DESIGN AND PROTOTYPE TESTS OF AUTO-ALIGNMENT OF A WHOLE-RING GIRDER *

TPS (Taiwan Photon Source) is a new 3-GeV ring to be constructed at NSRRC Taiwan. A motorized magnet girder system with six cam movers on three pedestals was designed and tested to provide precise adjustments about six axes. With three consecutive girders to form one section, the entire ring contains 72 girders. To align these girders precisely and quickly with little manpower, considering the deformation of the floor, limited space in the tunnel and frequent earthquakes in Taiwan, a wholering auto-alignment system is proposed for these girders. This system includes contact sensors between consecutive girders and a laser-PSD system between straight-section girders, in addition to electric-levelling sensors on each girder. An algorithm to operate the system has been defined and a program fulfilled for testing on a threegirder prototype system. The detailed design of the system and testing results are described in this paper. INTRODUCTION To align all magnets precisely is critical for a lowemittance ring. The traditional survey-alignment method takes excessive time and human power, and still fails to provide sufficient accuracy of position to adjust the girder system efficiently. An auto-alignment system was thus proposed to improve alignment accuracy with little manpower and decreased installation period. This system consists of motorized girder systems and sensors between each girder to form a feedback-controlled auto-tuning system. A prototype system with three girders was constructed for testing. The system construction, operating algorithm and testing results are described in this paper. CONSTRUCTION OF THE SYSTEM For convenient, quick and precise purposes, the girder was designed with reference channels to pre-align the magnets on one girder within 30 μm. The total mass of a girder assembly is about 12 tons. The prototype system consists of three girder systems to form one twenty-fourth section of the storage ring. Each girder system is composed of three pedestals with six cam movers to support and provide six-axis precise tuning [1,2], and an electronic levelling instrument to control the pitch and roll deviations of the girder . There are four contact sensors between consecutive girders to record sway, heave, surge and yaw relations. Between the straight-section girders, a dist-invar wire system is adopted to measure the surge distance and a laser-PSD [3] to record sway, heave and yaw. The traditional survey-alignment network using laser trackers provides an initial location of the girders. Combining these initial values with the relative position of consecutive and straight-section girders, the location of the girder in the entire ring is computed iteratively with a programme described as follows. OPERATING ALGORITHM The operating algorithm is established under a condition that the sensor accuracy is a few μm, so we can improve the position accuracy from the measured data for the original survey-alignment network combined with data from sensors via iterative computation. The new position of each fiducial point is computed from the positions of two adjacent points and the data read from the sensor according to this equation. ) 1 ( 2 / ]]} ) , , ( ) , , ( )[ 1 ( ) , , ( ) , , ( [ ]] ) , , ( ) , , ( )[ 1 ( )) , , ( ( ) , , ( {[ ) , , ( i i i i i ) 1 ( i ) 1 ( i ) 1 ( 1 Z Y X G Z Y X G W Z Y X WS Z Y X G Z Y X G Z Y X G W Z Y X S W Z Y X G Z Y X G nL nR n nR R n nL n n R n nL