Adjustment of 4 Drive Beam Quads positions on TM0 CLIC girders

1. BE/ABP-SU/ Adjustment of 4 Drive Beam Quads positions on TM0 CLIC girders

2. BE/ABP-SU/ Contents Introduction A priori data Fiducialisation Measurement devices Alignment procedures Supporting plate and shims Supporting plate equipped by screws Measurements results Conclusions

3. BE/ABP-SU/ Introduction • The CLIC mock up, under assembly in the building 169, is at the moment composed by the supporting system of 2 modules Type 0 and recently by 4 Drive Beam Quads. • The goal of the measurements and adjustments performed early November was to align the 4 DBQ: 2 DBQ with respect to 1 girder axis. • Alignments were done according to the 2 methods proposed by Nick Gazis (either by wedging, or by using screws)

4. BE/ABP-SU/ A priori data Fiducialisation • Fiducialisation of Boostec girder in CMM Olivetti (accuracy MPE about 6 µm) • Fiducials on cradles not used during • DBQ alignment because of a • temperature about 23°C • Fiducialisation of the 4 DBQ (and associated BPM) in the CMM Leitz Infinity (accuracy MPE under 1 µm)  Use of 4 fiducials during alignment • All components are mock-ups  fiducialisation of the beam pipe

5. BE/ABP-SU/ A priori data Measurement devices • Fiducials CCR 1.5’’ holders glued on girders and DBQ • CCR 1.5’’  error of sphericity and centering less than 0.0001’’ (about 2.5 µm) • Laser tracker Leica AT401  accuracy about 7 to 10 µm rms in that kind of measurement volume

6. BE/ABP-SU/ Alignment procedures Supporting plate and shims • Vertical adjustment by 3 shims make DBQ unstable  Using of 4 shims (not isostatic) • Lateral adjustment by using a mallet • Surprisingly not so bad! • Lateral gap between plate and girder doesn’t allow alignment  disassembling of DBQ / plate, adjusting, assembling • Fixing the supporting plate to the girder by using screws creates lateral misalignment • Dynamic following of the fiducials during screwing • WARNING: Even after tightening, the DBQ can move if it is hit

7. BE/ABP-SU/ Alignment procedures Supporting plate equipped by screws • 3rd adjustment screw inaccessible • Vertical wedging • All lateral threads were out of range • Manually repairing in place • Mechanical part blocks the supporting plate • Longitudinal displacing • Lateral screws generate stress and misalignment •  Return to first adjustment method

8. BE/ABP-SU/ Measurements results Z Z X X 3069 Y Y 3079 Final position of the DBQ beam pipe axis in the girder reference frame

9. BE/ABP-SU/ Conclusions • It’s a pity to accurately machine a supporting plate and to need to repair threads, to adjust lateral position (link DBQ / plate), etc. • Total alignment lasted about 4.5 days  Now we could perform it again within 2 days. • Alignment tolerance of 20 µm is not respected for all DBQ. • We are limited by adjustment systems and not by measurement device. • If a new adjustment system is designed, we would like to take part to the mechanical design and we will be happy to try again to align DBQ.