprising: - a measuring tube (2) for guiding the medium, wherein the measuring tube (2) has an outer surface; - at least two measuring electrodes (11, 12, 13, 14), - a measuring electronics (100), wherein the measuring electronics (100) is electrically connected to the at least two measuring electrodes and is configured to determine a measuring voltage; - a coil system (3) for generating a magnetic field that penetrates the measuring tube (2) at least partially, wherein the coil system (3) comprises at least one saddle coil (4), - a magnetic field guide (6) for guiding magnetic field lines outside the measuring tube (2), wherein the magnetic field guide (6) consists of a first field guide part (7a) and a second field guide part (7b) arranged opposite the first field guide part (7a), wherein the first and second field guide parts (7a, 7b) are completely separated by a gap (20), wherein the gap (20) is spanned in a cross-section through the magnetic-inductive flow meter (1) by a central angle α, for which 1° ≤ α ≤ 60°, in particular 5° ≤ α ≤ 40° and preferably less than 15°.

The invention relates to a method for manufacturing a saddle coil for a gradient coil unit comprising the following process steps: - providing a stabilizing layer, a planar and at least partially spiral conductor structure unit, and a powder designed to form a powder coating by heating; - applying the powder over a surface to a first surface of the stabilizing layer and / or applying the powder over a surface to a first side of the conductor structure unit, wherein the powder is exposed to a temperature between 140°C and 220°C and forms a coating film which at least partially wets the first surface and / or the first side; - fixing the conductor structure unit to the stabilizing layer by pressing the stabilizing layer with the conductor structure unit and by curing the coating film to form a powder coating.wherein the first side of the conductor structure unit faces the first surface of the stabilizing pad.

The disclosure relates to a method for producing a saddle coil for a gradient coil unit, comprising providing a stabilizing support, a planar and at least partially spiral-shaped conductor structure unit, and a powder designed to form a powder coating when heated; applying the powder as a surface layer to a first surface of the stabilizing support and / or as a surface layer to a first side of the conductor structure unit, the powder being exposed to a temperature of between 140° C. and 220° C. and forming a lacquer film that at least partially wets the first surface and / or the first side; and fixing the conductor structure unit to the stabilizing support by pressing the stabilizing support together with the conductor structure unit and by curing the lacquer film to form a powder coating, the first side of the conductor structure unit facing the first surface of the stabilizing support.

The invention provides a three-dimensional magnetic field coil design method suitable for magnetic compensation of a brain magnetic test area. The method comprises the following steps: S1, constructing an analytical model cylindrical coordinate system in the brain magnetic test area; s2, constructing a magnetic field analytical equation; s3, linearly superposing the barrel bottom fan-shaped coil pair and the barrel side saddle-shaped coil to form a radial coil based on a magnetic field analytical equation, and superposing the barrel side annular coil pair to form an axial coil, then optimizing the structural parameters of the radial coil and the axial coil based on an intelligent optimization algorithm, and constructing to obtain three groups of shimming coils and five groups of mutually independent linear gradient coils; and S4, describing interference magnetic field distribution in the brain magnetic test area through a vector spherical harmonic function, and adjusting the magnitude of current flowing in the coil so as to be matched with the interference magnetic field distribution. The method has the beneficial effects that the compensation coil capable of being highly matched with the magnetic field distribution trend of the brain magnetic test area under the interference condition can be designed, and the residual magnetic field in the single-end-opened cylindrical alloy barrel is accurately compensated.

A high-uniformity saddle-shaped shim coil design method for eliminating the magnetic shielding coupling effect, including decomposing the total magnetic induction intensity expression generated by the saddle-shaped coil group under the ferromagnetic boundary into two parts of the magnetic induction intensity generated by the coil group under the free boundary and the magnetic induction intensity generated by the coupling effect, obtaining the analytical expression of the magnetic induction intensity generated by the coil due to the coupling effect; through a multi-objective optimization algorithm, taking the ratio expression of the magnetic field generated by the coil due to the coupling effect to the magnetic field generated by the coil at the center under the ferromagnetic boundary and the ratio expression of the magnetic field generated by the coil under the ferromagnetic boundary to the magnetic field generated by the coil at the center as two objective functions, taking the straight line segment height, the circular arc segment spread angle and the coil turns and current of the four pairs of saddle-shaped coils as the optimization parameters for design, obtaining a set of optimal saddle-shaped coil group parameters, and eliminating the adverse effects of the coupling effect of the high magnetic permeability material on the coil generated magnetic field on the uniformity of the coil generated magnetic field from the source.

The invention provides a superconducting saddle-shaped coil framework structure which can be applied to the technical field of superconducting. The superconducting saddle-shaped coil framework structure comprises an inner supporting module which is constructed to be a saddle-shaped structure formed by twisting two opposite end portions of a three-dimensional runway-shaped annular structure, the outer side of the saddle-shaped structure is provided with a groove structure surrounding the saddle-shaped structure by a circle, and the groove bottom of the groove structure is provided with a supporting face matched with the outline of a radial inner layer of a saddle-shaped coil; the outer restraining module comprises at least one clamping block, and the clamping block is provided with a restraining face matched with the outline of the radial outer layer of the saddle-shaped coil; wherein the restraining surface and the supporting surface are oppositely arranged, and the restraining surface and the supporting surface are used for clamping the saddle-shaped coil under the condition that the clamping block is connected with the inner supporting module; the clamping blocks are detachably connected with the inner supporting module. The invention further provides a superconducting magnet and an assembly method thereof.

Techniques and apparatus for determining quadrant-based locations of casing defects based on multi-frequency, non-collocated, induction measurements are described. An electromagnetic (EM) inspection tool is operated inside of a well including multiple casings. The EM inspection tool includes a triaxial transmitter and multiple triaxial receivers, each being located at a different spacing from the triaxial transmitter. The triaxial transmitter is configured to emit primary time-varying magnetic field signals in a radial direction, a tangential direction, and an axial direction. Each respective primary time-varying magnetic field signal induces corresponding secondary time-varying magnetic field signal(s) in the radial direction, the tangential direction, and the axial direction that are detected by one or more of the triaxial receivers. Induction measurements of the casings are obtained using the EM inspection tool, and a quadrant of a casing in which a defect of the casing is located is determined based on the induction measurements.

The present application discloses a dual-channel radio frequency coil and a design method thereof, relating to the field of magnetic resonance imaging technology. The dual-channel radio frequency coil includes a solenoid coil and a saddle coil located outside the solenoid coil; the solenoid coil includes a spiral ring coil winding and a wire component; the spiral ring coil winding includes a plurality of turns of spiral ring coil; the saddle coil includes a first saddle coil group, a second saddle coil group and a matching circuit; the matching circuit includes a tuning component, a first coil assembly, a first tuning network capacitor, a first balun, a matching excitation element, a second balun, a second tuning network capacitor and a second coil assembly connected in sequence; the first coil assembly is connected to the first saddle coil group. The present application can improve signal receiving capability and imaging uniformity.

The invention relates to a magnetic-inductive flow meter (1), comprising: a measuring tube (2) for a conducting medium, the measuring tube (2) being divided into a first side and a second side by a longitudinal plane (LE) and having an outer side surface; -a magnetic field generating device (3), the magnetic field generating device (3) comprising: at least one saddle coil (4) arranged on the outer side surface, the coil wires of the saddle coil (4) defining a saddle coil interior (5), and a saddle coil core assembly (6) having at least one saddle coil core (7), the saddle coil core assembly (6) being arranged in the saddle coil interior (5), a minimum circular sector in which the saddle-shaped coil core assembly (6) is arranged is spanned through a central angle in a cross-section of the magnetic inductive flowmeter (1), the following being adapted for the central angle; and-at least four measuring electrodes (11, 12, 13, 14), at least two measuring electrodes (11, 13) of the at least four measuring electrodes (11, 12, 13, 14) being arranged on a first side and likewise at least two measuring electrodes (12, 14) of the at least four measuring electrodes (11, 12, 13, 14) being arranged on a second side, the central angle spans the smallest circular sector in the cross-section of the at least two measuring electrodes (12, 14) in which the first side is arranged, wherein the following are adapted for the central angle.

The application discloses a kind of based on array structure's magnetic field coil hybrid optimization design method, the multiple saddle coils are combined into coil array by the method, and on the basis of considering the coupling effect of high magnetic permeability material to coil magnetic field, the mathematical model of the magnetic field of single coil is solved, and the mathematical model of the magnetic field of saddle coil array is obtained according to superposition principle.The mathematical model is used to combine particle swarm optimization algorithm to optimize the best current integer ratio between the saddle coils in array, the current integer ratio of coil is converted into the linear combination of the number of turns and current of each coil, and particle swarm optimization algorithm is used again to optimize the minimum number of turns and optimal current required by each coil.Finally, the optimized magnetic field coil is generated by the coil path planning of depth-first search strategy.The application greatly improves the uniformity of coil, has no discretization error and simple structure, and is convenient for practical application.

The invention relates to a superconducting dipolar magnet structure for a particle accelerator, which comprises two saddle-shaped coils and two runway-shaped coils which are formed by winding superconducting cables, and the coils jointly form a particle beam channel with a rectangular cross section; the two saddle-shaped coils are arranged in a mirror symmetry mode, and the runway-shaped coils are arranged at the positions of middle pole heads in the saddle-shaped coils respectively. The superconducting dipolar magnet structure for the particle accelerator is formed by winding the superconducting cable, the magnetic field intensity is high, only a refrigerating machine needs to maintain a low-temperature environment, the energy consumption is low, an iron core can be added or not added, and the size and the weight are remarkably reduced.

The utility model discloses a coil forming frock includes: lower base, the lower base has first forming part and second forming part, the first forming part is arc structure, and the second forming part is horizontal structure, upper pressure seat, the upper pressure seat has first lower pressure part and second lower pressure part, the first lower pressure part with first forming part position corresponds and shape adaptation, and second lower pressure part with second forming part position corresponds and shape adaptation, and the upper pressure seat is configured as can move towards lower base direction, heating piece, heating piece sets up in lower base, to heat lower base, the utility model can solve the problem that traditional saddle coil exists and is pressed into shape difficultly, and the problem of low pressing forming efficiency.

The invention relates to a magnetic-inductive flow meter (1) for determining a flow-rate-based measurement variable of a flowable medium, comprising: - a measuring tube (2) for guiding the medium, the measuring tube (2) having an outer lateral surface; - at least two measuring electrodes (11, 12, 13, 14), - measuring electronics (100), the measuring electronics (100) being electrically connected to the at least two measuring electrodes and being designed to determine a measurement voltage; - a coil system (3) for generating a magnetic field which at least partly passes through the measuring tube (2), the coil system (3) comprising at least one saddle coil (4), and - a magnetic field guide (6) for guiding magnetic field lines outside the measuring tube (2), the magnetic field guide (6) consisting of a first field guide part (7a) and a second field guide part (7b) lying opposite the first field guide part (7a), the first and second field guide parts (7a, 7b) being completely separated by a gap (20), the gap (20) being spanned, in a cross-section of the magnetic-inductive flow meter (1), by a central angle α, for which the following applies: 1° ≤ α ≤ 60°, in particular 5° ≤ α ≤ 40°, α preferably being less than 15°.

The invention discloses a double-resonance transceiving separation device for magnetic resonance deuterium metabolism imaging, which comprises four supporting cylinders, the supporting cylinders are sequentially connected in a sleeving manner to form a layer structure, a radio frequency shielding layer supporting cylinder is arranged on the outermost layer, and a radio frequency shielding layer is arranged on the radio frequency shielding layer supporting cylinder; the 1H high-pass birdcage coil supporting cylinder is arranged on the second layer, and a 1H high-pass birdcage coil is arranged on the 1H high-pass birdcage coil supporting cylinder; a 2H saddle coil supporting cylinder is arranged on the third layer, and a 2H saddle coil is arranged on the 2H saddle coil supporting cylinder; the 2H double-array receiving coil supporting cylinder is arranged on the innermost layer, and a 2H double-array receiving coil is arranged on the 2H double-array receiving coil supporting cylinder; the 2H saddle coil and the 2H double-array receiving coil are respectively provided with a detuning circuit. According to the device, a double-resonance mode is adopted, and errors caused by replacement of resonance coils in 1H and 2H imaging experiments of traditional nuclear magnetic resonance are eliminated.

The present application relates to a SQUID-based radiofrequency detection and acquisition system and to an apparatus comprising the same. The radiofrequency detection and acquisition system, based on SQUIDs and arranged to be integrated into a nuclear magnetic resonance apparatus, comprises: a main detection antenna; a flux transformer, the flux transformer having an input winding connected to the main detection antenna; a low critical temperature SQUID device, the low critical temperature SQUID device capturing the magnetic flux generated by the output winding of the flux transformer and supplying a secondary detection signal; a cryogenic device, the cryogenic device cooling the SQUID device and the flux transformer; and a step of processing the secondary detection signal emitted by the SQUID device so as to supply an analog acquisition signal. The main detection antenna is of the volume type, comprising a Helmholtz coil or a saddle coil, or more complex volume geometries, in particular gradiometer geometries, and the step of processing the secondary detection signal comprises a flux-locked loop, the flux-locked loop being arranged to linearize the response of the SQUID device.

The present application discloses a magnetic resonance radio frequency array coil having multiple orthogonal coil pairs, including at least two orthogonal coil pairs arranged sequentially along a first direction. Each orthogonal coil pair is respectively composed of an annular coil and a saddle coil arranged insulated from the annular coil. The saddle coil is an "8"-shaped structure composed of a first coil body and a second coil body that are connected to each other and arranged sequentially along the first direction. Two annular coils of any two adjacent orthogonal coil pairs partially overlap for decoupling, and two saddle coils of any two adjacent orthogonal coil pairs partially overlap for decoupling. The radio frequency array coil of the present application optimizes the structures and distribution manners of the respective coil pairs, thereby improving the overall performance of the radio frequency array coil.

A shielded gradient coil assembly (40) to generate a gradient magnetic field, the assembly comprises on a plurality of radially inner and outer coaxial cylindrical surfaces a gradient field coil arrangement on the radially inner cylindrical surfaces including a longitudinal gradient field coil system (131) having one or more axial circumferential electrically conducting hollow z-field windings having a smaller transverse cross-section and a transverse gradient field coil system (132) having hollow (x,y)—field electrical conductors having a smaller transverse cross-section and arranged as saddle coils on the surfaces of the inner cylindrical surfaces. A gradient shield coil arrangement is provided on the radially outer cylindrical surfaces including a longitudinal gradient shield coil system (141) having one or more axial circumferential electrically conducting hollow z-shield windings having a larger transverse cross-section and a transverse gradient shield coil system (142) having solid electrical conductors arranged as saddle coils on the surfaces of the outer cylindrical surfaces. In this way an optimum combination is achieved of efficient direct and indirect cooling of the conductors while keeping eddy current effects at a low level.