Transcript Laser measurement of the LAT detector displacement
Laser measurement of the LAT detector displacement Jerzy Zachorowski
Instytut Fizyki UJ
Wojciech Wierba
Instytut Fizyki Jądrowej PAN
Optical measurements of detector position • Precision requirement: sub m m transverse 10 m m axially.
• Optical sensors non-contact measurements.
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Possible axial displacement sensors • Interferometers: resolution l /2 or better (down to nm), require continueous illumination, • Triangulation detectors: resolution m m, working distance cm • Photonic detectors: m m-resolution, minimal working distance 3
Position sensitive detectors • Position sensitive photodiodes • CCD (Charge Coupled Device) Matrices • Two detectors allow x,y, j tracking 4
Transverse position Proof-of-principle measurements • Simple CCD camera, • He-Ne red laser, • Laser translated in 50 m m steps 5
Camera pictures 6
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Problems • Color camera instead of B&W • Saturation of the detector • Big pixel size • Large beam 8
Position measurement 220 210 200 190 180 170 160 150 140 130 120 110 100 0 Linear Regression for direkt_B: Y = A + B * X Parameter ----------------------------------------------------------- A Value Error 92,57067 0,72927 B 0,12727 0,00128 ----------------------------------------------------------- (1) (2) 100 200 300 400 500 600 camera position [um] 700 800 900 1000 9
Result • Coefficient: 0,12727pixel/ m m • Resolution 1 m m if the accuracy of determination of the center of the light spot is better than 0.1pixel • Possible!
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To be done • Small-pixel camera, • Picture analysis algorithm, • Micro pointing stability of lasers, • Laser MTBF, • Two lasers? System reliability, • Exposure and readout synchronization.
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