Laser measurement of the LAT detector displacement Jerzy Zachorowski Instytut Fizyki UJ Wojciech Wierba Instytut Fizyki Jądrowej PAN

2 Optical measurements of detector position Precision requirement: sub-  m transverse 10  m axially. Optical sensors non-contact measurements.

3 Possible axial displacement sensors Interferometers: resolution /2 or better (down to nm), require continueous illumination, Triangulation detectors: resolution  m, working distance cm Photonic detectors:  m-resolution, minimal working distance

4 Position sensitive detectors Position sensitive photodiodes CCD (Charge Coupled Device) Matrices Two detectors allow x,y,  tracking

5 Transverse position Simple CCD camera, He-Ne red laser, Laser translated in 50  m steps Proof-of-principle measurements

6 Camera pictures

7

8 Problems Color camera instead of B&W Saturation of the detector Big pixel size Large beam

9 Position measurement

10 Result Coefficient: 0,12727pixel/  m Resolution 1  m if the accuracy of determination of the center of the light spot is better than 0.1pixel Possible!

11 To be done Small-pixel camera, Picture analysis algorithm, Micro pointing stability of lasers, Laser MTBF, Two lasers? System reliability, Exposure and readout synchronization.