A polyvalent harmonic coil testing method for small-aperture magnets

A method to characterize permanent and fast-pulsed iron-dominated magnets with small apertures is presented. The harmonic coil measurement technique is enhanced specifically for small-aperture magnets by (1) in situ calibration, for facing search-coil production inaccuracy, (2) rotating the magnet around its axis, for correcting systematic effects, and (3) measuring magnetic fluxes by stationary coils at different angular positions for measuring fast pulsed magnets. This method allows a quadrupole magnet for particle accelerators to be characterized completely, by assessing multipole field components, magnetic axis position, and field direction. In this paper, initially the metrological problems arising from testing small-aperture magnets are highlighted. Then, the basic ideas of the proposed method and the architecture of the corresponding measurement system are illustrated. Finally, experimental validation results are shown for small-aperture permanent and fast-ramped quadrupole magnets for the new linear accelerator Linac4 at CERN (European Organization for Nuclear Research)

Optimal positioning of a single local magnetic sensor for integrated dipole measurements

In this report, we seek the optimal position inside a dipole magnet where a single, small magnetic field sensor such as a Hall probe should be installed to derive with best accuracy the field integral along the magnet’s axis. An effective installation criterion would be useful for many real-time field monitoring and control applications in both synchrotron main rings and transfer lines, such as those found at CERN and in hadrontherapy centres. The main quantity of interest is the so-called magnetic length, i.e. the ratio between integral and local field measured at any given position inside the gap. First, we present a simple mathematical model which proves that, under certain conditions, an optimal position exists where the magnetic length is a constant with respect to excitation current, irrespective of the degree of saturation of the iron yoke. We then investigate analytically the impact of perturbations such as remanent field and eddy currents, which cause the magnetic length to be only approximately constant at best. Next, we analyze the computed field profiles of two representative magnets, the ISR and the ELENA bending dipoles, finding that the simulations qualitatively agree with expectations based on the analytical model. Finally, we analyze measurements of the ELENA and the HIE ISOLDE bending dipoles, finding that the ELENA results match reasonably well predictions. We conclude by summarizing the advantages and drawbacks of the solution proposed and outlining possible objectives of future work

Static metrological characterization of a ferrimagnetic resonance transducer for real-time magnetic field markers in particle accelerators

The metrological characterization of a magnetic field transducer based on ferrimagnetic resonance for real-time markers in particle accelerators is reported. The transducer is designed to measure the magnetic field with an uncertainty of ± 10-5 T. A case study on the new real-time field monitoring system for the CERN accelerators highlighting the performance improvement achieved through the new ferrimagnetic transducer is described. Preliminary experimental results of the characterization for static and dynamic fields are discussed

Metrological Performance of a Ferrimagnetic Resonance Marker for the Field Control of the CERN Proton Synchrotron

In particle accelerators, “field markers” provide a digital trigger when the magnetic field crosses a given threshold. In this paper, the metrological characterization of a magnetic field marker, based on a ferrimagnetic resonance transducer referencing the flux sensed by a coil, is reported. The experimental results of a validation test campaign at the European Organization for Nuclear Research (CERN) to test the marker in static as well as fast ramping fields (up to 2.5 T/s) are illustrated. The repeatability of ±4 μT attained in the range (60 to 100) mT is very promising to increase the performance of the Proton Synchrotron accelerator at CERN

Instruments and Methods for the Magnetic Measurement of the Super-FRS Magnets

The Super-FRS is a new fragment separator to be built as part of the Facility for Antiproton and Ion Research (FAIR) [\ref{fair_{w}eb}] at Darmstadt. The acceptance tests and magnetic measurements of the superferric separation dipoles and multiplets (containing quadrupole and higher-order magnets) will be performed at CERN in collaboration with GSI/FAIR [\ref{abstract_{f}acility}]. This paper presents the methods and challenges of the magnetic field measurements, and the required instruments for measuring the transfer function, field quality, and magnetic axis. A prototype for each system has been produced in order to validate the measurement methods, the instruments, and the mechanical integration. In this paper will present the design and production of the prototypes, the design of the instruments for the series measurements, and the results of the metrological characterization

Preliminary Test Results of the First of Series Multiplet for the Super-FRS at FAIR

The first of series (FoS) multiplet built for the Super-FRS at GSI/FAIR was delivered to a dedicated magnet test facility at CERN. After a series of tests at room temperature, it was cooled down to 4.5 K and is now under cold powering test. The commissioning of the CERN test facility is performed in parallel with the magnet testing. The quadrupole and the sextupole magnet enclosed in the cryostat module are superferric magnets with a large aperture diameter of 380 mm. The yoke length of the quadrupole magnet and the sextupole magnet is 1200 mm and 500 mm, respectively. The features of the magnets are vacuum impregnated racetrack coils made of Nb-Ti conductor and a maximum integrated gradient of 11.4 T/m × m for the quadrupole magnet and 20 T/m$^{2}$ × m for the sextupole magnet, respectively. This paper presents the design issues of the magnets, especially of the quadrupole magnet, an overview of a qualification process of the multiplets, and preliminary test results

Design, production, and testing of superconducting magnets for the Super-FRS

International audienceThe Super FRS is a two-stage in flight separator to be built next to the site of GSI, Darmstadt, Germany as part of FAIR (Facility for Anti-proton and Ion Research). Its purpose is to create and separate rare isotope beams and to enable the mass measurement also for very short lived nuclei. Due to its three branches a wide variety of experiments can be carried out in frame of the NUSTAR collaboration. Due to the large acceptance needed, the magnets of the Super-FRS have to have a large aperture and therefore only a superconducting solution is feasible. A superferric design with superconducting coils was chosen in which the magnetic field is shaped by an iron yoke. For the dipoles this iron yoke is at warm and only the coils are incorporated in a cryostat. The multiplets, assemblies of quadrupoles and higher order multipole magnets, are completely immersed in a liquid Helium bath. With the exception of special branching dipoles all superconducting magnets of Super-FRS have been contracted and are being built by Elytt in Spain (dipoles) and ASG in Italy (multiplets). The cold test of all magnets will take place in a dedicated test facility at CERN. This contribution will present the status of manufacturing of dipoles and multiplets, and also gives a short overview on the test facility