Post on 22-Jul-2020
transcript
RS
232
A new cavity ring-down instrument for airborne monitoring of N2O5, NO3, NO2 and O3 in the upper troposphere lower stratosphere
A.A. Ruth1, S.S. Brown2, H. Dinesan1, W.P. Dubé2, M. Goulette1, G. Hübler2, J. Orphal3, A. Zahn3
1. Physics Department & Environmental Research Institute, University College Cork, Cork, Ireland2. 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 instrumentfor the in-situ detection of 4 gas species in theUpper Troposphere Lower Stratosphere (UTLS):NO3, N2O5, NO2 and O3. The instrument will beinstalled in the CARIBIC container [1] on board acommercial Lufthansa aircraft (Airbus 340-600). Itsdesign is based on similar instruments from NOAA[2,3]. Species detection is based on cavity ring-down spectroscopy. The instrument enables tostudy the transport of nitrogen oxides and ozone toand from the UTLS and to investigate the nocturnaloxidative capacity of this region of the atmospherewhich can show large variability as a function ofaltitude [4,5]. The project will contribute to a betterunderstanding of the atmospheric chemistry of theUTLS and its role in global climate change.
Two cavities (1) and (3) are operated at 662 nm (NO3 and N2O5).
Two cavities (2) and (4) are operated at 405 nm (NO2 and O3).
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 nmRed laser: 662 nmHR mirrors:𝑅 = 99.999% (Blue)𝑅 = 99.999(5)% (Red)Time resolution: 1sDAQ: 1 MS/s
The design of the instrument was completed at theend of 2015. The construction is on-going, and thedevice will be tested in the lab during summer 2016. Ifsuccessfully executed, the instrument is expected tobe installed in the CARIBIC container during winter2016-2017. The instrument is expected to deliver databetween 2017 and 2020.Estimates on precision and accuracy of the device fordetection on the four trace species as outlined in the«Expected Results» section are based on previouspapers [2,3,6]. The critical parameters to beestablished are the inlet transmission efficiencies, theminimal measurable ring-down time difference Δ𝜏 =𝜏0 − 𝜏 , the optimum sampling rate of the DAQsystem, and flow-related noise in the cavities,especially for the heated cavity.
(1) NO3 (max absorption)
(4) O3 + NO NO2 + O2
(3) N2O5 NO3 + NO2
heat
(2) NO2 (max absorption)
References[1] C. Brenninkmeijer et al., Civil Aircraft for the regular investigationof the atmosphere based on an instrumented container: The newCARIBIC system, Atmos. Chem. Phys. 7 (2007) 4953-4976.[2] H. Fuchs et al., Determination of inlet transmission andconversion efficiencies for in situ measurements of the nocturnalnitrogen oxides, NO3, N2O5 and NO2, via pulsed cavity ring-downspectroscopy, Anal. Chem. 80 (2008) 6010-6017.[3] N. Wagner et al., Diode laser-based cavity ring-down instrumentfor NO3, N2O5, NO, NO2 and O3 from aircraft, Atmos. Meas. Tech. 4(2011) 1227-1240.[4] S.S. Brown, J. Stutz, Nighttime radical observations andchemistry, Chem. Soc. Rev. 41 (2012) 6405-6447.[5] S.S. Brown et al., Variability in nocturnal nitrogen oxideprocessing and its role in regional air quality, Science 311 (2006) 67-70.[6] R.J. Wild et al., A Measurement of total reactive nitrogen, NOy,together with NO2, NO, and O3 via cavity ring-down spectroscopy,
Env. Sci. & Tech. 48 (2014) 9609-9615.
α = absorption coefficient [cm–1]c = speed of light [cm s–1]𝜏, 𝜏0 = ring-down time [s] (withand without sample respectively)𝑛 = number density [cm–3]𝑅𝐿 = cavity length /sample length𝜎 = absorption cross section [cm2]𝑇𝐸 = inlet transmission efficiency
Methodology
α =1
c
1
𝜏−1
𝜏0
𝑛 = α𝑅𝐿𝜎𝑇𝐸
rela
tive
det
ecto
r si
gnal
time [𝜇s]
𝜏0 (no sample)
𝜏
wavelength [nm]
𝜎[1
0–1
9cm
2] 𝜎
[10–1
7cm
2]
laser excitation laser excitation
Info on NO3 and NO2 is used to also retrieve N2O5 and O3 number densitites.
Gas Flow System
50
0 m
m
Power consumption: ~320 WFlight duration (autonomy): ~50 hoursWeight: max. 60 kg
Design
≈ 44 km, empty cavity ring-down time 𝝉𝟎 ≈ 𝟏𝟒𝟕 𝛍𝐬). Flow control, datacollection, analysis, and zeroing procedures are fully automated and controlledby dedicated electronics and software within the device.
Exhaust
N2O5 cavity
NO3 cavity
NO2 cavity
O3 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
V9V10
V11
V6
Pump
Buffervolume
V7
2 µm140 °C, 31 cm
75 °C
°°°° °°°°
burst disk 1
burst disk 2
T1
T2
T4
T3T5
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
PG6PG5
PG7
NOBottle2000ppm
NOBottle100ppm
PR3
PR4
PG3
PG4
Zero air 1
Zero air 2
PG2
PR2
We would like to thankScience Foundation Ireland forsupporting this project underthe Strategic Partnership Pro-gramme (contract: (14/SPPI3010) ).
We like to thank Nick Wagnerand Rob Wild (NOAA) forproviding the Allan Plot datato us.
Acknowledgement
NO3 0.8 pptv (in 1 s)N2O5 1.0 pptv (in 1 s) NO2, O3 25 pptv (in 1 s)
Precision Accuracy
Expected Performance
The accuracies include uncertainties in theliterature cross-sections and theirtemperature dependence, where known.
Integration time [s]
Alla
n D
ev 2σ
[pp
tv]
Alla
n D
ev 2σ
[pp
tv]
Integration time [s]
NO
3[p
ptv
]
N2O
5[p
ptv
]
From [3]:
Elapsed time [s] Elapsed time [s]
NO3 N2O5
0.8 pptv
0.2 pptv
0.2 pptv
1.0 pptv
NO3 0.2 pptv (in 1 min)N2O5 0.2 pptv (in 1 min)NO2, O3 5 pptv (in 1 min)
− 9 / + 12 % [3]− 8 / + 11 % [2]
± 3 % [6]
Allan Plots(expected !)
DAQ Embedded System
PressureGauges
cDAQ-9137-Windows
ElectronicValves
Mass FlowControllers Laser
Controllers
4 2 4
PPTs
PMTData
RS
485
Manifoldcard
711 89
US
B
BB
9
US
B
USB2USB1
US
B
RS
232
US
B
USB hub7 ports
RS232
US
B
US
B
PMTControl
Pump
HumiditySensor
Converter
TemperatureControllers
USB hub4 ports
MasterComputer
CommunicationModule
NI 9223 9402 9269 9269 9375 9220 9212
Thermocouples
Exhaust
N2O5 cavity
NO3 cavity
NO2 cavity
O3 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
V9V10
V11
V6
Pump
Buffervolume
V7
2 µm140 °C, 31 cm
75 °C
°°°° °°°°
burst disk 1
burst disk 2
T1
T2
T4
T3T5
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
PG6PG5
PG7
NOBottle2000ppm
NOBottle100ppm
PR3
PR4
PG3
PG4
Zero air 1
Zero air 2
PG2
PR2
Flow to Vx