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22-Nov-0522-Nov-05 [email protected]@nbi.dk 11
TPC CalibrationTPC Calibrationwith laser trackswith laser tracks
B.B.S. NielsenS. Nielsen & G. Renault & G. Renaultfor thefor the
ALICE CollaborationALICE Collaboration
Niels Bohr InstituteNiels Bohr Institute
22-Nov-0522-Nov-05 [email protected]@nbi.dk 22
Installation work on laser systemInstallation work on laser system
Installation work still to be done:Installation work still to be done: Mount laser optics on TPC endcapsMount laser optics on TPC endcaps Build laser tent/hut in clean roomBuild laser tent/hut in clean room Install laser (Spectron from Copenhagen or new Ekspla)Install laser (Spectron from Copenhagen or new Ekspla) Take care of operational safetyTake care of operational safety Align all laser optics with UV beam --- Align all laser optics with UV beam --- this could be time this could be time
consumingconsuming
How to run the laser in the clean room:How to run the laser in the clean room: DCS should work, but it is also possible to adjust by handDCS should work, but it is also possible to adjust by hand Laser free running (10 Hz) --- supply trigger like cosmicsLaser free running (10 Hz) --- supply trigger like cosmics Operate each TPC half separately --- may have a fair Operate each TPC half separately --- may have a fair
amount of some setup time to change amount of some setup time to change
22-Nov-0522-Nov-05 [email protected]@nbi.dk 33
First steps at NBIFirst steps at NBI
What has been done?What has been done? My Aliroot installed (soon on the HEHI www)My Aliroot installed (soon on the HEHI www) Aliroot environment installed (Config.C)Aliroot environment installed (Config.C) First Simulation+Reconstruction chain doneFirst Simulation+Reconstruction chain doneWhat needs to be done?What needs to be done? Simulate laser tracks in the TPC (in Aliroot)Simulate laser tracks in the TPC (in Aliroot) Reconstruct laser tracks in the TPCReconstruct laser tracks in the TPC Extract drift velocity (Temperature gradient)Extract drift velocity (Temperature gradient) Study misalignment effects on reconstructed laser tracksStudy misalignment effects on reconstructed laser tracks
Man power (NBI): Johann, GaMan power (NBI): Johann, Gaëlël, B, Børgeørge
22-Nov-0522-Nov-05 [email protected]@nbi.dk 55
Why do we needWhy do we needlaser tracks in the TPC?laser tracks in the TPC?
In order to align and calibrate the TPC with In order to align and calibrate the TPC with Straight tracks:Straight tracks:
Correct distortions in the z-direction due toCorrect distortions in the z-direction due to– Temperature gradient (drift velocity gradient Temperature gradient (drift velocity gradient
measurement)measurement)– Mechanical misalignment (reconstructed straight tracks)Mechanical misalignment (reconstructed straight tracks)
Take into account: Take into account: – Distortion due to ExB effects (calibration)Distortion due to ExB effects (calibration)– Space-Charge in the drift volume (calibration)Space-Charge in the drift volume (calibration)
22-Nov-0522-Nov-05 [email protected]@nbi.dk 66
Laser tracks principleLaser tracks principle
2 2 (2*4.66eV) impurity ionization (2*4.66eV) impurity ionization NN22(trace), IP~5-8 eV(trace), IP~5-8 eV
Ne,CONe,CO2 2 (90/10), IP~10eV(90/10), IP~10eV
Metal structures will emitMetal structures will emit
photo-electronsphoto-electrons
y
z
x
E
B drift
laser track
