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 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