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Collette A.,Colorado Center for Lunar Dust and Atmospheric Studies | Robertson S.,University of Colorado at Boulder | Robertson S.,NASA
Advances in Space Research | Year: 2012

We present a novel instrument concept to measure the energy and mass spectra of ions incident on the lunar surface, based on the E-parallel-B or Thomson-parabola device used extensively as a diagnostic in the plasma fusion community. The Apollo-era Suprathermal Ion Detector Experiment (SIDE) was the first instrument package to perform in-situ measurements of ions incident on the lunar surface. The ions can originate from a variety of sources, including the solar wind, the Earth's magnetotail, and photoionization of the thin lunar atmosphere. The species and energy distribution of ions arriving at the lunar surface depend in a complicated and poorly-understood fashion on the phase of the lunar day, the position of the Moon with respect to the Earth, and on the local plasma environment. The SIDE instrument used a stepped electrostatic mass analyzer in combination with a stepped crossed-field (Wien) velocity filter to analyze incoming ions. The stepped mode of operation limited both the resolution of the device (6 energy steps, 20 velocity steps, in conjunction with a 20-step dedicated energy analyzer) and the temporal resolution (2.6 min for a full energy-velocity scan). A modern diagnostic tool with significant heritage in the plasma fusion community is the E-parallel-B analyzer. This instrument is capable of analyzing the charge-to-mass ratio and momentum of individual particles. Each ion passing through a region with parallel E and B fields is deflected to a unique location on a 2D target according to its energy and mass. Energy and mass spectra can then be recorded using a 2D sensing technique; for example, a microchannel plate backed by a cross-delay-line (XDL) readout. The E-parallel-B design has the additional advantage of being physically compact and requiring modest field magnitudes, with electric fields on the order of a few kV/m and magnetic fields of tens to hundreds of Gauss, neither of which require exotic construction or heavy components. © 2012 COSPAR. Published by Elsevier Ltd. All rights reserved. Source


Hartzell C.M.,University of Colorado at Boulder | Wang X.,University Ofspreads | Scheeres D.J.,University of Colorado at Boulder | Horanyi M.,Colorado Center for Lunar Dust and Atmospheric Studies | Horanyi M.,University of Colorado at Boulder
Geophysical Research Letters | Year: 2013

The cohesion between small dust particles plays an important role in determining the electrostatic force required to loft charged dust off a surface. On airless, celestial bodies, the cohesive bond between dust particles can be stronger than the gravitational force. Assuming that the charge on dust particles is given by Gauss' law, a theoretical model considering both cohesive and gravitational forces has predicted that intermediate-sized particles require the smallest electric field strength to loft. We experimentally confirm that, for a given electric field, intermediate-sized particles are lofted, while smaller and larger particles do not move. Key Points Intermediately-sized dust grains are easiest to electrostatically loft Cohesion drives the electric field required to loft small dust grains in plasma Experiment and theory confirm the importance of cohesion for small grains. ©2013 American Geophysical Union. All Rights Reserved. Source


Shu A.,Colorado Center for Lunar Dust and Atmospheric Studies | Shu A.,University of Colorado at Boulder | Shu A.,Laboratory for Atmospheric and Space Physics | Collette A.,Colorado Center for Lunar Dust and Atmospheric Studies | And 24 more authors.
Review of Scientific Instruments | Year: 2012

A hypervelocity dust accelerator for studying micrometeorite impacts has been constructed at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) at the University of Colorado. Based on the Max-Planck-Institüt für Kernphysik (MPI-K) accelerator, this accelerator is capable of emitting single particles of a specific mass and velocity selected by the user. The accelerator consists of a 3 MV Pelletron generator with a dust source, four image charge pickup detectors, and two interchangeable target chambers: a large high-vacuum test bed and an ultra-high vacuum impact study chamber. The large test bed is a 1.2 m diameter, 1.5 m long cylindrical vacuum chamber capable of pressures as low as 10-7 torr while the ultra-high vacuum chamber is a 0.75 m diameter, 1.1 m long chamber capable of pressures as low as 10 -10 torr. Using iron dust of up to 2 microns in diameter, final velocities have been measured up to 52 km/s. The spread of the dust particles and the effect of electrostatic focusing have been measured using a long exposure CCD and a quartz target. Furthermore, a new technique of particle selection is being developed using real time digital filtering techniques. Signals are digitized and then cross-correlated with a shaped filter, resulting in a suppressed noise floor. Improvements over the MPI-K design, which include a higher operating voltage and digital filtering for detection, increase the available parameter space of dust emitted by the accelerator. The CCLDAS dust facility is a user facility open to the scientific community to assist with instrument calibrations and experiments. © 2012 American Institute of Physics. Source


Thomas E.,Colorado Center for Lunar Dust and Atmospheric Studies | Thomas E.,University of Colorado at Boulder | Auer S.,A&M Associ. | Drake K.,Colorado Center for Lunar Dust and Atmospheric Studies | And 9 more authors.
Planetary and Space Science | Year: 2013

We report on the implementation of an FPGA signal processing system for a dust accelerator at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS). The accelerator is used for hypervelocity impact studies, including cratering and ejecta studies (ionized and neutral gases created by impact, light flashes, etc.). In addition to these research goals, the accelerator is used for the calibration of in situ dust measurement instruments. For the accelerator to be useful as a scientific tool, it must be able to detect and select accelerated dust particles before they enter the experimental apparatus. An analog detection system is capable of detecting and selecting micron-sized dust grains in-flight through a simple analog trigger. Depending on how many false triggers are allowable for the specific application, users can set the trigger level to be arbitrarily close to the noise band. To observe and select nanometer-sized grains in-flight with higher detection accuracy, a digital filtration system using cross- correlation filters has been developed to extract small signals embedded in noise. Results show the FPGA system outperforms an analog method in the total number of particle detections, the highest velocity detected, and the lowest charge detected. They also show the possibility of detecting and selecting, in real-Time, nano-sized grains in laboratory dust accelerator experiments. Methods described herein can also be adapted to any real-Time signal processing problem where the signals belong to a known family of shapes. Source


Shua A.,Colorado Center for Lunar Dust and Atmospheric Studies | Shua A.,University of Colorado at Boulder | Shua A.,Laboratory for Atmospheric and Space Physics | Bugiel S.,Max Planck Institute for Nuclear Physics | And 11 more authors.
Planetary and Space Science | Year: 2013

Thin, permanently polarized Polyvinylidene Fluoride (PVDF) films have been used as dust detectors on a number of missions including the Dust Counter and Mass Analyzer (DUCMA) instrument on Vega I and 2 to comet IPHalley, the High Rate Detector (HRD) on the Cassini Mission to Saturn, the Student Dust Counter (SDC) on New Horizons to Pluto, the Dust Flux Monitor Instrument (DFMI) on the Stardust mission to comet 81P/Wild 2, the Space Dust (SPADUS) instrument on the Earth orbiting Advanced Research and Global Observation Satellite (ARGOS) and the Cosmic Dust Experiment (CDE) on the Aeronomy of Ice in the Mesosphere (AIM) mission in orbit around the Earth. Due to their low power requirements and light weight, large surface area detectors can be built for observing low dust fluxes. The operation principle behind metal-coated PVDF detectors is that a micrometeorite impact removes a portion of the metal surface layer, exposing the permanently polarized PVDF dielectric underneath. This changes the local electric potential near the crater, and the surface charge of the metal layer, which can be recorded as a transient current. The dimensions of the crater determine the strength of the potential change and thus the signal generated by the PVDF. Currently used scaling laws relating impactor parameters to crater geometry, which are used to predict PVDF response, are suspected to have systematic errors. Work is being undertaken to develop a new crater diameter scaling law using iron particles in PVDF. Cratered samples are analyzed using a 3D reconstruction technique using stereo image pairs taken in a Scanning Electron Microscope (SEM) and cross sections taken in a Focused Ion Beam (FIB). We report on the details of the reconstruction techniques and the initial findings of the crater parameter scaling law study. © Published by Elsevier Ltd. Source

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