Detectors and Analog Electronics

1. Detectors and Analog Electronics Bill Crain The Aerospace Corporation 310-336-8530 Bill.crain@aero.org

2. Introduction • Functional Description • Activities since PDR • Requirements vs. Capability • Signal Flow and Interface Block Diagram • Detector and Signal Description • Board Designs • Electronics • Test and simulation results • Layouts • Analyses • Summaries • Peer Review • Next Steps • Conclusion

3. Functional Requirements • Responsive to Instrument Reqs. Doc. 32-01205 • Functional requirements unchanged since PDR • Measure LET of high LET particles in thin detectors • Measure LET of low LET particles in thick detectors • Provide high energy resolution over range of LETs • Robust to temperature drift and radiation environments • Electronics • Detector Board (detector substrate) • Telescope Board inside Telescope housing • Analog Processing Board (APB) in E-box • No architectural design changes since PDR

4. Functional Block Diagram Detector Boards Telescope Board Analog Processing Board Thin Preamps Shaping / Scaling Thick Baseline Restorer Bias Networks To Digital Board Thin Discrim. Thick Thermistor Test Pulser Thin Detector Monitor Dosimeter Thick New Since PDR

5. Activities since PDR • Schematics, layouts, and assembly procedure completed • Breadboard tests performed on preamp and test pulser • Spice simulations performed on shaping amplifier • Tested Micron detectors similar to CRaTER designs • Fabricated and tested engineering model boards • Completed parts derating, thermal stress, and worst-case analyses • Presented electrical design at Goddard peer review

6. Requirements vs. Capability Summary Electronics design meets requirements derived from Instrument Specification

7. Bias Network dv/dt & Analog Pulse Silicon Shaping Scaling Preamp Pole-Zero Signals Detector Amp Amp Cancellation Low Lev. Digital Timing Amp Discrim. Signals Test Injection Baseline Restorer Signal Flow Diagram • Single fixed gain linear transfer function • 3 pole pseudo-gaussian response (2 complex, 1 real) • Low level discriminator used for singles counters and coincidence • Baseline restorer corrects for offset drift Analog Board Pulse Processing (1 of 6 strings shown) Telescope Board

8. Interface Block Diagram • Interface conforms to electrical ICD 32-02052 rev B • Power and bias voltages supplied by digital board • Shaped pulses and discriminator signals supplied by analog board • 78 pin D-sub connector • Added dosimeter HK • Interface Test

9. Detector Specification (1) • Documented in 32-05001 rev C • No significant changes since PDR • Micron Semiconductor Limited • Lancing, Sussex, UK • Detector Type • Ion-implanted semiconductor doping to form P+ junction on N-type silicon • Good carrier lifetime for thick detectors and excellent depletion layer uniformity • Detector Mount • Attached to small FR4 substrate with low out-gassing adhesive • 3 bond wires per contact • 4 AWG 28 wires (ohmic side, junction contact, guard ring, and ground plane)

10. Active Dimension (35mm) ~ 1mm Gd/FP P+ Contact Grid Gd/FP P+ implant window 0.1 um Active Volume (depletion region) Thickness 140 um thin; 1,000 um thick E-field N window 0.1 um N contact Detector Specification (2) • Circular detectors having active area of 9.6 cm2 • Two different detector thicknesses: thin and thick • note: state-of-the-art is 20um for thin and 2,000um for thick detectors • Guard ring on P-side to improve surface uniformity

11. Detector Specification • Detector requirements unchanged since PDR

12. Detector Issues on Other Programs • Recent problems on STEREO • Failures of flex ribbon cable due to overstress • Leakage current rise in vacuum • CRaTER mitigation • No flex cable. Interconnect wires are light-weight and flexible. • Worst-case analysis demonstrates over 10x margin on leakage current to accommodate drift • Detector screening prior to flight model selection • Keep abreast of latest developments on other programs using Micron detectors • Bi-weekly technical interchange with Micron • Close contact with STEREO science and engineering team at CalTech

13. Detector Verification • Verification process includes performance tests and environmental tests on all flight detectors • Performance metrics verified by inspection or test per verification plan • Micrometer measurements • Depletion vs. capacitance plots • Leakage current vs. temperature and time plots • Process control data • System test performance • Environmental tests include bond pull, random vibration, thermal cycling, and thermal vacuum (thick only) • All detectors serialized • Stored in dry nitrogen cabinet

14. RFB CFB Ao Vpk = Qtot/CFB qμnNe(t)E qμpNh(t)E Cdet CFB (Ao) >> Cdet Signal Description • Different signal characteristics for thin and thick detectors are accounted for in design Signal model includes electron and hole drift currents

15. Introduction • Functional Description • Activities since PDR • Requirements vs. Capability • Signal Flow and Interface Block Diagram • Detector and Signal Description • Board Designs • Electronics • Test and simulation results • Layouts • Analyses • Summaries • Peer Review • Next Steps • Conclusion

16. Telescope Electronics Design One of six detector strings • Schematic 32-01010 • Detector Bias Network • Detector operates at FD+30V at BOL • Bias network designed to maintain full depletion at worst-case leakage • Preamp • Amptek A250 hybrid • External IF9030 jFET • Connector • Positronic SCBM 24W7 combo-Dsub pigtail • 7 shielded contacts, 18 std Amptek

17. Telescope Breadboard Test Results (1) • Thin detector preamp • Interfet IF9030 jFET • 15 pF compensation • 0.5 mA bias current • 1 mV / MeV • Thick detector preamp • Interfet IF9030 jFET • 2 pF compensation • 5 mA bias current • 10 mV / MeV

18. Telescope Breadboard Test Results (2) • Preamp’s full-scale range is 2x below saturation onset test analysis

19. Telescope Board Layout Bottom Top

20. Telescope Board Construction • Assembly 32-10101 • Design • Complies with requirements in IPC-2221 and IPC-2222 • 8 layers • Isolated grounds on each preamp • Chassis ground planes on top and bottom • Construction • 0.093 in. finished thickness • Polyimide • Coupons to be sent to MIT and Goddard

21. Analog Board Electronics (1) To DPB Second-order active filter with signal inversion First-order filter with non-inverting gain From TEL x6 Res + RH1814 RH1814 Unity Gain Buffer x6 RH1814 Res SMB test connector Gain stage X10 Shaping details next slide One-shot ACS14 ACS74 5 us RH1814 Slow integrator RH119 x6 RH1078 Gate Thres Dosimeter Hybrid RH119 <Thres Test Pulser Low Range Current Pulse Detector Leakage Current Amplifier Control Test Pulser High Range To DPB RH1078

22. Shaping Scaling Pole/Zero Analog Board Electronics (2) • Shaping amplifier • Fast settling • Meets noise requirements • Discriminator • T/N ratio = 10 BOL, 3.2 EOL • Noise occupancy < 0.1% • Baseline Restorer • Gated integrator improves accuracy

23. Spice Results Actual circuit Monte-carlo Simulation

24. Analog Board Electronics (3) • Dosimeter • Measures total dose in silicon • 5 mRad increments up to 86 kRad • Utilizes three 5V analog housekeeping channels • Designed by Aerospace internal research project • Approved by LRO QAM as technology demo • Fault-tolerant external interface circuitry • Will not drive CRaTER design, cost, or schedule! Custom charge Integrator ASIC Micron silicon detector

25. Analog Board Layout Bottom Top

26. Analog Board Construction • Assembly 32-10101 • Design • Complies with requirements in IPC-2221 and IPC-2222 • 8 layers • Construction • 0.100 in. finished thickness • Polyimide • Coupons to be sent to MIT and Goddard

27. Introduction • Functional Description • Activities since PDR • Requirements vs. Capability • Signal Flow and Interface Block Diagram • Detector and Signal Description • Board Designs • Electronics • Test and simulation results • Layouts • Analyses • Summaries • Peer Review • Next Steps • Conclusion

28. Worst-case Analysis • Documented in 32-04011 • Analysis considered temperature and radiation effects • Maximum detector leakage and its effect on bias and noise • Worst-case high LET particle impact on detector and its effect on recovery time and input stage health • Opamp baseline drift and its effects on discriminator accuracy and A/D converter input stability • No performance impact or damage from worst-case predictions

29. Detector Leakage Effects (1/2) • Designed for worst-case prediction at 35C and 20 krads, per LRO spec 32-01002.0301, and detector proton dose results are in bounds • Detector bias voltage drop constrained to stay above full depletion Ref: J. B. Blake

30. Detector Leakage Effects (2/2) • Detector thermal noise requirements are met at EOL with a shaping amplifier time constant of 1 usec +/- 20%

31. High Z Particle Impact Effects • Heavy ions up to Uranium simulated by J. Mazur • Effects on input jFET are non-destructive • Large recovery time constant is incurred on thick detector, but… • Flux is ~10-8 /(m2-sec-sr-MeV/n); on the order of micro-meteorioid strike Ref: Joe Mazur

32. Op-amp Drift • Used post-irradiated input offset drift specifications from Linear Technologies data sheet • Unacceptable without baseline restorer circuit • Discriminator signal baseline shift 5X threshold • A/D input signal drifts 10X requirement • Baseline restorer solves drift problem • RH1078 has virtually zero input offset drift • Discriminator signal baseline controlled 100X below threshold • A/D input drift limited to less than 0.2% full scale

33. Parts Stress Analysis • Documented in 32-04010 • Reviewed by Mission Assurance Manager • INST-002 derating requirements satisfied • No thermal stress issues

34. Radiation Analysis • All op-amps and digital chips are tolerant to over 100 krads as guaranteed by Linear Technologies and Intersil • Datasheet specifications given up to 300 krads • No parts susceptible to latchup • SEU extremely rare • Only digital parts are those used in discriminator one-shot • Intersil parts immune for LET < 100 MeV/cm2/mg • If one did occur, the effect would be one extra count in telemetry. No lockup in analog system.

35. Peer Review Status • Held at GSFC, May 21, 2006 • Presented detailed schematics of Telescope Board and Analog Processing Board • No action items • Discussion of single-event-transient behavior of opamps and its effect on data

36. Next Steps • Complete testing of EM electronics • Characterize linearity and noise • Investigate deleterious effects of overload and effects on discriminators • Integrate detectors and run beam test at LBL • Validate signal / noise performance • Include single event transient tests • Deliver EM to MIT • Update layouts for flight • Finalize assembly procedures and electrical test procedures for flight build

37. Summary • Specifications and ICDs up-to-date • No major revisions since PDR • Breadboard tests show readiness for fabrication • Engineering model board testing going well • Peer review successfully completed