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Solid State Telescope Davin Larson SSL

Solid State Telescope Davin Larson SSL. Overview. Overview Requirements Science Requirements Performance Requirements Basic Design Capabilities. SST Science Requirements.

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Solid State Telescope Davin Larson SSL

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  1. Solid State Telescope • Davin Larson • SSL

  2. Overview • Overview • Requirements • Science Requirements • Performance Requirements • Basic Design • Capabilities

  3. SST Science Requirements • SST-1: The SST shall perform measurements of the tailward-moving current disruption boundary speed using the finite gyroradius technique (4.1.1.2, 4.1.1.5). • SST-2: The SST shall measure the time-of-arrival of superthermal ions and electrons of different energies emanating from the reconnection region to determine the Rx onset time (4.1.1.3, 4.1.1.5). • SST-3: The SST shall compute the partial energy moments due to the superthermal ions and electrons in the magnetotail plasma sheet (4.1.1.3, 4.1.1.6, 4.1.1.7, 4.1.1.9, 4.1.1.10). • SST-4: The SST shall obtain measurements of ion and electron distribution functions with one spin time resolution (<10sec required) (4.1.1.2, 4.1.1.3). • SST-5: The SST shall measure energetic electron fluxes as close to Earth as 6RE geocentric, at all local times. (Radiation belt science- tertiary objective – achieved by nominal design). • SST-6: The SST shall measure energetic ions in the solar wind, at the magnetopause and in the magnetosheath (Dayside science – secondary objective – achieved by nominal design).

  4. SST Performance Requirements • SST-7: The SST shall measure energetic particles over an energy range of 30-300keV for ions and 30-100keV for electrons found in the magnetotail plasma sheet (SST-1, SST-2). • SST-8: The SST energy sampling resolution, dE/E, shall be better than 30% for ions and electrons (SST-1, SST-2). • SST-9: The SST shall be capable of measuring differential energy flux in the range from: 10^2 to 5x10^6 for ions; 10^3-10^7 for electrons (keV/cm2-s –st- keV) whilst providing adequate counts within a 10 second interval. (exact values TBD) (SST-1, SST-2) • SST-10: The SST shall measure over 90o in elevation with a minimum resolution of 45o (SST-1, SST-2, SST-3, SST-4). • SST-11: The SST shall have an azimuthal resolution of 45o (SST-1, SST-2, SST-3, SST-4). • SST-12: The SST shall supply the high energy partial moments at one spin time resolution (SST-3) • SST-13: SST calibration shall ensure <20% relative flux uncertainty over the ranges defined above (SST-1, SST-2).

  5. SST Sensor Unit • Each sensor unit is a dual-double ended telescope with 2 oppositely directed look directions for electrons and 2 for ions. (2 units/ spacecraft provide 4 look directions / species) Electrons Ions Magnet Ions SST THEMIS 3 PIPS Detectors Parylene foil Electrons

  6. SST Design changes • The original design: • WIND-like sensors with the ESTEC PDFE chip. • 3 look directions for each species (0o, +36o, -36o). • Spin plane (0o) had additional low geometric factor (10%) detector. • Geometric factors same as WIND. 19”x7” panel i+ e-

  7. SST Basic Design • New Design • Now have 4 elevations angles for each geometric factor (instead of 3 elevations for high GF, 1 for low GF) • Increased dynamic range for all look directions. • Simpler design allows some mass savings. • Preamps located very close to detectors allows low noise measurement. 19”x7” panel (Remainder of S/C not shown)

  8. SST Block Diagram • SST Sensor Block Diagram (1 of 10 channels shown) Bias Voltage Test Pulser DAC Thresh Gain FPGA Coincidence Logic & Accumulators PD To DPU A225F Preamp Shaper ADC BLR Memory Det/Preamp Board ADC Board ACTEL Board

  9. SST Block Diagram • SST Block Diagram Sensor Unit Formatter/ Moment Computer (1 ACTEL) To Processor Sensor Unit (In IDPU)

  10. SST Capabilities • Capabilities: • Amptek 225F has ~6 keV noise (with 1.5 cm2 detector) this will give <18 keV threshold for electrons (slightly higher threshold for ions due to dead layer). • Each outer detector has two active areas (ratio: x100) for dual geometric factor response. Each active area has a separate electronics chain that can be powered off. Dynamic range of combined system should be >10^6 • Thick inner detector will measure electrons up to ~1 MeV and ions up to >12 MeV • Foil / Magnet system used to stop electrons and ions <400 keV.

  11. Design Changes • Under Study: • Solid State Detectors are sensitive to radiation damage. In particular, the very high flux of low energy (<100 keV) ions can change the energy calibration of the ion detectors over time (presumably by changing the thickness of the dead layer). • The electron detectors are not sensitive to this problem because the foil will stop these ions. • Difficult to calibrate in flight without flying a radiation source. • Possible Solution: • Use mechanical door (shutter) to reduce the entrance aperture during high flux periods thus reducing the total accumulated ion flux. ~25 gm/door. • Simultaneously solves dynamic range problem. Eliminates need for separate low geometric factor electronics chain. • Only needed on the ion detectors.

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