Jose Luis Sirvent Supervisor: Jonathan Emery Student Meeting 19 September 2011

 1.Introduction & Objectives  2.Schema proposed  3.Components to use.  4.Optical path  5.Sources of losses  6.Next Steps

 A) Objective: ◦ Accurate Position Measures ◦ Absolute position measurement (Motor control)  Solid rotor resolver Rotasyn® (Mohamed) ◦ Relative position measurement (Optical system)  Based in disk encoder, should be more precise (Me)

 B) Introduction: ◦ Technical Student, I’ll do here my master thesis ◦ I’ll contribute in the work of Julien, Mohamed, Jonathan & Juan in the OPS for the VWS. ◦ Optical system based on encoder disk in transmission or reflection (In order to obtain the relative position of the folk). ◦ First approach to study: Transmission ◦ The optical system must work under the next conditions:  Position measurement every: 500 µrad  Accuracy: 25 µrad  Ultra High Vacuum  Operation Temperature: 200 ºC  Service life: 20 years  Cumulated ionizing radiation: 20KGy (1KGy/year)  Cables length: 250m

 Schema Proposed for the transmission approach

 1. Laser Diodes (850nm) ◦ A) KLD085VC (VCSEL)  2.5mW to 4mW  Max If 12 mA  Op Temp: 0 to 85 deg ◦ B) PL85B002ST83-T-0 (ST)  2mW to 5mW  Max If 45mA ◦ C) OPF372A (ST)  30µW (may not work)  Max If 100mA  Op Temp: -40 to 85 deg

 2. Optical Fiber ◦ FPC FIBRE OPTIQUE ST-ST 1M ◦ Multimode fiber with ST Connectors ◦ Duplex ◦ Bandwidh nm ◦ Working in the first transmission window ◦ Diamètre, faisceau:0.0625mm ◦ Attenuation ≤ 3.5 dB/Km (850nm) ◦ Insertion Loss ≤ *0.35 dB ◦ Final model: 500m ◦ Simulator model: 2m ◦ Pz=Pi*e -αz ◦ α=A(dB/Km) /4.34*10 3 * Typical for St Connectors, verified with Sabritec

 3. Hybrid ST-SMA 905 adapter ◦ Interface between fiber and Feedthrough ◦ Typical Insertion Loss:  0.35 dB (ST Connector)  >1dB (SMA 905) *according to Newport

 4. FeedThrought ◦ Materials: SS, Polyimide, Fused Silica RoHS ◦ Gender: Male / Bare Polished ◦ Max. Bake Temperature: 250ºC ◦ Max. Operating Temperature: 250ºC ◦ Max. Vacuum Level: 1x Torr ◦ Contact Material: 62.5 Micron ◦ Operating Wavelength: Optimized for 850nm and 1300nm ◦ Numerical Aperture: 0.27 ± 0.02Fiber (AN) or (0.22) ◦ Profile: Graded-Index, Multimode ◦ Alpha= Asin(0.27)  15.6 deg ◦ Laser Diameter= (0.27*D*2)+62.5

 5. Optical Disk ◦ Material: Borofloat ◦ n Borofloat = 1.46 (850nm) ◦ Pattern in Chrome (brilliant) ◦ Possible Problems:  Light area much bigger than certain holes  Light Duality  Interference Pattern in receiver?  Could this be good or bad?

 6. Optical Receivers  A) KPGX1G (GaAs) ◦ TIA: Transimpedance amplifier ◦ Input power monitoring ◦ Optical sensitivity: -24dB ◦ Photo-electric conversion efficency: 3.9 mV/µW  B) OPF562 (SI) ◦ TIA: Transimpedance amplifier ◦ SMA or ST connector (Better with SMA, directly to the feedthrough) ◦ Optical sensitivity: ? ◦ Photo-electric conversion efficency: 7 mV/µW  C) KPIX150-H333 (SI) ◦ TIA: Transimpedance amplifier ◦ Optical sensitivity: -31dB ◦ Photo-electric conversion efficency: 40 mV/µW  D) KPIXA1G-H33 (SI-APD) ◦ TIA: Transimpedance amplifier ◦ Optical sensitivity: -33dB ◦ APD Responsivity: 0.45 A/W  E) PDSIU500-ST-83 (SI) ◦ Perfect couple for the PL85B002ST83-T-0 ◦ Responsivity: 0.45 A/W

 1. Study of Light: This study can be done in two ways ◦ A. Laser as a constant light distribution *  Traditional optics principle ◦ B. Laser as a Gausian light distribution **  Gausian optics: More realistic and accurate… but more difficult *The literature consider this approach suitable for light coupling in multimode fiber. ** Gausian optics are applied when coupling lignt in monomode fibers

 2. The optical path through the Disk ◦ The radius of the light is bigger with the distance

 3. The Fresnel Reflexion Effect:  Effect produced in the intersection of two environments with different refraction index.  This happens 4 times: Fiber - Vacuum Vacuum - Disk  Disk - Vacuum Vacuum – Fiber Loses in disk: nvac= 1, nfloat= 1.46 LossFres = dB Loses in Fiber-vacuum… nfiber ? n vacuum n disk

WIRE SCANER OPTICAL POSITION SENSOR n(vacuum)1 FEEDTHROUGHDISKLASER BEAM nf Thickness (D2)500micronsAlpha10.27radians Core Diameter62.5micronsnd (float) d microns Numerical Aperture (A.N.)0.27 Distance to disk (D1)500micronsFIBERAlpha20.19radians Length2metersd microns Att3.5dB/Km LOSSES (Lc)Alpha30.27radians Fresnell Disk-Vacuum dBd microns Fresnell Fiber-Vacuum dB Insertion Losses ST 0.35*41.4dBIntersection with Pattern Insertion Losses SMC 1*22dBPattern (um) Optical Fiber0.007dBGaps Free Space dB Total Losses dB Pr3.37%Ps Power Balance Ps 5mW dBm Pr mW dBm

 A) Check these calculus in the test bench and verify the existence of other possible sources of losses. ◦ Is the dispersion of the fiber applicable for our signals (850nm)? (exists pulse enlargement in 500 meters?) ◦ Apply possible optical penalizations and effects (if rise times are significant there would be a delay).

 B) Is this scheme optimal for detection? ◦ Check other possible approaches  1. Check the possibilities and losses in reflection  2. Usage of collimator in reflection or/and transmission.

Jose Luis Sirvent Student Meeting 19 September 2011