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Beam Wire Scanner: Optical position sensor assembly and performance tests. BWS Design meeting Jose Luis Sirvent PhD. Student XX/03/2014. Position Sensors and Secondary Particle Shower Acquisition. X Axis: Optical position sensor. Resolver. Y Axis: Diamond Detector.
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Beam Wire Scanner:Optical position sensor assembly and performance tests BWS Design meeting Jose Luis Sirvent PhD. Student XX/03/2014
Position Sensors and Secondary Particle Shower Acquisition X Axis: Optical position sensor Resolver Y Axis: Diamond Detector Y Axis Diamond Detector measurements X Axis Optical position sensor measurements
1. Optical Position SensorWorking Principle • Primary Electronics: Control LD power and adapt PD signal to be acquired by ADC. • Optical Circulator: Directs the light form the LD to the sensor system and the reflected signal to the PD. • Optical Feedthrough: Overcomes the vacuum barrier. • Lens system: Focuses the light from ~9um (fibre core) to ~20um (reading spot) and collects reflections. • Encoder disc: Made of Soda-lime glass with high reflectivity Cr. Tracks. • Characteristics: All optic sensor system (in tunnel) working with SMF 9/125um @ 1310nm Photodiode Signal
1. Assembly Tests:Focusers Housings and Caps • We have 4 sets: • 2 x Schaffter + Kirrchoff • 2 x Thorlabs + Asphericon • Focusers fixation system: • Schaffter + Kirrchoff : 2 Screws @ 180 deg. • Thorlabs + Asphericon: 2 Screws + Pressure
1. Assembly Tests:Disc Holder • The disc holder consist of two pieces: • A) Shaft attachment • B) Compressing Ring • There was an small problem in the compressing ring: • Manufacturing drawings: Step to fit disc Diam. ~ 39.9 mm • Physical piece: Step to fit disc Diam. ~ 40.9 mm • Solved modifying the piece Thanks William! • To Consider: • Materials dilatation: • Different design • 2. Amount of pressure on screws: • Special tool for fixation • 3. Mounting references: • The disk should always be mounted in • the same angular position. Key in disk?. • If calibration is always performed • alignment by eye is OK.
1. Assembly Tests:Adjustment tools and Caps • Good: • The micrometric screws took some time to arrive • The pieces fit perfectly • To Consider: • The caps are very thick and for the focuser clamping with the screw quite a lot of strength is needed. The screw could be damaged or what is worse, the focusers housing while fixed in the crown. • We’ll perform a small modification on the caps making a slit after the adjusting screw
1. Assembly Tests:The whole system in the Crown • Good: • The focuser systems (housing and adjusting elements) fits perfectly and slides softly • The micrometric screws adjusting range is correct • The space for mounting the SMF and the slits are not forcing the fibre to bend • To consider: • The fixing screws are not the best ones (not flat and scratch the focusers housing) • Too much strength needed to fix/release the cap to the focuser housing, if adjusted and dismounted the adjustment could be lost. • The fibres are quite rigid and need free space to bend (We’ll have space enough to not force them?) SMF UHV High Temp Patchcords SMF UHV Feedthroughs
1. Assembly Tests:Complete system mounted and fibre routing • Good: • The Focusers are perfectly aligned with the disc (90 degrees) and in the correct track (I cannot verify if completely in the centre…) • To consider: • The fibre routing is not trivial, it’s quite rigid and we should avoid force it to bend too much. • The use of a flexible tube to route the fibre would be a good idea (protection & routing) • We are using now 1m of special UHV SMF for High Temp (Too long, we’d need a loop inside)
2. Performance Tests:The Set-Up used CH_1 CH_2
2. Performance Tests:The Software used • Matlab-Based Script with user interface for quick tests: • Standalone operation • Analyses the two channels independently • Extracts position information • Checks that every pulse has been correctly detected • Extracts disc eccentricity (position error) • Applies calibration curves, corrected positions • Checks the calibration reliability/repetitivity • Extracts errors after calibration • Available on-line with demo files and user guide: • https://issues.cern.ch/browse/BIWS-483
2. Performance Tests:Channel 1: Pulses detected correctly & 10um Track in good conditions Scan Region Revolution - Scan Region Complete Revolution
2. Performance Tests:Channel 2: Pulses detected correctly & 10um Track in good conditions
2. Performance Tests:Disc Eccentricity Detected & Calibration curves: Prototype Complete Revolution 5e-4 Rad Scan Region Revolution - Scan Region
2. Performance Tests:Disc Eccentricity Detected & Calibration curves: Prototype Complete Revolution 5e-4 Rad Scan Region Revolution - Scan Region Projected Error Eccentricity Fork 10cm (P.E.): P.E= 2.5e-4 * 0.1m = 25mm Disc centre offset (e): 2.5e-4 = e / 0.5D D = 136.5 e = 17mm
2. Performance Tests:Disc Eccentricity Detected & Calibration curves: Lab.Test-Bench 2e-3 Rad P.E. = 100mm e = 68mm
2. Performance Tests:Disc Eccentricity Correction (1x Scan region): Prototype P.E. = 0.601mm
2. Performance Tests:Disc Eccentricity Correction (4 x Scan region): Prototype P.E. = 1.1mm
2. Performance Tests:Disc Eccentricity Correction (1x Revolution – Scan Region): Prototype P.E. = 1.501mm
2. Performance Tests:Disc Eccentricity Correction (3x Revolution – Scan Region): Prototype P.E. = 1.8mm
