SWIA Front End Peer Review

SWIA Science Goals Primary Goal: Measure solar wind and magnetosheath flow around Mars Additional Goals: Constrain charge exchange rates Measure basic space plasma processes throughout Martian system

SWIA Requirements Ion Velocities: 50-1000 km/s Energy Resolution: 15% or better Angular Resolution: 10° in sun direction, 30° elsewhere Time Resolution: 1 minute or better FOV: 180°x40° or better Sensitivity: 1x107-1x1010 eV/(cm2 sr s eV)

SWIA Instrument Capability Ion Velocities: 50-1000 km/s 5 eV – 25 keV energy range ✔ Energy Resolution: 15% or better 14% FWHM, 9% FWHM w/ attenuator ✔ Angular Resolution: 10° in sun direction, 30° elsewhere 4.5°x7° (4.5°x3° attenuated) sun, 22.5° elsewhere ✔ Time Resolution: 1 minute or better 4 second basic measurement cadence✔ FOV: 180°x40° or better 360°x90° (w/ some obstructions) ✔ Sensitivity: 1x107-1x1010 eV/(cm2 sr s eV) 5x104-5x1011 eV/(cm2 sr s eV)✔

SWIA Instrument One-Time Cover And Attenuator Deflectors Anode/MCP Preamp/ MCP HV HVPS Purge S/C Connector Digital PFDPU Connectors LVPS HV Enable Plug

SWIA Block Diagram LVPS Analyzer Preamps and MCP HV HVPS for Sweep & Deflectors Digital Processing/FPGA Anode/MCP

SWIA Front End Block Diagram

SWIA Interconnect Diagram

SWIA Analyzer Design Cylindrical R-Z Projection 2-d Projection of 3-d simulation R4 R2 R3 R1 R0 Toroidal Analyzer (Same Geometry as Cluster CODIF) Radii: 0.622, 3.17, 3.38, 5.19, 5.88 cm Focuses particles at 90 degrees (R4-R3)/R3 = 2*(R2-R1)/R1

SWIA Response Phi Angle Theta Angle Energy Narrow Phi Response, Gaussian Energy/Theta Response

SWIA Attenuator 2-d Projection of 3-d simulation Un-Attenuated Slit attenuator provides factor of ~25 attenuation for high flux solar wind Attenuator also provides higher energy/angle resolution

SWIA Deflectors 2-d Projection of 3-d simulation EMC requires positive deflectors => Pushing ions rather than pulling them Most deflection occurs near analyzer => Curved deflectors with straight 50 degree extensions

SWIA Deflection Response Linear Deflection Response Vs. Angle Un-Attenuated Plus V = Top Deflector Minus V = Bottom Deflector Angular FWHM Variation Attenuated

SWIA Deflection Response Peak of Energy Pass-Band Constant Some Collimation at High Deflection Voltages Leads to Reduction in FWHM FWHM Constant Un-Attenuated Attenuated Some Reduction in Geometric Factor at High Deflection Angles Geometric Factor Constant

SWIA MCP Mounting/Anodes Analyzer Exit Spyder Plate (Captures Exit Grid) MCP Entrance Grid Anode Pads Spring Fingers Clamp MCPs Spacer/ MCP Contact MCP Chevron Pair (front face biased to -2 to -3 kV) (output face at -50 V)

SWIA Anode Board MCP Contact Large Anode Pad Connectors To Preamp Small Anode Pads Other electrical components on bottom side. Signals routed through board on vias.

SWIA Anode Board Schematics Ground Return Resistor Sets MCP Output Voltage 24 anodes split 12 to each connector 10 small plus 2 large anodes 12 remaining large anodes

SWIA Anode Schematic Details Drain resistor provides DC current path Surge limit resistor Clamp diodes suppress voltage spikes

SWIA Preamp/MCPHV Board Connector from Anode 12 X A121 Preamps MCP HVPS Shield Wall 12 X A121 Preamps Connector from Anode Connectors to digital

SWIA Preamp Schematics (1 of 2) Caps for noise suppression Connector from Anode Connector to Digital Test Pulse Divider Caps for noise suppression

SWIA Preamp Schematics (2 of 2) Separate preamp thresholds for small and large anodes

SWIA Preamp Schematic Details Threshold Adjust Dead Time Set to 100 ns 5V Digital Output Pulse Width Set to 50 ns Test Pulse Input Capacitively Coupled Preamp Input AC-Coupled

Extra Slides Follow

SWIA Test Pulser Scheme E = Energy Step Number (varies from 0 to 95) 1X during the 4s CYCLE D = Deflector Step Number (varies from 0 to 23) 96X during the CYCLE M = (E + D) MODULO 128 N = M if (M<128) else 127-M TPFREQ = SCLK/(65 -N) TPFREQ is divided into four different test frequencies on the anode board, each of which is sent to six non-adjacent anodes (alternating pattern)

SWIA Deflection Voltage Sweep Black: Sweep Voltage Blue: Deflector 1 Red: Deflector 2 Top Plot: Voltages (kV) Bottom Plot: Ratio of Deflector Voltages to Sweep Voltage

SWIA Count Rates Geometric Factor 0.005 cm2 sr eV/eV (360° full sensor) Includes grids, MCP efficiency 4.5° anodes in solar wind direction, 22.5° anodes elsewhere A121 preamplifier count rate capability 12 MHz periodic ~10 c/s sensor background Dead time corrections become important at ~2 MHz High current MCP count rate capability ~2 MHz per small anode Attenuator gives additional factor of ~25 dynamic range Min flux: 5x104 => 3 c/s in small anodes, 16 c/s in big anodes Max flux: 5x1011 => 1.3 MHz in small anodes w/ attenuator

SWIA Basic Data Products SWIA produces three basic data products P0 = Full resolution data product Huge data volume Mainly for calibration purposes P1 = Reduced resolution data product 48 energies X 16 angles X 4 deflection angles 20% energy resolution, 22.5 degree angular resolution Mainly for magnetosheath/magnetosphere P2 = Reduced coverage data product Pick region of phase space centered around solar wind beam 48 energies X 10 angles X 12 deflection angles 10% energy resolution, 4.5 degree angular resolution For solar wind measurements