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Carrie A. Kauffman, Kyle N. Crabtree, Benjamin J. McCall

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Presentation on theme: "Carrie A. Kauffman, Kyle N. Crabtree, Benjamin J. McCall"— Presentation transcript:

1 A Continuous Supersonic Expansion Discharge Nozzle For Rotationally Cold Ions
Carrie A. Kauffman, Kyle N. Crabtree, Benjamin J. McCall Department of Chemistry, University of Illinois June 23rd, 2009

2 Motivation Molecular ions Organic Reaction Intermediates Combustion
Atmospheric Chemistry Interstellar Chemistry + Simulation of N2+ of the A 2∏u – X 2∑g+ (4-0) Due to the low temperatures and pressures that occur in the interstellar medium, ions dominate the chemistry due to their low reaction barriers. In order to probe these species, laboratory spectra are needed. In addition, spectra of these molecular ions would aid in the understanding of organic reaction intermediates, combustion processes, and atmospheric chemistry.

3 Sensitive Cooled Resolved Ion BEam Spectroscopy Supersonic Source
For more on the progress of SCRIBES, stay for the next two talks.

4 Supersonic Expansion Barrel Shock Mach Disk Low Pressure Region
High Pressure Gas Small Orifice Adiabatic Process, dq = 0 dU = dq –dw dU = -PV Tvib >> Trot > Ttrans , where Trot ~ K

5 Design Considerations
Maximize ion density Modular Leak tight Robust Compatible with SCRIBES

6 Previous Reported Discharge Designs

7 First Generation - Corona
Advantages Disadvantages Continuous Materials Chosen No modular components Compatibility Engelking, P.C.; Corona Excited Supersonic Expansion. Rev. Sci. Instrum., 1986, 57,

8 Slit Design Advantages Disadvantages Materials Chosen
Integration with SCRIBES Clustering Pulsed 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,

9 Nozzle Design Advantages Disadvantages Compatibility with SCRIBES
Pulsed Modular Materials McCarthy, M. C., Chen, W.; Travers, M. J. & Thaddeus, P. Microwave Spectra of 11 Polyyne Carbon Chains. Astrophys. J. Suppl., 2000, 129,

10 Design 1-3 Atmosphere of backing pressure
Orifice Size: 250 to 1000 micron with varying geometry Typical Chamber Pressure 100 mTorr

11 Source Nitrogen Gas Running Voltage: -200 to -500 V
Running Current: 30 mA Operation Time: 100+ Hours

12 Characterization of the source
Ion Current Optimization of Cooling Capabilities

13 Summary Design Continuous Supersonic Expansion Nozzle Discharge
Modular Self-Aligning Robust

14 Acknowledgements SCS Machine Shop McCall Research Group Ben McCall

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