Response in electrostatic analyzers due to backscattered electrons: Case study analysis with the Juno Jovian Auroral Distribution Experiment-Electron instrument

Abstract

In this study, we introduce a model to characterize electron scattering in an electrostatic analyzer. We show that electrons between 0.5 and 30 keV scatter from internal surfaces to produce a response up to ~20% of the ideal, unscattered response. We compare our model results to laboratory data from the Jovian Auroral Distribution Experiment-Electron sensor onboard the NASA Juno mission. Our model reproduces the measured energy-angle response of the instrument well. Understanding and quantifying this scattering process is beneficial to the analysis of scientific data as well as future instrument optimization.

Energetic particle signatures of magnetic field‐aligned potentials over Jupiter's polar regions

“…A Maxwellian‐like distribution centered on ~300 keV is clearly evident in the upward moving electrons and not the other pitch angles, suggesting a coherent acceleration structure aligning the particles parallel to the local magnetic field. The very slight “bump” near 300 keV in f ( p ) trap at 1% level is likely due to scattering within the instrument [ Mauk et al ., ; Clark et al ., ]. The half width at half maximum (HWHM) of the field‐aligned portion of the pitch angle distribution is ~10°, which suggests a beam collimated along the field.…”

Modeling the response of a top hat electrostatic analyzer in an external magnetic field: Experimental validation with the Juno JADE‐E sensor

“…For example, magnetic field strengths on the order of a few Gauss or less can have a considerable affect on the sensor's response function for electron energies below~5 keV. Electron scattering was found to be important for energies between~1 keV to greater than 50 keV [Clark et al, 2013]. Lastly, it was shown in McComas et al [2013] that electron relativistic effects are nonnegligible for energies above 20-30 keV.…”

“…Journal of Geophysical Research: Space Physics 10.1002/2016JA022583 electron scattering [Clark et al, 2013] for the JADE-E sensor as well as other plasma sensors [e.g., Collinson et al, 2009;Randol et al, 2010].…”

“…However, they usually do not include all the complexities of a real instrument (e.g., electron scattering, residual magnetic fields, and fabrication accuracy). Differences arise from these "complexities" that are hard to predict or incorporate into the design phase [e.g., Risley, 1970;Vampola, 1998;Clark et al, 2013]. As an example, Figure 1 illustrates the region of influence of three independent effects in the firstorder response typically derived from the methods listed above [Clark et al, 2013;McComas et al, 2013].…”

“…Differences arise from these "complexities" that are hard to predict or incorporate into the design phase [e.g., Risley, 1970;Vampola, 1998;Clark et al, 2013]. As an example, Figure 1 illustrates the region of influence of three independent effects in the firstorder response typically derived from the methods listed above [Clark et al, 2013;McComas et al, 2013]. Methods to emulate the testing environment (i.e., space or laboratory conditions), whether it is through simulation or experiment, are needed to better characterize the response.…”