THERMAL LASER EXCITATION BY SUPERSONIC MIXING IN A GAS DYNAMIC NOZZLE
A Continuous Supersonic Expansion Discharge Nozzle For Rotationally Cold Ions
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Transcript of A Continuous Supersonic Expansion Discharge Nozzle For Rotationally Cold Ions
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Carrie A. Kauffman, Kyle N. Crabtree, Benjamin J. McCall
Department of Chemistry, University of Illinois
June 23rd, 2009
A Continuous Supersonic Expansion Discharge Nozzle For
Rotationally Cold Ions
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MotivationMolecular
ions◦ Organic Reaction
Intermediates◦ Combustion◦ Atmospheric
Chemistry◦ Interstellar
Chemistry
Simulation of N2+ of the A 2∏u – X 2∑g
+
(4-0)+
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For more on the progress of SCRIBES, stay for the next two talks.
Supersonic Source
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Supersonic ExpansionBarrel Shock
High Pressure
Gas Small Orifice
•Adiabatic Process, dq = 0dU = dq –dw dU = -PV
•Tvib >> Trot > Ttrans , where Trot ~ 0.5-30 K
Low Pressure Region
Mach Disk
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Compatible with SCRIBES
Leak tight
Robust
Modular
Maximize ion density
Design Considerations
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Previous Reported Discharge Designs
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First Generation - Corona
Engelking, P.C.; Corona Excited Supersonic Expansion. Rev. Sci. Instrum., 1986, 57, 2274-2277.
Advantages DisadvantagesContinuous Materials Chosen
No modular componentsCompatibility
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Slit Design
Broks, B.; Brok, W.; Remy, J; van der Mullen, J.; Benidar, A.; Biennier, L. & Salama, F.; Modeling the Influence of Anode-Cathode Spacing in a Pulsed Discharge Nozzle. Spectrochim Acta B, 2005, 60, 1442-1449.
Advantages DisadvantagesMaterials Chosen Integration with SCRIBES
ClusteringPulsed
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Nozzle Design
McCarthy, M. C., Chen, W.; Travers, M. J. & Thaddeus, P. Microwave Spectra of 11 Polyyne Carbon Chains. Astrophys. J. Suppl., 2000, 129, 611-623.
Advantages DisadvantagesCompatibility with SCRIBES
Pulsed
Modular Materials
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Design
• 1-3 Atmosphere of backing pressure
•Orifice Size: 250 to 1000 micron with varying geometry
•Typical Chamber Pressure 100 mTorr
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Source
•Nitrogen Gas
•Running Voltage: -200 to -500 V
•Running Current: 30 mA
•Operation Time: 100+ Hours
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Characterization of the source
Ion Current
Optimization of Cooling Capabilities
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SummaryDesign Continuous Supersonic Expansion
Nozzle Discharge
Modular
Self-Aligning
Robust
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Acknowledgements
SCS Machine Shop
McCall Research Group
Ben McCall