NBI TPC laser calibration system Børge Svane Nielsen Niels Bohr Institute GSI, 10 December 2001 Table of Contents System Goals 1 Design of laser system: from laser to narrow beams 2 Precision: production, installation and alignment 10 Production, installation and alignment 11
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NBI
TPC laser calibration system
Børge Svane Nielsen
Niels Bohr Institute
GSI, 10 December 2001
Table of Contents
System Goals 1
Design of laser system: from laser to narrow beams 2
Precision: production, installation and alignment 10
Production, installation and alignment 11
NBI System Goals
System Goals
Planned use of laser calibration system:
– Electronics testing– Sector alignment– Drift velocity measurement– Drift distortions: temperature effects, space charge and ExB effects
Goals for laser track layout and precision:
– 1 mm UV laser beams through most of TPC volume– 1–5 mip equivalent ionization– cross sector boundaries appropriately– radial beams at different z and
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– production + installation precision: � 10-20 mm @ 2-3 m– alignment precision: � 0.2 mm
Collaboration:
– Alexei Lebedev (STAR) can collaborate part-time– will probably supply micro-mirrors from Moscow
NBI Design of laser system: from laser to narrow beams
Issues relating to TPC design:
– Placement of beam transport pipe between TPC and space frame– Laser rods not back-to-back– High voltage rod moved to 5 o’clock position– Space for optics boxes on TPC end-plates– 50 mm pipes at � 120 mm above TPC end-plates– 44 mm laser rods– � 15 mm optical holes through central electrode ring– specify type(s) of glue and materials
Missing design issues:
– Details in rod mechanics and micro-mirror support– Quartz window in central electrode hole?– Details in optics for beam transport (e.g. polarisation issues)– Details in beam monitoring and steering– One or two lasers?
– Micro-mirror production and measurement probably as for STAR– Assembly and measurement of rod pieces at NBI– Full rod assembly and measurement at CERN
Issues relating to TPC assembly:
– Rod installation: can we assure�
mechanically to ��� or better?– Alignment measurements on assembled TPC, before service
support wheel: look through rods from end-plate to end-plate
– Measure some spots from HeNe laser inside TPC before chambers?To be studied and put into schedule: time and access
Optics and laser control and monitoring:
– Detailed design and production in parallel with rod production– Production and assembly at NBI– Installation and alignment on TPC end-plates– Laser hut and beam transport in surface test area– Laser hut and beam transport in ALICE