Plasma Detector Research Articles

The Juno New Frontiers mission

Peering down through the clouds and deep into Jupiter's atmosphere, Juno reveals fundamental processes of the formation and early evolution of our solar system. Using a simple, solar powered, spinning spacecraft in an innovative, highly elliptical polar orbit, Juno avoids Jupiter's highest radiation regions. The mission combines high heritage instruments and spacecraft with an experienced science and engineering team. The designs of the individual instruments are straightforward and have excellent heritage from previous space missions. Juno's scientific payload includes a dual frequency gravity/radio science system, a six wavelength Microwave Radiometer (MWR) for atmospheric sounding and composition, a dual-technique magnetometer, plasma detectors, energetic particle detectors (EPDs), a radio/plasma wave experiment, and an Ultraviolet Imager/Spectrometer. Juno's payload also includes a color camera to provide the public with their first glimpse of Jupiter's poles. Juno will launch in July, 2010 or August, 2011 and arrive at Jupiter 5.2 years later. The nominal mission ends one year after Jupiter arrival with a deorbit into Jupiter's atmosphere.

Effect of plasmaspheric drainage plumes on solar‐wind/magnetosphere coupling

Evidence is uncovered that plasmaspheric drainage plumes flowing into the dayside reconnection site mass load the reconnection rate and thereby reduce the coupling of the solar wind to the Earth's magnetosphere. Solar‐wind/magnetosphere coupling is statistically analyzed with the 1963–2003 OMNI2 data set matched up with the AE, AU, and PCI geomagnetic indices. Times when plasmaspheric drainage plumes are flowing are discerned using multiple spacecraft with plasma detectors in geosynchronous orbit. It is found that for a given value of −vBz of the solar wind, the geomagnetic indices AE, AU, and PCI are statistically lower when plasmaspheric drainage plumes are present than when plumes are not present. This is taken as a measure of a weakened coupling of the solar wind to the Earth's magnetosphere caused by the plumes. An Addendum examines the effects of polar‐cap saturation on the auroral electrojet index.

Spacecraft potential effects on electron moments derived from a perfect plasma detector

Abstract. A complete computation of the effect of the spacecraft potential on electron moments is presented. We adopt the perfect detector concept to estimate how measured density, velocity and temperature are affected by the constraints imposed by the detector, such as the finite lower energy cutoff and the spacecraft potential. We investigate the role of the potential in different plasma regimes usually crossed by satellites. It appears that the solar wind is the region where the moments are most compromised, as the particle temperature is low. To a lesser extent the moments calculated in the magnetosheath may also deviate from the real moments, displaying up to 40% overestimation for the density under typical detector operation. The analysis allows us to identify a range of spacecraft potential values which minimizes the variation in the estimation; it is found that it corresponds to the common value adopted by potential controlling experiments.

Determination of levothyroxine and its degradation products in pharmaceutical tablets by HPLC-UV-ICP-MS

A new analytical methodology using high-performance liquid chromatography (HPLC) coupled to inductively coupled plasma mass spectrometry (ICP-MS) was applied to study the presence of possible degradation products in levothyroxine tablets. The analytical methodology takes advantage of the element-specific and highly-sensitive I detection provided by ICP-MS and is applied to the speciation of: 3,3′,5,5′-tetraiodothyronine (T4); 3,3′,5-triiodothyronine (T3); 3,5-diiodothyronine (T2); 3,3′,5,5′-tetraiodothyroacetic acid (TTAA4); 3,3′,5-triiodothyroacetic acid (TTAA3); and 3,5-diiodothyroacetic acid (TTAA2). Chromatographic conditions were optimized by using UV absorption at 225 nm and ICP-MS detection of 127I. Complete chromatographic resolution of the levothyroxine degradation products within 25 min was obtained using 22% (v/v) acetonitrile at pH 2.3, adjusted with 0.08% (v/v) trifluoroacetic acid. The introduction of the mobile phase containing acetonitrile was performed by post column on-line dilution (1∶3.3) of the chromatographic eluent with a 2% (v/v) nitric acid solution using a PTFE tee. The separations with either detector were good with little detector effect on the resolution. The peak broadening caused by on-line dilution was insignificant. The detection limits obtained with UV detection ranged from 28.9 to 34.5 µg l−1, whereas those obtained with the plasma detector were about 175–375 times better (lower). Finally, the analytical methodology was applied to the determination of possible iodine species originated by degradation of T4 in synthetic and commercial levothyroxine sodium tablets.

SPECIATION OF METHYLCYCLOPENTADIENYL MANGANESE TRICARBONYL AND ITS DERIVATIVES: A REVIEW

ABSTRACT Methylcyclopentadienyl manganese tricarbonyl (MMT) is an organomanganese compound that is used as an octane enhancer for gasoline and other fuels. The widespread use of this compound has been suggested to be harmful to human health. In order to accurately assess its impact, high sensitivity instrumentation for the determination of MMT and its derivatives is required. In this paper, three instrumental approaches are reviewed for this analysis. Walton and coworkers [1] employed high-performance liquid chromatography (HPLC) coupled to a flame laser-excited atomic fluorescence spectrometry (LEAFS) detector to evaluate the organomanganese compound responsible for organ damage in rats following subcutaneous injection of this compound. Gas chromatography (GC) was coupled to an alternating current plasma (ACP) detector by Ombaba and Barry [2] for the determination of MMT in gasoline and fuel samples. Butcher et al. [3] employed HPLC with diode laser atomic absorption spectrometry (DLAAS) for the determination of MMT in water, gasoline, and urine. The conclusion of this paper is a comparison of the analytical capabilities of these instruments.

Distinguishing the populations of natural meteoroids and space debris by GORID in geostationary orbit

The Geostationary Orbit Impact Detector, GORID, is a dust impact plasma detector flying aboard the Russian Express-2 telecommunications spacecraft in geostationary orbit. The detector is the flight spare instrument of the successful Ulysses interplanetary dust detector which has contributed major results such as the detection of interstellar dust within our solar system. GORID is an active sensor, returning time resolved impact data, with approximate mass and direction information, from a rather different environment to interplanetary space. The geostationary ring is likely to be populated by a significant component of orbital debris, and data returned so far have shown some unusual characteristics, interpreted as relatively slow, large, highly charged debris particles. The data also appear to show diurnal and seasonal effects probably correlated with natural meteoroids and the detector's time dependent exposure geometry. This paper investigates the orbits of debris and meteoroids that the detector can sample as a function of time of day and time of year, in order to help the analysis of the GORID data.

Development of chiral HPLC for selenoamino acids with ICP-MS detection:application to selenium nutritional supplements.

The enantiomeric separation of three underivatized seleno-amino acids, D,L-selenocystine, and D,L-selenomethionine, and D,L-selenomethionine, with UV and ICP-MS detection is described. An HPLC column with a chiral crown ether stationary phase and a mobile phase of 0.10 M HCIO4 was used. Absolute detection limits obtained with UV detection ranged from 34.5 to 47.1 ng whereas those obtained with the plasma detector were ca. 40-400 times better. The separations with either detector were good, with the little detector effect on the resolution. Ten commercially available dietary selenium supplements were analyzed using the chiral column to identify and quantify the selenium species present with both detection modes. Selenium species were easily identified using ICP-MS detection, whereas UV detection was not viable because of interferences from the sample matrix and inadequate sensitivity. Selenium species that were unretained using the chiral column were identified using anion exchange chromatography. Total amounts in the samples were also measured using a conventional digestion and enzymatic digestion with ICP-MS detection.

Japanese contribution to in-situ meteoroid and debris measurement in the near Earth space

This paper reviews major results of present studies and recent developments for future missions in the Japanese space program regarding in-situ measurement and collection of micrometeoroids and orbital debris in the near Earth space. Japan’s contribution in this area began with the post flight impact analysis of the Space Flyer Unit (SFU) satellite which was returned to Earth in 1996 after 10-month exposure in space. Despite a decade later than similar efforts first conducted in the USA and Europe, it resulted in a record of over 700 hypervelocity impact signatures, which now forms the nation’s first database of real space impacts being open to public in the Internet. Together with laboratory impact tests, both morphological and elemental analyses of the impact craters yielded new insights of the meteoroid to debris ratio as well as flux variation compared with the previous spacecraft. The next step was a passive aerogel exposure in the STS-85 shuttle mission in 1997. No hypervelocity impact was found there but its experience has been incorporated for designing a microparticle collector to be on-board the Japan Experiment Module-Exposed Facility of the International Space Station. All of such “passive” collection of micro-impact features, however, still leave the significant uncertainty in the quest of their origins. Therefore an aerogel-based “hybrid” dust collector and detector (HD-CAD) is currently under the development. It measures time of impact and deduces impactors’ orbital and physical parameters by detecting impact flash while still capturing them intact. The system is suitable for both (1) sample return missions in LEO as well as to parent bodies of meteoroids, i.e., comets and asteroids, and (2) one-way mission to where the thermal and plasma environment is such that impact induced plasma detectors may suffer from significant noise, e.g., a Mercury orbiter and a solar probe. Together with unambiguous dust samples from a comet by STARDUST and an asteroid by MUSES-C as references, the HD-CAD in the LEO will be able to deduce the accretion rates of the cometary and asteroidal dust grains on the Earth.

The topology of intrasector reversals of the interplanetary magnetic field

A technique has been developed recently to determine the polarities of interplanetary magnetic fields relative to their origins at the Sun by comparing energetic electron flow directions with local magnetic field directions. Here we use heat flux electrons from the Los Alamos National Laboratory (LANL) plasma detector on the ISEE 3 spacecraft to determine the field polarities. We examine periods within well‐defined magnetic sectors when the field directions appear to be reversed from the normal spiral direction of the sector. About half of these intrasector field reversals (IFRs) are cases in which the polarities match those of the surrounding sectors, indicating that those fields have been folded back toward the Sun. The more interesting cases are those with polarity reversals. We find no clear cases of isolated reverse polarity fields, which suggests that islands of reverse polarity in the solar source dipole field probably do not exist. The IFRs with polarity reversals are strongly associated with periods of bidirectional electron flows, suggesting that those fields occur only in conjunction with closed fields. We propose that both those IFRs and the bidirectional flows are signatures of coronal mass ejections (CMEs). In that case, many interplanetary CMEs are larger and more complex than previously thought, consisting of both open and closed field components.

Heliospheric links explorer (HELIX)

The proposed HELIX mission will provide stereoscopic images of solar mass ejections from their origins on the Sun to their arrival at Earth. With an array of telescopes and plasma detectors, it will investigate magnetic helicity conservation in the heliosphere. Helicity conservation, which has been used successfully to describe the behavior of plasmas in fusion experiments, may explain why there are solar ejections and how they evolve in interplanetary space. HELIX uses two identical spacecraft in heliocentric ecliptic orbits. One remains near Earth and the other drifts so that it will see solar features up to five days before they are visible from Earth. This will provide advance warning of areas on the Sun that can provide geomagnetic storms at Earth.

Determination of (methylcyclopentadienyl)manganesetricarbonyl in gasoline by capillary gas chromatography with alternating current plasma emission detection

(Methylcyclopentadienyl)manganesetricarbonyl (MMT) commonly used as an antiknock agent in gasoline is determined by capillary gas chromatography with an alternating current plasma (ACP) detector. The ACP selectivity, the ratio of the peak area response of MMT per gram Mn to the peak area response for a hydrocarbon per gram of carbon, was found to exceed five orders of magnitude. Detection limits for MMT and a closely related organomanganese analyte, bis(pentamethylcyclopentadienyl)manganese (BPM), were calculated to be 62 and 69 pg/s (as Mn), respectively. Precision of the methodology was 6.6% relative standard deviation ( n = 10) for both MMT and BPM.

Electric Field Measurements on the GEOTAIL Satellite.

The electric field detector (EFD) on board GEOTAIL measures the electric field by two different techniques, one by the probe technique and the other by electron beam technique. The probe technique (EFD-P) gives electric field in the plane perpendicular to the satellite spin axis by measuring the voltage difference between the two sphere probes; each deployed 50 meters from the spacecraft in the opposite direction. The electron beam technique (EFD-B), measures the drift motion of the gyration center of artificially emitted electrons to obtain the electric field. The drift motion of the electrons is measured by two methods, one by measuring the drift motion itself and the other by measuring the time of the return flight of electrons to the spacecraft. To realize these measurements, EFD is equipped with two additional capabilities. One is the capability to measure the spacecraft potential relative to the ambient plasma and the other is that to control the spacecraft potential by emitting ions. The reliability of the electric field measurements can be improved greatly by employing the probe and beam techniques at the same time. The potential control of the spacecraft enables the plasma detectors onboard GEOTAIL to measure low energy ions which would otherwise be repelled by the positive potential of the spacecraft. This article describes the outline of the electric field experiments on GEOTAIL with emphasis on the principles of the measurements, the configuration of the hardware, the raw data processing, as well as the preliminary results from the initial operation with the intention of providing the basis for the studies which use the GEOTAIL electric field data.

Comprehensive supercritical fluid extraction/gas chromatographic analysis for organic compounds in soil matrices with an element-selective radiofrequency plasma detector

A coupled supercritical fluid extraction (SFE), high-speed gas chromatography (GC), and element-selective radiofrequency plasma detection (RPD) system was evaluated for the analysis of volatile organic compounds in soil matrices. The effect of GC carrier gas (carbon dioxide) and plasma reagent gas (oxygen) on the selectivity and sensitivity of the RPD was studied to establish the optimal operational conditions. The selectivities obtained were 3500 (Cl/C) for chlorine and 2600 (S/C) for sulfur. The detection limits were 24.8 and 9.2 pg s -1 for chlorine and sulfur, respectively. Complete quantitative analysis could be easily accomplished within 10 min

Hypervelocity impact testing of micrometeorite capture cells in conjunction with a PVDF thin-film velocity/trajectory sensor and a simple plasma velocity detector

Five different small particle capture cell designs were evaluated for their ability to capture fragments and residue from 10–200 μm diameter glass projectiles and oblong olivine crystals impacting at 1–15 km/s in sufficient quantity for chemical and isotopic analyses. Aluminum multi-foils (0.1–100 μm thick with ≈10, 000 and 1800 μ m spacing), foil covered germanium crystals, and 0.50 and 0.120 g/cm 3 Aerogels, were positioned behind either multi-film (1.4–6.0 μm thick) polyvinylidene fluoride (PVDF) velocity/trajectory sensor devices of a simple wire-grid plasma velocity detector. All capture cells collected significant amounts of impactor debris behind the PVDF sensors from nominal 100 μm diameter glass projectiles and olivine crystals which struck the sensor at velocities up to 6.4 km/s. At velocities >8 km/s little or no debris penetrated the second PVDF film. Results were incolsive for velocities between 6.5 and 8 km/s. Plasma detector results showed identifiable impactor residue on Al foils for velocities up to 8.7 km/s and impact tracks with apparent debris imbedded in the Aerogels for velocities up to 12.7 km/s. Maximum foil penetration of glass spheres and olivine crystals were the same, but more particulate debris was associated with olivine crystal ipacts versus glass impacts. Foil spacing beyond one particle diameter had no effect on total penetration. Aerogels are identified as a capture cell media that warrants further investigation. The Al multi-foil capture cell with 100 μm net spacers is identified as the most effective of the other designs and offers the advantages of compact structure, low secondary ejecta from impacts, and easy recovery of impactor debris for analysis.

Noise analysis of the reflected power signal from a microwave-induced plasma gas chromatographic detector

Noise analysis of the signal from a non-optical microwave plasma detector for gas chromatography is presented. The signal in this detector is reflected microwave power. White noise, low-frequency 1/ f noise and high-frequency discrete noise were the major noise types observed in the frequency window considered (0−200 Hz). The overall magnitude of the noise spectra exhibited a marked dependence on the degree of coupling of power to the microwave cavity and, to a lesser extent, on the flow-rate of the plasma gas. The noise did not change consistently as the plasma tube cooling-water flow-rate was changed.

Evaluation of a radio frequency plasma for oxygen‐selective detection in capillary gas chromatography

AbstractA radio frequency plasma detector for capillary GC has been modified for oxygen‐selective detection. Purification of the plasma gas and purging of both ends of the discharge region with helium were crucial to minimizing oxygen background emission from impurities in the plasma. With a pure helium plasma, eluting hydrocarbons released oxygen from the discharge region resulting in interfering signals on the oxygen channel. These interfering signals were efficiently reduced by using a methane‐doped (0. 15%) low power RF plasma (15 W) sustained in a high make‐up flow (150 mL/min). With this plasma, a 103:1 oxygen‐to‐carbon selectivity and a 100 pg oxygen/s detection limit were obtained. The detector was linear over three orders of magnitude. The detection system has been used to screen for oxygenated compounds in two environmental samples.

Nitrogen-selective detection for gas chromatography with a helium radiofrequency plasma detector. Invited lecture

A helium r.f. plasma was characterized for the selective detection of nitrogen in gas chromatographic eluents by atomic emission spectrometry. Nitrogen emission was detected at 868 nm. The principle sources of background emission at that wavelength were identified. The largest single source was back-diffusion from the discharge exit. There were also significant contributions from impurities in the high-grade make-up and reagent gases. An avalanche photodiode was evaluated as a photodetector and found to be superior to a photomultiplier tube for this application. End-on and side-on optical collection geometries were modelled by a computer. The detection limit for nitrogen in the discharge was 57 pg s–1.

Selective Determination of Pentafluorobenzyl Ester Derivatives of Carboxylic Acids by GC Using Microwave Plasma and Mass Selective Detection

A highly selective, sensitive method for determination of carboxylic acids in water has been developed that is based on fluorine-selective gas chromatography (GC) detection of pentafluorobenzyl ester derivatives. The atmospheric-pressure helium microwave-induced plasma detector is well suited for fluorine-specific detection of these derivatives, which were well resolved by capillary GC and displayed a characteristic fragmentation behavior when examined by GC-mass selective detection. For demonstration purposes, a number of carboxylic acids, ranging from C1 to C20, were examined and found to be derivatized with yields greater than 90%, and a sample of creek water was examined for its carboxylic acid content.

The determination of arsenic and selenium by HPLC combined with alternating current plasma detection and post‐column hydride formation

AbstractA helium alternating current plasma detector in combination with HPLC has been evaluated for the determination of arsenic and selenium‐containing compounds after post‐column hydride generation. The construction, operation, and optimization of the system is presented. Detection limits for the compounds under study ranged from 45–60 pg/s. Determination of arsenic and selenium in spiked river water samples has been used to demonstrate the applicability of the technique.

Performance of a Laminar Flow Torch/Microwave Plasma Detector for Gas Chromatography

The performance of a laminar flow plasma torch as a part of an emission detector for gas chromatography (GC) is evaluated. The effect of plasma gas flow rate on peak height and chromatographic resolution is discussed. Operation stabilities, both short-term and long-term, are presented together with calibration plots for the test elements, carbon and chlorine, as components of separated solvents.