Curie Family (Jacques and Pierre in back, discoverers of the piezoelectric effect) Paris, France, circa 1880

Transcription

1 Curie Family (Jacques and Pierre in back, discoverers of the piezoelectric effect) Paris, France, circa 1880

2 Piezoelectric Nozzle Technology Aerosol Generation Edgewood Aerosol Science Solder Deposition MEMS Devices (MicroFab Technologies) Aroma Generation (MicroFab Technologies) Bioactive Arrays (MicroFab Technologies)

3 Trace Explosive Standards Using InkJet Printing Technology Fluorescein + TNT RDX Fingerprint 2.5 cm NIST JetLab II Printer System 2.5 cm (pending)

4 Vaporjet Calibrator for IMS-Based Trace Explosive Detectors ^ (and CWA) Mike Verkouteren, Greg Gillen Surface and Microanalysis Science Division National Institute of Standards and Technology Gaithersburg, Maryland, USA and David Taylor MicroFab Technologies Austin, Texas, USA

5 Why a Calibrator? Tens of thousands trace detectors deployed Multiple venues (e.g. airports, embassies, consulates, check-points, sports stadiums, courthouses, federal buildings, ports/harbors) Given improvements in sensitivity, vapor detection more practical and preferable Vapor processing important in particle detection Reliable standards needed to maintain and improve throughput, accuracy, and sensitivity

6 Outline Vaporjet Calibrator Description Design Droplet formation Droplet vaporization Application Testing IMS detectors Testing portal filters Summary

7 NIST Vaporjet Calibrator Objectives Reliable and dynamic, on-demand trace compound delivery Pulsed or steady-state Programmable concentration-time profiles (6 independent jet nozzles) Transfer standard, traceable to primary standards Basis for future improvement of vapor detection technology PIEZOELECTRIC NOZZLES CAMERA-MICROSCOPE RTD Strobed LED Array

8 Vaporjet Components 5 cm

9 Vaporjet System

10 Projected Range in Delivered Trace Vapor Concentrations Compound concentration in solvent (5 to pg/µl) Droplet jetting rate (40 to 4000 Hz) Number of nozzles (1 to 6) Flow rate of air (1 to 80 LPM) Picograms per liter air Equilibrium Vapor Pressure (25 C) RDX 1 TNT 2 PETN 3 10, Parts per trillion (v/v)

11 5000 µm

12

13 Droplet Emergence 40 µs Intervals Vaporjet Conditions Nozzle 1 Liquid: isobutanol Voltage: 41 v Dwell: 41 µs Echo: 0 v Frequency: 1 khz Airflow: 0 LPM 50 µm

14 Droplet Diameter Measurement Average diameter, micrometers Drop ejection Tail merges oscillation Gradual evaporation Time since ejection, microseconds

15 Droplet Formation Piezoelectric Parameters Diameter (um) Extreme Average Extreme dwell Voltage base Time echo Diameter (um) Dwell Time (us) Average Jetting Frequency (Hz) Diameter (um) Average Voltage & Dwell (V & us)

16 Surface-to-Droplet Heat Transfer Regimes Avoiding the Bounce during Vaporization Isobutanol droplets (bp 108 ºC) 130 ºC 210 ºC Isobutanol droplets (bp 108 ºC) Bernardin et al Int J. Heat Transfer 40, 247.

17 IMS Detector Response to Vapors

18 VaporJet + IMS Detectors Continuous Jet Mode Conditions Air flowrate: 10 LPM Rel. humidity < 10 % Sheath: 80 to 150 ºC Sampled air: 116 ºC PETN: Hz RDX: Hz TNT: Hz

19 Vaporjet RDX IMS Response IMS Response (a.u.) Instrument = GE VT2 Drift T = default Drift Flow = default Vaporjet Parameters Nozzle 2 Voltage = 45 v Dwell = 45 us Airflow = 10 L/m Air T = 115 deg.c Air RH < 10 % 10 ng/ul RDX in isobutanol 1000 Hz 500 Hz Hz Vapor Sampling Time (s)

20 Vaporjet PETN - IMS Response Instrument = GE VT2 Drift T = default Drift Flow = default IMS Response (a.u.) Vaporjet Conditions Voltage = 42 v Dwell = 42 us Airflow = 10 L/m Air T = 116 deg.c Air RH < 10 % 10 ng/ul PETN in isobutanol 500 Hz 2000 Hz 1000 Hz Vapor Sampling Time (s)

21 Vaporjet TNT - IMS Response Instrument = GE VT2 Drift T = default Drift Flow = default IMS Response (a.u.) Hz 2000 Hz 1000 Hz Vaporjet Parameters Voltage = 41 v Dwell = 41 us Airflow = 10 L/m Air T = 115 deg.c Air RH < 10 % 10 ng/ul TNT in isobutanol Hz Vapor Sampling Time (s)

22 Portal Vapor Collection Efficiency

23 Heat Tint on Portal Collector Filters During heating, oxide coating forms on stainless steel Does this affect collection performance of vapor stage? Unheated 250 ºC 500 ºC Bekaert Bekipor 316L Stainless Steel

24 Vapor Collector System SS 316L Fiber Mesh Bekaert Bekipor ST 60 AL3 Heat-Sink Block, Thermo-Electric Cooler, Collector Filter, and PTFE Mask

25 Explosive Vapor Collection System Pulsed Jet Mode Conditions Air flowrate: 5 LPM RH: <10 % to >80% RTD: 130 ºC Sheath: 80 to 220 ºC Collector: 50 ºC RDX: 2000 droplets TNT: droplets

26 TNT Vapor Collection Filter Collection Efficiency 4.6 % ± 4.5 % 5.1 % ± 3.4 % 4.7 % ± 3.3 % Vaporjet Conditions Nozzle 1: TNT Voltage: 41 v Dwell: 41 µs Sheath: 80 ºC to 220 ºC Collection: 50 ºC Air flow: 5 LPM Rel. humidity < 10% Instrument: Barringer IonScan 400B Desorber: 220 ºC Drift Tube: 168 ºC

27 RDX Vapor Collection 900 Dry Air Humid Air Dry Air 800 IMS Response (a.u.) Vaporjet Conditions Nozzle 2: RDX Voltage: 47 v Dwell: 47 µs Sheath: 80 to 200 ºC Instrument: Barringer IonScan 400B Desorber: 220 ºC Drift Tube: 168 ºC 0 Σ = 59 % Σ = 86 % Σ = 34 % Collection and Analysis Sequence : 2 ng RDX introduced

28 Summary & Challenges Promising approach to generating trace vapor airstream standards Reliability Reproducibility Solvent effects Memory issues Temperature/solvent optimization Calibrating the Calibrator Orthogonal methods