1. An electrostatic ion trap for Fourier transform mass spectrometry
Matt Lappin

2. Overview Motivation and background Fourier transform mass spectrometry
Electrostatic harmonic potential ion trap
Design and functionality
Simulation
Electronics and peripheral systems

3. Motivation Titan Saturn’s moon Titan has interesting properties
Methane cycle akin to Earth’s water cycle
Organonitrogen rich atmosphere and organic “sand” on the surface
Electrostatic discharge during rare sandstorms could provide activation energy for a reaction to produce a basic amino acid
Titan

4. Motivation Voyager and Cassini missions successful in probing Titan
Simulations of Titan’s atmosphere indicate that there is the potential for life
Many mission proposals to visit Titan in the coming decade to search for life, and a critical instrument to include would be a mass spectrometer

5. Motivation Space bound mass spectrometer must be:
Small
Low power
Precise over the desired mass range of amu, as this is where the chemicals necessary for life will be found
The electrostatic ion trap mass spectrometer proposed here meets these requirements

6. Overview Motivation and background Fourier transform mass spectrometry
Electrostatic harmonic potential ion trap
Design and functionality
Simulation
Electronics and peripheral systems

7. FOURIER TRANSFORM MS
Mass spectrometry involves ionizing a compound and measuring the abundance of ions produced at each mass level
FTMS detects oscillation in the time domain of these ions and converts the time domain signal into a frequency spectrum
Oscillation is engineered so that the frequency is related to the mass to charge ratio

8. FOURIER TRANSFORM MS
Mention that this happens at vacuum
Time domain signal
Magnetic field of strength B causes oscillation of ions with frequency w = qB/m
Detection plates provide time domain signal
Fourier transform provides frequency spectrum, which is proportional to mass spectrum

9. FOURIER TRANSFORM MS
RF Sweep to Accelerate the Ions
Most mass spectrometers detect ions (destructively) using an electron multiplier. ICR detects ions from their image charge
Transient Ion Image Current Signal
Mass Spectrum

10. Orbitrap Electrostatic Complicated ion injection
Tranverse oscillation frequency related to m/z

11. Overview Motivation and background Fourier transform mass spectrometry
Electrostatic harmonic potential ion trap
Design and functionality
Simulation
Electronics and peripheral systems

12. The autoresonant ion trap MS
A.V. Ermakov and B.J. Hinch of Rutgers used a similar trap in their autoresonant ion trap mass spectrometer (ART-MS)
Verified f is proportional to 1/(m/z)½ for ions in the mass range Da
ART-MS uses resonant ejection, not FT-MS, which requires RF sweep
Ermakov, A.V.; Hinch, B.J. An autoresonant ion trap mass spectrometer. Rev. Sci. Instrum. 81,
(2010); doi: /

13. The electrostatic harmonic potential ion trap
Plate to protect macor filament clamp (0V)
3A current source
The trap is 2.5” long and has a 1” diameter.
1 kV, switched
Can be pulsed to 10V
Held at a positive potential (5V)
Just discuss components, not functionality
To detector (0V) for image current detection

14. Ion production and analysis
5 V
0 V
Electron impact ionization

15. Ion production and analysis
5 V
0 V

16. Ion production and analysis
1000 V
0 V

17. SIMION simulation parameters
Pulse time: 5 microseconds
Trapping potential delay: 17 microseconds
Trapping duration: 1 millisecond
250 kHz
Scientific Instrument Services, Inc., Ringoes, NJ,

18. Vacuum Chamber/Flange
10-pin instrumentation
BNC
SHV

19. Construction Source Trap Signal plate Trapping plates(1kV)
Stainless steel plates and alumina tubes/spacers: Kimball Physics eV parts
Assembled by Caltech CCE Insturment Shop

20. Electronics
Vacuum

21. Electronics
Need for high speed switch on nano second

22. Signal Detection Circuits
Very low level signal, careful amplification
Image Credit: Amptek, Inc.
Image Charge Detection Mass Spectrometry: Pushing the Envelope with Sensitivity and Accuracy. John W. Smith, Elizabeth E. Siegel, Joshua T. Maze, and Martin F. Jarrold. Analytical Chemistry (3),

23. Summary and Conclusions
Verified that the instrument should work based on SIMION simulation
Instrument assembly is in progress
Tests to come after the completion of assembly

24. Acknowledgments
I would like to thank all members of the Beauchamp group, especially Professor Beauchamp and graduate student Daniel Thomas, for all of your help. I would also like to thank Jeff Groseth in the CCE Electronics shop for helping with the assembling the electronics for the spectrometer, and the CCE Machine shop for help with machining and assembling parts of the instrument.