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The choice of a 3D-laser tracker for controlling several delicate operations during the fabrication process of the LHC magnets gave the idea to measure simultaneously, with a single mole, the centre axis of the cold bore tube and the magnetic axis of the magnet. This mole houses at the same cross-section point four tangential coils for detecting the magnetic axis, a corner cube for detecting the centre of the mole and a mechanical system to centre the mole inside the cold bore tube. This contribution described the principle, the equipment and the preliminary results related especially to the magnetic axis measurement.

I presented analytic forms for fitting magnet strength with hysteresis. It will provide fits to MI Dipole strength at the 3E-4 level.

It will reflect on various successes and mostly failures, some of which we were warned about at previous IMMW's.

A novel kind of harmonic coil probe (the Mole) has been developed for the measurement, in warm conditions, of magnetic field quality, field direction and axis of the superconducting LHC dipoles and associated sextupole and decapole corrector windings. The Mole houses a set of radial rotating coils and travels inside the magnet aperture by means of an externally driven two-way traction belt. The coil rotation is driven by an ultrasonic piezoelectric motor, being tested in view of future devices for cold measurements as the only type of electrical motor compatible with a strong magnetic field. A light spot is generated by a LED source and projected optically into the coil center on the coil rotation axis. The position of this virtual light spot is measured by an optical system that includes a telescope, a CCD camera and a DSP carrying out image processing algorithms. The position is then transferred with high accuracy to the magnet fiducial reference line by means of a system of jigs. In this paper we describe the characteristics of the Mole, its capability in terms of resolution and accuracy of measured harmonics, field direction and magnetic axis position, and a comparative analysis of the results obtained on a LHC dipole using the Mole as well as other measurement systems.

To measure the energy of the LEP machine (Large Electron Positron collider) at high energies, a spectrometer is installed in the tunnel because the polarization is working well under 60 GeV. Field maps of the spectrometer have been undertaken so that the ratios of integrals Bdz can be known with a precision of few 10E-5. The previous LEP magnetic measurement stand has been modified by includind a carbon fiber arm which is practically not sensitive to temperature fluctuations. A description of the stand is given with first measurement results.

To improve the reproducibilty from cycle to cycle of an accelerator a B_train is implemented and refined with the help of NMR (Nuclear Magnetic Resonance probes) markers. This B-train is linked to the field of the main bending magnets. For the Cern-SPS machine it is also proposed to improve the reproducibility of the focusing elements by including a "G_train" linked to the gradient of the main quadrupoles. The evaluation of different options will be presented.

This talk will present the influence of different coil winding approximations (sector, sector with same center of mass, rectangular and rectangular with tilt) in the computation of coil geometric factors used in the magnetic field measurement of the LHC magnets. Results are provided for tangential coil 15m long shaft used at CERN.

This talk will present a method proposed for finding in warm condition the magnetic axis of the 15m long dipole magnets built for the LHC. The goal of the method is to improve the accuracy of the measurement of the magnetic field of dipoles in warm condition (low current, low field) in order to compute their harmonics with a good enough accuracy to be able to find the magnetic axis. The method involves the use of low AC current using the current frequency as an amplifier (derivate of flux proportionnal to the frequency)and a signal processing method (synchronous demodulation) to recover the harmonics from the modulated signal read by the rotating coils.

This would include a brief overview of the expansion at Triumf with the building of the ISAC project, focusing on some of the major magnets, the equipment used to measure them, and the results for both dipoles and multipole magnets. All these magnets are DC and room temperature.

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In the context of the LHC superconducting dipoles production it is foreseen to perform acceptance tests, including field measurements of the collared coils assembly to estimate, at an early production stage, the possible significant deviations from the expected multipole component value of these magnets. A sensitive measuring probe and efficient data acquisition are the consequence of a low magnetisation current necessary to limit the coils heating. The knowledge of the magnetic field geometry is very important, especially for multipole magnets. In order to get this information two systems have been conceived. First, a mole miming the magnetic one but equipped only with position sensors laser beam as reference line, target and CCD camera) to complement the magnetic measurement. A second system equipped with magnetic sensors (4 static tangential coils and AC excitation current for the magnet) and position sensors (3D-laser tracker and light reflector) allow the detection of the magnetic field axis and the cold bore axis. Another capability of this system is to work for several field configurations (n=1, 2, 3, 4 and 5). This conference contribution describes these two systems and gives the preliminary performance results.

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We shall describe the mapping procedure, setup and give preliminary results of the magnet mapping of the PHENIX magnets. We used the surface mapping technique, where the flux of the magnetic field through the closed surface surrounding the volume of interest is measured. Given the absence of the current sources inside the surface, the magnetic potential satisfies Laplace equation, which is solved using Green's function method. Reconstructed field is compared to the measurements made on the inside of the volume of interest and to TOSCA simulations.

Helical dipoles with 360 degrees rotation of the dipole field over 2.4 m length are being built for the RHIC spin physics program. The integral dipole field for such magnets is ideally zero, and should be below 0.05 T.m for central dipole field strength of 4 T. The integrated dipole field is measured using a long rotating coil. Errors introduced in the measurement of integral field due to typical coil construction errors will be presented, and illustrated using experimental data.

In conventional magnetic measurement using search coil, an integrator using operational amplifier or Voltage to Frequency Converter with a combination of counter is used to acquire magnetic field information. The purpose of integration is not only to get the magnetic information but to improve Signal to Noise ratio. The Integrator, however, usually have has a difficulty in reducing long term drift of the operational amplifier. The voltage to frequency converter also have similar problem as well as a resolution. We have developed a new technique by applying a digital processing capability of FFT analyzer to integrate the output voltage of search coil. This is very useful to diminish drift effect when magnets are excited periodically as in most of the accelerator.

Parameters of modern experimental set-ups depend on the precision of the magnetic field monitoring in the conditions of a real experiment. As a rule, the conditions of modern experiments (ATLAS, CMS, ALISE, LHC-B) have their special requirements to radiation hardness of the magnetometric apparatus used in the given set-up. Specialized magnetic-calibration stands have been manifactured (0.025¸ 5T) to investigate sensors of the magnetic field for radiation hardness at the Joint Institute for Nuclear Research (JINR). The superconducting stand has a magnet fields up to 5 T with a field homogeneity up to 0.001%/cm in a warm work volume of 60 cm³. The warm stand has a function of a magnet fields up to 2 T with a field homogeneity up to 0.01%/cm in a gap 30 mm and diameter 50 mm. Characteristics of different magnetic field sensors were studied before exposure and after it.

A 'pulsed wire' bench was built at SLAC. We used the system for two measurements: Finding the axis of a quadrupole and determination of the transverse fields of a permanent magnet stack.

A C-shaped storage ring magnet with a circumference of 45m and powered by superconducting coils has been built and operated for the Muon g-2 experiment currently in progress at BNL. The goal of this experiment is to measure the Anomalie a = (g-2)/2 to a precision of 0.35 ppm, a 20-fold improvement over the previous experiment done at CERN about 25 years ago. This requires good field homogeneity and precise field measurements in the muon storage region which has a circular aperture of 9cm diameter. The field measurement equipment and the shimming tools used will be discussed.

Brief description of the VISA FEL experiment.Design of the in-vacuum undulator and its vacuum vessel. Alignment tolerance and error budget. Magnet sorting and matching. Pulsed wire measurements. Trajectory shimming. Determining the magnetic axis.

Fiducialization concept. Description of the straightness interferometer, the optical wire finders and the zero-force gauge bar. Referencing the magnetic axis to fiducials. Alignment concept. The two-axis straightness interferometer. Aligning the undulator sections to the beamline.

A spectrometer has been installed along the beam path of the LEP accelerator in order to measure the beam energy with a relative accuracy of 10e-4. A bending magnet is flanked on either side by three beam position monitors (BPM) used to determine the deflection angle of the beam. This angle, together with the integral of the magnetic field along the beam trajectory, allows the calculation of the beam energy. In order to reach the desired accuracy on the energy a relative precision of a few 10e-5 on the magnetic field integral is necessary. The field inside the magnet has been mapped first in a dedicated laboratory setup based on a moving arm equipped with one NMR and two Hall probes. In the same laboratory another system was setup to cross check the magnetic field integral and perform the mapping again after the magnet transportation and positioning in the LEP ring. This measurement was carried out using a mole sliding inside the vacuum pipe. Two NMR probes as well as a search coil were mounted on the mole and used to sample the field value every 10 mm. The longitudinal position was monitored by a laser interferometer while the transverse positioning was ensured by the precise mechanical construction of the mole running in the vacuum chamber. Several field maps have been carried out at different field levels and at different temperatures in order to ensure a good extrapolation to the actual run conditions. Four NMR probes were installed in between the vacuum chamber and the lower pole, in four fixed locations. Those same probes remain available during the normal spectrometer operation and are used to extrapolate the real field integral. A full description of the mapping mole system together with the measurement procedure is given. A summary of the results is also presented with particular focus on the reproducibility and accuracy of this technique. A comparison with the results of the first system used in the laboratory is provided.

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