LPW Preamp/Sensor Overview Greg Delory, LPW Co-I [email protected] MAVEN PFP Pre-CDR Peer...

LPW Preamp/Sensor Overview

Greg Delory, LPW [email protected]

MAVEN PFP Pre-CDR Peer Review May 10, 2011

mailto:[email protected]

2MAVEN PFP Pre-CDR Peer Review

Overview

• LPW sensor consists of:– Preamp: analog circuitry for current and voltage measurements– Whip: antenna used by the preamp

• LPW preamp design based on:– FAST (relays, switching from voltage to current mode)– THEMIS (similar/identical op-amps, temperature requirements)

• LPW preamp is:– Similar to THEMIS for temperature requirements– Less than THEMIS for radiation requirements– Lower in complexity than FAST preamp


LPW Sensor Design

• Whip – an antenna, a conductor through which voltage and current in the plasma are measured– Needs to be of sufficient size for high coupling capacitance and current collection area– Requires coating for chemical/structural durability and surface uniformity (Titanium Nitride)

• Stub, Guard – each biased at a controlled voltage depending on measurement mode– Mitigates photoelectron effects in voltage mode, end effects in current mode

• Preamp enclosure – houses preamplifier electronics at the base of the whip antenna.– High impedance interface to the plasma / buffer for driving boom cable

Whip – 50 x 0.635 cm “Stub” “Guard”

Preamp Enclosure


LPW Sensor EM (1)


LPW Sensor EM (2)


Preamp – Since PDR

• No major changes• Decisions made for critical active/unique parts (see next

slides)• Added Whip guard to reduce input capacitance of final

sensor assembly• Comprehensive measurement and test program


Integrated Sensor Tests


Sensor Tests: Voltage Mode

2m cal chamber1 Meg/chamber capacitive coupling

Resistive Coupling

Capacitive Coupling

Input Capacitance = 13 pF


Assembled EM Unit

EM Whip, preamp, boom, harness in RBSP-derived cal chamber.

Test stimulus delivered through coupler block


Assembled EM Unit

DFB/BEBExternal power suppliesMISG


Complete Signal Chain


Current Status Summary

• Few changes from PDR• EM Sensor, boom fabrication and assembly complete• LPW Whips fabricated, and currently out for coating• Tests of integrated preamp/sensor assembly yielded no

surprises• First tests with complete EM system conducted

– No major anomalies, but more analysis needs to be done• Electronics boards back at LASP – will continue testing

boom/sensor combination here @ SSL


Work Remaining for CDR/FM Build

• Relay Life Test– Happening now

• Preamp Qualification Model (QM)– Flight-quality board, low CTE Arlon 85NT construction– Used to verify temperature predicts (~-170 to +80 C)

• Integrated EM system test:– Understand details of instrument response– Perform complete calibration

Backup Slides


LPW Preamp Circuit

V _ W A V E S

G U A R D 1

R 1 1 0 k

+1 2 VC 5

2 2 p FS TU B

G U A R D 2

C 1

1 u F

-1 2 V

R 8

1 5 0 k

W H I P _ G U A R D

+

-

U 2

O P 1 5

3

26

7 14 5

C 3

2 2 p F

G N D _ F I E L D _ S I G N A L

<D o c > 1 . 2

M A V E N L P W P R E A M P Q M A

A

1 1F rid a y , M a rc h 1 1 , 2 0 1 1

S c h e m a t ic M o d if y D a t e = F rid a y , M a rc h 1 1 , 2 0 1 1 1 9 : 3 3 : 2 6

Tit le

S ize D o c u m e n t N u m b e r R e v

D a t e : S h e e t o f

R E L A Y +

R 4 1 K

K 1

Te le d y n e 4 2 2 D D

31

2

87

6

91 0

45

R 1 0

1 0 0

S TU B

+1 2 V

C 2

0 . 1 u F

R 91 0 0 K

C 4

1 5 0 0 p F

-1 2 V

R 7 5 0 k

R 65 0 M

Is o la ted Ground Plane

-1 2 V

W H I P _ I N P U T

TE M P +

R E L A Y -_ TE M P -

V _ C U R R E N TR 5

1 0 0 k

R 1 2 5 k

+

-

U 1

O P 1 6

3

26

7 14 5

B I A S _ S W E E P

+

BYPASS CAPS

+1 2 V

D 1 D T-4 7 112

R 1 1

1 M

TOP VIEW OF DT-471

J1 (n o co n n e cto r -b a re p a d s o nPC B)

Relay pos ition s how nin v o ltage mode

+1 2 V

-1 2 V

R 3

1 0 0

G U A R D


Parts Selection (1)

• Voltage mode op-amp:– Candidates at PDR were OP-16A, OP-15A– Chose OP-16A due to superior frequency response– Similarity with OP-15A = confidence it will pass qualification– OP-15A remains a valid, swap-in backup

• Current mode op-amp:– Candidates at PDR were AD-549 and OP-15A– Chose OP-15A satisfies measurement requirements – chosen

due to reliability history – AD-549 has superior sensitivity, but less heritage

• Teledyne 422DD Latching Relay– Same as PDR. Heritage from FAST– Undergoing life tests now (several million cycles)


Parts Selection (2)

• DT-471 Temperature sensor– Same as PDR– Tested in benchtop environment

• 50M surface mount chip resistor– Special order from SOTA– Same basic specification/design as 75M resistor used in RBSP

• Remaining components are standard passives


EM Preamp Tests


Preamp Voltage Mode Results

Benchtop Preamp Tests1 Meg/3.3 pF coupling

Resistive Coupling

Capacitive Coupling

Board InputCapacitance = 9 pF


Current Mode Tests

1. Pick point on simulated V-I curve

2. Corresponding point on impedance curve

• Verified sensitivity from ~nA to 200 uA levels

• Instability noted at high coupling impedances

• Verified and mitigated through stability analysis (22 pF lead cap)

Simulate voltage, current, and coupling impedance encountered in different measurement regimes.


Whip Coating

• TiN – Titanium Nitride– Required for chemical durability (atomic oxygen resistance)– Work function uniformity (ensures accurate Ne, Te

measurements)• Has significant heritage

– Cassini (IRF/Iowa 1997 - , Saturn), Astrid-2 (1998 - 1999, Earth’s ionosphere)

– Cusp (NASA 35.033 sounding rocket, GSFC 2002)– Rosetta (IRF 2004 - , comet)– Demeter (CNRS/ESTEC 2004 - , Earth’s ionosphere)– Swarm (IRF 2011 - , Earth’s ionosphere)


Whip Coating (2)

• Previous TiN applications have been tested for uniformity and durability (Wahlström, 1992; Steigies, 2005) (SEM, electrical tests, others…)

Result after Nitriding illustrated by cross section of structure after Nitriding of titanium and Ti-6Al-4V, respectively (Scanning Electron Microscopy) A=fine grained TiN, B= Ti2N, C=Mixed phases, D=bulk material+nitrogen (increased hardness), E=Bulk material, F= β-phase.

LPW Preamp/Sensor Overview Greg Delory, LPW Co-I [email protected] MAVEN PFP Pre-CDR Peer...

Documents

Transcript of LPW Preamp/Sensor Overview Greg Delory, LPW Co-I [email protected] MAVEN PFP Pre-CDR Peer...