1. SWIA Front End Peer Review

2. 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

3. 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)

4. SWIA Instrument Capability
Ion Velocities: 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)✔

5. 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

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

7. SWIA Front End Block Diagram

8. SWIA Interconnect Diagram

9. 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

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

11. 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

12. 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

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

14. 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

15. 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)

16. 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.

17. 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

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

19. 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

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

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

22. 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

23. Extra Slides Follow

24. 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)

25. 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

26. SWIA Count Rates
Geometric Factor 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

27. 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