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Dual-Band Search Coil Magnetometer (SCM) for RPWI consortium : concept & design report. (September 19, 2010) LPP (Laboratory of Plasma Physics) L2E (Laboratory of Electronic and Electromagnetism) & University of Kanazawa 1 OUTLINE 1) 2) 3) 4) 5) Team organization Overview Heritage Sensors : principle & design Preamplifier : principle, ASIC design and results 6) SCM performances, mass & power consumption budget 7) Open questions 8) Conclusion 2 TEAM ORGANIZATION Institute Role P. Canu Scientist T. Chust Scientist Y. Zouganelis Scientist D. Alison LPP SCM tests & EGSE C. Coillot SCM technical manager P. Leroy ASIC design & SC design support G. Sou (+ Ph.D student: A. Rhouni) M. Ozaki S. Yagitani L2E U. Kanazawa ASIC design Science, SCM design support and EMC support 3 OUTLINE 1) 2) 3) 4) 5) 6) 7) 8) Team organization Overview Sensors : principle & design Preamplifier : principle, ASIC design and results Heritage SCM performances, mass & power consumption budget Open questions Conclusion 4 OVERVIEW DB-SCM is a part of RPWI. DB-SCM will measure weak magnetic field (up to few fT/sqrt(Hz)) in frequency range => divided in LF1 [0.1Hz;4kHz] and LF2 [1kHz; 20kHz] . X =>200mm It consists in: -Tri-axis dual band search-coil sensors mounted on a boom, -2 Low noise & low power consumption preamplifier per sensor (1 for LF1 and 1 for LF2) mounted close to the sensors. 5 OVERVIEW : SCIENTIFIC OBJECTIVES Study the electrodynamics of the Jovian system: • Determine the wave electric & magnetic fields (KAW, ICW, Whistler waves …) in the magnetosphere of Jupiter (“rotator” theme) • Characterize the interaction of the flowing Jovian magnetosphere with the Galilean moons (“binary system” theme) “High-frequency” electromagnetic wave processes: - Reconnection / large-scale instability (both Jupiter’s & Ganymede’s magnetospheres) - Particle acceleration and heating (both electrons & ions) - Energy transfer (wave-particle interaction, mode coupling, turbulence) - Mass loading (ion pick-up) Frequency bandwidth: 0.1 Hz - 20 kHz. 6 OUTLINE 1) 2) 3) 4) 5) Team organization Overview Heritage Sensors : principle & design Preamplifier : principle, ASIC design and results 6) SCM performances, mass & power consumption budget 7) Open questions 8) Conclusion 7 Heritage The search coil magnetometer (SCM) is part of a long line of LPP (formerly CETP and CRPE) SCMs, developed for major space missions, including: Ulysses, Galileo, Cassini, Cluster, more recently THEMIS and currently for Bepi-colombo and MMS. Example of Themis sensors (17cm length), tri-axis structure (560gr) and preamplifier (200gr and 100mW): 8 Heritage LF-SC Bepicolombo Heritage: Mast axis LF-SC Bracket Collaboration between University of Kanazawa and LPP. DB-SC Tri-axis structure mounted on a 4.6m comprising 2 low frequency search-coil and one dual-band search-coil (1Hz up to 640kHz). Spacecraft spin axis Preamplifier combines 2 low frequency preamplifier for LF sensors and one 3D preamplifier for the dual band sensor (70gr, 200mW) using components qualified up to 70kRad. 9 OUTLINE 1) 2) 3) 4) 5) Team organization Overview Heritage Sensors : principle & design Preamplifier : principle, ASIC design and results 6) SCM performances, mass & power consumption budget 7) Open questions 8) Conclusion 10 Sensors : search-coil (SC) principle Search-coil: N turns wounded around a high permeability magnetic core. Magnetic core « amplifies » external magnetic field. Magnetic amplification µapp depends on µr and shape of the core. Winding :Flux variation (Bout*S) induces a voltage proportional to number of turns (N): e N d with B dS dt e( j ) jN1Sµapp Bout 11 Sensors : search-coil (SC) principle Search-coil: N turns wounded around a high permeability magnetic core. Magnetic core « amplifies » external magnetic field. Magnetic amplification µapp depends on µr and shape of the core. Winding :Flux variation (Bout*S) induces a voltage proportional to number of turns (N): e N d with B dS dt e( j ) jN1Sµapp Bout Electrokinetic's representation : Search-coil behaves like a source voltage “e” applied on a RLC circuit : N1*S*µapp L1 d/dt 1 R1 2 7.5H Bout e 1k Vout C1 55p 0 Natural resonance of the sensor reduces dynamic and frequency range. 12 Sensors : search-coil (SC) principle Search-coil behavior using a feedback-flux Winding voltage is amplified (Vout) : Vout G0Vin Output generates a current such as: I I CR Bout--- Direct amplification --- Feedback flux Vout G0Vin R R Current generates a mutual-flux inside magnetic core : 1 N1 B µapp S L1 I1 M 21I Vin j ( N1S µapp B M 21I ) (1 L1C1 2 ) jR1C1 13 Sensors : search-coil (SC) principle Search-coil behavior using a feedback-flux Winding voltage is amplified (Vout) : Vout G0Vin Output generates a current such as: I I CR Bout--- Direct amplification --- Feedback flux Vout G0Vin R R Current generates a mutual-flux inside magnetic core : 1 N1 B µapp S L1 I1 M 21I Vin j ( N1S µapp B M 21I ) (1 L1C1 2 ) jR1C1 By combining : I G0Vin R and Vout G0Vin we deduce : N1S µapp RCR G0 jN1S µapp Vout M M 21 B (1 L1C1 2 ) j ( R1C1 21 G0 ) RCR Go= 100 Resonance is flattened. On flat part, gain is independent from temperature variation Frequency range remains limited by the resonance 14 Sensors : dual-band SC principle Extension of the magnetic field measurement at frequencies beyond 10kHz : LF2 (alone) : 400 turns winding LF2 winding LF2 (400turns)+LF1 (10000 turns) LF1 winding LF2 winding LF2 LF1+LF2 15 Sensors : dual-band SC principle Extension of the magnetic field measurement at frequencies beyond 10kHz : LF2 (alone) : 400 turns winding LF2 (400turns)+LF1 (10000 turns) LF1 winding LF2 winding LF2 winding LF2 LF1+LF2 What happens ? Current through the LF1 winding: N1*S*µapp L1 d/dt 1 2 7.5H Bext I1 e R1 1k C1 55p Vout I1 0 N1 BSµ app j 1 R1 jL1 jC1 I1 N1BSµapp L1 Expression of I is replaced inside equation of flux 2 N 2 B µapp S L2 I 2 M12 I1 2 N 2 Bµapp S L2 I 2 M 12 N1 Bµapp S ( N 2 N 2 ) Bµapp S L2 I 2 L1 2 L2 I 2 magnetic field can not be measured with a second winding after the resonance of the first one. 16 Sensors : dual-band SC principle Principle of the mutual reducer to extend frequency bandwidth Mutual reducer consists in an added cylinder of magnetic material. The flux from the self-induction is diverted through the mutual reducer Flux seen under a path from magnetic core to LF2 winding : LF1winding LF winding HF winding LF2-bis winding (E-6) Weber 6 5 4 3 Mutual reducer Magnetic core 2 1 mm 0 0 Mutual flux seen by LF2 winding is notably reduced. 2,5 5 7,5 17 Sensors : dual-band SC principle Behavior of dual-band sensor using a mutual reducer: LF2-bis : 400 turns winding + LF1(10000 turns) + mutual reducer LF1 LF2-bis LF1winding LF winding HF winding LF2-bis winding Mutual reducer Magnetic core Transfer function of the LF2 on a LF1 winding is possible by using a “mutual reducer” Frequency range can be extended up to MHz 18 Sensors : dual-band design for EJSM Dual-band search-coil design for Bepi-Colombo (MMO-PWI): Ketron Peek tube + copper sheet for ES shielding LF & MF windings +potting inside the tube + Ferrite mutual reducer Machined magnetic core Length=112mm, Diameter=16mm Ketron Peek tube + copper sheet for ES shielding LF & MF windings +potting inside the tube + Ferrite mutual reducer Machined magnetic core EJSM dual-band sensor is designed to improve the sensitivity between 2 kHz and 20 kHz, with no loss of sensitivity at lower frequencies and little extra mass. EJSM sensor is designed to permit to manage very close resonances between LF1 Length=112mm, and Diameter=16mm LF2 (improvement from BepiColombo design) EJSM sensor will be longer than Bepicolombo sensor to permit to reach lower sensitivity (20cm for EJSM instead of 10cm for Bepicolombo) Low temperature ferromagnetic material are under study 19 OUTLINE 1) 2) 3) 4) 5) Team organization Overview Heritage Sensors : principle & design Preamplifier : principle, ASIC design and results 6) SCM performances, mass & power consumption budget 7) Open questions 8) Conclusion 20 Preamplifier: principle, ASIC design and results Synoptic of the search-coil preamplifier: Preamplifier required two stages: First stage must achieve high gain, low input noise and manage the flux feedback, - Second stage must have high gain, low power consumption and filtering abilities. - LF1 ASIC Preamplifier specifications: Input noise: 4 nV/√Hz @ 10 Hz Gain: 83 dB Power consumption: < BEPICOLOMBO preamplifier (40mW) (ASIC + Search-coil) NEMI: 0.6 pT/√Hz @10 Hz LF2 ASIC Preamplifier specifications: Input noise: 1.5 nV/√Hz @ 1 kHz Gain: 83 dB Power consumption: < 40mW 21 Preamplifier: principle, ASIC design and results MP3 MP2 MP7 MP4 MP10 Vcc = 3 V MP0 R2 MP1 MP5 MP8 R5 MP6 MP9 gnd Vout Vss = -3 V R0 R1 Vin C2 R6 MN0 MN1 R4 C1 CL MN2 MN3 MN4 MN5 MN6 R3 A1 A2 22 22 Preamplifier: principle, ASIC design and results The preamplifier has been fabricated in CMOS 0.35 µm four metal technology : 1) Low power consumption : 12mW 2) Design of rad tolerant transistors using guard rings Low noise preamplifier ASIC for LF1 is under pre-environmental tests: 1. Tested under radiation dose (Cobalt 60) up to 150kRad 2. Thermal tests has to be done Low noise preamplifier ASIC for LF2 is under design. Microphtograph of 2.2 x 2.3 mm chip containing one amplifier 23 Preamplifier: principle, ASIC design and results Measured transfer function of the LF1 ASIC amplifier : Gain is close to design : 83dB Low cut-off frequency is >60kHz Measured input voltage noise spectrum : comparison between MMS/Bepicolombo preamplifier and ASIC preamplifier for EJSM : Input noise is 3.5nV/sqrt(Hz) @1kHz - Input noise @10Hz is close to the objective (4nT/sqrt(Hz)). - 24 Preamplifier: principle, ASIC design and results LF1 ASIC preamplifier + MMS search coil (10cm length) Transfer function and Noise Equivalent Magnetic Induction of EJSM ASIC combined to a 10 cm search coil (MMS design). 25 Preamplifier: principle, ASIC design and results LF1 ASIC preamplifier tested in Radiation (facilities test at Louvain la Neuve) up to 300kRad Current available datas goes up to 150kRad on 10 samples. Ability of the current ASIC design to withstand severe Radiation environment is partially proofed. 26 OUTLINE 1) 2) 3) 4) 5) Team organization Overview Heritage Sensors : principle & design Preamplifier : principle, ASIC design and results 6) SCM performances, mass & power consumption budget 7) Open questions 8) Conclusion 27 SCM Performances: design goal for RPWI EJSM Dual-Band Search Coils (DB-SC) in red. Design hypotesis : preamplifier located close to the sensor… possibly inserted inside the hollow of the ferromagnetic core. Noise Magnetic Induction (fT/sqrt(Hz)) 1,E+05 1,E+04 Bepi-Colombo 1,E+03 1,E+02 Cluster 1,E+01 Galileo 1,E+00 1,E+00 1,E+01 1,E+02 1,E+03 Frequency (Hz) 1,E+04 1,E+05 1,E+06 28 SCM Performances: mass/power budget Optimized design using 20 cm Dual-Band Search Coil sensors (a) 1 mm Al thickness is assumed (b) In case of PA mounted on the boom (c) +/-5V is assumed. Number of DB-SC sensors 3 Bandwidth 0.1 Hz to 4 kHz (LF1 band) 1 kHz to 20 kHz (LF2 band) Sensitivity 8 pT/√Hz @ 1 Hz 0.6 pT/√Hz @ 10 Hz 0.06 pT/√Hz @ 100 Hz 10 fT/√Hz @ 1 kHz 4.5 fT/√Hz @ 10 kHz Mass (DB-SC + PA(a)) < 700 g (+ cables ~85 g/m)(b) Power (under +/-5V) 240 mW (c) Length 20 cm Location boom (3.75 m from S/C) Electrical interface 6 analog signals to LFR Heritage: Ulysses (ESA/NASA), Galileo & Cassini (NASA), Cluster (ESA), THEMIS (NASA). Current fabrication: MMS (NASA), Bepi Colombo (ESA/JAXA) 29 OUTLINE 1) 2) 3) 4) 5) Team organization Overview Heritage Sensors : principle & design Preamplifier : principle, ASIC design and results 6) SCM performances, mass & power consumption budget 7) Open questions 8) Conclusion 30 OPEN QUESTIONS & REQUIREMENTS Environment : – Maximum intensity of Jovian magnetic field seen by EJSM ? What are the radiations at sensor location ? – What is the expected temperature range for sensors ? And electronic ? Calibration signal for SCM is TBD. Telemetry is TBD (sampling rate, dynamic, rate, mode.. 12 bits could be sufficient). EMC cleanliness: disturbances from other experiments should not exceed the magnetic field measured by SCM… EJSM plan to be filled by SCM… What is the policy for receiver : differential or grounded ? Available voltage supplies : preferred is Analog +/-5V 31 OPEN QUESTIONS & REQUIREMENTS Accomodation of tri-axis sensor on MLA boom/MAG boom ? Option 1 : SCM alone on a boom (as for CLUSTER, DSP, THEMIS and Bepicolombo…) Option 2 : SCM on MLA boom: Requirement 1: SCM should be as far as possible from spacecraft (>3m), for THEMIS it was 1m and signal is noisy and requires cleaning to be analyzed. Requirement 2: SCM to MLA minimum distance has to be validated Option 3 : SCM on MAG boom : Requirement 1: If MAG is digital… SCM disturbances will be prohibitive Requirement 2: Interference measurement has to be done Requirement 3:Excitation lines of Fluxgate has to be extremely stable in frequency and amplitude.. The two frequencies excitation should be as close as possible. Accomodation of preamplifier, 2 options : Option 1: Preamplifier located close to the sensor (lower capacitance but stronger environment : thermal and radiation) Will depend on shielding efficiency of sensor and temperature ! Option 2 :Preamplifier on the spacecraft (higher capacitance and worst 32 sensitivity) CONCLUSION Dual band search-coil has been designed for EJSM. Dual Band Search-coil prototype manufacturing has started => expected before AO. Ferromagnetic material for low temperature are under investigation (in collaboration with LPC2E) A low noise, low frequency ASIC preamplifier adapted for LF1 [0.1Hz-4kHz] part of EJSM search coil magnetometer has been designed, fabricated, tested (electrical & radiations tests) and validated. A second ASIC more adapted to LF2 [1kHz-20kHz] (lower background noise but higher low frequency noise) has been designed and will be fabricated before December 2011 and fully tested before AO. 33 THANK YOU ! 34 100kHz Search Coil: conception pour haute sensibilité Optimized design using 50 cm Search Coil sensor Number of SC sensors 1 Bandwidth 10 kHz to 600 kHz (MF band) Sensitivity 0.3 fT/√Hz @ 30 kHz 0.12 fT/√Hz @ 100 kHz 0.3 fT/√Hz @ 300 kHz 0.6 fT/√Hz @ 600 kHz Mass (SC + PA(a)) < 350 g (+ cables ~40 g/m )(b) Power 40 mW Length 50 cm Location boom ( > 5 m away from S/C) Electrical interface 1 analog signal to MFR (a) 1 mm Al thickness (box: ~7 g) (b) PA mounted on the boom Heritage: Ulysses (ESA/NASA), Galileo & Cassini (NASA), Cluster (ESA), THEMIS (NASA). Current fabrication: MMS (NASA), Bepi Colombo (ESA/JAXA) 35