Computer Modeling of an Ion Trap Mass Analyzer, Part I: Low Pressure Regime

Nikolić, D.; Madzunkov, S.; Darrach, M. R.

doi:10.1007/s13361-015-1236-5

Cited by 6 publications

(13 citation statements)

References 35 publications

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“…These set the upper limit on the pressure within vacuum chamber not to exceed 2.7 × 10 −4 Pa, which for xenon gives a 50% chance of ion-neutral collision every 14 ms. On the other hand, the ion-ion interaction is negligible if the number of ions being confined within the trap does not exceed 5000 during analysis phase. QIT-MS-S has well defined response as a function of both the pressure and the space charge [15] and is further supported by simulations which we use to predict the instrument response under various measurement conditions [16].…”

Section: Qit-ms-smentioning

confidence: 56%

“…QITMS-S is designed to operate under low-pressure conditions, where ion-neutral collisions as well as ion-ion interaction can be neglected [15]. Previous simulations [16] and measurements show that few collisions of ions with rest gas during analysis phase have negligible effect to peak shapes. These set the upper limit on the pressure within vacuum chamber not to exceed 2.7 × 10 −4 Pa, which for xenon gives a 50% chance of ion-neutral collision every 14 ms. On the other hand, the ion-ion interaction is negligible if the number of ions being confined within the trap does not exceed 5000 during analysis phase.…”

Section: Qit-ms-smentioning

confidence: 99%

“…On the other hand, the most abundant krypton isotope 84 Kr will be created only 0.08% of the time, and thus, will contribute 4 ± 2 ions in each 50 ms duty cycle. To remedy this problem, we make use of resonant ejection technique [16], such that during the ionization phase we simultaneously destabilize trajectories of select m/q ions. This is done by adding two additional low-amplitude phase-inverted RF drives to the QIT-MS-S. For trapping conditions used in this study, the frequencies for removing 36 Ar + and 40 Ar + ions are 108.2 kHz and 96.9 kHz, respectively.…”

Section: Model Of the Qit-ms Sensormentioning

confidence: 99%

“…Immediately after their creation, ions are propagated through the RF quadrupole electric field using 1 ns time steps. Ion velocities and positions are updated by modified Verlet algorithm [16]. Propagation of ions is stopped if the duty cycle has ended, a collision with electrode surfaces has been recorded, or ion has been detected.…”

Section: Model Of the Qit-ms Sensormentioning

confidence: 99%

“…The QIT-MS sensor is no exception, and details of its response function are found elsewhere [15]. We have also developed a simulation program [16] capable of predicting QIT-MS sensor performance under a wide range of operational parameters. In this study, we go step further and simulate planetary atmosphere 'skimmer' probe equipped with the QIT-MS instrument and analyze its performance based on the models of atmospheric chemical composition and probe trajectory.…”

Section: Introductionmentioning

confidence: 99%

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Response of QIT-MS to Noble Gas Isotopic Ratios in a Simulated Venus Flyby

2019

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The primary objective of the present study is to investigate the science return of future Venus atmosphere probe mission concepts using the Quadrupole Ion Trap (QIT) Mass Spectrometer (MS) Instrument (QIT-MS-I). We demonstrate the use of Monte-Carlo simulations in determining the optimal ion trapping conditions and focus the analysis on retrieving isotope ratios of noble gases in the model sample of the Venus atmosphere. Sampling takes place at a constant velocity of ~10 km/s between 112–110 km altitude and involves the use of getter pumps to remove all chemically-active species, retaining inert noble gases. The enriched sample is leaked into passively pumped vacuum chamber where it is analyzed by the QIT-MS sensor (QIT-MS-S) for 40 minutes. The simulated mass spectrum, as recorded by the QIT-MS-S, is deconvoluted using random walk algorithm to reveal relative abundances of noble gas isotopes. The required precision and accuracy of the deconvolution method is benchmarked against the a priori known model composition of the atmospheric sample.

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Section: Qit-ms-smentioning

confidence: 56%

Section: Qit-ms-smentioning

confidence: 99%

Section: Model Of the Qit-ms Sensormentioning

confidence: 99%

Section: Model Of the Qit-ms Sensormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Response of QIT-MS to Noble Gas Isotopic Ratios in a Simulated Venus Flyby

2019

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Quadrupole Ion Trap Mass Spectrometer for Ice Giant Atmospheres Exploration

et al. 2021

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To date, a variety of different types of mass spectrometers have been utilized on missions to study the composition of atmospheres of solar system bodies, including Venus, Mars, Jupiter, Titan, the moon, and several comets. With the increasing interest in future small probe missions, mass spectrometers need to become even more versatile, lightweight, compact, and sensitive.For in situ exploration of ice giant atmospheres, the highest priority composition measurements are helium and the other noble gases, noble gas isotopes, including 3He/4He, and other key isotopes like D/H. Other important but lower priority composition measurements include abundances of volatiles C, N, S, and P; isotopes 13C/12C, 15N/14N, 18O/17O/16O; and disequilibrium species PH3, CO, AsH3, GeH4, and SiH4. Required measurement accuracies are largely defined by the accuracies achieved by the Galileo (Jupiter) probe Neutral Mass Spectrometer and Helium Abundance Detectors, and current measurement accuracies of solar abundances.An inherent challenge of planetary entry probe mass spectrometers is the introduction of material to be sampled (gas, solid, or liquid) into the instrument interior, which operates at a vacuum level. Atmospheric entry probe mass spectrometers typically require a specially designed sample inlet system, which ideally provides highly choked, nearly constant mass-flow intake over a large range of ambient pressures. An ice giant descent probe would have to operate for 1-2 hours over a range of atmospheric pressures, possibly covering 2 or more orders of magnitude, from the tropopause near 100 mbar to at least 10 bars, in an atmospheric layer of depth beneath the tropopause of about 120 km at Neptune and about 150 km at Uranus.The Jet Propulsion Laboratory’s Quadrupole Ion Trap Mass Spectrometer (QITMS) is being developed to achieve all of these requirements. A compact, wireless instrument with a mass of only 7.5 kg, and a volume of 7 liters (7U), the JPL QITMS is currently the smallest flight mass spectrometer available for possible use on planetary descent probes as well as small bodies, including comet landers and surface sample return missions. The QITMS is capable of making measurements of all required constituents in the mass range of 1–600 atomic mass units (u) at a typical speed of 50 mass spectra per second, with a sensitivity of up to $10^{13}$ 10 13 counts/mbar/sec and mass resolution of $m/\Delta m=18000$ m / Δ m = 18000 at m/q = 40. (Throughout this paper we use the unit of m/q = u/e for the mass-to-charge ratio, where atomic mass unit and elementary charge are $1~\text{u} = 1.66\times 10^{-27}~\text{kg}$ 1 u = 1.66 × 10 − 27 kg and $1\text{e} = 1.6\times 10^{-19}$ 1 e = 1.6 × 10 − 19 C, respectively.) The QITMS features a novel MEMS-based inlet system driven by a piezoelectric actuator that continuously regulates gas flow at inlet pressures of up to 100 bar.In this paper, we present an overview of the QITMS capabilities, including instrument design and characteristics of the inlet system, as well as the most recent results from laboratory measurements in different modes of operation, especially suitable for ice giant atmospheres exploration.

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