Vibrating Wire System Research Articles

Single Stretch Wire and vibrating wire measurement system for characterization of multipole accelerator magnets

A stretch wire magnetometer is a versatile instrument and can be treated as the primary standard of magnetic qualification of accelerator magnets. Bhabha Atomic Research Centre has developed a Stretch wire magnetic measurement system to cater to the requirements of magnetic measurements on accelerator magnets. This bench also includes a vibrating wire system. The scheme used in this instrument for measurements of magnetic flux ensures drift compensations after each scan. This feature along with post-signal processing gives an accuracy of homogeneity measurements comparable to that of a rotating coil magnetometer. Unlike conventional stretch wire systems, wire moves in the r-z plane (along r-axis) at different azimuthal angles. This provides the opportunity for drift compensation at each scan. This has immensely enhanced the measurement accuracy of non-homogeneity of integral fields to less than 3 units. The same is cross-verified with a rotating coil system. The comparison between rotating coil and stretch wire is presented. The Paper gives the step-wise procedure for the measurement of key performance indicators of an accelerator magnet. This paper brings out salient features of the system along with design and calibration results.

Research on magnetic center measurement of quadrupole and sextupole using vibrating wire alignment technique in HEPS-TF

In order to meet the extremely low emittance requirement, the magnets in the storage ring of high-energy photon source (HEPS) need to have a stable support and precise positioning. In HEPS-TF, the key and difficult technologies of HEPS should be researched and developed. Vibrating wire alignment technique is one important project of HEPS-TF. It can be used to pre-align the quadrupoles and sextupoles on one girder with high precision. A vibrating wire measurement system was set up and tested to verify the magnetic center measurement precision and the magnet adjustment error. There are one sextupole and one quadrupole installed on a multipole girder. Vibrating wire is stretched through mechanical center of the magnet apertures and supported by the test benches on the two sides. A single conducting wire is stretched through the magnet aperture and electrified by alternating current. The wire will vibrate for a period of Lorentz force. By matching the current frequency to one mode of natural frequency of the wire, the vibrating amplitude will be enhanced. And by measuring the vibrating amplitude, the magnetic field at the wire position can be got. Moving the wire across the magnet aperture in the transversal or vertical direction, the distribution of magnetic field and magnetic center position can be measured. According to the magnetic center position error to adjust the magnet. Measure the magnetic center of all magnets installed on the multipole girder one by one, and adjust their magnetic center to a line. The magnetic center measurement precision is better than ±3 μm, and the magnet adjustment error is less than 6 μm. The vibrating wire system design and a series of magnetic center measurement experiments have gained good achievements. It has been proved the vibrating wire system is designed reasonable and using the vibrating wire to align the magnets installed on a multipole girder is feasible and can reach a high precision.

Design and Magnetic Performance of Small Aperture Prototype Quadrupoles for the SwissFEL at the Paul Scherrer Institut

The Paul Scherrer Institut is building an X-ray free electron laser (SwissFEL) providing a source of intense, ultra-short pulses of coherent radiation in the wavelength range of 0.1 to 0.7 nm. In this facility, there will be 162 small aperture quadrupoles of two types (22- and 12-mm aperture), which both include horizontal and vertical steering functions, under preparation for the linac and the undulator line. Before the series production, eight full-scale prototypes of the final design were built in collaboration between Industry and the Paul Scherrer Institut. This paper describes the features of the quadrupole design and the measurement challenges and reports the main results obtained during the magnetic measurements. The integrated field gradient, the field profile, the harmonic content, and the magnetic axis are measured using four independent systems well suited for small bore apertures: an 8 mm and a 19-mm diameter rotating coil, a Hall probe, and a vibrating wire system. The results of the integrated transfer function and of the field quality are given and discussed.

A Sensitive Magnetometer for Very Small Areas

A vibrating wire system for measuring weak magnetic fields is described for use in very small spaces. Quartz crystals are used for drivers to get sufficient velocity with very small displacements. To adjust the driving voltage to correspond exactly to the natural crystal frequency, the crystal is also used to regulate the oscillator.