C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 128 September 2005 Detectors and Analog Electronics Bill Crain The Aerospace Corporation

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 228 September 2005 Introduction Design Overview Requirements Flowdown Detector Specification Signals, Noise, and Processing Board Descriptions Interface Diagram Power Consumption Trade Studies Summary

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 328 September 2005 Detector Electronics Design Overview Electronic Board Designs –Telescope Board –Analog Processing Board (APB) in E-box Heritage approach from Polar CEPPAD/IPS unchanged from proposal –Linear pulse processing system with Amptek front-end –Circuits designed specifically for CRaTER requirements Functional requirements summary –Measure LET of high LET particles in thin detectors –Measure LET of low LET particles in thick detectors –Provide good resolution for TEP effects –Robust to temperature drift and environments

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 428 September 2005 Thin Thick Thin Thick Thin Thick Preamps Bias Networks Thermistor Telescope BoardAnalog Processing Board Shaping Scaling Baseline Restorer Timing Trigger Detector Boards To Digital Board Functional Block Diagram

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 528 September 2005 Analog Signal Flow Diagram Single fixed gain, linear transfer function All detector channels use same topology

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 628 September 2005 Requirements Traceability Electronics Req.Thin Det.Thick Det.Parent Req.Affectivity Amplifier strings33CRaTER-L3-01Board sizes Max. Energy Deposit1 GeV100 MeVCRaTER-L3-01Preamp range, closed- loop stability Low E Threshold Timing Threshold 2 MeV <1.3 MeV 200 keV <130 keV CRaTER-L3-01Gain, baseline restorer, shaping time Noise (rms)< 400 keV< 40 keVCRaTER-L3-01 CRaTER-L2-08 Preamp, shaping time, thermal Max. Singles Rate 1.25 kHz CRaTER-L3-10Shaping time, preamp time constant Integral non-linearity0.1% CRaTER-L2-08Preamp, shaping amp Stability / drift0.1% CRaTER-L3-01 CRaTER-L2-08 Preamp, bias network, baseline restorer Internal Calibration256:1 CRaTER-L3-08Test pulser

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 728 September 2005 Detector Specification (1) Document released rev 02 August 1, 2005 Micron Semiconductor Limited –Lancing Sussex, UK 20 years experience in supplying detectors for space physics –CEPPAD, CRRES, WIND, CLUSTER, ACE, IMAGE, STEREO, and more… Detector Type –Ion-implanted doping to form P+ junction on N-type silicon –Very stable technology –Advantages to science include good carrier lifetime, stable to environmental conditions, and thin entrance windows

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 828 September 2005 Detector Specification (2) Circular detectors having active area of 9.6 cm 2 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 Very thin dead layers (windows) reduce energy loss, lower series resistance, and reduce noise Gd/FPP+ Contact GridGd/FP Active Volume (depletion region) P+ implant window N window 0.1 um Thickness 140 um thin; 1,000 um thick Active Dimension (35mm) N contact E-field ~ 1mm

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 928 September 2005 Detector Specification (3) Detector drawings (Micron) –Note: this is not the present mount design Guard ring Al. contact grid reduces surface resistivity Al. contact plane

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 1028 September 2005 Detector Design Requirements Summary RequirementSpecification Active area9.6 cm 2 circular Active dimension35 mm Active dimension tolerance+/- 0.1 mm ThicknessThin = 140 um, Thick = 1000 um Thickness tolerance+/- 10 um Thickness uniformity+/- 10 um Window0.1 um ohmic, 0.1 um junction MetalizationOhmic surface and junction grid 3000 Å +/ Å Full depletion (FD)Thin = 20 – 40V, Thick = 150 – 200V Operating voltage maxThin = 2 x FD, Thick = FD + 30V CapacitanceThin = 700 pF, Thick = 100 pF Leakage current max (20C)Thin = 300 nA junction, 200 nA guard Thick = 1,000 nA junction, 700 nA guard Drift (max 40C)6 x 20C Stability1% 40C for 168 hours Alpha resolutionThin = 45 KeV, Thick = 35 KeV FWHM

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 1128 September 2005 Detector Specification (4) ISO9001 –Full traceability and serialization –Travelers maintained Qualification tests prior to flight detector shipment –Bond pull test –Random vibration test –Thermal cycling –Stability Verification matrix specifies test criteria –Leakage current –Capacitance –I-V characteristic –Alpha resolution / pulser noise measurement

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 1228 September 2005 Detector Verification Matrix Eye Chart From Rev 02

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 1328 September 2005 Proton Energy Deposition Simulations Reference: M. Looper Thin 150MeV incident EThick 150MeV incident E Thin 1000MeV incident EThick 1000MeV incident E Nominal Threshold GEANT4

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 1428 September 2005 Iron Energy Deposition Simulation Reference: J.B. Blake

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 1528 September 2005 Signal Characteristics DetectorMin SignalMax SignalCollection Time Detector Capacitance Feedback Capacitance Thin555E3 e-h pairs (88 fC) 275E6 e-h pairs (44 pC) 3 nsec e-drift 9 nsec h-drift 700 pF15 pF Thick55E3 e-h pairs (8.8 fC) 27.5E6 e-h pairs (4.4 pC) 38 nsec e-drift 115 nsec h-drift 100 pF1.5 pF qμ n N e(t) Eqμ p N h(t) E C det C FB R FB C FB (A o ) >> C det Ao V pk = Q tot /C FB

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 1628 September 2005 Signal Processing (1) Combined dynamic range of thin/thick pair is 5,000 Thin threshold to provide overlap with thick range Thin Detector Signal –Preamp input stage designed for 97% charge collection High gain input jFET for large dynamic input capacitance 4% drift in operating point will result in 0.1% in output peak –Large feedback capacitance needed to handle Fe deposit Preamp compensation to maintain closed-loop stability Thick Detector Signal –Not as sensitive to detector capacitance –Designed for low noise to maintain reliable 200 KeV low threshold and meet resolution requirement

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 1728 September 2005 Noise Model (1) Reference: Helmuth Spieler IFCA Instrumentation Course Notes 2001 DetectorInput Capacitance Leakage Current Shunt Resistance Series Resistance Preamp noise (e na ) Thin700 pF Det. 160 pF jFET+stray C C 6 Meg ohms100 ohms0.6 nV/√Hz Thick100 pF Det 10 pF jFET+stray C C 6 Meg ohms100 ohms2.0 nV/√Hz + input cap. T=peaking time F=shaping factors

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 1828 September 2005 Noise Model (2)

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 1928 September 2005 Noise Model (3) 20C BOL

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 2028 September 2005 Signal Processing (2) Noise dominated by thick detector leakage current Shaping time same for both thin and thick detectors –~1 usec for comfortable PHA input timing –3-pole gaussian shaping improves symmetry –2-complex poles shortens tail Coincidence Timing –Noise occupancy in 1-usec coincidence window < 0.1% –Threshold to noise ratio (T/N) ~ 3.2 for timing discriminator –Timing discriminator threshold ~ 130 keV Anticipated BOL T/N ratio is ~ 10 Allows margin for leakage current drift up to 10 uA

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 2128 September 2005 Signal Processing (3) Other factors affecting noise performance –Bias resistor on thin detector sized to minimize voltage drop –Bias resistor on thick detector sized to minimize noise –Detector shot noise doubles every 8 C Beneficial to operate cold; preferably below 20 C

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 2228 September 2005 Signal Processing (4) Pileup is rare due to low event rate and relatively short shaping time –Exception: occasional periods of high ESP flux Coincidence timing uncertainty from leading edge trigger is small –Amplified timing discriminator reduces time walk to acceptable 10% uncertainty Ballistic deficit is not an issue due to short collection times relative to peaking time of shaper Output voltage scaled for PHA input specifications

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 2328 September 2005 Telescope Board Details Thin/thick detector pair use same design topology Signal collected on P-contact Guard signal shunted to ground No guard leakage noise AC coupling to isolate DC detector leakage current Low noise / high gain JFET input stage (InterFET) with Amptek A250 hybrid MIL-STD-5510 polyimide 8- layer construction

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 2428 September 2005 Analog Processing Board Details Single board in E-box contains 3 thin and 3 thick detector processing channels –Polyimide laminate, MIL-STD-55110, 8-layers, in. –Interfaces to digital board in same box Components –Linear Technology radiation tolerant opamps for shaping stages, BLR, and comparators –Analog Devices rad tolerant op-amp for test pulser interface and bias monitoring (see trade study chart) Pole-zero cancellation circuit included to prevent undershoot

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 2528 September 2005 Analog Interface Block Diagram ICD rev 01 +/- 6V power, 5V Thin and thick bias voltages Unipolar gaussian signals input to peak-hold circuits Low-level triggers for coincidence timing Test pulser level and clocking signals

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 2628 September 2005 Power Estimate Total estimated power dissipation is < 1 Watt

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 2728 September 2005 Trade Studies Considering detector bias current monitor –Housekeeping item to provide leakage current for each detector –No impact on noise or failure modes –Useful for diagnostic purposes especially during environmental testing of flight units

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 2828 September 2005 Summary Detectors are well-established technology from experienced supplier Detector specification and Analog/Digital ICD documents have been released Electronics design meets requirements of instrument requirements document

C osmic R Ay T elescope for the E ffects of R adiation Bill Crain, PDR Slide 2928 September 2005