Open-Atmosphere Phase-Shift Cavity Ringdown Instrument NOAA’s Ark

1. Troy Owens, John Trytko, Adam Ornstein, Dmitriy Polyakov, Michael Tanksalvala Open-Atmosphere Phase-Shift Cavity Ringdown InstrumentNOAA’s Ark

2. Conceptual Background • System measures the phase shift of light to determine the concentration of particles in the air • Light accumulates a media-dependent phase shift as it resonates in the cavity • Higher concentration of particles induce a larger phase shift • This is used in conjunction with other instruments to compute specific concentrations of various aerosols John Dmitriy Michael Adam Troy

3. Beam Splitter Laser Controller Photodiode Ringdown Cavity Laser Phase Shift Detector Kebabian, Paul L., Scott C. Herndon, and Andrew Freedman. "Detection of Nitrogen Dioxide by Cavity Attenuated Phase Shift Spectroscopy." Analytical Chemistry 77.2 (2005): 725. Print. John Dmitriy Michael Adam Troy

4. ApplicationsandAdvantages • Applications: • Reference for specialized particle-detecting systems • Measure aerosol content in open air • Air quality • Advantages: • Compact and portable • Turn-key (no knowledge of instrument required) • Self-aligning optics • Autonomous data collection John Dmitriy Michael Adam Troy

5. Goals • Low Priority • Achieve awesomeness – easy with lasers • Detect phase shift on optical breadboard • Medium • Automated laser alignment system • Data storage • No use of external lab equipment • High • Compact (backpack size) system • Entirely autonomous (after easy startup) John Dmitriy Michael Adam Troy

6. FunctionalOutlineofApproach Power Optics CMOS Camera Alignment μ-Controller Photo Diode A/D Operating System Battery SD Card User I/O Clock John Dmitriy Michael Adam Troy

7. Constraints • Successful signal detection • Cavity must establish and maintain an optical standing wave • Mechanical stability • Meaningful output from photodiode • Final output in specified file format • Time!!! John Dmitriy Michael Adam Troy

8. Safety and Environmental Impact • Environmental impact • Difficult to dispose of parts • Beam doesn’t interfere with the environment • Safety • Laser can damage eye • Low power laser John Dmitriy Michael Adam Troy

9. Laser Safety • Class IIIa-IIIb (continuous wave, 1 to 20 mW) • Visible wavelengths (350 – 800 nm) • Low power/area (< 2 mW/cm2) • Hazards • Corneal damage only (safe exposure time is roughly .25 seconds) • Non-permanent retinal damage if viewed for 1 to 2 seconds, permanent viewed for longer • Do not look into the laser John Dmitriy Michael Adam Troy

10. ManufacturabilityandSustainability • Manufacturability • Intended for singular creation • Mass production unlikely • Easily portable • Sustainability • Low power consumption • Durable parts and reliable electronics John Dmitriy Michael Adam Troy

11. DetailsofDesign

12. The Optics • Laser controller (enabling phase detection) • Concave mirrors for the cavity • Controllable mirror mounts (enabling feedback control) • Beam-splitter • Photodiode (signal measurement) • CMOS Camera (sensor for feedback) John Dmitriy Michael Adam Troy

13. Beam Splitter Laser Controller Photodiode Ringdown Cavity Laser Phase Shift Detector Image obtained from: http://www.chem.ualberta.ca/~xu/research/crds.htm John Dmitriy Michael Adam Troy

14. Active Feedback/Alignment • Objective: Maintain maximum signal power • Keeps beam pointed at photodiode using PID Controller • If signal is lost, methodically scans over area to try to find it • Concave mirrors provide small amount of passive beam alignment John Dmitriy Michael Adam Troy

15. Controllable Mirror Mounts • Constructed from normal mirror mounts and (disassembled) piezoelectric buzzers • Piezoelectric ceramic expands when voltage is applied John Dmitriy Michael Adam Troy

16. Laser Controller Laser Beam Splitter CMOS Camera Alignment System Micro- Controller John Dmitriy Michael Adam Troy

17. Construction and Testing • Create circuit to connect camera to computer • Helps for debugging during and after development • Enables good capstone demo • Add controllable mirror and microcontroller • Beam-steering functionality • Software-based PID signal maximization • Signal-finding • Add second mirror and integrate it into PID John Dmitriy Michael Adam Troy

18. Beam Splitter Laser Controller Photodiode Laser Alignment System John Dmitriy Michael Adam Troy

19. Obstacles • Processing Time • Camera can output millions of datapoints • 20 MHz processor • Number of Cameras • Signal strength at Camera • Contingency plan: Using concave mirrors provides a self-aligning force, so even without active feedback, measurements can be made John Dmitriy Michael Adam Troy

20. Operating System and μC • SD Card • Storage of phase, timestamp, and “valid bit” • OS Storage (cold-start) • Clock • Microcontroller oscillator • Timestamps John Dmitriy Michael Adam Troy

21. Battery Phase Shift Detector Hardware Clock Micro- Controller User Interface Operating System SD Solid State Drive John Dmitriy Michael Adam Troy

22. Operating System and μC • SD Card • Storage of phase, timestamp, and “valid bit” • OS Storage (cold-start) • Clock • Microcontroller oscillator • Timestamps John Dmitriy Michael Adam Troy

23. OS I/O and Functions Data Processing Data Formatting Time Management OS / μC ADC SD Card Time I/O John Dmitriy Michael Adam Troy

24. Operating System SD John Dmitriy Michael Adam Troy

25. DivisionofLabor John Dmitriy Michael Adam Troy

26. Schedule John Dmitriy Michael Adam Troy

27. Budget John Dmitriy Michael Adam Troy

28. FundingandGrants • NOAA • Providing optical parts (mirrors, mounts, laser controller, optical breadboard, laser) • Will keep the prototype upon completion • UROP Funding (Pending) • Up to $1000 funding • Requires a report upon completion John Dmitriy Michael Adam Troy

29. Potential Issues / Contingency Plan • Not able to integrate OS with Optics • Will demonstrate the systems separately at Expo • Not able to construct casing for a portable device • Demonstrate the project on separate breadboards at Expo John Dmitriy Michael Adam Troy

30. Questions? Bob Tom Carissa Alex Sam Image obtained from: http://www.picgifs.com/graphics/noahs-ark/ John Dmitriy Michael Adam Troy