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TPC Calibration with laser tracks

TPC Calibration with laser tracks. B. S. Nielsen & G. Renault for the ALICE Collaboration Niels Bohr Institute. Installation work on laser system. Installation work still to be done: Mount laser optics on TPC endcaps Build laser tent/hut in clean room

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TPC Calibration with laser tracks

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  1. TPC Calibrationwith laser tracks B.S. Nielsen & G. Renault for the ALICE Collaboration Niels Bohr Institute renault@nbi.dk

  2. Installation work on laser system Installation work still to be done: • Mount laser optics on TPC endcaps • Build laser tent/hut in clean room • Install laser (Spectron from Copenhagen or new Ekspla) • Take care of operational safety • Align all laser optics with UV beam --- this could be time consuming How to run the laser in the clean room: • DCS should work, but it is also possible to adjust by hand • Laser free running (10 Hz) --- supply trigger like cosmics • Operate each TPC half separately --- may have a fair amount of some setup time to change renault@nbi.dk

  3. First steps at NBI What has been done? • My Aliroot installed (soon on the HEHI www) • Aliroot environment installed (Config.C) • First Simulation+Reconstruction chain done What needs to be done? • Simulate laser tracks in the TPC (in Aliroot) • Reconstruct laser tracks in the TPC • Extract drift velocity (Temperature gradient) • Study misalignment effects on reconstructed laser tracks Man power (NBI): Johann, Gaël, Børge renault@nbi.dk

  4. Back up renault@nbi.dk

  5. Why do we needlaser tracks in the TPC? In order to align and calibrate the TPC with Straight tracks: • Correct distortions in the z-direction due to • Temperature gradient (drift velocity gradient measurement) • Mechanical misalignment (reconstructed straight tracks) • Take into account: • Distortion due to ExB effects (calibration) • Space-Charge in the drift volume (calibration) renault@nbi.dk

  6. Laser tracks principle • 2 g (2*4.66eV) impurity ionization • N2(trace), IP~5-8 eV • Ne,CO2 (90/10), IP~10eV • Metal structures will emit photo-electrons B drift y E x laser track z renault@nbi.dk

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