Optical Position Sensor for the BWS. Electronics for final prototype and focusers performance.

Optical Position Sensor for the BWS. Electronics for final prototype and focusers performance.

Jose Luis Sirvent BlascoPhD. Student

11-02-2012Student 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

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• 3.2 Assembly:

Two focusers mounted in 20 um configuration

Schaffter + Kirchhoff

10 um 20 um

Thorlabs + Asphericon

Configuration: Spot 10um (Complete turn)

Track Schaffter + Kirchoff Thorlabs + Asphericon

5 um

10 um

15 um

Configuration: Spot 10um (Detail)

Track Schaffter + Kirchoff Thorlabs + Asphericon

5 um

10 um

15 um

Configuration: Spot 20um (Complete turn)

Track Schaffter + Kirchoff Thorlabs + Asphericon

5 um

10 um

15 um

Configuration: Spot 20um (Detail)

Track Schaffter + Kirchoff Thorlabs + Asphericon

5 um

10 um

15 um

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 wavelenghts could 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.