Harmonic Coil Design, Fabrication and Commissioning for European XFEL Linear Accelerator Superconducting Magnets Field Measurements

Abstract

A harmonic coil assembly for the European XFEL superconducting magnet measurements was designed and fabricated in IHEP. Bare coil without protection tube was selected in order to save space and cover a larger measurement radius. The coil assembly can be moved along the anticryostat pipe and can be fixed at any position by rubber brakes touching on the inner surface of the pipe, which is a part of the magnet measurement dewar. The magnetic field can be measured by rotating the coil inside the anticryostat pipe at a selected position. The superconducting magnet package consists of a quadrupole, a horizontal and a vertical dipole. The harmonic coil includes a main coil for the quadrupole and for the dipole field measurement when the single coil mode is used to measure the main field component. Two bucking coils are available to compensate the quadrupole and dipole field respectively when the two-coil mode is used to measure the high order field harmonics. A skew coil with only 2 turns and open angle of 90 degrees can be used to cancel effects due to the angular differences between the main coil plane and the bucking coil plane. The harmonic coil was tested on quadrupoles for Korea Pohang Accelerator Laboratory (PAL), a high bucking ratio of 182 was reached. The coil was shipped and used in DESY to measure the XFEL superconducting magnets. The measurement precision and reproducibility were excellent and the driving and brake system worked well.

A magnetic field measurement system of superconducting quadrupole for linear accelerator

“…It is essential, to compensate the most dominant field and the next lower order feed down component in order to obtain accurate multipoles error from the observed signal. Therefore, the high-order multipoles components accuracy is improved obviously, typical at 10 −4 with respect to the quadrupole field [11,12]. Using the rotating coil, the offsets the magnetic center can be derived based on the feed-down technique [13].…”

“…The anti-cryostat contains of two isolation tubes, are non-magnetic and seamless stainless steel. The two tubes are strictly concentric and form a vacuum space in between [11]. The inclination measurement instrument is used to adjust the horizontal plane level of the magnet (figure 5(a)), and the coaxial error is detected by a laser tracker (figure 5(b)).…”

Precision Analysis and Design of Rotating Coil Magnetic Measurements System

“…Sci. 2020, 10, x FOR PEER REVIEW 2 of 16 than the Hall effect [4,5]. For this technique, a coil is put in a cylindrical rod called a "search coil" [6][7][8][9], and its length must be longer than the magnet, measuring more than 20% of the magnet's length.…”

“…In principle, the Hall effect works when a magnetic field acts in the perpendicular direction with the Hall probe and causes a voltage known as "Hall pressure" [3]. While rotating coil magnetic field measurement is also a magnetic field measurement, it is faster than the Hall effect [4,5]. For this technique, a coil is put in a cylindrical rod called a "search coil" [6][7][8][9], and its length must be longer than the magnet, measuring more than 20% of the magnet's length.…”

“…displays a magnetic field measuring device with two important components: (a) A rotating coil drive that consists of a cylinder rod for packing coils made from G10 material (diameter 63.5 mm, length 470 mm); (1) a Printed Circuit Board(PCB) board with a search coil inside (width 53 mm, length 430 mm); (2) multi-row angular contact ball bearings placed on a base made of aluminum as a support point for the cylinder rod; (3) a DC motor worm gear (100 W, 24 V, with a maximum current 4.6 A for driving the rotating coil); (4) flexible coupling for conveying power from the motor to the rotating coils(5). (b) Measurement and data collection, which consisted of electromagnet dipole magnets sized 0.4 Tesla (6), magnetic current sensor and Agilent 3440a for reading the current supplied to the electromagnet (7), slip ring coil voltage and NI-9238 voltage module for measuring the electromotive force obtained by measuring the magnetic field (8), incremental rotating encoder and NI-9505 Module for measuring the speed and angular position of the rotating coil (9), and a computer for recording the results of the experiment with the LabVIEW 2017 program(10).…”