38 research outputs found
Dielectronic Resonance Method for Measuring Isotope Shifts
Longstanding problems in the comparison of very accurate hyperfine-shift
measurements to theory were partly overcome by precise measurements on
few-electron highly-charged ions. Still the agreement between theory and
experiment is unsatisfactory. In this paper, we present a radically new way of
precisely measuring hyperfine shifts, and demonstrate its effectiveness in the
case of the hyperfine shift of and in
. It is based on the precise detection of dielectronic
resonances that occur in electron-ion recombination at very low energy. This
allows us to determine the hyperfine constant to around 0.6 meV accuracy which
is on the order of 10%
Histogrammatic Method for Determining Relative Abundance of Input Gas Pulse
To satisfy the Major Constituents Analysis (MCA) requirements for the Vehicle Cabin Atmosphere Monitor (VCAM), this software analyzes the relative abundance ratios for N2, O2, Ar, and CO2 as a function of time and constructs their best-estimate mean. A histogram is first built of all abundance ratios for each of the species vs time. The abundance peaks corresponding to the intended measurement and any obfuscating background are then separated via standard peak-finding techniques in histogram space. A voting scheme is then used to include/exclude this particular time sample in the final average based on its membership to the intended measurement or the background population. This results in a robust and reasonable estimate of the abundance of trace components such as CO2 and Ar even in the presence of obfuscating backgrounds internal to the VCAM device. VCAM can provide a means for monitoring the air within the enclosed environments, such as the ISS (International Space Station), Crew Exploration Vehicle (CEV), a Lunar Habitat, or another vehicle traveling to Mars. Its miniature pre-concentrator, gas chromatograph (GC), and mass spectrometer can provide unbiased detection of a large number of organic species as well as MCA analysis. VCAM s software can identify the concentration of trace chemicals and whether the chemicals are on a targeted list of hazardous compounds. This innovation s performance and reliability on orbit, along with the ground team s assessment of its raw data and analysis results, will validate its technology for future use and development
Major Constituents Analysis for the Vehicle Cabin Atmosphere Monitor
Vehicle Cabin Atmosphere Monitor (VCAM) can provide a means for monitoring the air within enclosed environments such as the International Space Station, the Crew Exploration Vehicle (CEV), a Lunar habitat, or another vehicle traveling to Mars. The software processes a sum total spectra (counts vs. mass channel) with the intention of computing abundance ratios for N2, O2, CO2, Ar2, and H2O. A brute-force powerset expansion compares a library of expected mass lines with those found within the data. Least squares error is combined with a penalty term for using small peaks
High-precision measurements of krypton and xenon isotopes with a new static-mode quadrupole ion trap mass spectrometer
Measuring the abundance and isotopic composition of noble gases in planetary atmospheres can answer fundamental questions in cosmochemistry and comparative planetology. However, noble gases are rare elements, a feature making their measurement challenging even on Earth. Furthermore, in space applications, power consumption, volume and mass constraints on spacecraft instrument accommodations require the development of compact innovative instruments able to meet the engineering requirements of the mission while still meeting the science requirements. Here we demonstrate the ability of the quadrupole ion trap mass spectrometer (QITMS) developed at the Jet Propulsion Laboratory (Caltech, Pasadena) to measure low quantities of heavy noble gases (Kr, Xe) in static operating mode and in the absence of a buffer gas such as helium. The sensitivity reaches 10^(13) cps Torr^(â1) (about 10^(11) cps Pa^(â1)) of gas (Kr or Xe). The instrument is able to measure gas in static mode for extended periods of time (up to 48 h) enabling the acquisition of thousands of isotope ratios per measurement. Errors on isotope ratios follow predictions of the counting statistics and the instrument provides reproducible results over several days of measurements. For example, 1.7 Ă 10^(â10) Torr (2.3 Ă 10^(â8) Pa) of Kr measured continuously for 7 hours yielded a 0.6â° precision on the ^(86)Kr/^(84)Kr ratio. Measurements of terrestrial and extraterrestrial samples reproduce values from the literature. A compact instrument based upon the QITMS design would have a sensitivity high enough to reach the precision on isotope ratios (e.g. better than 1% for ^(129,131â136)Xe/^(130)Xe ratios) necessary for a scientific payload measuring noble gases collected in the Venus atmosphere
Electronic drive and acquisition system for mass spectrometry
The present invention discloses a mixed signal RF drive electronics board that offers small, low power, reliable, and customizable method for driving and generating mass spectra from a mass spectrometer, and for control of other functions such as electron ionizer, ion focusing, single-ion detection, multi-channel data accumulation and, if desired, front-end interfaces such as pumps, valves, heaters, and columns
Formation of CO2 on a carbonaceous surface: a quantum chemical study
The formation of CO2 in the gas phase and on a polyaromatic hydrocarbon surface (coronene) via three possible pathways is investigated with density functional theory. Calculations show that the coronene surface catalyses the formation of CO2 on model grain surfaces. The addition of O-3 to CO is activated by 2530 K in the gas phase. This barrier is lowered by 253 K for the Eley-Rideal mechanism and 952 K for the hot-atom mechanism on the surface of coronene. Alternative pathways for the formation of CO2 are the addition of O-3 to the HCO radical, followed by dissociation of the HCO2 intermediate. The O + HCO addition is barrierless in the gas phase and on the surface and is more than sufficiently exothermic to subsequently cleave the H-C bond. The third mechanism, OH + CO addition followed by H removal from the energized HOCO intermediate, has a gas-phase exit barrier that is 1160 K lower than the entrance barrier. On the coronene surface, however, both barriers are almost equal. Because the HOCO intermediate can also be stabilized by energy dissipation to the surface, it is anticipated that for the surface reaction the adsorbed HOCO could be a long-lived intermediate. In this case, the stabilized HOCO intermediate could react, in a barrierless manner, with a hydrogen atom to form H-2 + CO2, HCO2H, or H2O + CO
The Mass Analyzer for Real-time Investigation of Neutrals at Europa (MARINE)
Presented herein is the progress on developing a new mass analyzer for analysis of the exospheres of planets, moons, and primitive bodies, such as found at Europa or Enceladus. Europa, one of Jupiter's four Galilean moons, may have a subsurface ocean plausibly containing the key ingredients for life as well as sources of chemical energy. Clues to the composition and chemical state of Europa's ocean can be found both on Europa's icy surface and in its tenuous atmosphere. Given the high scientific priority of assessing the habitability of Europa's ocean, the Europa Clipper notional payload includes a Neutral Mass Spectrometer whose purpose is to characterize the composition of ejected surface products during a series of flyby investigations. The Mass Analyzer for Real-time Investigation of Neutrals at Europa (MARINE) is capable of measuring the abundances of neutral particle species in Europa's exosphere including H_2O, O_2, CO_2, and SO_2, and determining their number density profiles at per-second sampling rates as a function of altitude above Europa's surface. MARINE will either detect tracers of potential subsurface biological activity in Europa's exosphere, or place upper limits on their surface abundances. It exceeds all requirements for the proposed investigations with margins ranging from 100 to 1000%, while remaining fully compatible with spacecraft accommodation constraints for mass, power, data volume, and field-of-view
SEIS: Insightâs Seismic Experiment for Internal Structure of Mars
By the end of 2018, 42 years after the landing of the two Viking seismometers
on Mars, InSight will deploy onto Marsâ surface the SEIS (Seismic Experiment for Internal
Structure) instrument; a six-axes seismometer equipped with both a long-period three-axes
Very Broad Band (VBB) instrument and a three-axes short-period (SP) instrument. These
six sensors will cover a broad range of the seismic bandwidth, from 0.01 Hz to 50 Hz,
with possible extension to longer periods. Data will be transmitted in the form of three
continuous VBB components at 2 sample per second (sps), an estimation of the short period
energy content from the SP at 1 sps and a continuous compound VBB/SP vertical axis at
10 sps. The continuous streams will be augmented by requested event data with sample
rates from 20 to 100 sps. SEIS will improve upon the existing resolution of Vikingâs Mars
seismic monitoring by a factor of ⌠2500 at 1 Hz and ⌠200 000 at 0.1 Hz. An additional
major improvement is that, contrary to Viking, the seismometers will be deployed via a
robotic arm directly onto Marsâ surface and will be protected against temperature and wind
by highly efficient thermal and wind shielding. Based on existing knowledge of Mars, it is
reasonable to infer a moment magnitude detection threshold of Mw ⌠3 at 40⊠epicentral
distance and a potential to detect several tens of quakes and about five impacts per year. In
this paper, we first describe the science goals of the experiment and the rationale used to
define its requirements. We then provide a detailed description of the hardware, from the
sensors to the deployment system and associated performance, including transfer functions
of the seismic sensors and temperature sensors. We conclude by describing the experiment
ground segment, including data processing services, outreach and education networks and
provide a description of the format to be used for future data distribution
Response of QIT-MS to Noble Gas Isotopic Ratios in a Simulated Venus Flyby
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