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Optical Position Sensor for the BWS. Electronics for final prototype and focusers performance. Jose Luis Sirvent Blasco PhD. Student 11-02-2012 Student Meeting . 2. Electronic development. 2.1 Motivation: Control laser power by software (D/A_FPGA) Laser protection against overcurrents
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Optical Position Sensor for the BWS. Electronics for final prototype and focusers performance. Jose Luis Sirvent Blasco PhD. Student 11-02-2012 Student Meeting
2. Electronic development • 2.1 Motivation: • Control laser power by software (D/A_FPGA) • Laser protection against overcurrents • Max supported current 35mA for the actual lasers (new ones will arrive soon) • Adapt signal from Photodiode (Differential) for digital sampling in the FPGA range (0-1V) • Signals with 3.9V offset & max 0.8Vpp • Integration for future developments and to ease the handling of such delicate devices. • Double channel for auto calibration and redundancy purposes • Incorporation of digital outputs (if reliable could save software processing, and simplify the final system)
2. Electronic development • 2.2 Before…
2. Electronic development • Laser protection system against over currents: • Limits the input voltage stage (to be seen if power line protection is also necessary) • Simulation validated with real data (not available)
2. Electronic development • 2.3 Circuit built: • Double low noise laser driver. • Double high speed photodiode driver. (190Mhz for 200mVpp signals) • Quadruple high speed comparators: Delay < 300ns
2. Electronic development • 2.3 Circuit built: • Integration of the Optical Circulators. • Power control FPGA_D/A and manual (both protected) • Precision low noise threshold selection and visualization (filtered Vref) • Direct connection for A/D & D/A converters
2. Electronic development • 2.4. First performance analysis: • PD Output (Yellow) VS Circuit output (Pink): • System max speed ~ 1MHz Perfect following at 2MHz • Delay < 5ns in both channels • Double comparator per channel: A) Counts, B) Turn reference
3.New RadHard lenses testing • 3.1 Comparison in Power Coupling and Tolerances of: • Co550 lenses system (Schaffter+ Kirchhoff) • 60FC-4-A4-03 & 5M-A8-03-S • Lens system M=2 (Spot ~20um) • 60FC-4-A4-03 & 5M-A4-03-S • Lens system M=1 (Spot ~10um) • Fused Silica Lenses system (RH) (Asphericon & Thorlabs) • A12-20FPX & A12-15FPX • Lens system M=2 (Spot ~20um) • 2x A12-15FPX • Lens system M=1 (Spot ~10um)
3.New RadHard lenses testing Schaffter + Kirchhoff • 3.2 Assembly: 10 um 20 um Two focusers mounted in 20 um configuration Thorlabs + Asphericon
3.New RadHard lenses testing • 3.2 Conclusion: • 1. In general tolerance behaviour as spected: • The bigger is the Magnification factor the bigger is the Disc-Lens tolerance • 20um spot sizes present good stability in a turn, however, in spite of using APC connector there are some F_P interferences. • 2.The power coupling in both focusers is similar, however for the 20um spot size configuration, Thorlabs+Asphericon presents better results. • 3. It’s not possible to measure 5um slits with a 20um focused spot • Compromise solution stability - power could be to measure 10um slits with 20um spot size. • 4. To be seen with mechanical team if Thorlabs+Asphericon 20um could be integrated. • Maybe too long distances? • 3.3 Remarks: • Why 1310nm and SMF 9/125um if visible wavelenghtscould be 532nm and SMF 3.5/125um? • With higher wavelengths the structure of the F.O and lenses in general experiment less radiation damage. (Also Standard in Telecommunications) • If for 1310 nm Damage in lenses is smaller, why to use F_Silica lenses and not Schaffter+Kirchhoff? • Corning CO-550 and ECO-550 do not provide data of radiation damage and it’s not possible to quantify the expected losses due to RIA in these materials. • It’s not possible to guarantee the stability of these materials after high irradiation, however F_Silica lenses have a lot of studies and know how.