Development of an autotuning magnet girder with high stability and accuracy

With the development of high-performance photon sources which have extremely low emittance, autotuning magnet girders have drawn more and more attention, especially for diffraction-limited storage rings and free-electron lasers. The biggest challenge is to simultaneously obtain high stability and high flexibility. In this paper, an autotuning magnet-girder prototype has been designed and developed. Topological optimization, multipoint supports, and locking systems have been applied for magnet-girder design to improve the stability. The modal analysis accords with the vibration test well. The natural frequency of the magnet-girder assembly is deduced as high as 45.6 Hz, which demonstrates good stability. Ball-cam movers have been chosen as adjustment mechanisms, and a closed-loop control scheme has been used to pursue high accuracy. The kinematic resolution is better than $1\mu \mathrm{m}$, and the accuracy is better than $1\mu \mathrm{m}$ within the adjusting range of $\pm 5\mathrm{mm}$. Besides, it can eliminate most of the calibration, which can save much manpower and time. The tests demonstrate that the magnet girder can be used for beam-based girder alignment with high stability and high accuracy.

Figure 1

Design sketch of the autotuning magnet-girder prototype.

Figure 2

Model for topological optimization.

Figure 3

Results of static optimization. (a) Convergence curve and (b) high pseudodensity elements.

Figure 4

Major factors of the deformation between the ball unit and cam mover. (a) Exploded structure and (b) cross section.

Figure 5

First-order FEA mode shapes of the magnet-girder assembly prototype, in the cases of (a) case 1, (b) case 2, and (c) case 3.

Figure 6

Tested results of case 2: (a) the first-order mode shape and (b) the transfer function of X-direction vibration.

Figure 7

Amplitude of harmonic response of the magnet on the side of the girder.

Figure 8

Kinetic design principle of the prototype: (a) diagram of Boyes clamp and (b) assumed balls and grooves.

Figure 9

The diagrammatic drawing of the one ball-cam mechanism.

Figure 10

Theoretical adjusting ranges in the directions of (a) horizontal and (b) vertical.

Figure 11

Length gauge distribution.

Figure 12

The theoretical adjusting resolutions in the directions of (a) horizontal and (b) vertical.

Figure 13

Standard deviations of transitions along the X direction for five times.

Figure 14

The backcalculated adjusting errors with gravity and the test results (up, tested errors with transition in the X direction; down, backcalculated errors in each direction; the blue lines are midvalues, and red lines are maximum and minimum boundaries).

Figure 15

The comparisons of the interactions: (a) the transition along the X direction and (b) the rotation in the roll direction.