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Performance of a New Low-Pressure Water-Based CN Instrument - Rogers, Hering, Stolzenburg, Oberreit, Quant - Outline challenge of measuring CNchallenge of measuring CN description of new “gap” instrumentdescription of new “gap” instrument evolution during ProgSci & T-REXevolution during ProgSci & T-REX examples of dataexamples of data June 2006
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why measure Condensation Nuclei ? characterize the air: clean background or pollutionclean background or pollution identify aerosol plumes air mass tracer identify regions of new particle formation estimate particle scavenging rates by clouds
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challenge of measuring CN how to cover entire altitude range of HIAPER ? CN instruments common; several commercial vendorscommon; several commercial vendors particles grow in supersaturated butyl alcoholparticles grow in supersaturated butyl alcohol vapor few µm counted with OPC lose sensitivity at low pressure (alt > ~10 km)lose sensitivity at low pressure (alt > ~10 km) threshold detection size changes with pressure butanol is toxic and flammablebutanol is toxic and flammable other special-purpose instruments use fluorinertother special-purpose instruments use fluorinert water as active fluid ?water as active fluid ?
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vapor pressure of water design range
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based on TSI-3786 aka Aerosol Dynamics / Quant Low-Pressure microprocessor, ethernet, USB, serial 300 ccm, 10 Hz d* ~ 5 nm d* ~ 5 nm
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flow diagram two pumps, speed control uses feedback from orifice Δp saturate 5°C growth 45°C
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WCN evolution during ProgSci T-REX Nov 9 #1 “loaner” delivery (partially modified instrument) Nov 22 – tF01 WCN data kills DSM serial Dec 1 – RF01 Flow not controlling; troubleshoot Dec 7 – RF03 WCN not on HIAPER Dec 8 – RF04 Re-install; flow not controlling Dec 9 – RF05 Remove WCN Dec 16 - RF09 #2 delivery; flow control is good Dec 20 – RF11 “out of water” after 1 hour at 42 kft Feb 16 – tf01 shorter inlet piping; flow control good Feb 22 – tf02 add drain bottle; faster water injection Mar 24 flush orifices; dry out filters
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RF04 – poor flow control set point 300
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rf09 – good flow control
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next ? compile performance history web sitecompile performance history web site modifications to firmware faster water injection ratemodifications to firmware faster water injection rate delivery of instrument #1 + trainingdelivery of instrument #1 + training compare CN measurements MASS, FCAS, RDMAcompare CN measurements MASS, FCAS, RDMA conference paper - International Aerosol Conf., 13G16 Airborne tests of a new low-pressure water-based CN instrument http://www.aaar.org/meetings/IAC2006/index.htm
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