1. University of California - Berkeley
THEMIS SCIENCE
WORKING TEAM MEETING
SST
Davin Larson
University of California - Berkeley

2. Overview Overview Instrument Description Instrument Design Data Modes
Data Warnings/Pitfalls

3. Instrument Description
Solid State Telescopes:
Measure Energetic Electrons and Ions
Energy Range:
H+: 25 keV to 6 MeV
Electrons 25 keV to ~800 keV
Angular Coverage:
Theta
4 look directions (+55, +25, -25, -55)
Resolution: ~ 30 deg FWHM
Phi
32 sectors
Resolution: ~20 deg FWHM
Geometric Factor: ~0.1 cm2-ster (~1/3 of WIND)
Mechanical Pinhole Attenuator: Lowers geometric factor by 150

4. Sensor Unit Schematic Foil Detector Al/Polyamide/Al Foil
Thick Detector
Open Detector
Foil
Collimator
Open Collimator
Attenuator
Attenuator
Sm-Co Magnet

5. Sensor Cross Section Each sensor unit is a:
Dual-double ended solid state telescope
Each double ended telescope (1/2 sensor) has:
Open collimator
Pinhole attenuator paddle
Reduces count rate during periods of high flux
Reduces radiation damage from intense fluxes of low energy ions
Magnet (Open side)
Filters out electrons <400 keV
Leaves ion flux nearly unchanged
Triplet stack of SSDs
DFE board
Preamp / shaping electronics
Thin Polyamide Foil
Filters out ions <~350 keV
Leaves electron flux nearly unchanged
Another attenuator paddle
Foil Collimator

6. (Data Acquisition & Processing)
Block Diagram
IDPU
Sensor
Unit 1
(2 DFEs A&B)
~2 m cable (x2)
DAP Board
(Data Acquisition & Processing)
Sensor
Unit 2
(2 DFEs A&B)
ETC Board
DCB
Heater Power
SMA Power
&
Backplane
DFE = Detector Front End
PCB
(Power Control Board)
SST Instrument:
2 Sensors with attenuators (4 DFEs)
2 Cable bundles
1 DAP Board (inside IDPU)
Other Boards

7. SST Mechanical Design Detector Board Composition (exploded view)
DFE Board Subassembly
BeCu Gasket (3)
Detectors (4)
KaptonHeater
Spring Clamp
PEEK Spacer (4)
Spring Plate (2)
Kapton Flex-Circuit (4)
AMPTEK Shield
Thermostat
Detector Board Composition (exploded view)

8. DFE Board Subassembly Relative Positions
SST Mechanical Design
DFE Board Subassembly Relative Positions
(2 per sensor)
Detector Stack Subassembly
Foil Frame
Multi-Layer Circuit Board (62 mil thickness)
AMPTEK Shielding
Thermostat

9. Sm-Co Magnet (4) (currently not visible)
SST Mechanical Design
Magnet-Yoke Assembly
Co-Fe Yoke (2)
Sm-Co Magnet (4) (currently not visible)
Aluminum Magnet Cage

10. SST Mechanical Design Attenuator Assembly SMA Lever (2) Attenuator (4)
Cam (2)

11. Honeywell SPDT Hermetically Sealed Switch (2)
SST Mechanical Design
Actuators and Position Switches
Honeywell SPDT Hermetically Sealed Switch (2)
SMA Actuator (2)

12. SST Mechanical Design Support Structure (front section)
Rigid Mounting Flange
Kinematic Flexure (2)

13. Bi-Directional Fields-of-View
SST Mechanical Design
A-Open
(ion)
B-Foil
(electron)
Bi-Directional Fields-of-View
A-Foil
(electron)
B-Open
(ion)

14. SST Mechanical Design SST-1 SST-2
Sensor Orientation Relative to Spacecraft Bus
SST-1
SST-2

15. Attenuator Actuation – CLOSED position
SST Mechanical Design
Attenuator Actuation – CLOSED position
Honeywell Switch (compressed-position)
Honeywell Switch (extended-position)
SMA Actuator (retracted)
SMA Actuator (extended)

16. Attenuator Actuation – OPEN position
SST Mechanical Design
Attenuator Actuation – OPEN position
Honeywell Switch (extended-position)
Honeywell Switch (compressed-position)
SMA Actuator (extended)
SMA Actuator (retracted)

17. SST Sensor Mass Summary: Sensor mass= 553.5 gm
Cable mass (173 cm) = 141 gm
Total x2= 1389 gm

18. Detectors stacked in “Triplet” sequence:
Detector System
Detectors stacked in “Triplet” sequence:
Foil (F) | Thick (T) | Open (O)
Area used  0.7 cm2
Front detectors F and O are 300 m thick while T is 600 m (with two detectors back to back)
Detectors associated with a system of coincidence/anticoincidence logic
F T O

19. Monte-Carlo simulation
Telescope Response
Monte-Carlo simulation
3D ray tracings are performed: a clean electron-proton separation is obtained
Particles’ angular distributions are determined ( 27  14 FWHM)
Efficiency plots of the electron-proton detectors are determined for different energies

20. Calibration results Typical Proton response SST Sensor 05 - Channel 435 40
45 keV 30

21. Intrument Configuration
Instrument Configuration
The SST Energy bins are controlled by DAP table.
Can be reconfigured with table upload.
Precision: 6 MeV/4096 = 1.5 keV
Log spaced
Only 1 mode currently defined.
The SST 3D (angular) distributions are binned by ETC angle map.
5 angle maps defined:
1 angle (omni)
6 angle (RDF)
32 angle
64 angle (burst, FDF)
128 angle