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RS232 A new cavity ring-down instrument for airborne monitoring of N 2 O 5 , NO 3 , NO 2 and O 3 in the upper troposphere lower stratosphere A.A . Ruth 1 , S.S. Brown 2 , H. Dinesan 1 , W.P. Dubé 2 , M. Goulette 1 , G. Hübler 2 , J. Orphal 3 , A. Zahn 3 1. Physics Department & Environmental Research Institute, University College Cork, Cork, Ireland 2. National Oceanic and Atmospheric Administration, Earth System Research Laboratory, R/CSD7, 325 Broadway, Boulder, CO 80305, USA 3. Karlsruhe Institute of Technology, Institute for Meteorology & Climate Research, D-76121 Karlsruhe, Germany The aim of this project is to build a new instrument for the in-situ detection of 4 gas species in the Upper Troposphere Lower Stratosphere (UTLS): NO 3 , N 2 O 5 , NO 2 and O 3 . The instrument will be installed in the CARIBIC container [1] on board a commercial Lufthansa aircraft (Airbus 340-600). Its design is based on similar instruments from NOAA [2,3]. Species detection is based on cavity ring- down spectroscopy. The instrument enables to study the transport of nitrogen oxides and ozone to and from the UTLS and to investigate the nocturnal oxidative capacity of this region of the atmosphere which can show large variability as a function of altitude [4,5]. The project will contribute to a better understanding of the atmospheric chemistry of the UTLS and its role in global climate change. Two cavities (1) and (3) are operated at 662 nm (NO 3 and N 2 O 5 ). Two cavities (2) and (4) are operated at 405 nm (NO 2 and O 3 ). Introduction Container (1.6 tons), over 100 atm. parameters, 15 instruments Dedicated inlet system Flight routes 2004-2015 (422 flights) CARIBIC hall at KIT CARIBIC Discussion Absorption Detection The detection is based on 4 high- finesse optical cavities (length 44 cm, finesse > 300000, effective path length Experimental Setup Specifications Blue laser: 405 nm Red laser: 662 nm HR mirrors: = 99.999% (Blue) = 99.999(5)% (Red) Time resolution: 1s DAQ: 1 MS/s The design of the instrument was completed at the end of 2015. The construction is on-going, and the device will be tested in the lab during summer 2016. If successfully executed, the instrument is expected to be installed in the CARIBIC container during winter 2016-2017. The instrument is expected to deliver data between 2017 and 2020. Estimates on precision and accuracy of the device for detection on the four trace species as outlined in the «Expected Results» section are based on previous papers [2,3,6]. The critical parameters to be established are the inlet transmission efficiencies, the minimal measurable ring-down time difference Δ = 0 − , the optimum sampling rate of the DAQ system, and flow-related noise in the cavities, especially for the heated cavity. (1) NO 3 (max absorption) (4) O 3 + NO NO 2 + O 2 (3) N 2 O 5 NO 3 + NO 2 heat (2) NO 2 (max absorption) References [1] C. Brenninkmeijer et al., Civil Aircraft for the regular investigation of the atmosphere based on an instrumented container: The new CARIBIC system, Atmos. Chem. Phys. 7 (2007) 4953-4976. [2] H. Fuchs et al., Determination of inlet transmission and conversion efficiencies for in situ measurements of the nocturnal nitrogen oxides, NO 3 ,N 2 O 5 and NO 2 , via pulsed cavity ring-down spectroscopy, Anal. Chem. 80 (2008) 6010-6017. [3] N. Wagner et al., Diode laser-based cavity ring-down instrument for NO 3 ,N 2 O 5 , NO, NO 2 and O 3 from aircraft, Atmos. Meas. Tech. 4 (2011) 1227-1240. [4] S.S. Brown, J. Stutz, Nighttime radical observations and chemistry, Chem. Soc. Rev. 41 (2012) 6405-6447. [5] S.S. Brown et al., Variability in nocturnal nitrogen oxide processing and its role in regional air quality, Science 311 (2006) 67- 70. [6] R.J. Wild et al., A Measurement of total reactive nitrogen, NO y , together with NO 2 , NO, and O 3 via cavity ring-down spectroscopy, Env. Sci. & Tech. 48 (2014) 9609-9615. α = absorption coefficient [cm –1 ] c = speed of light [cm s –1 ] , 0 = ring-down time [s] (with and without sample respectively) = number density [cm –3 ] = cavity length /sample length = absorption cross section [cm 2 ] = inlet transmission efficiency Methodology α= 1 c 1 − 1 0 =α relative detector signal time [ s] 0 (no sample) wavelength [nm] [10 –19 cm 2 ] [10 –17 cm 2 ] laser excitation laser excitation Info on NO 3 and NO 2 is used to also retrieve N 2 O 5 and O 3 number densitites. Gas Flow System 500 mm Power consumption: ~320 W Flight duration (autonomy): ~50 hours Weight: max. 60 kg Design ≈ 44 km, empty cavity ring-down time ≈ ). Flow control, data collection, analysis, and zeroing procedures are fully automated and controlled by dedicated electronics and software within the device. Exhaust N 2 O 5 cavity NO 3 cavity NO 2 cavity O 3 cavity Purge manifold Scrubber 1st-heating PRx : Pressure Regulators (2+2) PGx : Pressure Gauges (7) PTx : Pressure Transducers (4) Vx : Manual Valves on bottles (2) Vx : 2 way electric Valves (8) V3 : 3 way electric Valve (1) AFx : Aerosol Filters (6) MFCx : Mass Flow Controllers (8) V2 V3 V9 V10 V11 V6 Pump Buffer volume V7 2 μm 140 °C, 31 cm 75 °C °°°° °°°° burst disk 1 burst disk 2 T1 T2 T4 T3 T5 T6 T10 T7 T8 T9 T12 V5 2nd-heating 80 °C, 16 cm small filter V8 V1 V4 T13 T14 T15 T11 Flow to Vx NO BOX NO BOX OPTICAL CAGE OUTSIDE RACK AF6 PT1 PT2 PT3 PT4 MFC1 MFC2 MFC3 MFC4 MFC7 MFC6 AF3 AF4 AF5 AF2 AF1 MFC8 Sample MFC5 PR1 PG1 PG6 PG5 PG7 NO Bottle 2000 ppm NO Bottle 100 ppm PR3 PR4 PG3 PG4 Zero air 1 Zero air 2 PG2 PR2 We would like to thank Science Foundation Ireland for supporting this project under the Strategic Partnership Pro- gramme (contract: (14/SPPI 3010) ). We like to thank Nick Wagner and Rob Wild (NOAA) for providing the Allan Plot data to us. Acknowledgement NO 3 0.8 pptv (in 1 s) N 2 O 5 1.0 pptv (in 1 s) NO 2 , O 3 25 pptv (in 1 s) Precision Accuracy Expected Performance The accuracies include uncertainties in the literature cross-sections and their temperature dependence, where known. Integration time [s] Allan Dev 2σ [pptv] Allan Dev 2σ [pptv] Integration time [s] NO 3 [pptv] N 2 O 5 [pptv] From [3]: Elapsed time [s] Elapsed time [s] NO 3 N 2 O 5 0.8 pptv 0.2 pptv 0.2 pptv 1.0 pptv NO 3 0.2 pptv (in 1 min) N 2 O 5 0.2 pptv (in 1 min) NO 2 , O 3 5 pptv (in 1 min) − 9 / + 12 % [3] − 8 / + 11 % [2] ± 3 % [6] Allan Plots (expected !) DAQ Embedded System Pressure Gauges cDAQ-9137- Windows Electronic Valves Mass Flow Controllers Laser Controllers 4 2 4 PPTs PMT Data RS485 Manifold card 7 1 1 8 9 USB BB9 USB USB2 USB1 USB RS232 USB USB hub 7 ports RS232 USB USB PMT Control Pump Humidity Sensor Converter Temperature Controllers USB hub 4 ports Master Computer Communication Module NI 9223 9402 9269 9269 9375 9220 9212 Thermo couples Flow to Vx
