Title: The Performance Of A Continuous Supersonic Expansion Discharge Source
1The Performance Of A Continuous Supersonic
Expansion Discharge Source
- Carrie A. Kauffman, Kyle N. Crabtree, Benjamin J.
McCall - Department of Chemistry, University of Illinois
- June 24th, 2010
2Outline
3Motivation
4Motivation
Interstellar medium Diffuse Molecular
Clouds Temp 60 K Density 101103 cm-3 Dense
Molecular Clouds Temp 20 K Density 104106
cm-3
5Sensitive Cooled Resolved Ion BEam Spectroscopy
For more on SCRIBES, please stay for RE06.
6Production of Cold Molecular Ions
Trot 300 K
Trot 110-180 K
7Production of Cold Molecular Ions
Trot 110 K
-No spectral intensity dilution, reduced spectral
congestion -gt easy spectral assignment -Astrophyis
cally relevant temperatures-gt molecular
fingerprint for astronomers
8Continuous Supersonic Expansion Discharge Source
Small Orifice
Trot 5-30 K
High Pressure Gas
Low Pressure
9Continuous Supersonic Expansion Discharge Source
Leybold 3-Stage Pumping System Pumping speed
3600 L/s
10Basic Design
Gas Input
High Temp Silicone O-rings
Cathode
Macor Cap
Anode
Macor Spacer
11H3
Rotational Constant 43.56 cm-3
McCall, B.J. Ph.D. Thesis, University of Chicago,
2001.
12Experimental Set-up
13Source Conditions
- 2-3 bar of backing pressure
- Orifice Size flared like a trumpet 0.5 to 4.1 mm
in diameter - Typical Chamber Pressure 200-300 mTorr
- Negative voltage applied to cathode and anode
held at ground - Current 10-130 mA
14Sample Spectra
15Results
Low Current Regime
- ? column density with increasing discharge
current. - ? in rotational temperature with increasing
discharge current. - Operated for over 150 hours without source
failure.
16Results
High Current Regime
- ? column density
- No change in rotational temperature
- 50 hours of operation
17Comparison
This Work Xu et al.1 Tom et al.2 Davis et al.3
Type of Source Continuous nozzle Continuous slit-jet corona Pulse Nozzle Pulsed Slit
Rotational Temperature (K) 50-110 77 60-100 Not Reported
Ion Density (cm-3) 8 1010 to 2 1012 Not Reported 1 x 1011 5x1010
3. Davis et al. Chem. Phys. Lett. 2001, 344,
23-30.
1. Xu et al. Chem. Phys. Lett. 1995, 242 126-131.
2. Tom et al. J. Chem. Phys. 2010, 132, 081103.
18Summary
- Rotational temperatures in the range of 50-110
Kelvin. - Robust durable design capable of operating for
an extended period of time. - Ion densities comparable to pulsed sources?
Increased sensitivity! - Plans for improving this design will be tested by
studying the ?1 fundamental band of HN2.
19Acknowledgments
For more information visit the McCall Research
Group at http//bjm.scs.uiuc.edu