Abstract: The invention relates to a combined radiation therapy and magnetic resonance unit. For this purpose, in accordance with the invention a combined radiation therapy and magnetic resonance unit is provided comprising a magnetic resonance diagnosis part with an interior, which is limited in radial direction by a main magnet, and a radiation therapy part for the irradiation of an irradiation area within the interior, wherein at least parts of the radiation therapy part, which comprise a beam deflection arrangement, are arranged within the interior.

Abstract: The invention concerns a method for irradiating a target with a beam approaching target points, involving the following steps: Measuring at least one of the parameters relating to the position of the beam and the intensity of the beam, changing the beam as a function of the at least one measured parameter, particularly as a function of a variance relating to the at least one measured parameter. The method is characterized in that the at least one measured parameter is measured at the most once per target point. Furthermore, the invention concerns a device for irradiating a target in accordance with the invention-based method and a control system for controlling such a device.

Abstract: Performance of an electrohydrodynamic fluid accelerator device may be improved and adverse events such as sparking or arcing may be reduced based, amongst other things, on electrode geometries and/or positional interrelationships of the electrodes. For example, in a class of EHD devices that employ a longitudinally elongated corona discharge electrode (often, but not necessarily, a wire), a plurality of generally planar, collector electrodes may be positioned so as to present respective leading surfaces toward the corona discharge electrode. The generally planar collector electrodes may be oriented so that their major surfaces are generally orthogonal to the longitudinal extent of the corona discharge electrode. In such EHD devices, a high intensity electric field can be established in the “gap” between the corona discharge electrode and leading surfaces of the collector electrodes.

Abstract: A method for evaluating radiation model data in particle beam radiation applications, in particular in proton beam therapy of a determined target volume of malignant tissue within a patient, includes the following steps: a) gaining diagnostic data for a determined target volume to be irradiated; b) calculating a particle range in the predetermined target volume based on the diagnostic data for the determined target volume; c) designing a radiation model with particle beam characteristics based on the calculated particle range and optionally on a calculated dose depth distribution; d) applying a single pencil beam shot to the determined target volume at an elevated beam energy as compared to the particle beam characteristics of the radiation model; e) measuring the beam range of the single pencil beam shot downstream of the determined target volume; and f) comparing the measured beam range to a reference beam range calculated on the basis of the radiation model.

Abstract: A system to regulate gyrotron power is configured to raise the filament voltage of a gyrotron to a standby voltage, then set the filament voltage to the normal standby voltage plus a current offset voltage before pulsing the gyrotron. The system is further configured to increase the filament voltage to a boost voltage that is higher than the standby voltage, thereby inducing a temperature increase in the cathode that offsets the cooling effect of radiating. The system is also configured to analyze a beam power of the gyrotron and adjust the filament voltage to bring a beam current within a range, and reduce the filament offset to zero such that the filament voltage is equal to the standby voltage.

Abstract: An H-mode drift tube linac according to the present invention includes: an accelerator cavity which functions as a vacuum chamber and a resonator; drift tube electrodes for generating accelerating voltages in a charged particle transporting direction in the accelerator cavity; tuners for adjusting a distribution of electric fields generated at gaps between respective pairs of the drift tube electrodes; and antennas for measuring a variation of the distribution of the electric fields, the antennas being provided along the charged particle transporting direction in the accelerator cavity.

Abstract: A device for replenishing ionizable material in a field ionization apparatus is disclosed. The device comprises a heatable reservoir containing the ionizable material, a field ionization electrode structure, and a channel being in fluid communication with said heatable reservoir. The heatable reservoir and the channel are designed and constructed such that when the heatable reservoir is heated to an evaporation temperature of the ionizable material, a flux of vaporized ionizable material is directed along the channel to a tip of the field ionization electrode structure.

Abstract: The ion acceleration system or complex (T) for medical and/or other applications is composed in essence by an ion source (1), a pre-accelerator (3) and one or more linear accelerators or linacs (6, 8, 10, 13), at least one of which is mounted on a rotating mechanical gantry-like structure (17). The isocentrical gantry (17) is equipped with a beam delivery system, which can be either ‘active’ or ‘passive’, for medical and/or other applications. The ion source (1) and the pre-accelerator (3) can be either installed on the floor, which is connected with the gantry basement, or mounted, fully or partially, on the rotating mechanical structure (17). The output beam can vary in energy and intensity pulse-by-pulse by adjusting the radio-frequency field in the accelerating modules of the linac(s) and the beam parameters at the input of the linear accelerators.

Abstract: The invention comprises a charged particle cancer therapy system or synchrotron system using one or more switches to introduce a corresponding one or more resistors into a circuit linking a power supply to a magnet or an inductor during an applied power recovery phase between acceleration cycles of the synchrotron, which reduces time of reduction in power from an active applied power to a power suitable for use with a subsequent injection of charged particles into the synchrotron.

Abstract: The present invention relates to an irradiation unit for emitting a particle beam, a gantry including the irradiation unit, a squirrel cage structure located within and supported by the gantry, a frame arranged so as to be motionless, a moving floor including a plurality of elongated members forming a primary caterpillar, two moving floor guide units having a truncated circle shape, facing each other, attached to said squirrel cage structure and the motionless frame, respectively. Each of the two moving floor guide units includes at least a first rail, said the primary caterpillar being slidably arranged on the first rail. Each moving floor guide unit includes at least a second rail having a truncated circle shape and the moving floor includes at least one secondary caterpillar including elongated members flexibly connected to each other.

Abstract: Provided is a superconducting accelerator cavity and a method thereof with which product reliability can be enhanced and manufacturing costs can be reduced. A method of manufacturing a superconducting accelerator cavity includes a beam-pipe forming stage of forming a beam pipe by processing a superconducting material into a tube shape; an end-plate joining stage of joining, by welding, an inner circumferential surface of an end plate formed in a shape of a ring that forms an end of a jacket, which accommodates coolant, to an outer circumferential portion of an end in the beam pipe formed in the beam-pipe forming stage; and an end-cell joining stage of joining, by welding, an iris portion of an end cell, which is formed of a superconducting material in a shape of a ring so as to form a cavity portion, to an inner circumferential portion of the end of the beam pipe.

Abstract: A system includes a patient support and an outer gantry on which an accelerator is mounted to enable the accelerator to move through a range of positions around a patient on the patient support. The accelerator is configured to produce a proton or ion beam having an energy level sufficient to reach a target in the patient. An inner gantry includes an aperture for directing the proton or ion beam towards the target.

Abstract: A particle accelerator system for producing a charged particle beam having pulses of charged particles that have different energy levels from pulse to pulse. The system enables independent adjustment of the RF power delivered to first and second accelerating sections thereof without adjustment of the RF power generated by an RF source. Such independent adjustment enables the RF power provided to the first accelerating section to be maintained at a level appropriate for optimal particle capturing therein and for producing a tightly bunched beam of particles having different energy levels from pulse to pulse, while enabling the RF power provided to the second accelerating section to be varied in order to vary the energy levels of the charged particles of the charged particle beam from pulse to pulse.

Abstract: An apparatus for regulating power in an accelerator system includes a directional coupler for sensing a power reflected from an accelerator towards a power source, and a power modulator for reducing an output of the power source based on the sensed power. A method for regulating power in an accelerator system includes sensing a power reflected from an accelerator towards a power source, and reducing an output of the power source based on the sensed power.

Abstract: A rapidly twisted electromagnetic accelerating structure includes a waveguide body having a central axis, one or more helical channels defined by the body and disposed around a substantially linear central axial channel, with central portions of the helical channels merging with the linear central axial channel. The structure propagates electromagnetic waves in the helical channels which support particle beam acceleration in the central axial channel at a phase velocity equal to or slower than the speed of light in free space. Since there is no variation in the shape of the transversal cross-section along the axis of the structure, inexpensive mechanical fabrication processes can be used to form the structure, such as extrusion, casting or injection molding. Also, because the field and frequency of the resonant mode depend on the whole structure rather than on dimensional tolerances of individual cells, no tuning of individual cells is needed.

Abstract: The present invention relates to a cyclotron including two internal ion sources for the production of the same particles. The second ion source can be used as a spare ion source which strongly increases the uptime and the reliability of the cyclotron and reduces the maintenance interventions. Advantageously, the cyclotron is further characterized by an optimized close geometry of the different elements within the central region of the cyclotron. The cyclotron of the invention may be further characterized by an adaptation and optimization of the shape of first and second internal ion source to avoid particle losses during the first turn of acceleration. The cyclotron may be further characterized by an adaptation and optimization of the shape of the counter-Dee electrode assembly and possibly the Dee-electrode assembly in order to improve the acceleration field in-between the gaps.

Abstract: There is obtained a particle beam therapy system in which the beam size is reduced. There are provided an accelerator 14 that accelerates a charged particle beam; an irradiation apparatus that has a beam scanning apparatus 5a, 5b for performing scanning with the charged particle beam and irradiates the charged particle beam onto an irradiation subject; and a beam transport apparatus 15 that has a duct for ensuring a vacuum region or gas region that continues from the accelerator 14 to a beam outlet window 7 disposed at a more downstream position than the beam scanning apparatus 5a, 5b, and that transports the charged particle beam exiting from the accelerator 14 to the irradiation apparatus.

Abstract: Target respiration information is created in which a patient respiration pattern is set in advance to a cycle suitable for an operation cycle of a synchrotron, and the target respiration information is informed to the patient, so that a patient respiration timing becomes a state suitable for an operation of the synchrotron in such a manner that the patient consciously matches with the informed information.

Abstract: A proton acceleration system is provided for accelerating protons within a target. The system includes a laser source generating a laser beam having a wavelength ?L and intensity and a target formed of foil having a selected thickness. The target is irradiated by the laser beam and transformed into a plasma that has a target density. This causes a treatment energy to be emitted from the foil due to the irradiation. The thickness of the foil of the target is selected so that the foil has a thickness within a range of optimal thickness ?s to 2×?s, wherein ?s is less than the laser wavelength and is a function of the laser intensity, laser wavelength, and target density sufficient to achieve radiation pressure acceleration (RPA).

Abstract: A method is described wherein the acceleration of a beam of charged particles is achieved using the properties of conductors to limit the penetration of magnetic and electric fields in short times compared to natural time constants. This allows the use of induction electric fields with a Curl localized to a gap to accelerate particles while coupling the accelerated beam to a power supply. Two methods of coupling the particle beam to the power supply are disclosed as exemplary.

Abstract: A klystron has a hollow beam electron gun that has a circular planar electron emitting surface. A hollow electron beam is directed from the electron gun through a plurality of drift tubes, resonant chambers and magnetic fields to a collector. The hollow electron beam does not experience significant radial movement and can operate at a lower beam voltage which reduces the required length of the RF interaction circuit and lowers the risks of RF arcing.

Abstract: A charged particle beam irradiation system includes a synchrotron which accelerates an ion beam, an irradiation apparatus for irradiating an object with the ion beam introduced from the synchrotron, detection means for measuring an amount of accumulated charge of the ion beam that orbits in the synchrotron immediately before an extraction control period in an operating cycle of the synchrotron, and beam extraction control means for controlling extraction of the ion beam based on the measurement result of the accumulated beam charge amount so that extraction of a total amount of the ion beam is to be completed with an expiration of an extraction control time, the extraction control time representing a length of the extraction control period of the synchrotron and being set in advance.

Abstract: A light module for signaling comprising an assembly module (1), defined by a body with any geometry and ordinarily in the form of a box (2), including a rear closing (3) and a frontal lens (4) and, between said parts, an electronic circuit (5) and a corresponding set of light emitting diodes (6), being said electronic circuit (5) constituted by the following blocks: a source (7) to regulate the feeding voltage of other blocks within five volts with low quiescent current; synchronism (8) for electrical conditioning if an eventual reference signal for foreign synchronism occurs; blinking sequence generator (9) with means to define the period of time during which the set of lights (6) is on and off.

Abstract: A particle accelerator (100) comprises a power supply arrangement (110), a plurality of solid-state switched drive sections (120), a plurality of magnetic core sections (130) and a switch control module (140). The drive sections (120) are connected to the power supply arrangement (110) for receiving electrical power therefrom, and each drive section comprises a solid-state switch, electronically controllable at turn-on and turn-off, for selectively providing a drive pulse at an output of the drive section. The magnetic core sections (130) are symmetrically arranged along a central beam axis, and each magnetic core of the sections is coupled to a respective drive section (120) through an electrical winding connected to the output of the drive section.

Abstract: The invention discloses a microwave supplying apparatus including a microwave generator, a first power divider, a second power divider, a first waveguide, and a second wave guide. The first waveguide is connected to the microwave generator and has a first output terminal and a second output terminal to divide a microwave generated by the microwave generator along a first direction. The second power divider is connected to the first output terminal and has a third output terminal and a fourth output terminal to divide the microwave along a second direction. The first waveguide and the second waveguide are connected to the third output terminal and the fourth terminal respectively and receive the microwave through the first power divider and the second power divider to respectively output the microwave fields with approximate intensity distributions.

Abstract: A particle accelerator including an electrical field system and a magnetic field system that are configured to direct charged particles along a desired path within an acceleration chamber. The particle accelerator also includes a mechanical device that is located within the acceleration chamber. The mechanical device is configured to be selectively moved to different positions within the acceleration chamber. The particle accelerator also includes an electromechanical (EM) motor having a connector component and piezoelectric elements that are operatively coupled to the connector component. The connector component is operatively attached to the mechanical device. The EM motor drives the connector component when the piezoelectric elements are activated thereby moving the mechanical device.

Abstract: The present invention relates to a pulsed beam particle accelerator which can be used for particle radiation therapy. More particular, a device and method are provided to control the number of particles within a beam pulse. The particle accelerator comprises means for varying the number of particles within each beam pulse of said pulsed ion beam from a minimum value to a maximum value as function of the value of a beam control parameter. For each particle irradiation the required number of particles for each beam pulse is controlled by defining a value for said beam control parameter based on calibration data.

Abstract: An electrode for fixed-frequency particle accelerators geometrically compensating for relativistic mass increase by placing the acceleration gap at the location of the particle at each peak of the accelerating electric field.

Abstract: An object of the invention is to provide the orbit control device for modulating the orbital deviations of the charged particle beam and its control method, wherein in the synchrotron making use of induction cells, the charged particle beam orbit control device is comprised of the digital signal processor for controlling the generation timing of an induced voltage in response to the beam position signal from the beam position monitor for sensing the deviations of the charged particle beam on the design orbit of the synchrotron from the design orbit and to the passage signal from the bunch monitor for sensing the passage of the bunch and the pattern generator for generating a gate signal pattern for on/off-selecting the switching electric power supply a according to the master gate signal generated by the digital signal processor.

Abstract: Multi-energy radiation sources comprising charged particle accelerators driven by power generators providing different RF powers to the accelerator, capable of interlaced operation, are disclosed. Automatic frequency control techniques are provided to match the frequency of RF power provided to the accelerator with the accelerator resonance frequency. In one example where the power generator is a mechanically tunable magnetron, an automatic frequency controller is provided to match the frequency of RF power pulses at one power to the accelerator resonance frequency when those RF power pulses are provided, and the magnetron is operated such that frequency shift in the magnetron at the other power at least partially matches the resonance frequency shift in the accelerator when those RF power pulses are provided. In other examples, when the power generator is a klystron or electrically tunable magnetron, separate automatic frequency controllers are provided for each RF power pulse.

Abstract: According to certain embodiments, a linear accelerator comprises a nanotube, a particle, and an energy source. The nanotube has a cylindrical shape, and the particle is disposed within the nanotube. The energy source is configured to apply energy to the nanotube to cause the particle to accelerate.

Abstract: A system for accelerating particles includes an RF cavity that contains a ferrite core and a liquid dielectric. Characteristics of the ferrite core and the liquid dielectric, among other factors, determine the resonant frequency of the RF cavity. The liquid dielectric is circulated to cool the ferrite core during the operation of the system.

Abstract: An ion radiation therapy machine provides a steerable beam for treating a tumor within the patient where the exposure spot of the beam is controlled in width and/or length to effect a flexible trade-off between treatment speed, accuracy, and uniformity.

Abstract: A dc accelerator system able to accelerate high currents of proton beams at high energies is provided. The accelerator system includes a dc high-voltage, high-current power supply, an evacuated ion accelerating tube, a proton ion source, a dipole analyzing magnet and a vacuum pump located in the high-voltage terminal. The high-current, high-energy dc proton beam can be directed to a number of targets depending on the applications such as boron neutron capture therapy BNCT applications, NRA applications, and silicon cleaving.

Abstract: An apparatus for use in a process to regulate power for a particle accelerator includes a first circulator, a second circulator, a tee coupled between the first and the second circulator, and a tuner coupled to the tee. An apparatus for use in a process to regulate power for a particle accelerator includes a first circulator, a second circulator, a 3-dB coupler coupled between the first and the second circulator, and a tuner coupled to the 3-dB coupler.

Abstract: A cascade accelerator (1), with two sets (2, 4) of capacitors (26, 28) which are each connected in series, interconnected by diodes (24, 30) in the form of a Greinacher cascade (20), is to have in a compact construction a particularly high attainable particle energy. Therefore, the cascade accelerator has an acceleration channel (8) which is formed through openings in the electrodes of the capacitors of a set (2), directed to a particle source (6) arranged in the region of the electrode with the highest voltage (12), wherein the electrodes are insulated to each other apart from the acceleration channel (8) with a solid or liquid insulation material (14).

Abstract: Provided is a charged particle beam radiation control device that controls radiation of a charged particle beam, the charged particle beam radiation control device including: a controller which controls an acceleration voltage for accelerating charged particles, wherein the controller includes a set acceleration voltage controller which selects a non-radiation state of a charged particle beam by setting an acceleration voltage of a radiation state of the charged particle beam to a reference acceleration voltage and changing the acceleration voltage to a set acceleration voltage larger or smaller than the reference acceleration voltage.

Abstract: A magnetic field crosses non-uniform rotating electric radial fields which are generated between a central electrode and a series of circumferential outer electrodes. Synchronous charging and partial discharging is applied to the outer electrodes, generating a rotating non-axisymmetric field. Charged particles may then be accelerated and held in a circular orbit, regulated by the magnitude and frequency of the charging of the electrodes, with a radius given by Bqwr=Eq+mw2r. The circular beam of particles so formed may be used for a variety of applications, which also includes fusion energy applications due to the high kinetic energy possible in the apparatus and the mechanism of energy recovery of scattered particles. Isotopic separation by charge to mass ratio is also possible, the device being essentially a cyclotron with radial electrodes.

Abstract: A charged particle beam decelerating device includes a high-frequency cavity 34 provided on an orbit of a charged particle beam 1, and a phase synchronizing device 40 for synchronizing the charged particle beam 1 in the high-frequency cavity with a phase of a high-frequency electric field 4. By moving the high-frequency cavity 34 or changing an orbit length of the charged particle beam 1, the charged particle beam in the high-frequency cavity is synchronized with a phase of the high-frequency electric field 4.

Abstract: A cyclotron that includes a magnet yoke that has a yoke body that surrounds an acceleration chamber and a magnet assembly. The magnet assembly is configured to produce magnetic fields to direct charged particles along a desired path. The magnet assembly is located in the acceleration chamber. The magnetic fields propagate through the acceleration chamber and within the magnet yoke. A portion of the magnetic fields escape outside of the magnet yoke as stray fields. The magnet yoke is dimensioned such that the stray fields do not exceed 5 Gauss at a distance of 1 meter from an exterior boundary.

Abstract: A fast electromagnet device (140) receives a high voltage from a pulse power supply through a coaxial cable and excites an electromagnet at high speed, so as to bend a charged particle beam. The fast electromagnet device (140) includes a kicker magnet (150) and an auxiliary circuit (160). The kicker magnet (150) is equivalent to a circuit element of a lumped constant circuit, is formed with a space penetrating in the traveling direction of the charged particle beams, instantaneously generates a magnetic field in the penetrated space with a high voltage applied, and bends the charged particle beams passing through the penetrated space. The auxiliary circuit (160) constitutes a matching circuit in combination with the kicker magnet (150), so that the input impedance of the matching circuit and the characteristic impedance of the coaxial cable connected to the input terminal of the matching circuit are matched.

Abstract: An electron injector including an electron source and a conducting grid situated close to the electron source, one or more RF accelerating/bunching cavities operating at the same fundamental RF frequency; a DC voltage source configured to bias the cathode at a small positive voltage with respect to the grid; a first RF drive configured to apply an RF signal between the cathode and grid at the fundamental and third harmonic RF frequencies; and a second RF drive configured to apply an RF drive signal to the accelerating/bunching cavities. Electrons are emitted by the cathode and travel through the grid to the accelerating/bunching cavities for input into an RF linac.

Abstract: A terahertz sheet beam klystron (TSBK) includes an electron gun configured to generate a sheet electron beam and a drift tube through which the sheet beam is propagated. The drift tube is provided with multiple resonant cavities and includes a drift tube circuit including an input RF circuit through which an input RF signal is introduced and an output RF circuit through which an output RF signal is extracted, a collector, and a vacuum envelope. The output RF circuit is configured such that Qe (extraction Q) of the drift tube circuit is comparable to Q0 (unloaded Q) of the drift tube circuit, thereby improving the efficiency of the drift tube circuit.

Abstract: In a charged particle accelerator, voltage of several tens of kV is applied between accelerating electrodes. In such a case, electric discharge is sometimes generated between the accelerating electrodes. In the charged particle accelerator, part or entirety of the accelerating electrodes is coated with an electric discharge suppressing layer made of ceramics or alloy having a high melting point as compared with metal. When impurity fine particles are accelerated by an electric field and collide with the electrodes, the electric discharge suppressing layer made of ceramics or alloy prevents metal vapor from being easily generated from the electrodes and an ionized plasma from being easily produced, thus suppressing electric discharge between the electrodes.

Abstract: A rapidly twisted electromagnetic accelerating structure includes a waveguide body having a central axis, one or more helical channels defined by the body and disposed around a substantially linear central axial channel, with central portions of the helical channels merging with the linear central axial channel. The structure propagates electromagnetic waves in the helical channels which support particle beam acceleration in the central axial channel at a phase velocity equal to or slower than the speed of light in free space. Since there is no variation in the shape of the transversal cross-section along the axis of the structure, inexpensive mechanical fabrication processes can be used to form the structure, such as extrusion, casting or injection molding. Also, because the field and frequency of the resonant mode depend on the whole structure rather than on dimensional tolerances of individual cells, no tuning of individual cells is needed.

Abstract: An electron cooling system and method for increasing the phase space intensity and overall intensity of ion beams in multiple overlap regions, including a vacuum chamber to allow a single electron beam to be merged and separated with multiple ion beams, an electron supply device including a cathode to generate the electron beam, an electron collector device including a collection plate to collect the electron beam, multiple magnetic field generation devices to guide the electrons on their desired trajectories, and multiple electrodes to set the velocity of the electron beam independently in each overlap region. By overlapping the electron and ion beams, thermal energy is transferred from the ion beams to the electron beam, which allows an increase in the phase space density and overall density of the ion beams.

Abstract: A medical gantry that focus the beam from the beginning of the gantry to the exit of the gantry independent of the rotation angle of the gantry by keeping the beam achromatic and uncoupled, thus, avoiding the use of collimators or rotators, or additional equipment to control the beam divergence, which may cause beam intensity loss or additional time in irradiation of the patient, or disadvantageously increase the overall gantry size inapplicable for the use in the medical treatment facility.

Abstract: A proton acceleration system is provided for accelerating protons within a target. The system includes a laser source generating a laser beam having a wavelength ?L and intensity and a target formed of foil having a selected thickness. The target is irradiated by the laser beam and transformed into a plasma that has a target density. This causes a treatment energy to be emitted from the foil due to the irradiation. The thickness of the foil of the target is selected so that the foil has a thickness within a range of optimal thickness ?s to 2×?s, wherein ?s is less than the laser wavelength and is a function of the laser intensity, laser wavelength, and target density sufficient to achieve radiation pressure acceleration (RPA).

Abstract: Techniques for reducing an electrical stress in a acceleration/deceleration system are disclosed. In one particular exemplary embodiment, the techniques may be realized as an acceleration/deceleration system. The acceleration/deceleration system may comprise an acceleration column including a plurality of electrodes having apertures through which a charged particle beam may pass. The acceleration/deceleration system may also comprise a plurality of voltage grading components respectively electrically coupled to the plurality of electrodes. The acceleration/deceleration system may further comprise a plurality of insulated conductors disposed proximate the plurality of voltage grading components to modify an electrical field about the plurality of voltage grading components.

Abstract: A betatron magnet having at least one electron injector positioned approximate an inside of a radius of a betatron orbit, the betatron magnet further includes a first guide magnet having a first pole face and a second guide magnet having a second pole face. Both the first and the second guide magnet have a centrally disposed aperture and the first pole face is separated from the second pole face by a guide magnet gap. A core is disposed within the centrally disposed apertures in an abutting relationship with both guide magnets. The core has at least one core gap. A drive coil is wound around both guide magnet pole faces. An orbit control coil has a core portion wound around the core gap and a field portion wound around the guide magnet pole faces. The core portion and the field portion are connected but in opposite polarity.