Simulations as a tool for higher mass resolution spectrometer: Lessons from existing observations 1G. Nicolaou, 1M. Yamauchi, 1,2H. Nilsson, 1M. Wieser, 3A. Fedorov, 1D. R. Castillo and 2L. Berčič Motivation ESCAPE: M5 Mission Science Objective: How and at what rate is Earth slowly losing its atmosphere to space? Determine escape mechanisms High resolution measurements: Distinct ion species and their isotopes Requirement 1Swedish Institute of Space Physics (IRF), Kiruna, Sweden 2Luleå University of Technology, Kiruna, Sweden 3Institut de Recherche en Astrophysique et Planetologie (IRAP), CNRS/Universite de Toulouse, Toulouse, France

Simulations as a tool for higher mass resolution spectrometer: Lessons from existing observations 1G. Nicolaou, 1M. Yamauchi, 1,2H. Nilsson, 1M. Wieser, 3A. Fedorov, 1D. R. Castillo and 2L. Berčič Heritage ICA (Rosetta) and IMA (Mars Express/ Venus Express): Examples of successful separation of H2O, O, O2 and CO2 Modifications NOIA (ESCAPE proposed mission) Geometrical modifications-Electrostatic Analyser and magnets shape/size 1Swedish Institute of Space Physics (IRF), Kiruna, Sweden 2Luleå University of Technology, Kiruna, Sweden 3Institut de Recherche en Astrophysique et Planetologie (IRAP), CNRS/Universite de Toulouse, Toulouse, France

Lessons from observations Simulations as a tool for higher mass resolution spectrometer: Lessons from existing observations 1G. Nicolaou, 1M. Yamauchi, 1,2H. Nilsson, 1M. Wieser, 3A. Fedorov, 1D. R. Castillo and 2L. Berčič Lessons from observations Unwanted effects: Sector and mass channel cross-talk, contamination, noise More to be considered Different detector design Understand the nature of contamination → how to remove or avoid Better calibration on response → mass/sector sensitivity knowledge 1Swedish Institute of Space Physics (IRF), Kiruna, Sweden 2Luleå University of Technology, Kiruna, Sweden 3Institut de Recherche en Astrophysique et Planetologie (IRAP), CNRS/Universite de Toulouse, Toulouse, France

ICA/IMA design and principle The Ion Composition Analyser (ICA) on ROSETTA and the Ion Mass Anylyser (IMA) on MEX/VEX ICA/IMA design and principle Credit : E. Behar (Left) ICA/IMA instrument cross section. Ion trajectories through the instrument are shown. (middle) azimuth sectors orientation and (right) elevation direction detected during the elevation scans

Mass detection Deflectors: Elevation selection ESA: E/q selection Magnets: m/q selection The MCP is “divided” in 16 azimuth sectors and 32 mass rings: For the same E/q heavier species land closer to the center

Simulations of ICA/IMA response Goal: to achieve as realistic simulation as possible SIMION: 3-d ion tracing software The actual flight model design files are used Studied: position of different species in the MCP Purpose: compare with flight data Extrapolate to low energies Modifications for better performance a) Instrument design in SIMION software, b) cross section of instrument and c) top vie if MCP in SIMION ion tracing software

Compared to calibration ICA calibration: available for one sector few species Energies>300eV ICA simulation: Cannot resolve sector differences Uniform response “Perfect” magnets

Directions for improvement Geometrical modifications for better mass peak separation (introduced by Nicolaou et al.,2016) a) Cross section of a simplified ICA-IMA like design with spherical ESA and a modified designed with toroidal ESA, and longer magnets. Trajectories of different species through the magnets are also shown. b) top view of the detector for the two designs. The distributions show better seperation for the modified model.

Proposed instrument: Nitrogen-Oxygen Ion Detector (NOID) Instrument for ESCAPE proposal (ESA’s M5) Based on ICA/IMA design (geometrical modifications only) More to be consider: narrower sectors, magnets of different shape, MCP of different shape (Nicolaou et al., 2016)

Flight data: Lessons we learned Mass peaks can be successfully fitted to the IMA-MEX data: From Castillo et al., 2017 Gaussian fitting does not work all the time!!!

Flight data: Lessons we learned ICA data is more challenging: Broader signal Many possible species from the comet Many heavy species are recorded in low E/q Strong mass bin and azimuth cross talk Limited calibration (not at all <300eV/q)

Flight data: Lessons we learned Challenges Mass rings (bins) cross talk Inactive mass rings (give no signal) Non uniform background

Flight data: Lessons we learned Non-uniform response Noise analysis Energies where no-signal is expected would give ideally uniform background Not the case Each anode has different sensitivity?

Flight data: Lessons we learned Azimuth sectors cross-talk: Selected periods when solar wind beam illuminates specific sector Find extremely correlated signal in other sectors Quantify the cross-talk and remove (already done for protons)

Flight data: Lessons we learned “ghost” counts: particles scattered over the mass anodes “ghost” counts pollute the information of ion mass ICA Data IMA (MEx)Data “ghost” counts have been removed in order to fit the IMA data mass peaks Not “clean” “clean”

Conclusions Preliminary geometrical modifications of the existing design are promising for higher mass resolution Flight data indicate more problems: mass/azimuth cross-talk Contamination Non uniform response (diff. efficiency of sectors and anodes) Directions of improvement: Re-design sector/anode system Understand the contamination Calibrate the response in more detail

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