Preamp PRE Boom Electronics Board BEB EFW-EMFISIS E-Field

Preamp (PRE) Boom Electronics Board (BEB) EFW-EMFISIS E-Field I/F (EFW-EMF) John Bonnell Jane Hoberman, Michael Ludlam Space Sciences Laboratory University of California, Berkeley 3 -4 Sept. 2008 EFW INST+SOC PDR 309

EFW – PRE, BEB, EFW-EMF Outline • Motivation – Biasing, Floating Grounds, and all that. • • Preamp Boom Electronics Board (BEB) EFW-EMFISIS E-Field Interface (EFW-EMF) Test Plans • For Each: – – Performance requirements. Block Diagram or Schematic Layout Status 3 -4 Sept. 2008 EFW INST+SOC PDR 310

EFW – PRE, BEB, EFW-EMF Motivation (In Words) • • • The EFW Sensors, Preamp, BEB and EFW-EMFISIS interface represent the primary analog signal path for E-field measurements on RBSP. Measuring 0. 1 m. V/m DC E-fields required accuracies of 0. 1% in the magnetosphere: – tens of m. V of signal in the presence of tens to hundreds of m. V/m of effective common-mode or systematic noise (photocurrents, SC charging), or tens of volts of common mode signal. Non-linear coupling (I-V curve) of EFW sensors to E-field can be optimized through current biasing (factor of 100 decrease in susceptibility to systematic error sources and density fluctuations). Current biasing of sensors drives volts to tens of volts floating potential differences between sensors and SC ground. High effective source impedance (plasma sheath, ten of MΩ), and low-noise and low-leakage current requirements (systematic error reduction again) drive use of low-voltage preamps in floating ground configuration. Deflection and collection of stray photoelectron currents prior to impingement upon sensor also reduces DC biases (WHIP/USHER and GUARD surfaces). 3 -4 Sept. 2008 EFW INST+SOC PDR 311

EFW – PRE, BEB, EFW-EMF Motivation (In Pictures) Sensor I-V curve and sheath impedance Sensor and SC Floating Potentials SC photoelectrons Sensors ambient e- photo e- plasma e- 3 -4 Sept. 2008 EFW INST+SOC PDR 312

EFW – PRE, BEB, EFW-EMF Performance Requirements • • Formal requirements presented in Sys. Eng presentation. Informally: – Measure few tenths of m. V/m to few hundreds of m. V/m 2 D DC E-fields associated with global convection, ULF waves, and shock-driven effects (spin plane). – Measure few m. V/m to few hundreds of m. V/m 3 D DC E-fields (spin plane and spin axis) associated with same. – Measure 3 D E-field fluctuations up to a 6 k. Hz at amplitudes up to hundreds of m. V/m associated with energetic electron acceleration, scattering and transport. – Deliver low-noise analog E-field signals to EMFISIS-WAVES from 10 Hz to 400 k. Hz to allow for measurement of tens of m. V/m E-field fluctuations associated with energetic electron acceleration, scattering, and transport, as well as detection of the upper hybrid line for cold plasma density estimation. – Measure SC potential fluctuations associated with quasi-DC and low-frequency plasma density and fluctuations. • These measurement requirements drive the design of the Preamp, the Boom Electronics Board (BEB) and EFW-EMFISIS E-Field interface. 3 -4 Sept. 2008 EFW INST+SOC PDR 313

EFW – Preamp 3 -4 Sept. 2008 EFW INST+SOC PDR 314

EFW – Preamp SPB Schematic 3 -4 Sept. 2008 EFW INST+SOC PDR 315

EFW – Preamp AXB Schematic 3 -4 Sept. 2008 EFW INST+SOC PDR 316

EFW – Preamp Response Model • Sheath impedance is Rs || Cs, and connects to SPHERE. • Output load is Cc || (Rc + RL), connected to Vout. 3 -4 Sept. 2008 EFW INST+SOC PDR 317

EFW – Preamp Frequency Response Parameter Rs [Mohm] Cs [p. F] Description SPB Sheath resistance Sheath capacitance AXB 50 14. 2 6. 4 Re [kohm] ESD protection – resistor 100 Ce [kohm] ESD protection – bypass capacitor 10 Ri [Tohm] Follower -- input resistance 1 Ci [p. F] Follower – input capacitance 7 Output resistor 100 Ro [ohm] Lc [m] d. C/d. L [p. F/m] d. R/d. L [ohm/m] RL [kohm] Cable length 48 7 Cable cap/length 75 Cable resistance/length 1. 5 Load resistance 100 • Confirmed via test using THEMIS=EFI Flight Spare Pre and prototype RBSP-EFW 50 -m cable, Nov 2007. 3 -4 Sept. 2008 EFW INST+SOC PDR 318

EFW – Preamp Enclosures SPB AXB fine wire usher surface • SPB enclosure directly derived from THEMIS-EFI (20 units onorbit 19 months); minor modifications to accommodate DDD-mitigation caps. OP-15 and rad shield guard surface OP-15 and rad shield • AXB enclosure is AXB sensor (spherical shell). • Includes 7 -mm Al equivalent 4π radiation shields around OP-15. SPB cable Hinge (Guard) Whip (Stub or Usher) Sphere 3 -4 Sept. 2008 EFW INST+SOC PDR 319

EFW – Preamp Layouts • SPB and AXB Preamp PWB layouts derived directly from THEMIS-EFI, with minor modifications to accommodate DDD-mitigation capacitors, as well as different mounting and packaging of AXB units. • Board material is Thermount (Arlon 85 NT), to minimize differential CTE over broad temperature ranges: SPB AXB • -135 C to + 90 C; THEMISEFI experience. • -150 C to +70 C; RBSPEFW CBE. 3 -4 Sept. 2008 EFW INST+SOC PDR 320

EFW – Preamp Contribution to DC Error Budget • Contribution of preamp to DC error budget is negligible: • worst case NTE DC errors are 24 m. V (SPB) and 48 m. V (AXB). • OP-15 VOS and IBIAS contribute < 3 m. V at BOL and over temperature (THEMIS-EFI). • OP-15 is 100 -krad(Si) part, but increases in VOS and IBIAS values and fluctuations noted at the 40 -60 k. Rad(Si) TID, leading to enhanced shielding design (7 -mm Al-equivalent; ≈20 krad(Si) mission dose [MDR Dose-Depth Model]) [Uni. Sys Report PPM-98 -008 (1998)]. 3 -4 Sept. 2008 EFW INST+SOC PDR 321

EFW – Preamp AC Error Budget (Noise and Sensitivity) • EFW sensitivity requirement (S/N = 1) marked in DASHED RED. • EMFISIS E-field buffer sensitivity requirement (S/N =1) marked in SOLID RED. • Most likely conducted noise source (THEMIS-EFI experience) is floating supply switching frequency, which is out-of-band (450 k. Hz; dashed blue line). 3 -4 Sept. 2008 EFW INST+SOC PDR 322

EFW – Preamp Dynamic Range and Design • Goal of 400 m. V/m at up to 6 k. Hz (driver is recent observations of large-amplitude narrowband whistler mode waves in inner magnetosphere). • Testing at 24 Vpp (equivalent to 40 Vpp with nominal AC gain of 0. 6) using THEMIS-EFI Flight Spare preamps. • Driver for increase in floating supply voltage (± 10 to ± 15 V). 3 -4 Sept. 2008 EFW INST+SOC PDR 323

EFW – Preamp DDD Testing and Mitigation • adding necessary 350 -mil Al equivalent shield to SPB and AXB preamp enclosures drove MOI and stability ratios. • adding > 0. 1 n. F DDD-mitigation caps to preamp input would severely attenuate AC response. • All pins of OP-15 tested in both powered and unpowered state: • 1000 pulses, 10 -p. F capacitor, +/- 1500 V [as per RBSP EMECP]. • Only susceptible pins were COMP inputs: • Addition of DDD-mitigation caps from COMP inputs to FGND. • Connection of N/C pin to FGND (no floating conductors allowed). • Impacts on performance: • to be tested, Sep-Oct 2008; not expected to impact performance. 3 -4 Sept. 2008 EFW INST+SOC PDR 324

EFW – Boom Electronics Board (BEB) 3 -4 Sept. 2008 EFW INST+SOC PDR 325

BEB Requirements • Functional Requirements – Spin Plane and Axial Booms and Sensors, for each provide: • Floating Ground Driver • “Bias”, “Guard”, “Usher” programmable potentials with readback. • AC test signal source – Changes from THEMIS-EFI Design: • • • Increase in FGND range from ± 100 V to ± 225 V. Deletion of DBRAID driver. DAC commanding moved off-board (DCB function). ACTEST generation moved off-board (DCB function); switching maintained. Accommodation of EFW-EMFISIS E-Field I/F Buffers. Allowance for “Solo-BEB” contingency operation. 3 -4 Sept. 2008 EFW INST+SOC PDR 326

BEB Requirements, con’t. Preamp Signal Characteristics: • DC Voltage Level: ± 185 Vdc wrt. AGND. • AC Dynamic Range: • 200 Vpp wrt. AGND (<100 Hz). • 26 Vpp wrt. FGND (>100 Hz). • Bandwidth: DC – 400 k. Hz. Floating Ground Driver Specification: • Input: Preamp Output Signal (V 1. . V 6). • Input Filter: 300 Hz (3 d. B). • Output Dynamic Range: ± 185 Vdc wrt. AGND. • Output: references Preamp floating power supply (± 15 Vdc wrt. FGND). • Opposing booms matched to 0. 1% accuracy. Bias, Usher, Guard Specification: • Reference Input: Preamp Output Signal (V 1. . V 6). • Reference Input Filter: 300 Hz (3 d. B). • Output Dynamic Range: Vref± 40 Vdc wrt. AGND. • full-scale DAC → Vref + 40 Vdc. • DAC Resolution: 1 n. A or 10 m. V (12 -bit DAC provides XXX n. A) • Opposing booms matched to 0. 1% accuracy (BIAS only). • DAC step response: better than 10 ms (matches typ. Sensor response). Parts: • Selection, Derating, Radiation, Gen’l Specs: as per RBSP EFW PAIP and Matrix. 3 -4 Sept. 2008 EFW INST+SOC PDR 327

EFW – BEB Functional Block Diagram 3 -4 Sept. 2008 EFW INST+SOC PDR 328

EFW BEB Preliminary PWB Layout (1) • THEMIS-EFI BEB with modifications: • Maintain front panel and backplane connector layout. • remove DBRAID Driver. • remove FPGA and ACTEST buffers. • Accommodate smaller transistors and larger caps. • Accommodate EFWEMF buffers along front side. 3 -4 Sept. 2008 EFW INST+SOC PDR 329

REVISED 3 -4 Sept. 2008 EFW BEB Preliminary PWB Layout (2) EFW INST+SOC PDR 330

EFW – BEB Mechanical Assembly • BEB and EFW-EMF I/F is loaded at top of IDPU chassis. • EMI shield between bottom of BEB and top of DFB. 3 -4 Sept. 2008 EFW INST+SOC PDR 331

EFW -- BEB Design Status • BEB Breadboard – 225 -V Bias and (FGND) designs verified. – Preliminary DC gain and AC response measured. • Engineering Model – BEB schematic update complete: • Trace sizing and spacing for 225 -V design. • Parts stress analysis complete. – PWB board layout in progress: • Initial placement complete. • Layout to be completed by early Sep 2008. – Parts testing: • See summary at end of section. 3 -4 Sept. 2008 EFW INST+SOC PDR 332

EFW – EMFISIS-EFW E-Field I/F 3 -4 Sept. 2008 EFW INST+SOC PDR 333

EFW – EFW-EMFISIS E-Field I/F Design Requirements [EFW to EMFISIS Interface ICD] … Subsection 2. 2. 3 EFW TO EMFISIS EFW will provide to EMFISIS buffered analog probe voltage difference signals for three orthogonal pairs of electric field sensors. Over the frequency range from 10 k. Hz to 400 k. Hz, these signals will have a 100 d. B (TBR) dynamic range evaluated over a bandwidth of 1 Hz and a sensitivity of 3· 10 -17 (V/m)2/Hz (TBR) at 100 k. Hz for the two spin plane components. Over the frequency range from 10 Hz to 12 k. Hz, there shall be a 100 d. B (TBR) dynamic range evaluated over a bandwidth of 1 Hz and a sensitivity of 3· 1014(V/m)2/Hz (TBR) at 1 k. Hz for the two spin plane components. For the axial component signals, these requirements shall be reduced by a factor of 100 in sensitivity and 20 d. B in dynamic range. The maximum magnitude of the measured signals for all components to be handled by the interface shall be 50 m. V/m at 1 k. Hz. 3 -4 Sept. 2008 EFW INST+SOC PDR 334

EFW – EFW-EMFISIS E-Field I/F Block Diagram • Differential buffers for each of the three axes of E-field measurements. • Differential signal and reference ground sent via shielded twisted pair in the EFW-to-EMFISIS harness to the EMFISIS-WAVES package. 3 -4 Sept. 2008 EFW INST+SOC PDR 335

EFW – EFW-EMFISIS E-Field I/F Schematic • 10 -Hz high-pass RC filter on input. • Precision resistors and trim capacitors to achieve 40 d. B AC CMRR. • Requirement for DDDmitigation capacitor on output TBD (analysis/test required). 3 -4 Sept. 2008 EFW INST+SOC PDR 336

EFW – PRE, BEB, EMF Parts Selection and Testing Part Number Part Type STX 83003 250 V rated transistor 2 SA 1627 Test Plan Radiation Status Comments transistor for BEB output stage Plastic part, will be lot screened to IEEE-INST 002, section S 1 Will be tested In house 250 V rated transistor for BEB output stage Plastic part, will be lot screened to IEEE-INST 002, section S 1 Will be tested In house HA-5127 Op Amp EMFISIS buffer 883 part, DPA and PIND Test Will be tested In house M 49467 P 07332 K Capacitor 3. 3 n. F, 600 V Feedback from HV output PPL-21 Does not apply To be ordered M 49467 P 07102 J Capacitor 1 n. F, 600 V Filter on HV output PPL-21 Does not apply To be ordered M 49467 P 07103 K Capacitor 10 n. F, 600 V Filter on 225 V power PPL-21 Does not apply To be ordered M 49267 P 07333 J Capacitor. 033 u. F, 600 V EMFISIS filter PPL-21 Does not apply To be ordered M 49467 P 07103 K Capacitor 10 n. F, 600 V Input filter on floater driver PPL-21 Does not apply To be ordered D 55342 K 09 B-1 K Resistor 1 K, 1 W Filter on 225 V power PPL-21 Does not apply To be ordered D 55342 K 08 B-2. 74 M Resistor, 2. 74 M High value resistor PPL-21 Does not apply To be ordered 3 -4 Sept. 2008 Purpose EFW INST+SOC PDR 337

EFW – PRE, BEB, EMF Functional Testing • Preamp: Significant Reuse of THEMIS GSE and Procs. • Board-Level Functional Tests (DC and AC gain, offset, phase; Input impedance, VOS, IBIAS; power). • Thermal Qualification and Acceptance (as required). • BEB: • Board-Level Functional Tests (DC and AC response: gain, offset, phase; DAC commanding, gain, and offset; Analog HSK readback; power). • EFW-EMFISIS I/F: • Board-Level Functional Tests (AC Response: gain, phase, offset; AC CMRR; power). • Integrated EFW IDPU ETU conducted noise tests. • EFW-EMFISIS combined ETU noise testing. 3 -4 Sept. 2008 EFW INST+SOC PDR 338

EFW – PRE, BEB, EFW-EMF BACKUP SLIDES 3 -4 Sept. 2008 EFW INST+SOC PDR 339

EFW – Preamp Biasing and Frequency Response Impact of Bias on Frequency Response Model; THEMIS-EFI (SPB, red; AXB, green). 3 -4 Sept. 2008 EFW INST+SOC PDR 340

EFW -- BEB Floating Ground Driver • Design Heritage: – CRESS, FAST, Polar, CLUSTER, THEMIS. – Changes in parts driven by 225 -V design: • 2 N 3439, 2 N 5416 → STX 83003, 2 SA 1627. • Higher voltage capacitors on feedback, filters. 3 -4 Sept. 2008 EFW INST+SOC PDR 341

EFW -- BEB Generic Bias Circuit (bias, usher, guard) • Design Heritage: – CRESS, FAST, Polar, CLUSTER, THEMIS. – Changes in parts driven by 225 -V design: • 2 N 3439, 2 N 5416 → STX 83003, 2 SA 1627. • Higher voltage capacitors on feedback, filters. 3 -4 Sept. 2008 EFW INST+SOC PDR 342