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Discovering Energy-Resolved ENA Distribution in the Heliosphere with IBEX-Hi Sensor

Join a journey to the Heliosheath in Kauai, Hawaii with the IBEX-Hi Sensor that detects Energetic Neutral Atoms (ENAs) from the outer heliosphere. Learn how the instrument subsystems work to provide an energy-resolved all-sky ENA distribution, background rejection, coincidence measurement techniques, and more. Dive into the design of the IBEX-Hi, a large single-pixel ENA camera with multiple subsystems ensuring accurate data collection. Explore calibration results, data products, noise, and background rejection methods, as well as predicted IBEX triple coincidence count rates. Stay updated on the current status of IBEX-Hi and its promising performance in detecting positive ENAs.

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Discovering Energy-Resolved ENA Distribution in the Heliosphere with IBEX-Hi Sensor

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  1. Voyagers in the Heliosheath Kauai, Hawaii. The IBEX Hi Sensor: Detecting ENAs from the Outer Heliosphere Dan Reisenfeld & the IBEX Team January 12, 2009

  2. Outline • How instrument subsystems work to provide energy-resolved all-sky ENA distribution • Background Rejection • Coincidence measurement technique • Temporal resolution • Predicted count rates • Current status

  3. IBEX-Hi Design: Large Single Pixel ENA Camera • Four major subsystems • Entrance • ENA-to-ion conversion • Energy analysis • Coincidence detector • Entrance • Rejects ions & electrons, collimates neutrals • ENA to ion conversion • Converts neutrals to positive ions • Energy analysis • Selects energy passband • 0.3 – 6 keV • Coincidence Detector • Identifies ENA, rejects noise

  4. Collimator Angular Response • Simulation of single pixel response (measured response matches this)

  5. Calibration Results Match End-to-End Simulation • ESA + foil throughput: Good agreement between IBEX-Hi electro-optic model and calibration results

  6. IBEX-HI Detector Section / Background Monitor Energetic Ion Background Monitor

  7. Instrument Response Functions

  8. Calibrated Geometric Factor • Assuming an energy independent flux over the ESA passband: Values of G from the response function, in cm2 sr eV/eV.

  9. Data Products: Double & Triple Coincidences Long TOF window = 100 ns • 13 coincidence types: Short TOF Window = 7 ns time Start (A,B,C) * Highly unlikely that a trigger in CEM C in the short window is a valid ENA event

  10. Event type probabilities: Triples Event-type ratios can be used to distinguish signal from backgrounds

  11. Noise & Background Rejection • Ions: • energies within passband of ESA transmission rejected by positive potential on collimator • Correlation with background monitor • Electrons: • rejected by negative potential on collimator entrance ring • Photons (Vis, UV & X-ray): • Flux mitigated by 3 foils (conversion & detector section), ESA serration and blackening, coincidence detection • correlation with background monitor • Penetrating radiation: • Triple coincidence, detectors not aligned • correlation with background monitor

  12. Penetrating Background Rates (Calibration)

  13. Continuous Sampling of ENA Measurements vs. ecliptic latitude 6 months • Best statistics at high latitudes • Possibility of observing time variability in heliosheath/TS on time scales < 6 months? 1 month 14 days 7 days

  14. Time Resolution of ENA Measurements Energy width of ESA passbands introduces uncertainty in ENA arrival time Travel time to 100 AU Time uncertainty within energy passbands (60- 120 days) Time [days]

  15. Aspera/MEX Flux and Other Models of ENA Flux at 1 AU ENA flux predictions at a given energy range over ~5 decades!

  16. Predicted IBEX Triple Coincidence Count Rates Increasing sensitivity with energy flattens steep flux distributions Detection Limit

  17. IBEX HI Status • Commissioning completing this week • All systems operating nominally • Detector gains as before launch • Positive ENA detection: • Heliospheric • Magnetospheric

  18. IBEX-HI is performing fantastically… Wait for it! Doubles (aAB) Triples (aABC, bABC, abABC)

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