C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, CDR Slide 1 Detectors and Analog Electronics Bill Crain The Aerospace Corporation 310-336-8530

Cosmic RAy Telescope for the Effects of RadiationBill Crain, CDR Slide 1

Detectors and Analog Electronics

Bill Crain

The Aerospace Corporation

310-336-8530

[email protected]


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


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


Thin

Thick

Thin

Thick

Thin

Thick

Preamps

Bias Networks

Thermistor

Telescope Board Analog Processing Board

Shaping / Scaling

BaselineRestorer

Discrim.

Detector Boards

ToDigitalBoard

Functional Block Diagram

Detector Monitor

Test Pulser

Dosimeter

New Since PDR


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


Requirements vs. Capability Summary

Derived Requirement

Thin Detector Thick Detector

Parent Requirements

Design Capability Evidence

Amplifier strings 3 3 CRaTER-L3-01 Comply Board layouts

Maximum Energy Deposit

980 MeV 100 MeV CRaTER-L2-06

(7MeV/micron)

2 x requirement on preamp

1 x on shaping amp

Breadboard test results

Minimum Energy Threshold

2 MeV 200 keV CRaTER-L2-05

(0.2MeV/micron)

0.65 x requirement Design analysis

Thermal Noise (rms)

< 400 keV < 40 keV CRaTER-L2-05 Thin = 38 keV rms

Thick = 12 keV rms

Design analysis

Non-linearity 0.3% 0.3% CRaTER-L2-07

(0.5% resolution)

Comply Spice simulations

Stability / drift 0.3% 0.3% CRaTER-L2-07 0.2% Worst-case analysis

Maximum Count Rate

1 kHz 1 kHz CRaTER-L3-11 10 kHz Breadboard test results

Internal Calibration Variable amplitude

Variable amplitude

CRaTER-L3-09 LOW RANGE 0.04 – 10% FS

HIGH RANGE 0.40 – 100% FS

Breadboard test results

Electronics design meets requirements derived from Instrument Specification


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

Analog PulseSignals

dv/dt &Pole-Zero

Cancellation

ShapingAmp

Amp

BaselineRestorer

Preamp

Low Lev.Discrim.

SiliconDetector

BiasNetwork

TestInjection

ScalingAmp

Digital TimingSignals


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

MIT

+/- 5Valg, 5Vdig

Shaped Pulse Signals

Discriminators

Test Pulser Level

Detector Bias

Temps / Dosimeter HK

Low Test Trigger

3 thin, 3 thick

Analog Processing

Aerospace

Digital Processing & Power

3 thin, 3 thick

Power Supply

Pulse HeightAnalysisSystem

SpacecraftInterfaceHigh Test Trigger


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)


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

Gd/FP P+ Contact Grid Gd/FP

Active Volume(depletion region)

P+ implant window

N window

0.1 um

0.1 um

Thickness140 um thin;1,000 um thick

Active Dimension

(35mm)

N contact

E-field

~ 1mm


Detector Specification• Detector requirements unchanged since PDR


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


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


Signal Description

Detector Min Signal Max Signal Collection Time

C det C fb Design Considerations

Thin 555E3 e-h pairs

(88 fC)

275E6 e-h pairs

(44 pC)

3 ns e-drift

9 ns h-drift

700 pF 39 pF Design for large signals and stable operation while avoiding slew limiting

Thick 55E3 e-h pairs

(8.8 fC)

27.5E6 e-h pairs

(4.4 pC)

38 nsec e-drift

115 nsec h-drift

100 pF 3.9 pF Optimize for

low noise

qμnNe(t)E qμpNh(t)E

PreAmp

Cdet

CFB

RFB

CFB (Ao) >> Cdet

AoVpk = Qtot/CFB

• Different signal characteristics for thin and thick detectors are accounted for in design

Signal model includeselectron and hole drift currents








Telescope Electronics Design

Test Input&

FeedbackNetwork

Positive Bias

Test Pulser

Signal

JFET

Detector Bias Network

A250

P-contactG G

N-contact

Active Volume

Bias Grounding NetworkBias CurrentMonitor

Amptek

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


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


Telescope Breadboard Test Results (2)

• Preamp’s full-scale range is 2x below saturation onsetanalysis test


Telescope Board LayoutTop Bottom


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


Analog Board Electronics (1)

RH1814

Second-order active filterwith signal inversion

RH1814

First-order filterwith non-inverting gain

RH1814

Gain stageX10

RH1814

Unity Gain Buffer

RH119

One-shotACS14ACS74

RH119

GateRH1078

Slow integrator

+

Thres

<Thres

Res

Res

To DPB

SMB testconnector

Test PulserLow Range

RH1078

Detector LeakageCurrent Amplifier

To DPBTest PulserHigh Range

Current Pulse

DosimeterHybrid

Co

ntr

ol

x6

x6

From TEL

Shaping details next slide

5 us

x6



• 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

ScalingShaping

Pole/Zero


Spice Resultslh1814-opamp_tuned-Monte Carlo Transient-4-Graph Time (s)

700.00n 750.00n 800.00n 850.00n 900.00n 950.00n1000.00n 1.05u

(V)

2.92

2.93

2.94

2.95

2.96

2.97

2.98

2.99

3.00

lh1814-opamp_tuned-Monte Carlo Transient-4-Graph Time (s)

2.00u 3.00u 4.00u 5.00u 6.00u 7.00u 8.00u

(V)

-10.00m

-8.00m

-6.00m

-4.00m

-2.00m

0.0

2.00m

4.00m

6.00m

8.00m

lh1814-opamp_tuned-Monte Carlo Transient-4-Graph Time (s)

1.00u 2.00u 3.00u 4.00u 5.00u 6.00u

(V)

-1.50

-1.00

-500.00m

0.0

500.00m

1.00

1.50

2.00

2.50

3.00

Actual circuit Monte-carlo Simulation



• 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!

Micron silicon detector

Custom chargeIntegrator ASIC


Analog Board LayoutTop Bottom


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








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


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


Detector Leakage Effects (2/2)

• Detector thermal noise requirements are met at EOL with a shaping amplifier time constant of 1 usec +/- 20%


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


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

Detector Discriminator Drift

Discriminator Requirement

A/D Input Drift

A/D Requirement

Thin 300 uV 60 mV 5 mV 9 mV

Thick 300 uV 60 mV 5 mV 9 mV


Parts Stress Analysis

• Documented in 32-04010• Reviewed by Mission Assurance Manager

• INST-002 derating requirements satisfied

• No thermal stress issues


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.


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


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


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

Documents

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, CDR Slide 1 Detectors and Analog Electronics Bill Crain The Aerospace Corporation 310-336-8530