Abstract: A lithographic apparatus is arranged to transfer a pattern from a patterning device onto a substrate. The lithographic apparatus includes an acoustical sensor to measure a first acoustic vibration in a sensor measurement area in the lithographic apparatus. An actuator is provided to generate a second acoustic vibration in at least an area of the lithographic apparatus. Further, a control device is provided having a sensor input to receive a sensor signal of the acoustical sensor and an actuator output to provide an actuator drive signal to the actuator. The control device is arranged to drive the actuator so as to let the second acoustic vibration at least partly compensate in the area the first acoustic vibration.

Abstract: In an embodiment, a lithographic apparatus includes an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate, and a passive noise damper configured to dampen gas borne noise caused by movement of a movable part of the lithographic apparatus.

Abstract: The invention relates to a magnetic resonance imaging system which comprises means for generating a static magnetic field and a gradient coils system for generating a time varying magnetic gradient field by use of a first electrical current and a second electrical current. The gradient coils system is located in the magnetic field and the gradient coils system has a plurality of vibrational modes. Lorentz forces are generated due to the interaction of the first and/or second electrical currents with the superposition of the static magnetic field and the magnetic gradient field. The gradient coils system and/or the first electrical current are adapted so that the integral of the in-products of said Lorentz forces and a vibrational mode of said plurality of vibrational modes is at a value close to zero, wherein said in-products are determined for all points of the gradient coils system, and wherein the integral is determined by summing the in-products determined for all the points.

Abstract: In an embodiment, a lithographic apparatus includes an illumination system configured to condition a radiation beam; a support constructed to support a patterning device, the patterning device being capable of imparting the radiation beam with a pattern in its cross-section to form a patterned radiation beam; a substrate table constructed to hold a substrate; a projection system configured to project the patterned radiation beam onto a target portion of the substrate, and a passive noise damper configured to dampen gas borne noise caused by movement of a movable part of the lithographic apparatus.

Abstract: A lithographic apparatus is arranged to transfer a pattern from a patterning device onto a substrate. The lithographic apparatus includes an acoustical sensor to measure a first acoustic vibration in a sensor measurement area in the lithographic apparatus. An actuator is provided to generate a second acoustic vibration in at least an area of the lithographic apparatus. Further, a control device is provided having a sensor input to receive a sensor signal of the acoustical sensor and an actuator output to provide an actuator drive signal to the actuator. The control device is arranged to drive the actuator so as to let the second acoustic vibration at least partly compensate in the area the first acoustic vibration.

Abstract: A magnetic resonance imaging (MRI) system (1) with an active vibration control is provided, in that a number of piezo-electric actuators (6) are positioned between at least one element (2, 3, 5, 9, 10) of the MRI system (1) and an associated support surface (8) and being connected in series with each other; and a control unit (11, 11?) is adapted to actively control the displacement of the number of piezo-electric actuators (6) in a way that unintentional mechanical movements of the MRI system (1) are reduced.

Abstract: The invention provides a magnetic resonance imaging (MRI) device (21), comprising a diagnostic space (25), a main magnetic system (22) for generating a main magnetic field in said diagnostic space, a gradient magnetic coil system (23) comprising a gradient coil for generating at least one gradient of the main magnetic field, and noise reducing means (29, 32) for reducing noise that is generated as a result of vibrations of the gradient coil. The noise reducing means comprise a sound-absorbing panel (29) disposed between the gradient coil and the diagnostic space. The sound-absorbing panel (29) comprises channels having an open end and a closed end.

Abstract: The invention relates to a magnetic resonance imaging (MRI apparatus comprising a main magnetic system for generating a main magnetic field in an examination volume which is enclosed by the main magnetic system. The MRI apparatus also comprises a magnetic gradient coil system comprising gradient coils. The gradient coil system is accommodated between the main magnetic system and the examination volume in order to generate gradients of the main magnetic field. The MRI apparatus also comprises a vacuum space. According to the invention, the gradient coil system only partly adjoins the vacuum space, that is, by way of its side which faces the vibrations caused by the gradient coil system in operation, while, in a specific embodiment, the end sides of the gradient coil system are available for electrical and mechanical connections outside the vacuum space.

Abstract: The present invention relates to a magnetic resonance imaging (MRI) device. The basic components of an MRI device are the main magnet system (2), the gradient system (3), the RF system and the signal processing system. According to the present invention, the magnetic resonance imaging (MRI) device has an eddy current shield system, wherein the eddy current shield system comprises at least one perforated eddy current screen (13, 14), and wherein the or each perforated eddy current screen (13, 14) is assigned to the main magnet system (2).

Abstract: The invention relates to an MRI system (1) comprising an examination volume (11), a main magnet system (13) for generating a main magnetic (field (B0) in the examination volume, a gradient magnet system (19) for generating gradients of the main magnetic field, and an anti-vibration system (39) for reducing vibrations of the gradient magnet system. According to the invention the anti-vibration system comprises a gyroscope (41) which is mounted to the gradient magnet system. As a result of the gyroscopic effect of the gyroscope, the vibrations of the gradient magnet system are effectively reduced. In an open type MRI system (1) according to the invention, a separate gyroscope (41, 43) is mounted to each of the two portions (21, 23) of the gradient magnet system (19), and each gyroscope has an axis of rotation (61) parallel to the main direction (Z) of the main magnetic field (B0).

Abstract: The invention relates to an open magnetic resonance imaging (MRI) magnet system (1) for use in a medical imaging system. The open MRI magnet system has two main coil units which are accomodated, at some distance from each other, in a first housing (2) and in a second housing (3), respectively. Between the two housings, an imaging volume (6) is present wherein a patient to be examined is placed. A gradient coil unit (9, 10) facing the imaging volume is present near a side of each of the two housings. Functional connections of the gradient coil units (9, 10), such as electrical power supply lines (13, 14) and cooling channels (15, 16) are provided in a central passage (4, 5) which is present in each of the two housings. As a result, these functional connections do not reduce the space in the imaging volume available for the patient.

Abstract: The invention relates to a magnetic resonance imaging (MRI) system (1) comprising an examination volume (11), a main magnet system (13) for generating a main magnetic field (B0) in the examination volume in a Z-direction, a gradient magnet system (19) for generating gradients of the main magnetic field, and an anti-vibration system (33) for reducing vibrations of the gradient magnet system caused by a mechanical load (MX, MY) exerted on the gradient magnet system as a result of electromagnetic interaction between the main magnetic field and electrical currents in the gradient magnet system. According to the invention the anti-vibration system (33) comprises a balance member (39), which is coupled to the gradient magnet system (19) by means of an actuator system (51) and a coupling device (49) allowing displacements of the balance member relative to the gradient magnet system.

Abstract: The invention relates to a magnetic resonance imaging (MRI) system (1) comprising an examination volume (11), a main magnet system (17) for generating a magnetic field (B0) in the examination volume, and a gradient magnet system (25) for generating altering gradients of the magnetic field in the examination volume. The gradient magnet system is accommodated in a housing (31) having a main wall (33) facing the examination volume and a substantially conical wall (35) facing away from the examination volume. The main wall and the conical wall enclose a substantially angular tip portion (47) of the housing. In order to limit the level of the acoustic vibrations in and around the MRI system (1) caused by mechanical vibrations of the angular tip portion (47), the MRI system comprises a plurality of acoustic resonators (55) which each comprise an elongate resonance volume (57) with an open end (59) and a closed end (61) and a length (L) between the open end and the closed end.

Abstract: Vibrations of the gradient coil carrier (18) medical MRI apparatus should be counteracted because they give rise to disturbing noise and macroscopic movements that deteriorate the image quality. In accordance with the invention the gradient coil system is suspended by means of weak resilient suspension elements (22) that are connected in series with piezo actuators (21). The actuators are controlled in such a way that macroscopic movements at low-frequency vibrations (order of magnitude of 10 Hz) that are due to the very resilient suspension are counteracted, and also that the high-frequency vibrations (order of magnitude of 700 Hz) that result from internal Lorentz forces are hardly transferred to the frame of the apparatus.

Abstract: The transfer of vibrations that generate noise should be avoided in medical MRI apparatus. In accordance with the invention the gradient coil system 40 is suspended by means of suspension elements 48 whose transverse stiffness is much smaller than their axial stiffness. Such suspension elements should be attached to the coil carrier 40 at a vibration-free point, that is, a point that does not exhibit vibrations in all three co-ordinate directions. The longitudinal direction of the suspension element 48 should coincide with the vibration-free direction. Preferably, the suspension element is provided with an active drivable element 37 (a piezo element) for virtually reducing the stiffness of the suspension element in the axial direction, thus compensating also for residual vibrations that could still be present in the vibration-free direction.

Abstract: Vibrations of the gradient coil carrier (18) medical MRI apparatus should be counteracted because they give rise to disturbing noise and macroscopic movements that deteriorate the image quality. In accordance with the invention the gradient coil system is suspended by means of weak resilient suspension elements (22) that are connected in series with piezo actuators (21). The actuators are controlled in such a way that macroscopic movements at low-frequency vibrations (order of magnitude of 10 Hz) that are due to the very resilient suspension are counteracted, and also that the high-frequency vibrations (order of magnitude of 700 Hz) that result from internal Lorentz forces are hardly transferred to the frame of the apparatus.

Abstract: The transfer of vibrations that generate noise should be avoided in medical MRI apparatus. In accordance with the invention the gradient coil system 40 is suspended by means of suspension elements 48 whose transverse stiffness is much smaller than their axial stiffness. Such suspension elements should be attached to the coil carrier 40 at a vibration-free point, that is, a point that does not exhibit vibrations in all three co-ordinate directions. The longitudinal direction of the suspension element 48 should coincide with the vibration-free direction. Preferably, the suspension element is provided with an active drivable element 37 (a piezo element) for virtually reducing the stiffness of the suspension element in the axial direction, thus compensating also for residual vibrations that could still be present in the vibration-free direction.

Abstract: A lamp electronic ballast with a piezoelectric cooling fan. Use of ballast-driven lamps is limited in some lighting applications by thermal considerations. For example, the problem of heat removal from compact fluorescent lamps with integrated ballasts has limited their use. Similarly, the use of ballast-driven fluorescent lighting in high hat and other closed luminaire applications has been limited by thermal considerations. Thermal management of ballasts for such thermally sensitive applications is provided by a piezoelectric fan integrated with the ballast. The power to drive the fan may be obtained from the same AC line input that supplies the ballast, or from an AC ripple voltage present at the output of a rectifier in the ballast, or from the output of the ballast to the lamp, or from any suitable circuit location in the ballast. The fan maybe a membrane-type spot-cooler comprising a thin membrane carried by a frame mounted adjacent a hot spot.