Reflections of ions in electrostatic analyzers: A case study with New Horizons/Solar Wind Around Pluto

Journal Article · Mon Nov 15 00:00:00 EST 2010 · Review of Scientific Instruments

DOI:https://doi.org/10.1063/1.3499367· OSTI ID:22075439

Randol, B M; Ebert, R W ^[1]; Allegrini, F; McComas, D J ^[2]; Schwadron, N A ^[3]

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1. Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, Texas 78229 (United States)
2. Space Science and Engineering Division, Southwest Research Institute, San Antonio, Texas 78228 (United States)
3. Department of Astronomy, Boston University, Boston, Massachusetts 02215 (United States)

Electrostatic analyzers (ESAs), in various forms, are used to measure plasma in a range of applications. In this article, we describe how ions reflect from the interior surfaces of an ESA, the detection of which constitutes a fundamentally nonideal response of ESAs. We demonstrate this effect by comparing laboratory data from a real ESA-based space instrument, the Solar Wind Around Pluto (SWAP) instrument, aboard the NASA New Horizons spacecraft, to results from a model based on quantum mechanical simulations of particles reflected from the instrument's surfaces combined with simulations of particle trajectories through the instrument's applied electrostatic fields. Thus, we show, for the first time, how reflected ions in ESAs lead to nonideal effects that have important implications for understanding the data returned by these instruments, as well as for designing new low-background ESA-based instruments. Specifically, we show that the response of SWAP widens considerably below a level of 10{sup -3} of the peak response. Thus, a direct measurement of a plasma distribution with SWAP will have an energy-dependent background on the order of {<=}10{sup -3} of the peak of the signal due to that distribution. We predict that this order of magnitude estimate for the background applies to a large number of ESA-based instruments because ESAs operate using a common principle. However, the exact shape of the energy-dependent response will be different for different instruments. The principle of operation is that ions outside the ideal range of energy-per-charge are deflected into the walls of the ESA. Therefore, we propose that a new design paradigm is necessary to mitigate the effect of ion reflections and thus accurately and directly measure the energy spectrum of a plasma using ESAs. In this article, we build a framework for minimizing the effect of ion reflections in the design of new ESAs. Through the use of existing computer simulation software, a design team can use our method to quantify the amount of reflections in their instrument and iteratively change design parameters before fabrication, conserving resources. A possible direction for the new design paradigm is having nonsolid walls of the ESA, already used in some applications.

• OSTI ID: 22075439
• Journal Information: Review of Scientific Instruments, Vol. 81, Issue 11; Other Information: (c) 2010 American Institute of Physics; Country of input: International Atomic Energy Agency (IAEA); ISSN 0034-6748
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY
79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COMPUTER CODES
COMPUTERIZED SIMULATION
DESIGN
DETECTION
ELECTRIC FIELDS
ELECTROSTATIC ANALYZERS
ENERGY DEPENDENCE
ENERGY SPECTRA
IONS
NASA
PARTICLES
PLASMA
PLASMA DIAGNOSTICS
PLUTO PLANET
QUANTUM MECHANICS
REFLECTION
SIGNALS
SOLAR WIND
TRAJECTORIES