An Impact Mass-Spectrometer for the Halley-Probe

The relative speed between Comet Halley and the presently planned Halley Probe will be approx. 55 km/s. At such a speed the method of impact ionization mass-spectrometry is perfectly suited to analysing cometary dust particles with masses from 10−16g to 10−10g. First results are reported by Dalmann et al. If a micrometeoroid hits the sensitive target, ions from both particle and target material are produced. The total number of ions is registered with a charge-sensitive amplifier and this signal Q allows the determination of the particle mass m (Q ∼ m). By an electric potential difference of 3 kV, ions are drawn into a field-free drift-tube. The ions are separated in time in the TOF-Spectrometer due to their different masses. The mass spectrum is registered as output current of the particle multiplier at the end of the TOF-tube. It gives information about the chemical composition of the detected particle. Characteristics of such spectra recorded with the Impact-Spectrometer currently used in the laboratory are the following: a) mass resolution m/Δm > 100 at 23 amu, b) flight-time (t ∼ 14 μs at 100 amu; the corresponding Δt ∼ 70 ns between 99 and 100 amu).

Download Full-text

What does really happen in a dust impact?

10.5194/egusphere-egu2020-20089 ◽

2020 ◽

Author(s):

Sascha Kempf ◽

William Goode ◽

Ralf Srama ◽

Frank Postberg

Keyword(s):

Rise Time ◽

Impact Ionization ◽

Dust Particles ◽

Ionization Mass ◽

Mass Spectrometers ◽

Ample Evidence ◽

In Situ Data ◽

The Impact ◽

Ionization Detectors

Our current understanding of the solar system&#8217;s micrometeoroid environment relies to a substantial extent on in-situ data acquired by impact ionization dust detectors such as Ulysses&#8217; and Galileo&#8217;s DDS or Cassini&#8217;s CDA. Such detectors derive the mass and speed of striking dust particles from the properties and evolution of the plasma created upon impact. In particular, empirical evidence suggests that the impact speed is a function of the duration of impact charge delivery onto the target - the so-called plasma rise time. Often, this dependence has been attributed to secondary impacts of target and projectile ejecta.&#160;During recent years the capabilities of laboratory impact detectors have been significantly improved. In particular we now have ample evidence that secondary ejecta impacts are not responsible for the rise-time dependence. In fact the plasma rise-time is rather related to the ionization of target contaminants in the vicinity of the impact site.&#160;In this talk we present new experimental data obtained with state-of-the-art impact ionization mass spectrometers, which shed new light on what is really going on during a hypervelocity dust impact. We further discuss the implications for the interpretation of dust data obtained with previous generations of impact ionization detectors.

Download Full-text

Evaluation of Marblewood Dust’s (Marmaroxylon racemosum) Effect on Ignition Risk

Applied Sciences ◽

10.3390/app11156874 ◽

2021 ◽

Vol 11 (15) ◽

pp. 6874

Author(s):

Miroslava Vandličkova ◽

Iveta Markova ◽

Katarina Holla ◽

Stanislava Gašpercová

Keyword(s):

Particle Size ◽

Dust Particles ◽

Wood Dust ◽

Sieve Analysis ◽

Granulometric Analysis ◽

Analysis Measurement ◽

Risk Research ◽

Minimum Ignition Temperature ◽

The Impact

The paper deals with the selected characteristics, such as moisture, average bulk density, and fraction size, of tropical marblewood dust (Marmaroxylon racemosum) that influence its ignition risk. Research was focused on sieve analysis, granulometric analysis, measurement of moisture level in the dust, and determination of the minimum ignition temperatures of airborne tropical dust and dust layers. Samples were prepared using a Makita 9556CR 1400W grinder and K36 sandpaper for the purpose of selecting the percentages of the various fractions (<63, 63, 71, 100, 200, 315, 500 μm). The samples were sized on an automatic vibratory sieve machine Retsch AS 200. More than 65% of the particles were determined to be under 100 μm. The focus was on microfractions of tropical wood dust (particles with a diameter of ≤100 µm) and on the impact assessment of particle size (particle size <100 µm) on the minimum ignition temperatures of airborne tropical dust and dust layers. The minimum ignition temperature of airborne marblewood dust decreased with the particle size to the level of 400 °C (particle size 63 μm).

Download Full-text

Dust in the Solar System

Zeitschrift für Naturforschung A ◽

10.1515/zna-1989-1002 ◽

1989 ◽

Vol 44 (10) ◽

pp. 877-882 ◽

Cited By ~ 13

Author(s):

H. Fechtig

Keyword(s):

Solar Irradiation ◽

Dust Particles ◽

Normal Density ◽

Dust Grains ◽

Cometary Dust ◽

In Situ Experiments ◽

Asteroidal Belt ◽

Comet Halley ◽

Cometary Origin

Abstract Properties of cometary dust particles are better known since the space missions to Comet Halley. Their properties (densities, atomic composition) are compared with relevant observations from lunar microcraters and in-situ experiments. At 1 AU in the eliptic, 2/3 of the dust grains are normal density particles, presumably of asteroidal origin and irregularly shaped, while the remaining 1/3 are low density particles, presumably of cometary origin, but due to solar irradiation in a processed state (corresponding to “Brownlee”-particles). Beyond the asteroidal belt only black cometary dust grains are observed which have recently been released from comet nuclei orbiting on highly eccentric trajectories.

Download Full-text

The Cosmic Dust Analyzer: Experimental Evaluation of an Impact Ionization Model

International Astronomical Union Colloquium ◽

10.1017/s0252921100049216 ◽

1971 ◽

Vol 13 ◽

pp. 299-310

Author(s):

J. F. Friichtenicht ◽

N. L. Roy ◽

D. G. Becker

Keyword(s):

Mass Spectrometer ◽

Relative Abundance ◽

Microprobe Analysis ◽

Impact Ionization ◽

Time Of Flight ◽

Cosmic Dust ◽

Dust Particles ◽

Flight Mass Spectrometer ◽

Fractional Ionization ◽

The Impact

Determination of the elemental composition of cosmic dust particles by means of an impact ionization time-of-flight mass spectrometer has been investigated at several institutions. In most configurations, the instrument supplies the identity of ion groups of both target and particle materials extracted from the impact plasma and the number of ions contained in each group. Experiments have shown that the fractional ionization of a given species is not constant with impact velocity nor is the fractional ionization the same for different kinds of atoms. A model of the impact ionization effect developed at TRW involves an equilibrium plasma condition with the consequence that the fractional ionization for an arbitrary atomic species can be specified by the Saha equation if the plasma volume (V) and temperature (T) are known. It follows that T can be determined by taking the ratio of the Saha equations for two elements present in the target in known concentration. (Taking the ratio negates the requirement of knowing V.) Given T, the procedure can be reversed to yield the relative abundance of elements contained in the impacting particle. To test the model, a PbZrO3-PbTiO3 target was bombarded with high velocity Fe, MoB, and NiAl particles and the number of Pb, Ti, and Zr ions was determined in a time-of-flight mass spectrometer. For each event, the relative abundance of Ti to Pb was taken as known (from electron microprobe analysis) and T was determined from the Ti-Pb measurement. The Zr to Pb ratio was found to be in good agreement with the microprobe analysis (0.38 calculated mean value compared to 0.34 actual). The result was valid for all particle materials and for a velocity range 17<v<47 km/s. T ranged from 3300 to 11 500° K and was only mildly velocity dependent.

Download Full-text

Determination of Impact Ionization Coefficients Measured from 4H Silicon Carbide Avalanche Photodiodes

Materials Science Forum ◽

10.4028/www.scientific.net/msf.556-557.339 ◽

2007 ◽

Vol 556-557 ◽

pp. 339-342 ◽

Cited By ~ 1

Author(s):

W.S. Loh ◽

C. Mark Johnson ◽

J.S. Ng ◽

Peter M. Sandvik ◽

Steve Arthur ◽

...

Keyword(s):

Impact Ionization ◽

Avalanche Photodiodes ◽

Submicron Devices ◽

Illuminating Light ◽

Factor Data ◽

Ionization Coefficients ◽

P Type ◽

Dark Currents ◽

The Impact

Hole initiated avalanche multiplication characteristics of 4H-SiC avalanche photodiodes have been studied. The diodes had n+-n-p SiC epitaxial layers grown on a p-type substrate. These 1 mm2 devices had very low dark currents and exhibited sharp breakdown at voltages of approximately 500V. The diodes multiplication characteristics appeared to be identical when the wavelength of the illuminating light from the top varied from 288 to 325nm, implying that almost pure hole initiated multiplication was occurring. The multiplication factor data were modelled using a local multiplication model with impact ionization coefficients of 4H-SiC reported by various authors. The impact ionization coefficients extracted from submicron devices by Ng et al. were found to give accurate predictions for multiplication factors within the uncertainties of the doping levels. This result suggests that their ionization coefficients can be applied to thicker bulk 4H-SiC structures.

Download Full-text

Destiny+ Dust Analyzer – Campaign & timeline preparation for interplanetary & interstellar dust observation during the 4-year transfer phase from Earth to Phaethon

10.5194/epsc2020-342 ◽

2020 ◽

Author(s):

Maximilian Sommer ◽

Harald Krüger ◽

Ralf Srama ◽

Takayuki Hirai ◽

Masanori Kobayashi ◽

...

Keyword(s):

Electric Propulsion ◽

Interstellar Dust ◽

Impact Ionization ◽

Interplanetary Space ◽

Dust Cloud ◽

Dust Particles ◽

Transfer Phase ◽

Moon System ◽

The Earth ◽

The Impact

The Destiny+ mission (Demonstration and Experiment of Space Technology for Interplanetary voyage Phaethon fLyby and dUst Science) has been selected as part of its M-class Space Science Program by the Japanese space agency JAXA/ISAS and is set to launch in 2023/2024. The mission target is the active asteroid (3200) Phaethon with a projected flyby in early 2028. The scientific payload consists of two cameras (the Telescopic Camera for Phaethon, TCAP, and the Multi-band Camera for Phaethon, MCAP), and the Destiny+ Dust Analyzer (DDA). DDA is the technological successor to the Cosmic Dust Analyzer (CDA) aboard Cassini-Huygens, which prominently investigated the dust environment of the Saturnian system. The DDA sensor is designed as a combination of impact ionization time-of-flight mass spectrometer and trajectory sensor, which will allow for the analysis of sub-micron and micron sized dust particles with respect to their composition (mass resolution m/&#916;m &#8776; 100-150), mass, electrical charge, velocity (about 10% accuracy), and impact direction (about 10&#176; accuracy). Besides attempting to sample the impact-generated dust cloud around Phaethon during the flyby, DDA will be actively observing the interplanetary & interstellar dust environment over the roughly four years spanning cruise phase from the Earth-Moon system through interplanetary space. After launch into a GTO-like orbit, Destiny+ will first employ its solar-electric propulsion system to spiral up to the lunar orbit within about 18 months, followed by a series of lunar swingbys and interim coasting phases in distant cislunar space, accumulating momentum to leave the Earth-Moon system at high excess velocity. The subsequent roughly 2-year interplanetary transfer to intercept Phaethon will be characterized by moderate orbital eccentricity of up to 0.1 and largely unpowered coasting phases. During these four years, the DDA sensor will benefit from a maximum pointing coverage range enabled by its dual-axis pointing mechanism and spacecraft attitude flexibility (during times of unpowered flight). This will allow for exhaustive mapping and analysis of the different interplanetary dust populations, as well as interstellar dust encountered in the region between 0.9-1.1 AU. Here, we give a progress report on the science planning efforts for the 4-year transfer phase. We present a tentative observation timeline that assigns scientific campaigns to different phases of the mission, taking into account results of various dust models, as well as operational and technical constraints.

Download Full-text

Comets and Constraints on Solar System Formation

Highlights of Astronomy ◽

10.1017/s1539299600009187 ◽

1992 ◽

Vol 9 ◽

pp. 347-354 ◽

Cited By ~ 3

Author(s):

A.Chantal Levasseur-Regourd

Keyword(s):

Solar System ◽

Oort Cloud ◽

Dust Particles ◽

Solar System Formation ◽

Cometary Dust ◽

System Formation ◽

Deuterium Enrichment ◽

Dust Complex ◽

Comet Halley

AbstractNew and important data have been obtained during the 1985-1986 return of comet Halley, including in situ observations of the nucleus and the coma. Since the interpretation of the observations is not straightforward, the results are presented in a rather conservative manner. Some clues to the solar system formation are suggested, e.g. the shape of the nucleus, its low density, the estimated mass of the Oort cloud, the elemental abundances in comet Halley. Constraints related to isotopie abundances (deuterium enrichment, possible anomalies in carbon isotopes) and to cometary dust (complex organic compounds, submicron sized dust particles) are extensively discussed.

Download Full-text

Experiments on Dust Collection for a Cometary Mission

Symposium - International Astronomical Union ◽

10.1017/s0074180900066833 ◽

1980 ◽

Vol 90 ◽

pp. 271-271

Author(s):

J. Kissel ◽

B. C. Clark ◽

D. Clair

Keyword(s):

Chemical Analysis ◽

Surface Analysis ◽

Metal Surfaces ◽

Dust Particles ◽

Dust Collection ◽

Analysis Techniques ◽

Cometary Dust ◽

Surface Analysis Techniques ◽

First Results

Experiments presently conducted at the Martin Marietta Denver facility to collect cometary dust during a Tempel 2 flyby are reviewed. It is shown that a number of viscid materials are quite suitable to collect particles up to 50 μm diameter at speeds up to 50 m/s. First results are presented for the more complicated setups using nonviscid metal surfaces for the collection of dust. These targets allow the use of surface analysis techniques for a more elaborate chemical analysis of the collected dust particles.

Download Full-text