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Instrument Design: STEIN

Explore innovative instrument design techniques for enhancing sensitivity, resolution, and efficiency in detecting charged particles in space. Learn about electrostatic analyzers, STE detectors, Parker Spiral instruments, and advanced toolchests aiding in particle trajectory analysis.

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Instrument Design: STEIN

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  1. Instrument Design: STEIN Jasper Halekas and Davin Larson Kyung-Hee Visit October 2009

  2. Space Physics Instrumentation • Usually want to: • Maximise sensitivity • Maximise energy/angular resolution and coverage • Minimize weight/power • Separate different species of charged particles (and sometimes neutrals!)

  3. Electrostatic Analyzer • Separates species very well, has very good energy/angular resolution • Low sensitivity, because of small geometric factor and need to sweep energy/angle • Can only measure one species in each detector

  4. STEREO STE (SupraThermal Electrons) • Prototype detector • Very good sensitivity • Measures all energies simultaneously • Can measure ions, electrons, neutrals • But - have to have some way to separate species! • Thin window detector, very sensitive electronics, allows measurements to a few keV • (few keV low energy threshold unprecedented for solid state detectors!)

  5. Parker Spiral Electrons Solar Wind Ions STE-U STE-U w/FOV and Preamp Mounts to side of IMPACT Boom Field of view along Parker spiral – with solar wind out of FOV 70x70 STE-U FOV

  6. THEMIS SST Energy range > ~20 keV, electrons and ions separated

  7. Basic design of SST instrument Foil Detector Al/Polyamide/Al Foil (stops ions <400 keV) Thick Detector Open Detector Foil Collimator Open Collimator Attenuator Attenuator Sm-Co Magnet (sweeps away electrons <400 keV)

  8. Foil Separation

  9. Toolchest 1: Interactions w/ Matter CASINO = " monte CArlo SImulation of electroN trajectory in sOlids "

  10. X Magnetic Deflection B = 500 G 1 cm 2 cm X 2 cm pixelated (8x8) detector • Energy Range 2 keV – 50 keV (full angular coverage), Angular Range ±30°. • Partial angular coverage for higher energies. • Poor angular resolution for lowest energies.

  11. Magnetic Deflection

  12. Magnetic Deflection

  13. Toolchest 2: Finite Element Magnetostatics • Define a discrete grid and solve for the magnetic potential from each element • Linghua Wang used a commercially available program for this work

  14. Toolchest 3: Tracing Particles The Lorentz Force Law provides the second order differential equation of motion for charged particles. We use the 4th order Runge-Kutta method with an adaptive time step to solve this ordinary differential equation

  15. 4 3 2 1 Electrostatic Deflection 2 cm E-Field Region Electrons Ions 2 cm W L

  16. Top View 5 cm 2 cm Ions High Energy Ions and Electrons 3 cm 4 mm Electric Field Region E = 100-1000 V/mm Electrons Side View

  17. Ion Pixel Electron Pixel High Energy Pixel E = 100 V/mm V = 400 V Electrons Ions

  18. Realistic Potential Distribution

  19. Toolchest 4: Finite Difference Electrostatics • We set the electrostatic potential of electrodes/deflectors • Then, in free space, the potential must satisfy Laplace’s equation • Davin Larson wrote code to solve on a grid using a finite difference method

  20. Particle Trajectories in Realistic Potential Distribution

  21. Trajectories: Low Energy Electrons Low Energy Ions Neutrals, High Energy Electrons and Ions Collimators Electrostatic Deflectors Pixelated Detectors (Mounted Back-to-Back) 5 cm Solar Orbiter STE

  22. Energy-Angle Response for Edge Pixels

  23. Energy-Angle Response for Middle Pixels

  24. Center Pixel Response (Electrons) Edge Pixel Response (Electrons) Deflection Voltage Left Sweep Right Sweep 4 kV 1.5 kV 600 0 600 1.5 kV 4 kV • Symmetric response for ions • Neutrals measured in center pixel – cleanly separated for energies below ~15-20 keV • Logarithmic voltage sweep with ten steps from 600V to 4 kV is optimal for • covering phase space. Need positive and negative sweeps to get all angles, • so 20 voltage steps desired.

  25. Telemetry • For edge pixels need 20 voltage steps • To deconvolve, prefer linear energy bins from 2-15 keV (no need to go higher for edge pixels) • Total sweep = 20V*14E*8pixels*8bits = 17920 bits • For center pixels, can sum all voltage steps (not true if you want to do neutrals). • Need 20 logarithmic energy bins to cover 3-100 keV at energy resolution of 0.2 • Total distribution = 20E*8pixels*8bits = 1280 bits • Total instrumental bits per sweep = 19200 • 200bps gives 96sTimeResolution • For CINEMA, Time Tag all Events

  26. Total Instrumental Count Rates at 1 AU (scale up by 25? at 0.2 AU)Shows need for Attenuator for Solar OrbiterSimilar Issue for Auroral Zone for CINEMA Quiet Time Un-Attenuated Quiet Time Attenuated Big SEP Event Un-Attenuated Big SEP Event Attenuated Red = Edge Pixel Black = Middle Pixel

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