1,721,153 research outputs found
A Rotating-Coil Magnetometer for Scanning Transversal Field Harmonics in Accelerator Magnets
No full textThis paper presents a rotating-coil magnetometer that was designed and validated for scanning local transversal field harmonics, required for extracting so-called pseudo-multipoles in accelerator magnets. The magnetometer consists of four layers of flexible printed circuits with a track thickness of 40 μm. The design aimed at maximizing the sensitivity factors for field harmonics up to order 13 and at a compensation ratio for the main component in the same range of what is achievable with standard rotating coils. Key innovative features of the induction coil are the shape for minimizing the sensitivity to the longitudinal field component and the manufacturing technology. The design, the uncertainty analysis of the manufacturing tolerances, as well as preliminary application results are presented
Correcting for background fields and multipole field errors in the localization of the magnetic axis in quadrupole magnets
No full textProof-of-principle demonstration of a translating coils-based method for measuring the magnetic field of axially-symmetric magnets
No full textIn axially-symmetric magnets for particle accelerators, the magnetic field is usually surveyed by expensive and time-consuming 3D Hall-probe mappers. Problems arise for a coherent treatment among beam physics requirements, magnet design and manufacturing, and magnetic measurements. For example, when the longitudinal direction of the mapper is misaligned with respect to the magnet, the measured fringe fields will show spurious components. In this paper, an alternative measurement method, exploiting the inherent axial symmetry of the magnetic field, is proposed. The magnetic flux linked with a pair of sensing coils is measured as a function of the longitudinal position. An induction transducer, sensitive to the longitudinal and radial components of the magnetic field, and a measurement system have been designed and prototyped. The experimental proof-of-principle demonstration of the method in comparison with a Hall-probe mapper is presented for a solenoid magnet
Vibrating-wire measurement method for centering and alignment of solenoids
No full textA method is proposed to center and align solenoids by means of a vibrating wire. The magnetic axis of a solenoid is defined as the path where the integral over the transversal field components takes its minimum. The wire, fed by an alternating current, oscillates in a plane that is perpendicular to the transversal magnetic field. When the wire position coincides with the magnetic axis, the transversal field components cancel out and therefore no motion is induced. To center and align the solenoid two wire resonance frequencies are excited for co- and counter-directional movements of the wire stages. The procedure to find the minimum oscillation amplitudes is sensitive to misalignment in the micrometer range. The experimental validation was carried out on a solenoid for the linear accelerator Linac4 at CERN
Rotating-coil calibration in a reference quadrupole, considering roll-angle misalignment and higher-order harmonics
No full textA method is proposed for calibrating the radius of a rotating coil sensor by relaxing the metrological constraints on alignment and field errors of the reference quadrupole. A coil radius calibration considering a roll-angle misalignment of the measurement bench, the magnet, and the motor-drive unit is analyzed. Then, the error arising from higher-order harmonic field imperfections in the reference quadrupole is assessed. The method is validated by numerical field computation for both the higher-order harmonic errors and the roll-angle misalignment. Finally, an experimental proof-of-principle demonstration is car-ried out in a calibration magnet with sextupole harmonic
Multipole correction of stretched-wire measurements of field-gradients in quadrupole accelerator magnets
No full textA correction of field gradients in quadrupole accelerator magnets measured by stretched-wire methods is described. The gradient is first measured by means of the single-stretched-wire method. By using the same experimental setup, the relative multipole-field errors of the quadrupole are then measured by means of the oscillating-wire technique and used for the correction scheme. Results of the experimental validation are presented for a prototype quadrupole for the CLIC accelerator study at CERN
A rotating coil transducer for magnetic field mapping
No full textA rotating coil transducer for local measurements of magnetic field quality in magnets is proposed. The transducer is based on (i) reduced-dimension rotating coils, as required e.g. for space charge computations, (ii) accurate transport, for longitudinal displacements inside the magnet aperture, and (iii) components with magnetic compatibility for negligible interference of the measurand field. This allows magnetic measurement requirements arisen from recently developed compact accelerator systems (with curvature radii of less than 5 m) for biomedical applications and physics research to be satisfied. In the paper, after presenting requirements and conceptual design, the architecture of the transducer is illustrated. Then, the experimental validation by tests of magnetic compatibility and rotation uniformity is reported. Finally, experimental results of repeatability, accuracy, and resolution in comparison with a reference system are discussed
Measuring field multipoles in accelerator magnets with small-apertures by an oscillating wire moved on a circular trajectory
No full textA method based on an oscillating wire for measuring the field quality in accelerator magnets with small apertures of the order of 10 mm is proposed. The wire is positioned step-by-step on the generators of a cylindrical domain inside the magnet ap erture, i.e. its end-points at the stages are moved on a circular trajectory. The amplitudes of the wire's forced oscillations are measured and related to field harmonics by a suitable analytical model. In this paper, the analytical model, the measurement procedure, and the measurement system architecture of the oscillating wire method are presented. The method is validated by comparison with the standard rotating-coil system. A case study on small-aperture, permanent-magnet quadrupoles constructed for th e Linac4 injector at CERN is illustrated
Performance analysis of miniaturized PCB coils for small-aperture magnet qualification
No full textThe metrological performance of a magnetic field transducer, consisting of a fyberglass cylinder hosting three PCB coils with a diameter of 7.5 mm, is analyzed. The transducer aims at facing the more challenging goals expected in the near future of particle accelerators, involving magnet apertures smaller than 1 cm. Main intents are to gain useful feedback to designers for optimizing the manufacturing and improving the metrological performance of the transducer
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