Laser Design Review, CERN, 27 Jan 2003Børge Svane Nielsen, NBI1 TPC Laser system Functions of the...
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Transcript of Laser Design Review, CERN, 27 Jan 2003Børge Svane Nielsen, NBI1 TPC Laser system Functions of the...
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 1
TPC Laser systemTPC Laser system
Functions of the system Basics of the design Construction tolerances and alignment Lab tests at NBI Status of system components Production status and installation
Design Review, CERN, 27 January 2003Børge S. Nielsen, J.J. Gaardhøje, N. Lindegaard
and Jørn Westergaard
Niels Bohr Institute
A. Lebedev, Brookhaven National Laboratory
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 2
Laser system objectives
• Electronics testing• Sector alignment• Drift velocity monitoring
– Pressure, temperature– Temperature gradients (stratification?)– ExB effects, space charge
• Two possible approaches:– Relative measurements, rely only on time stability of laser
ray position– Absolute measurements, requires knowledge of absolute
position of laser ray. More ambitious
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 3
TPC Laser principleTPC Laser principle
20-40 μJ/pulse, = 1 mm
266 nm, 100 mJ/pulse, 5 ns pulse, = 25 mm
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 4
Beam pattern inside TPCBeam pattern inside TPCRadial beamsStratetic sector boundary crossingsAvoid laser beam crossings8 ’layers’ of rays along z
336 laser tracks in full TPC
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 5
Spectron Laser Systems (UK): model SL805-10-UPGPulsed UV laser (Nd:YAG): 100 mJ / 5 ns pulse @ 266 nm, max 10 Hz expanded beam = 25 mm divergence < 0.35 mrad, pointing stability < 0.1 mrad remote controllable (RS-232)
Spectron Laser Systems (UK): model SL805-10-UPGPulsed UV laser (Nd:YAG): 100 mJ / 5 ns pulse @ 266 nm, max 10 Hz expanded beam = 25 mm divergence < 0.35 mrad, pointing stability < 0.1 mrad remote controllable (RS-232)
UV laserUV laser
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 6
Laser hut and laser beam transport (1)
Laser hut and laser beam transport (1)
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 7
Laser hut and laser beam transport (2)
Laser hut and laser beam transport (2)
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 8
Beam transport on TPC end plates (1)Beam transport on TPC end plates (1)
Shaft sideShaft side
Beam entrance90º mirrorBeam entrance90º mirror
Beam splitter 50/50Beam splitter 50/50
Prism 30º bendPrism 30º bend
Beam splitter 33/67Beam splitter 33/67
Beam monitorBeam monitor
Beam splitter 99/1Beam splitter 99/1Beam splitter 50/50Beam splitter 50/50
Prism 30º bendPrism 30º bend
Muon side beam entranceMuon side beam entrance
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 9
Beam transport on TPC end plates (2)Beam transport on TPC end plates (2)
Muon sideMuon side
Beam entrance90º mirrorBeam entrance90º mirror
Beam splitter 50/50Beam splitter 50/50
Prism 30º bendPrism 30º bend
Beam splitter 33/67Beam splitter 33/67
Beam monitorBeam monitor
Beam splitter 99/1Beam splitter 99/1Beam splitter 50/50Beam splitter 50/50
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 10
Muon arm side beam transport
Muon arm side beam transport
limited space between TPC and space frame move beam transport 10º from vertical plane adds 2 mirrors on shaft side + modifies beam transport on muon side
attach 50 mm pipe on outside of TPC permanently
special prismspecial prism
”knee” in beam transport on shaft side”knee” in beam transport on shaft side
”standard” prism”standard” prism
Muon sideMuon side
Shaft sideShaft side
We are currently considering to move back into the vertical planeWe are currently considering to move back into the vertical plane
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 11
Design in progress on opto-mechanical supports on end-plates (copy/modify STAR systems):
Optics on TPC end platesOptics on TPC end plates
Prism holder
Construction foreseen in NBI workshop
Laserbeam
Market survey on optical components for end-plates ongoing
Piezo-electric adjustment system from New Focus on order
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 12
Mirror adjustersMirror adjusters
Based on commercial piezo solution 3 fully adjustable mirrors per half-TPC
Ethernet interface
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 13
Laser rod with mirrorsLaser rod with mirrors
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 14
Mirror support ringsMirror support rings
All rings have been produced at NBI
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 15
Micro-mirror z positionsMicro-mirror z positions
(a)
(b) (b)
(b)
(a)
(a)
4 micro-mirrors per rod, at about (0, 1/3, 2/3, 1) length vary z positions slightly between odd (a) and even (b) rods
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 16
Alignment by Poisson spotAlignment by Poisson spot
Wide laser beam Ball or discScreen
Camerad
= 266 nm
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 17
Operational aspectsOperational aspects
Sensors and remote controls:
Remote setup and monitoring of laser CCD cameras for beam positioning: entrance mirrors on end plates end points on end plates end of laser rods Remote beam manipulation: 4 mirrors in laser hut 1 entrance mirror on each end plateData taking:
Test + special calibration runs: trigger from laser trigger laser ( several μs @ 10 Hz) Normal physics runs: low rate trigger from laser
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 18
Stability of laser and beamsStability of laser and beams
Design with micro-mirrors laser ray positions determined by the mirror positions and angles, not by the main laser beam or movable optics.
Mechanical stability of the TPC is good enough for precise (100 m) relative measurements once the TPC is installed.
During construction and installation, the TPC will undergo stresses due to handling (rotation) and change of loads (ROCs, cables etc).
’Absolute’ positions must refer to: TPC end plates, ROCs and Central Electrode.
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 19
Construction tolerances and alignment accuracy (1)
Construction tolerances and alignment accuracy (1)
What is known precisely and ’absolutely’ during construction? (100-150 m)
pad plane z and wire z and x/y position central electrode z position
Well measured relative to each other (100-150 m, 0.05 mrad): internal dimensions and angles in micro-mirror bundles micro-mirror bundles in support rings bundle support rings in uninstalled rods
Less well measured or prone to move during handling (500 m, 0.2 mrad):
rod positions relative to ROCs, central electrode and ALICE x,y,z
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 20
Construction tolerances and alignment accuracy (2)
Construction tolerances and alignment accuracy (2)
’Internal alignment’ and iterations (offline analysis) : electrons from central electrode ’absolute’ z electrons from ROC pad plane and wires ’absolute’ z, x/y laser tracks close to outer rods good relative alignment laser tracks are straight lines iterate to best ’absolute’ positions of laser rays track time variations
Additional alignment relative to end plates with horizontal and loaded TPC (100-200 m, 0.05 mrad):
measure rod / micro-mirror bundle positions by survey through rods (fiducial marks useful) measure some beams near inner cylinder with HeNe laser after rod installation
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 21
Status and TestsStatus and Tests
Laser lab at NBI Micro-mirror production in Moscow Tests of micro-mirrors at NBI Status of other components
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 22
Laser lab at NBILaser lab at NBI
power supply
1064 nm laser
doubler
532 nm
quadrupler
266 nm
expandingtelescope
amplifier
rod with micro-mirrors
CCD camera
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 23
Reflected 1 mm beamReflected 1 mm beam
FWHM=0.93mm
z=31cm z=200cm
FWHM=0.95mm
pure Fresnel diffraction
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 24
Reflected 1 mm beams (2)Reflected 1 mm beams (2)16 cm
47 cm
FWHM=1.00mm
1.17mm 0.93mm
19 cm
1.01mm
23 cm
1.10mm
31 cm
0.93mm
100cm
150cm
0.79mm
200cm
0.95mm
z=250 cm
1.14mm
beamdivergence0.35 mrad
Fresneldiffraction
Measured
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 25
Micro-mirror productionMicro-mirror production
1 mm quartz fibrescut at 45º, polished, coated7 micro-mirrors/bundle
All 60 bundles produced and delivered in September 2002, but problems with surface quality on some mirrors and mechanical precision on some cups preliminary: 46 accepted based on surface quality most of these will be accepted after being
mechanically improved at NBI
additional 30 bundles almost ready in Moscow
reflecting surfaces
brass cup
mechanical reference surface
Micromirror bundle
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 26
Angles measurements (1)Angles measurements (1)
and angles of all micromirror faces measured by goniometer in Moscow
0.0014 (5 arc sec)
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 27
Angles measurement (2)Angles measurement (2)
Re-calculation of angles to take into account offset centres of 7 mirrors
systematics in re-calculation still to be understood
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 28
Angles measurement (3)Angles measurement (3)
However: reference surface not good bundle not fixed to support in reproducible way
only relative angles any good from this measurement
Reference surface has beenturned off in NBI workshop toprovide good surface
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 29
Mirror surfaces (1)Mirror surfaces (1)
Looked at allmirror reflectionsafter 2.5 m.
Example:bundle 18+19
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 30
Mirror surfaces (2)Mirror surfaces (2)Analysed allmirror reflectionprofilesafter 2.5 m.
Example:bundle 18+19
Rejected badreflectivities andimage shapes.
Good mirrorsgenerally havequite uniformreflectivity
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 31
Mirror reflectancesMirror reflectances
Acceptance level: 150 (arbitrary units)
Preliminary accepted bundles (based on reflectivity and image quality): 46 bundles out of 61 received
Amplitudes of profiles on previous slide:
Micro-mirror number
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 32
Angles measurements @ NBI (1)
Angles measurements @ NBI (1)
All mirror angles have been re-measuredat NBI, using laser beam setup.
Estimated precision: 0.5 mrad (2 arc min) 0.5 mrad (2 arc min)
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 33
Angles measurements @ NBI (2)
Angles measurements @ NBI (2)
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 34
Angles measurements @ NBI (3)
Angles measurements @ NBI (3)
Mean = -0.08Sigma = 0.51
Mean = -0.29Sigma = 0.94
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 35
Linear measurements @ NBI
Linear measurements @ NBI
L
Mean = -0.23 mmSigma = 0.57 mm
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 36
Rod gluingRod gluing
1. Drill holes in short rods2. Mount mirror bundles in support rings.
3. Glue mirror support rings onto short rods. Theta alignment guaranteed by jig + machined surface
4. Glue short rods into full length rods. Phi alignment adjusted during gluing
5. Measurements on final rod possible before installation.
Foreseen for February-March at CERN.
Laser Design Review, CERN, 27 Jan 2003 Børge Svane Nielsen, NBI 37
Production status and installation schedule
Production status and installation schedule
Notes and presentations: http://www.nbi.dk/~borge/tpclaser/
Rod system: Micro-mirror bundles: ready ~1 Feb 2003 Mirror support rings produced Mirror testing: ongoing, fall 2002 + beginning 2003 Rod production at CERN: spring 2003
Optics system: Principle design: done Detailed design: spring 2003 Production and installation: mid 2003 - spring 2004
Commissioning: Together with TPC chambers: 2nd half 2004 + 2005
Integration: Principle design: done Install laser in UX25: 2005 + 2006