An integrated time-of-flight versus residual energy subsystem for a compact dual ion composition experiment for space plasmas.

M I Desai,R W Ebert,S E Weidner,F Allegrini,S A Livi,D J Mccomas,N Alexander,K Ogasawara

doi:10.1063/1.4921706

Abstract

We have developed a novel concept for a Compact Dual Ion Composition Experiment (CoDICE) that simultaneously provides high quality plasma and energetic ion composition measurements over 6 decades in ion energy in a wide variety of space plasma environments. CoDICE measures the two critical ion populations in space plasmas: (1) mass and ionic charge state composition and 3D velocity and angular distributions of ∼10 eV/q-40 keV/q plasma ions—CoDICE-Lo and (2) mass composition, energy spectra, and angular distributions of ∼30 keV-10 MeV energetic ions—CoDICE-Hi. CoDICE uses a common, integrated Time-of-Flight (TOF) versus residual energy (E) subsystem for measuring the two distinct ion populations. This paper describes the CoDICE design concept, and presents results of the laboratory tests of the TOF portion of the TOF vs. E subsystem, focusing specifically on (1) investigation of spill-over and contamination rates on the start and stop microchannel plate (MCP) anodes vs. secondary electron steering and focusing voltages, scanned around their corresponding model-optimized values, (2) TOF measurements and resolution and angular resolution, and (3) cross-contamination of the start and stop MCPs' singles rates from CoDICE-Lo and -Hi, and (4) energy resolution of avalanche photodiodes near the lower end of the CoDICE-Lo energy range. We also discuss physical effects that could impact the performance of the TOF vs. E subsystem in a flight instrument. Finally, we discuss advantages of the CoDICE design concept by comparing with capabilities and resources of existing flight instruments.

Highlights

Space environments such as the solar atmosphere, interplanetary medium, and planetary magnetospheres evolve in time and space through the dynamic transfer of mass, momentum, and energy between the embedded electromagnetic fields and the constituent plasma and energetic particle populations
We have developed a novel concept for a Compact Dual Ion Composition Experiment (CoDICE) that simultaneously provides high quality plasma and energetic ion composition measurements over 6 decades in ion energy in a wide variety of space plasma environments
This paper describes the CoDICE design concept, and presents results of the laboratory tests of the TOF portion of the TOF vs. E subsystem, focusing on (1) investigation of spill-over and contamination rates on the start and stop microchannel plate (MCP) anodes vs. secondary electron steering and focusing voltages, scanned around their corresponding model-optimized values, (2) TOF measurements and resolution and angular resolution, and (3) cross-contamination of the start and stop microchannel plates (MCPs)’ singles rates from CoDICE-Lo and -Hi, and (4) energy resolution of avalanche photodiodes near the lower end of the CoDICE-Lo energy range

Summary

Introduction

Space environments such as the solar atmosphere, interplanetary medium, and planetary magnetospheres evolve in time and space through the dynamic transfer of mass, momentum, and energy between the embedded electromagnetic fields and the constituent plasma and energetic particle populations. Energetic particle instruments covering the energy range from tens of keV up to a few MeV use either solidstate detectors (SSDs) to measure the residual energy (E) of the incoming particles (e.g., Cassini/Low-Energy Magnetospheric Measurement System–LEMMS3) or the Time-ofFlight (TOF) vs Residual Energy (E) measurements in SSDs (e.g., PEPSSI on New Horizons). Energetic particle instruments covering the energy range from tens of keV up to a few MeV use either solidstate detectors (SSDs) to measure the residual energy (E) of the incoming particles (e.g., Cassini/Low-Energy Magnetospheric Measurement System–LEMMS3) or the Time-ofFlight (TOF) vs Residual Energy (E) measurements in SSDs (e.g., PEPSSI on New Horizons4) Instruments such as the CHarge-Energy-Mass-Spectrometer (CHEMS) on Cassini use electrostatic analyzers (ESAs) to perform energy-per-charge (E/q) analysis followed by the TOF vs E technique to determine the mass, energy, and ionic charge state of suprathermal ions.. Instruments such as the CHarge-Energy-Mass-Spectrometer (CHEMS) on Cassini use electrostatic analyzers (ESAs) to perform energy-per-charge (E/q) analysis followed by the TOF vs. E technique to determine the mass, energy, and ionic charge state of suprathermal ions. In contrast, plasma populations from a few eV up to tens of keV are typically measured using simple ESAs that select ions in a narrow E/q range (e.g., New Horizons/Solar Wind Around Pluto5) focus them onto electron multiplier detectors such as microchannel plates (MCPs) or channel electron multipliers (CEMs) or use an ESA followed by TOF measurement that provide the speed of the incoming particles (e.g., Jovian Auroral Distributions Experiment—JADE on Juno6)

Objectives

Methods

Results

Conclusion