DOCSLIB.ORG

A New Quadrupole Ion Trap Mass Spectrometer for Measuring Noble Gases in Planetary Atmospheres G

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
A New Quadrupole Ion Trap Mass Spectrometer for Measuring Noble Gases in Planetary Atmospheres G Abstract #1158 (LPI nº 2083) A NEW QUADRUPOLE ION TRAP MASS SPECTROMETER FOR MEASURING NOBLE GASES IN PLANETARY ATMOSPHERES G. Avice1, A. Belousov2, S. Madzunkov2, K. A. Farley1, J. Simcic2, D. Nikolic2, M. R. Darrach2, C. Sotin2 *[email protected], 1California Institute of Technology, Division of Geological and Planetary Sciences, Pasadena, USA. 2Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA. Motivation and presentation of the instrument Sequence 1 Sequence 2 Kr, Xe Relative abundances and isotope ratios of noble gases in Ionization Ejection planetary atmospheres can answer fundamental ques- Top electrode Alumina ceramic Trapping Detection tions: Cathode/Filament spacer holder Adapted from [4] i) What was the delivery mix (Solar/Chondritic/Cometary) Ring electrode to planetary atmospheres? Anode Einzel lens Focus { Exit Bottom electrode ii) To what extent are silicate portions (mantle, crust) of ter- ELECTRON GUN restrial planets degassed? RF (ring) iii) How much of the atmosphere was lost by atmospheric escape and what is the timing of this escape? Photonis 5901 Magnum Anode (Ionizer) 0V 20 mm TM electron multiplier -110V Detector Neg. Grid 0V z symmetry axis -120V Venus is a missing piece of the noble gaz puzzle [1]. Com- Detector Pos. Grid Fig. 1: Picture of the ion trap. Ions are created by electron-impact in the mm-sized +120V pact missions recently suggested to use a noble gas qua- 0V drupole ion trap mass spectrometer (QITMS) [2] deve- space between the top and bottom electrodes. A radiofrequency signal (about 1 MHz) applied to the ring electrode traps the ions [2]. Ramping the voltage applied 0 5 10 15 20 25 loped at JPL (Fig. 1) [3] to measure noble gases in the to the ring electrode ejects ions in both directions along the z-axis. Light masses time (ms) Venus atmosphere. are ejected first. An electron multiplier (channeltron) detects the ejected ions. Fig. 2: Measurement sequence with ionization and ejection. Main questions Standard gases, samples and procedure - Is the instrument able to measure small amounts (<10-13 mol) 1 shot from the standard bottle = 2x10-14 mol of 84Kr and 8x10-16 mol of 132Xe. Atmopheric isotope ratios. of noble gases in static mode & without a cooling gas? Standard shots Samples - Does the precision meet requirements for answering Aliquots of gas are first expanded in a 0.5 L volume. Resi- Gas from acid-resistant residues of the Allende meteo- questions in planetary sciences? dual reactive gases are purified with D50/D100 capacitorr rite was extracted by laser step-heating. Reactive gases getters (SAES) during 10 mn. Gas is introduced into the were removed by a Ti sponge getter at 650 ºC. Kr and 4 L chamber enclosing the QITMS and in static vacuum Xe were separated by condensation on the walls of a Krypton (pumped closed). Pressure equilibrates within 2 mn after quartz tube held at liquid nitrogen temperature. 4 10 introduction. ++ Xenon 80 Xe 86 84 103 Precision Kr/ Kr = 0.3181 ± 0.0005 (1.6 ‰, 60 mn, N = 1005) s.e.m = N measured error 60 2 One complete isotopic spectrum counting statistics 10 10 total counts is collected every cycle (20-50 40 1 ms) meaning that measuring the 10 density gas during few minutes allows Kr ratio to compile hundreds of isotope 20 84 1 ratios (Fig. 5). The precision fol- Kr/ mass 86 Fig. 3: Isotopic spectrum showing Kr and Xe from a standard shot. lows closely the counting statis- 0 1 Note the log scale. Other peaks are hydrocarbon fragments. tics predicted by the Poisson’s 0.26 0.28 0.30 0.32 0.34 0.36 86Kr/84Kr law (Fig. 6). Fig. 5: Example of the distribution of 103 86Kr/84Kr ratios Sensitivity and signal evolution collected over 1h of measurement. error in % of the Sensitivity depends on the emission current 1.0 Reproducibility and reaches 1.2x1013 cps/torr of gas. a 86 84 2 0.1 Potential improvements: Kr/ Kr = 0.3182 ± 0.0007 (2‰, 1 , reduced = 1.8) 0.9 0.320 i) collecting all ions with a second detector 0 500 1000 1500 ii) changing the type of filament to get a more Kr 0.319 84 # accumulated ratios focused electron beam Kr/ 0.318 86 84 normalized signal Fig. 6: Evolution of the error on the Kr/ K ratio with 0.8 86 iii) changing the type of getter for a better puri- 0.317 accumulation of the isotope ratios. The error follows fication of the residual gas Kr signal (2x103 cps) closely the Poisson’s law. Methane signal (~104 cps) 0 2 4 6 8 10 Signal decreases faster than predicted by ion 0.7 # of measurement 0 1000 2000 b Several aliquots (10 over 3 days) of the consumption (Fig. 4). This is likely due to a 129Xe/132Xe = 0.9514 ± 0.005 (5‰, 1 , reduced 2 = 0.91) time (s) standard were measured to characte- growing contribution from residual gas (mainly 0.97 CH ). Fig. 4: Evolution of the Kr and CH4 signals with time. rize the external reproducibility (Fig. 7). 4 Xe 0.96 It matches the internal precision 132 1.20 0.95 Xe/ meaning that the QITMS is able to pro- Allende meteorite (HF/HCl residue) Results obtained on samples 129 0.94 duce virtually identical results over 1.15 time. Changing the source conditions Results of the measurement of gases 0 2 4 6 8 10 (energy and focus) changes the values 1.10 extracted from HF-HCl residue of the # of measurement 86 84 129 132 of isotope ratios. meteorite Allende are similar to values Fig. 7: Reproducibility of the Kr/ Kr (a) and Xe/ Xe (b) ratios. 1.05 reported in the literature [5]. For Xe relative to air example, the 40Ar/36Ar ratio is lower Preliminary Conclusions and Potential Improvements 132 Air - JPL QITMS is able to measure noble gases in static mode for extended periods of time (>10 h) Xe/ i 1.00 than 50. The isotopic composition of - Counting statistics follows the Poisson’s law Xe (Fig. 8) matches the Q component - Precision and reproducibility meet requirements for a mission sampling the Venus atmosphere 0.95 ion trap measurement found in meteorites [5]. Chondritic Xe, Busemann et al. (2000) - Future investigations: potential improvements in sensitivity, RF stability, measurement of light noble gases - QITMS would be proposed for integration on the Cupid’s Arrow small satellite mission (see Abstract #1763) 128 130 132 134 136 mass Fig. 8: Isotopic spectrum of Xe in the Allende meteorite. [1] Chassefière et al. (2012) Planet. & Space Sci. 63-64; [2] Paul & Steinwedel (1953) Zeit. fur Naturforsch. A 8; [3] Madzunkov & Nikolic (2014) J. Am. Soc. Mass Spectrom. 25; [4] March (1997) J. of Mass Spectrom. 32; [5] Busemann et al. (2000) MAPS 35..
Load more

Recommended publications
  • Mass Spectrometry: Quadrupole Mass Filter
    Advanced Lab, Jan. 2008 Mass Spectrometry: Quadrupole Mass Filter The mass spectrometer is essentially an instrument which can be used to measure the mass, or more correctly the mass/charge ratio, of ionized atoms or other electrically charged particles. Mass spectrometers are now used in physics, geology, chemistry, biology and medicine to determine compositions, to measure isotopic ratios, for detecting leaks in vacuum systems, and in homeland security. Mass Spectrometer Designs The first mass spectrographs were invented almost 100 years ago, by A.J. Dempster, F.W. Aston and others, and have therefore been in continuous development over a very long period. However the principle of using electric and magnetic fields to accelerate and establish the trajectories of ions inside the spectrometer according to their mass/charge ratio is common to all the different designs. The following description of Dempster’s original mass spectrograph is a simple illustration of these physical principles: The magnetic sector spectrograph PUMP F DD S S3 1 r S2 Fig. 1: Dempster’s Mass Spectrograph (1918). Atoms/molecules are first ionized by electrons emitted from the hot filament (F) and then accelerated towards the entrance slit (S1). The ions then follow a semicircular trajectory established by the Lorentz force in a uniform magnetic field. The radius of the trajectory, r, is defined by three slits (S1, S2, and S3). Ions with this selected trajectory are then detected by the detector D. How the magnetic sector mass spectrograph works: Equating the Lorentz force with the centripetal force gives: qvB = mv2/r (1) where q is the charge on the ion (usually +e), B the magnetic field, m is the mass of the ion and r the radius of the ion trajectory.
    [Show full text]
  • Electrification Ionization: Fundamentals and Applications
    Louisiana State University LSU Digital Commons LSU Doctoral Dissertations Graduate School 11-12-2019 Electrification Ionization: undamentalsF and Applications Bijay Kumar Banstola Louisiana State University and Agricultural and Mechanical College Follow this and additional works at: https://digitalcommons.lsu.edu/gradschool_dissertations Part of the Analytical Chemistry Commons Recommended Citation Banstola, Bijay Kumar, "Electrification Ionization: undamentalsF and Applications" (2019). LSU Doctoral Dissertations. 5103. https://digitalcommons.lsu.edu/gradschool_dissertations/5103 This Dissertation is brought to you for free and open access by the Graduate School at LSU Digital Commons. It has been accepted for inclusion in LSU Doctoral Dissertations by an authorized graduate school editor of LSU Digital Commons. For more information, please [email protected]. ELECTRIFICATION IONIZATION: FUNDAMENTALS AND APPLICATIONS A Dissertation Submitted to the Graduate Faculty of the Louisiana State University and Agricultural and Mechanical College in partial fulfillment of the requirements for the degree of Doctor of Philosophy in The Department of Chemistry by Bijay Kumar Banstola B. Sc., Northwestern State University of Louisiana, 2011 December 2019 This dissertation is dedicated to my parents: Tikaram and Shova Banstola my wife: Laxmi Kandel ii ACKNOWLEDGEMENTS I thank my advisor Professor Kermit K. Murray, for his continuous support and guidance throughout my Ph.D. program. Without his unwavering guidance and continuous help and encouragement, I could not have completed this program. I am also thankful to my committee members, Professor Isiah M. Warner, Professor Kenneth Lopata, and Professor Shengli Chen. I thank Dr. Fabrizio Donnarumma for his assistance and valuable insights to overcome the hurdles throughout my program. I appreciate Miss Connie David and Dr.
    [Show full text]
  • A Researcher's Guide to Mass Spectrometry‐Based Proteomics
    Proteomics 2016, 16, 2435–2443 DOI 10.1002/pmic.201600113 2435 TUTORIAL A researcher’s guide to mass spectrometry-based proteomics John P. Savaryn1,2∗, Timothy K. Toby3∗ and Neil L. Kelleher1,3,4 1 Proteomics Center of Excellence, Northwestern University, Evanston, Illinois, USA 2 Comprehensive Transplant Center, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA 3 Department of Molecular Biosciences, Northwestern University, Evanston, Illinois, USA 4 Department of Chemistry, Northwestern University, Evanston, Illinois, USA Mass spectrometry (MS) is widely recognized as a powerful analytical tool for molecular re- Received: February 24, 2016 search. MS is used by researchers around the globe to identify, quantify, and characterize Revised: May 18, 2016 biomolecules like proteins from any number of biological conditions or sample types. As Accepted: July 8, 2016 instrumentation has advanced, and with the coupling of liquid chromatography (LC) for high- throughput LC-MS/MS, a proteomics experiment measuring hundreds to thousands of pro- teins/protein groups is now commonplace. While expert practitioners who best understand the operation of LC-MS systems tend to have strong backgrounds in physics and engineering, consumers of proteomics data and technology are not exposed to the physio-chemical principles underlying the information they seek. Since articles and reviews tend not to focus on bridging this divide, our goal here is to span this gap and translate MS ion physics into language intuitive to the general reader active in basic or applied biomedical research. Here, we visually describe what happens to ions as they enter and move around inside a mass spectrometer. We describe basic MS principles, including electric current, ion optics, ion traps, quadrupole mass filters, and Orbitrap FT-analyzers.
    [Show full text]
  • Arxiv:1512.05503V4 [Physics.Plasm-Ph] 14 Mar 2016
    Multipole Electrodynamic Ion Trap Geometries for Microparticle Confinement Multipole Electrodynamic Ion Trap Geometries for Microparticle Confinement under Standard Ambient Temperature and Pressure Conditions Bogdan M. Mihalcea,1, a) Liviu C. Giurgiu,2 Cristina Stan,3 Gina T. Vi¸san,1 Mihai Ganciu,1 Vladimir E. Filinov,4 Dmitry Lapitsky,4, b) Lidiya Deputatova,4 and Roman Syrovatka4 1)National Institute for Laser, Plasma and Radiation Physics (INFLPR), Atomi¸stilorStr. Nr. 409, 077125 M˘agurele, Ilfov, Romania 2)University of Bucharest, Faculty of Physics, Atomistilor Str. Nr. 405, 077125 M˘agurele, Romania 3)Department of Physics, Politehnica University, 313 Splaiul Independent¸ei, RO-060042, Bucharest, Romania 4)Joint Institute for High Temperatures, Russian Academy of Sciences, Izhorskaya Str. 13, Bd. 2, 125412 Moscow, Russia Trapping of microparticles and aerosols is of great interest for physics and chemistry. We report microparticle trapping in case of multipole linear Paul trap geometries, operating under Standard Ambient Temperature and Pressure (SATP) conditions. An 8-electrode and a 12-electrode linear trap geometries have been designed and tested with an aim to achieve trapping for larger number of particles and to study microparticle dynamical stability in electrodynamic fields. We report emergence of planar and volume ordered structures of microparticles, depending on the a.c. trap- ping frequency and particle specific charge ratio. The electric potential within the trap is mapped using the electrolytic tank method. Particle dynamics is simulated using a stochastic Langevin equation. We emphasize extended regions of stable trap- ping with respect to quadrupole traps, as well as good agreement between experiment and numerical simulations.
    [Show full text]
  • Quadrupole and Ion Trap Mass Analysers and an Introduction to Resolution a Simple Definition of a Mass Spectrometer
    Quadrupole and Ion Trap Mass Analysers and an introduction to Resolution A simple definition of a Mass Spectrometer ◗ A Mass Spectrometer is an analytical instrument that can separate charged molecules according to their mass–to–charge ratio. The mass spectrometer can answer the questions “what is in the sample” (qualitative structural information) and “how much is present” (quantitative determination) for a very wide range of samples at high sensitivity Components of a Mass Spectrometer Atmosphere Vacuum System Sample Ionisation Mass Data Detector Inlet Method Analyser System How are mass spectra produced ? ◗ Ions are produced in the source and are transferred into the mass analyser ◗ They are separated according to their mass/charge ratio in the mass analyser (e.g. Quadrupole, Ion Trap) ◗ Ions of the various m/z values exit the analyser and are ‘counted’ by the detector What is a Mass Spectrum ? ◗ A mass spectrum is the relative abundance of ions of different m/z produced in an ion source -a “chemical fingerprint” ◗ It contains – Molecular weight information (generally) – Structural Information (mostly) – Quantitative information What does a mass spectrum look like ? ◗ Electrospray mass spectrum of salbutamol + 100 MH 240 OH NH tBu HO Base peak HO % at m/z 240 241 0 60 80 100 120 140 160 180 200 220 240 260 280 300 What information do you need from the analysis ? ◗ Low or High Mass range ◗ Average or Monoisotopic mass (empirical) ◗ Accurate Mass ◗ Quantitation - precision, accuracy, selectivity ◗ Identification ◗ Structural Information
    [Show full text]
  • CHAPTER 5 Mass Spectrometry, Cont'd Part 2
    CHAPTER 5 Mass Spectrometry, Cont’d Part 2 5.2.6.3 Quadrupole ion trap mass filter: While the operation of the ion trap was characterized shortly after the linear quadrupole in 1960 by Paul and Steinwedel, its application in the chemical laboratory was severely limited. This was due to difficulties associated with manufacturing a circular electrode and performance problems. These performance problems were overcome when a group at Finnigan MAT lead by Stafford discovered two breakthroughs that lead to the production of a commercially available ion trap mass filter. The first ion trap developed used a mode of operation where a single mass could be stored in the trap when previously all of the ions had to be stored. Their next important discovery was the ability for 1 mtorr of helium gas to improve the instruments resolution. The helium molecules’ collisions with the ions reduced their kinetic energy and subsequently focused them towards the center of the trap. After these initial hurdles were cleared, many new techniques were developed for a diverse set of applications especially in biochemistry. This is a result of its comparative advantage over the quadrupole when analyzing high molecular mass compounds (up to several thousand m/z units) to unit resolution in commonly encountered instruments. The ion trap is also an extremely sensitive instrument that allows a molecular weight to be determined with a small number of molecules. The ion trap is also the only mass filter that can contain ions that need to be analyzed for any significant duration of time. This allows the instrument to be particularly useful in monitoring the kinetics of a given reaction.
    [Show full text]
  • Mass Analyzers Ion Movement
    Mass Analyzers Árpád Somogyi CCIC MSP OSU Summer Workshop Ion movement • Biased metal plates (electrodes, lenses) used to move ions between ion source and analyzers • Electrodes and physical slits used to shape and restrict ion beam • Good sensitivity is dependent on good ion transmittance efficiency in this area Ionization Mass Detector source analyzer inlet all ions sorted Data ions system 1 Ion detection • Ions can be detected efficiently w/ high amplification by accelerating them into surfaces that eject electrons Ionization Mass Detector source analyzer inlet all ions sorted Data ions system Detectors TOF 2 Ion energy • Kinetic energy of ions defined by E = zeV = qV = ½ mv2 E = kinetic energy m = mass v = velocity e = electronic charge (1.60217e-19 C) z = nominal charge V = accelerating voltage Learning Check Consider two electrodes, one at 1000 V and one at ground (0 V) 1000 V0 V + ion will travel with kinetic energy of ___________ 3 Question: Consider an ion source block and an extraction lens. How would you bias the block and lens if you want the ions to be accelerated by a) 8000 eV (appropriate for magnetic sector) b) 5 eV (appropriate for entering a quadrupole) c) 20,000 eV (appropriate for entering a TOF) Notice: accelerating voltages vary with analyzer (has consequences for MS/MS) • High voltage (keV energy range) – magnet (B) – electrostatic (E) – time-of-flight (TOF) • Low voltage (eV energy range) – quadrupole (Q) – ion trap (IT, LT, OT) – ion cyclotron resonance (ICR) 4 Mass Resolution • Mass spectrometers separate ions with a defined resolution/resolving power • Resolving power- the ability of a mass spectrometer to separate ions with different mass to charge (m/z) ratios.
    [Show full text]
  • Constructing a Paul Trap for Undergraduate Laboratories
    Constructing a Paul Trap for Undergraduate Laboratories Steven Ban, Matthew Bledsoe, Peter Chang, Garrett Wen May 4, 2016 Abstract For our project, we wanted to build an oscillating system to trap charged particles. We decided to build a Paul trap, which is a form of ion trap that uses alternating electric fields to confine charged particles in the center of the device. We were able to accomplish this using spherical brass electrodes, thick copper wires, a wire ring, and a step up transformer to give us the high voltage we needed from the wall. Our Paul trap worked very well, trapping charged plaster dust, which we illuminated with a bright green laser so that we could easily see the particles in the trap. In this paper, we will primarily focus on how to recreate our experiment, and on our results. 1 Introduction The quadrupole ion trap, or the Paul trap in honor of its inventor Wolfgang Paul who for which claimed the 1989 Nobel Prize, is a device that can confine charged particles using interactions between electric fields. Due to Earnshaw's theorem, we know that charged particles cannot be trapped stably by static electric fields alone. There are several different methods for trapping charged particles, and the Paul trap accomplishes this using AC voltage to generate alternating electric fields on a pair of hyperbolic electrodes (in our case, two brass spheres), suspended on either side of a ring electrode (a simple wire ring in our setup). This setup, when the hyperbolic electrodes are connected such that the hyperbolic electrodes are always at the same potential, and with opposite polarity of the ring electrode, generates an electric field that is zero at the center of the ring and everywhere else provides a time- averaged restoring force back towards the center of the ring.
    [Show full text]
  • Quadrupole Quad. Ion Trap
    Mass Analyzers Ion Trap, FTICR, Orbitrap CU- Boulder CHEM 5181: Mass Spectrometry & Chromatography Prof. Jose-Luis Jimenez MS Last Update: Oct. 2014 Interpretation Some slides from Dr. Joel Kimmel (2007) Lectures High Vacuum Sample Ion Mass Detector Recorder Inlet Source Analyzer 1 Business Items • Questions or comments? • Labview – Megan C is done 2 Review Clicker Q on Quadrupoles To operate a quadrupole in a scanning mode, where individual m/z values are transmitted one after the other (e.g., m/z = 100; 101; 102 …) A. U is held constant, while V is scanned B. V is held constant, while U is scanned C. U is held constant, while V and ω are scanned D. U and V are both changed B. A or B 3 Types of Mass Analyzers • Time-of-flight (TOF) • Quadrupoles • Ion traps • Ultrahigh resolution – Orbitrap – Ion-Cyclotron Resonance (ICR) • Sector – Magnetic – Electric • Hybrids & specialized 4 Quadrupole Ion Traps Ring electrode (r) End cap electrodes (z) Fundamental RF: Fixed frequency (1.1 MHz) variable voltage (up to 7 kV) applied to Ring Electrode DC: An optional DC voltage may be applied to the ring electrode, which will affect the stability of ion trajectories Resonance AC: Fixed frequency voltage applied to end caps for resonant ejection or fragmentation Note that ions enter and exit along z axis Pressure (1 mTorr) dampens extra kinetic energy and E of repulsion 5 3D Ion Trap Pictures Hand-held dimensions 6 Ion Motion Inside an Ion Trap From Lambert •RF fields induce oscillations in r and z directions •A “trapped” ion is stable along both axes 7 “Space Charge” Effects • Trapping lots of ions in a small volume – Ions repel each other – Good performance based on ions responding to external E field (as in quad simulation).
    [Show full text]
  • Ion Sources and Mass Analyzers in Protein Characterization
    Ion Sources and Mass Analyzers in Protein Characterization Principles of MS and MS/MS Matrix Assisted Laser Desorption Ionization (MALDI) Electrospray Ionization (ESI), Nano-ESI Time of Flight Quadrupole Mass Filter Quadrupole Ion Trap Fourier Transform Ion Cyclotron Resonance Mass Spectrometry Lenses and prisms focus and refract light. Analogous systems can focus and deflect ions in a vacuum. 1. Get molecules into the gas phase & ionize them. 2. Give the ions a defined energy or velocity. 3. Separate or sort the ions on the basis of that defined property. 4. Detect the ions & assign their masses. A very simple mass spectrum of Carbon Dioxide Copyright ASMS: http://www.asms.org/whatisms/p5.html Online Separations with MS Detection Sensitivity, Specificity, Transparency of Data Differentiation of Co-eluting analytes Looking at MS Data: LC/MS Data is Three Dimensional Mass spec data systems generate “total ion chromatograms” by integrating spectra and plotting intensity versus time. It is analogous to that generated using a diode array UV-detector on an HPLC system. The data is fundamentally 3-dimensional. A “selected ion chromatogram” is the same graph of intensity over time for a defined m/z. It is analogous to a UV chromatogram for a single wavelength. Looking at MS Data: Mass spectra show m/z, not mass Mass spectrometers separate molecules on the basis of their mass to charge ratio, not their mass. That means the x-axis is not necessarily reflective of M. Mass spectra are normalized to the abundance (intensity) of the highest peak in a given spectrum. The y-axis is always scaled from 0-100.
    [Show full text]
  • A New Quadrupole Ion Trap Mass Spectrometer for Measuring Noble Gases in Planetary Atmospheres
    49th Lunar and Planetary Science Conference 2018 (LPI Contrib. No. 2083) 1158.pdf A NEW QUADRUPOLE ION TRAP MASS SPECTROMETER FOR MEASURING NOBLE GASES IN PLANETARY ATMOSPHERES. G. Avice1, A. Belousov2, S. Madzunkov2, K. A. Farley1, J. Simcic2, D. Ni- kolic2, M. R. Darrach2, C. Sotin2. 1California Institute of Technology, GPS division, 1200 E. California Blvd, Pasa- dena, CA 91125, USA, [email protected], 2Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109, USA. Introduction: Noble gases are powerful tracers of Instrumentation and calibration: physical processes such as the delivery of volatile ele- Description of the QITMS. The JPL-QITMS con- ments to planetary atmospheres through meteorit- sists of three electrodes. In the current configuration, ic/cometary bombardment [1,2], atmospheric escape, the top and bottom (end-cap) electrodes are grounded degassing from the silicate parts of planets, etc. In this whereas the ring electrode receives a high-voltage ra- context, understanding the isotopic composition of Xe diofrequency signal (1-2 kV). Gas neutrals are ionized in planetary atmospheres is a high priority since Xe by electron-impact in the mm-sized space between isotope ratios can answer fundamental questions such electrodes via a side-mounted electron gun composed as i) What is the delivery mix (Chondrit- of a Ta cathode and an Einzel lens. A voltage ramp ic/Solar/Cometary) to planetary atmospheres?; ii) To applied to the ring electrode ejects ions along the z- what extent is the silicate portion of a planet de- axis (Fig. 1). Ions are detected with a MAGNUM gassed?; iii) How much of the atmosphere was lost Channeltron electron multiplier operated in pulse- through atmospheric escape and what is the timing of counting mode.
    [Show full text]
  • Quadrupole Ion Traps (QIT) • Time‐Of‐Flight (TOF) Mass Analyzers
    11/17/2014 Updated: 17 November 2014 Print version CEE 772: Instrumental Methods in Environmental Analysis Lecture #20 Rosa Yu & Dave Reckhow Mass Spectrometry and Instrumentation CEE 772 #20 1 Content • A brief introduction to mass spectrometry • Mass spectrometry instrumentation – Important MS instrument performance factors – Types of mass spectrometers: • (Triple) Quadrupole Mass Spectrometer • Quadrupole Ion Traps (QIT) • Time‐of‐flight (TOF) Mass Analyzers Ion source ➡ Mass filtration/separation ➡ Detection CEE 772 #20 2 1 11/17/2014 Content • A brief introduction to mass spectrometry • Mass spectrometry instrumentation – Important MS instrument performance factors – Types of mass spectrometers: • (Triple) Quadrupole Mass Spectrometer • Quadrupole Ion Traps (QIT) • Time‐of‐flight (TOF) Mass Analyzers Ion source ➡ Mass filtration/separation ➡ Detection CEE 772 #20 3 Mass Spectrometry Introduction Ion Formation Mass Analysis Detection • Ionization: • Electrospray Ionization • Electron Impact/Chemical Ionization • MALDI (matrix assisted laser desorption ionization) • Mass Analysis/Separation: • Use electric and magnetic fields to apply a force on charged particles to control the trajectories of ions • Detection: • Electron multiplier CEE 772 #20 4 2 11/17/2014 The effect of electromagnetic fields on ions • The relationship between force, mass, and the applied fields can be summarized in Newton's second law and the Lorentz force law. 1. Newton's second law: F = ma the force causes an acceleration that is MASS dependent 2. Lorentz force
    [Show full text]