A Mole for warm magnetic and optical measurements

A Mole for warm magnetic and optical measurements of LHC dipoles 1 L Bottura 1, M Buzio 1, G Deferne 1, H Jansen 2, C Glöckner 2, A Köster 2, P Legrand 1, A Rijllart 1, P Sievers 1 , F Villar 1 1 CERN, European Organization for Nuclear Research - 1211 Geneva 23, Switzerland 2 Frauenhofer Institut IPT, Aachen, Germany Eleventh International Magnet Measurement Workshop September 21 - 24, 1999 Brookhaven National Laboratory, Upton, New York, USA Thursday, 23 Sept. 1999 Berkner B 10: 50 -11: 20 1 Also published in the proceedings of the 16 th International Conference on Magnet Technology, Ponte Vedra Beach, IL, 26 Sept- 2 Oct 1999 A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

A Mole for Warm Magnetic and Optical Measurements of LHC Dipoles ¨ ¨ ¨ Introduction Mechanical layout VR Demo 1 Magnetic performance Optical performance Conclusions 1 http: //home. cern. ch/m/mtauser/www/applications/mole/virtualmole. wrl A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Introduction ¨ Why use a mole ? ¾ Purpose: measure magnetic axis ¾ Cold measurements done for max. efficiency with 15 m long coil shaft, obstructing line-of-sight to the coil center Þ travelling probe is needed ¾ Additional duties: warm field quality of all dipoles, cold field of samples ¨ Requirements for series measurements ¾ ¾ Coil center position: precision better than 0. 1 mm Warm measurements: 50 mm, B 25 m. T Rugged, quick and simple to setup and operate As many off-the-shelf components as possible A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Mole test bench overview magnet front reference bench (telescope) rear reference bench (transport motor, cable connections) A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Front reference bench Telescope CCD camera mole support shell (closed) focusing system Sliding support A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Rear reference bench Axis transfer jig Mole Cable receptacle Transport motor A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Front reference bench optical alignment targets ( 4) Laser for alignment measurement axis transfer carbon fiber jig Telescope/CCD/DSP unit granite table transport belt A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Status ¨ Warm Mole ¾ First unit accepted and under commissioning ¾ Two more units to come, will perform warm test of all LHC dipoles ¾ Can be readily adapted to warm quadrupole tests ¨ Cold Mole ¾ Order started, last design details now being finalized ¾ Will perform cold tests for a sample populations of LHC dipoles to get warm-cold axis correlation ¾ Further units may be slightly modified for cold quadrupole tests A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Mechanical layout ¨ Main features ¾ ¾ ¾ three 750 mm long radial coils coil drive: Shinsei travelling-wave ultrasonic piezo motor 4096 CPR Heidenhein angular encoder On-board feedback auto-leveling system Spring-loaded roller system Motorized traction belt drive Two granite benches to establish reference positions LED+lens system to create virtual light-spot in the coil centre Telescope + CCD camera + DSP to measure light-spot position All functions remotely controlled via RS 232 Auxiliary optical system to transfer axis to magnet fiducials A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Main components Piezo motor 3: 1 reduction gearbox Wyler encoder Coil Potentiometer Elastic coupling (with helical groove for the cable) Ball-bearing support flange A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Longitudinal transport · closed-loop pre-tensioned Inconel transport belt · feedback-controlled DC motor drive · referencing given by optical barriers at both ends of the magnet (selfcalibration at the end of each trip) · max. velocity about 1 m/s · precision of positioning better than 0. 5 mm · mole must be switched manually between apertures A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Longitudinal reference position spring-loaded roller LED viewing aperture Optical barrier (receptor) lower half-shell support front transport belt attachment A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Safety · interlock system: mole will stop if covers are removed, transport cable gets tangled, transport motor drains overcurrent · reduced velocity close to the edges · longitudinal position cross-checked with two independent measurements (angular encoder + linear potentiometer) A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Autoleveling ¨ Why autoleveling ? ¾ ¾ ¨ imperfections of beam pipe/rollers rotation of container during travel observed rotation up to 2~3°/m transport belt & cable may be twisted coil must be level prior to measurement How does it work ? ¾ ¾ ¾ DC motor engaged in container to rotate coil+encoder+piezo motor feedback system using wide-range level meter precision achieved better than 4 mrad time needed less than 5 s autoleveling done at the end of each longitudinal movement A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Auto-leveling mechanism Inner gear (linked with container) Wide-range level meter Motor shaft gear Roller (fixed tangentially by friction) A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Auto-leveling mechanism travel Start autolevel End of travelling Final configuration A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Optical measurement 1. Telescope ¾ accurately leveled and aligned wrt magnet ¾ mounted on rails to serve both apertures 2. CCD camera ¾ 752 582 pixel, 6. 00 4. 96 mm size ¾ self-aligned to telescope via reference marks 3. DSP image processor ¾ threshold filtering + center of gravity calculation ¾ measurements internally averaged over multiple takes ¾ software calibration map A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Virtual lightspot the virtual image remains in the coil center even when the mole rotates LED Magnifying lens Virtual lightspot A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Optical measurement ¨ Performance ¾ 4 mm 14 mm 20 m range ¾ total error 60 m ¾ measurement time 4 s at closest range A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Optical system calibration A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Optical system calibration A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Example: optical measurement A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Focusing system ¨ How does it work ¾ ¾ no autofocus needed longitudinal position sent to the camera at the end of each movement focusing motor follows a software calibration table total error if out-of-focus 1 m/mm A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Magnetic performance ¨ Harmonic Coils ¾ 41 750 mm fiberglass/epoxy coil support ¾ 3 radial coils with 400 turns, 3. 4 m 2 area ¾ 1 coil for main dipole, 1 for dipole compensation + 1 spare ¨ System precision ¾ ¾ Main dipole: better than 10 -4 Dipole angle: better than 0. 2 mrad Multipoles: generally better than 2· 10 -6 relative to B 1 bucking factor 2000 A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Example: multipoles A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Example: calibrated dipole angle A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Axis Transfer ¨ Why transfer the magnetic axis ? ¾ harmonics, and hence magnetic axis, are measured in the coil reference frame ¾ the center of the coil is measured in the telescope reference frame ¾ the magnetic axis is needed in the reference frame of the magnet fiducials ¨ How the transfer will be done ¾ the granite tables establish two reference positions per aperture, vertically and laterally reproducible within 20 m ¾ reference positions are measured by the telescope ¾ relative position of magnet fiducials and granite tables is measured by means of an auxiliary laser system ¾ relative position of coil center wrt magnet fiducials can thus be computed A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Axis Transfer Granite jig reference line Granite table reference line Mole coil position along magnet Magnet fiducial line Auxiliary alignment laser beam Granite table jig Telescope frame A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Axis Transfer Z Magnetic center (z) Magnet fiducial line Mole coil position Marble table jigs line Marble table reference line Y Telescope reference frame A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Problems encountered ¨ ¨ Unsteady velocity of piezo-motor, getting worse with motor heating Micro cables and connectors delicate and difficult to handle Fine alignment of the lens Image distortion due to thermal gradients in the magnet A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Piezo motor rotation speed ¨ Rotation speed quality ¾ encoder detects low-frequency rotation speed oscillations up to 8% ¾ oscillation amplitude gets larger as motor heats up ¾ oscillations interfere with measured harmonics (errors in b 2 up to 0. 5 units observed) ¨ Improvements under way ¾ optimization of stiffness and damping of the coil/motor link to minimize response ¾ fine tuning of motor speed map (t) to minimize excitation ¾ enhanced motor cooling ¾ automatic off-line filtering of spurious harmonics A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Piezo motor rotation quality Forward run Backward run average A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Piezo motor rotation quality A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Piezo motor rotation quality A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch

Conclusions 1. 2. 3. 4. 5. Magnetic and optical performance generally exceeding specifications Well suited for industrial-type test environment Test bed for further technological improvements (piezo-motor, remote encoders, etc. ) Software integration under way Minor improvements under way: smoother velocity control, better optics alignment A mole for warm magnetic and optical measurements of LHC dipoles IMMW XI, Brookhaven National Laboratory, 21 -24 Sept. 1999 marco. buzio@cern. ch