An electrostatic ion trap for Fourier transform mass spectrometry Matt Lappin

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

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

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

Motivation Space bound mass spectrometer must be: Small Low power Precise over the desired mass range of 1-300 amu, as this is where the chemicals necessary for life will be found The electrostatic ion trap mass spectrometer proposed here meets these requirements

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

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

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

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

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

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

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 1-300 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, 013107 (2010); doi: 10.1063/1.3276686

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

Ion production and analysis 5 V 0 V Electron impact ionization

Ion production and analysis 5 V 0 V

Ion production and analysis 1000 V 0 V

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

Vacuum Chamber/Flange 10-pin instrumentation BNC SHV

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

Electronics Vacuum

Electronics Need for high speed switch on nano second

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 2011 83 (3), 950-956

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

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.