Siegfried Auer

Low-charge detector for the monitoring of hyper-velocity micron-sized dust particles

A new low-noise beam detector was developed, assembled and tested for the Heidelberg dust accelerator facility. The detector was used to determine in situ the charge, speed and mass of individual dust grains flying through a highly shielded metal cylinder with a length of 200 mm and integrated with a charge-sensitive amplifier Amptek model A250F/NF. Micron-sized latex and iron particles were fired at speeds between 5 and 50 km s−1. The detector characterizes dust particles with a primary charge of 1 fC, a speed of 20 km s−1 and a size of 0.1 µm with a signal-to-noise ratio of 6. The noise of the integrated detector system is typically 0.15 fC (950 electrons) in a bandwidth from 2 kHz to 10 MHz. The new detector allows the control and selection of particles either with a lower surface potential (low-conductive surfaces of polyaniline-coated polystyrene particles), or smaller grains with very small primary charges (sub-micron-sized grains with speeds above 10 km s−1).

Characteristics of a dust trajectory sensor.

Trajectories of cosmic dust particles are determined by the measurement of the electrical signals that are induced when a charged grain flies through a position-sensitive electrode system. A typical dust trajectory sensor has four sensor planes consisting of about 16 wire electrodes each. Two adjacent planes have orthogonal wire directions. The sensor is highly transparent and mechanically robust, provides a large sensitive area, large field of view, and can, at least in principle, achieve unlimited precision. While a sensor model had already undergone limited testing in the dust laboratory, its response as a function of position and angle of incidence of the trajectory and as a function of sensor dimensions was generally unknown. To better understand its characteristics, the operation of a sensor model consisting of three planes and seven wires per plane was simulated using the COULOMB computer program. We show that the response of the reduced model can be applied to a model with more planes and more wires per plane. The effect of a trajectorys position and angle on the signal strength is discussed as well as the influence of geometrical parameters such as wire diameter, distance between wire planes, and wire length. We found a greater effect of the wire diameter on the signal strength, and a lesser effect of the plane distance, than expected. A set of similarity rules is provided for the design of a larger sensor. Finally, we discuss the optimization of the sensor for different applications.

The charge and velocity detector of the cosmic dust analyzer on Cassini

Abstract The cosmic dust analyzer aboard the Cassini spacecraft includes a charge and velocity detector which senses electric charges >10 −15 C of individual cosmic dust grains as they enter the instrument. Charge is an important property of each grain, because it affects its orbital dynamics and is a measure of its size. The duration and shape of the charge signal are also important, because they reveal the grains location and velocity relative to the spacecraft. The velocity, in turn, can be expressed in a heliocentric coordinate system and orbital parameters can be derived and aid in the identification of the grains origin. We describe the operation of the charge and velocity detector, present results of laboratory calibrations using charged hypervelocity dust particles, show the first dust charge signal obtained from interplanetary space, and discuss potential applications of an advanced charge detector for future space missions.

Novel instrument for Dust Astronomy: Dust Telescope

The analysis of dust particles in space can tell us about their origin and interaction with the space environment that helps understanding the evolution of the solar system and the universe.1 2 There has been a significant advancement in dust detector/analyzer technology over the past decades; going from simple impact counters to the measurement of chemical composition and accurate dust trajectory determination. The Dust Telescope (DT) is the state of the art instrument that combines the Dust Trajectory Sensor (DTS) and the Chemical Analyzer (CA). A laboratory prototype of DT has been built and tested at the Heidelberg dust accelerator facility. The instrument combines a large target area, high mass resolution, wide dynamic range and trajectory measurement with accuracy better than 1% in speed and 0.1° degree in directionality for micron and submicron sized particles. Potential applications of the DT include the analysis of interstellar and interplanetary dust present in our Solar System, and the surface composition analysis of airless bodies such as the Moon, Europa, Ganymede, Enceladus or the Martian satellites.

Development of the nano-dust analyzer (NDA) for detection and compositional analysis of nanometer-size dust particles originating in the inner heliosphere

A linear time-of-flight mass spectrometer is developed for the detection and chemical analysis of nanometer-sized particles originating near the Sun. Nano-dust particles are thought to be produced by mutual collisions between interplanetary dust particles slowly spiraling toward the Sun and are accelerated outward to high velocities by interaction with the solar wind plasma. The WAVES instruments on the two STEREO spacecraft reported the detection, strong temporal variation, and potentially high flux of these particles. Here we report on the optimization and the results from the detailed characterization of the instruments performance using submicrometer sized dust particles accelerated to 8-60 km/s. The Nano Dust Analyzer (NDA) concept is derived from previously developed detectors. It has a 200 cm(2) effective target area and a mass resolution of approximately m/Δm = 50. The NDA instrument is designed to reliably detect and analyze nanometer-sized dust particles while being pointed close to the Suns direction, from where they are expected to arrive. Measurements by such an instrument will determine the size-dependent flux of the nano-dust particles and its variations, it will characterize the composition of the nano-dust and, ultimately, it may determine their source. The flight version of the NDA instrument is estimated to be <5 kg and requires <10 W for operation.

Characteristics of a new dust coordinate sensor

A new in-beam dust coordinate sensor (DCS) at the Colorado Center for Lunar Dust and Atmospheric Studies (CCLDAS) dust accelerator facility has been constructed and is now in use. The dust sensor operates by measuring the image charges induced on two planes of wire electrodes by passing charged dust particles. Applications for the DCS include the quantitative evaluation and improvements of the focusing and steering elements of the accelerator, and the correlation of particle velocity and mass with impact sites using precision particle location. For focusing and steering improvements, particle positions to 0.25 mm are plotted in real-time. It is possible to determine a typical particles position within the beamline to < 0.1 mm. The design, simulation and results of the DCS are further discussed.

Frontiers in In-Situ Cosmic Dust Detection and Analysis

In‐situ cosmic dust instruments and measurements played a critical role in the emergence of the field of dusty plasmas. The major breakthroughs included the discovery of β‐meteoroids, interstellar dust particles within the solar system, Jovian stream particles, and the detection and analysis of Enceladuss plumes. The science goals of cosmic dust research require the measurements of the charge, the spatial, size and velocity distributions, and the chemical and isotopic compositions of individual dust particles. In‐situ dust instrument technology has improved significantly in the last decade. Modern dust instruments with high sensitivity can detect submicron‐sized particles even at low impact velocities. Innovative ion optics methods deliver high mass resolution, m/dm>100, for chemical and isotopic analysis. The accurate trajectory measurement of cosmic dust is made possible even for submicron‐sized grains using the Dust Trajectory Sensor (DTS). This article is a brief review of the current capabilities of...

Dust Telescope: A New Tool for Dust Research

Dust particles in space carry information about their birth at a remote site in space and time not accessible to direct investigation. When we know where dust particles come from, we can derive from their state and composition important knowledge about the processes by which they were formed. This information can be gained by a combination of trajectory analysis together with the physical and chemical analysis of dust particles. Potential targets of a dust telescope can be interstellar dust phenomena (e.g. local interstellar medium or dusty stellar systems like beta-Pictoris), interplanetary phenomena (e.g. meteor stream dust, cometary, or asteroidal dust, or dust from the moon), or even space debris (e.g. fine grains from solid rocket burns). It is proposed to use a 1 m 2 dust telescope with 50° aperture. Such an instrument would detect 5 and 0.5 interplanetary dust grains of 10 −15 g and 10 −12 g per day, respectively. A state-of-the-art dust telescope consists of an array of parallel mounted dust analyzers. Potential components are a high resolution impact mass spectrometer, a dust analyzer for the determination of physical and chemical dust properties, a dust momentum sensor, and a large-area impact detector with trajectory analysis. A first example of such a dust telescope is carried by the proposed Galactic DUNE mission. The goal of DUNE is the analysis of interstellar grains near Earth.