A Low Power & Low Noise Multi-Channel ASIC for X-Ray and Gamma-Ray Spectroscopy
AMICSA 20101Multi-channel DetectorReadout Integrated Circuitswith ADCs for X-ray andGamma-ray Spectroscopy inSpaceSindre Mikkelsen1, Dirk Meier1, Jahanzad Talebi1, Suleyman Azman1, Gunnar Mæhlum11Integrated Detector Electronics ASMonday, September 6th 2010, 15:00 – 15:30
AMICSA 20102AbstractWe are developing detector readout integrated circuits (ROICs) for X-ray and Gamma-ray spectroscopy.The ROICs are applications specific (ASICs) for satellite instrumentation in space. The ICs described inthis article belong to the VATA family with integrated analog-to-digital converters (ADCs) for fullydigital readout of x-ray and gamma-ray detectors. The VATAs are ideal for the readout of cadmium zinctelluride (CZT), cadmium telluride (CdTe), silicon pads and strips, and large area avalanche photodiodes(APDs) with scintillators. The VATAs contain 32 and 64 pre-amplifiers each followed by pulse shapingcircuits and level comparators for triggering and address encoding. Each channel contains a WilkinsonADC that generates a 10-bit digital word proportional to the amplitude of the input pulse. Uponinteraction of radiation in the sensor the VATA delivers digital signals proportional to the energy of thephoton as well as a digital address corresponding to the point of interaction. The power dissipation is aslow as 0.2 mW per channel during normal operation.VATAs are currently under test for the soft gamma-ray detector (SGD) and the hard x-ray imager (HXI)on board of the ASTRO-H satellite mission to launch in 2014 (formerly NeXT). Both detectors areCompton cameras based on silicon pads and strips, CdTe pixels and pixels, and APDs with BGOscintillators. ASTRO-H will help to study the evolution and structure of the universe. ASICs of the samefamily are also under test for one instrument in the Mercury Plasma Particle Experiment (MPPE) onboard of the BepiColombo mission to Mercury and for the FOXSI rocket experiment. This articledescribes the VATA architecture and presents results from tests in the lab.
AMICSA 20103IntroductionA Family of recently developed Multi-Channel RadiationDetector Readout ASICs.• Radiation Energy Spectroscopy• Radiation ImagingThe ASIC family is at the moment being utilized for thefollowing space missions:• ASTRO-H (JAXA)• BepiColombo MMO (JAXA)• FOXSI (NASA/JAXA)Criteria for the ASICs• Very low power dissipation• Low electronic noise• Size and weight – high level of electronic readout integration
AMICSA 20105Space Application (2)BepiColombo MMOGM-I supplies ROICs for the MPPE instrument.Picture: JAXA
AMICSA 20106Astro-H, BepiColombo (HXI, SGD, MPPE)• The Hard X-ray Imager (HXI)– 4 layers of double-sided silicon strip detectors(DSSD) absorbs soft X-rays (<30keV), buttransparent for hard X-rays (>30keV)– 1 layer of double-sided CdTe detector detects hardX-rays (20keV...80keV)– BGO well is active shield• The Soft Gamma-ray Detector (SGD) is a– non-focusing soft gamma-ray, 10—600 keV– narrow-FOV Compton telescope, rejectsbackground radiation• GM-I delivers the Read Out Integrated Circuits for theSilicon and CdTe detectors• BepiColombo MMO MPPE• Single sided strip detector• Measure High Energy Particle energy toinvestigate the the structure and dynamics of theMercurys magnetosphere.JAXA /KIPAC[Watanabe,vertex 2009]
AMICSA 20107Design criteria• ASTRO-H SGD (VATA450), launch 2014:– Very low power– Medium DNR• ASTRO-H HXI (VATA461), launch 2014and FOXSI (VATA451), launch 2011:– Low noise, medium power– Low DNR• BepiColombo MPPE (VATA460), launch Aug. 2013:– Low power– High DNR– Medium noise– Large temperature range
AMICSA 20109VATA-ASIC Basic FunctionalityFunctionality ConceptInput: Readout of 32/64 radiationsensors/electrodes/strips/pixels32/64 parallel & independent inputs channels,current inputSignal processing• amplitude spectroscopy• simultaneously and independent32/64 x analog signal processing:• charge sensitive amplifiers CSAs,• Semi-Gaussian shapers,• Discriminators•10 bit ADC (integrating)•Digital signal processingData sparsification •Analog amplitude discriminators to identifyevents•Digital data processing to minimize data outputOutput: Delivers•Asynchrounous trigger signal•Digitized amplitude and pixel addressThe trigger is set immediately after firstcrossing of amplitude threshold. Digital data isread out synchrounously by the system.
AMICSA 201013ADC Architecture• 32/64 channels converted inparallel• Integrating single slope ADC(”Wilkinson”)• 10 bit resolution• 10MHz conversion clockspeed• 1mW/channel powerconsumption default, tunablebetween 0.5-2mW• 6 bit programmable offsetcorrection• Common mode calculation• Termination of conversionphase when all channels havebeen convertedVoltageramp10bitcounterCMdetectorAin 0Ain 1Ain 63Digitaldelay+-10 bit ADClatch10Digitaldelay+-10 bit ADClatch10Digitaldelay+-10 bit ADClatch10Do 0Do 1D0 63CM
AMICSA 201014Back-End Architecture• Digital datareduction• Output dataformat:– Status bits– Triggermap– ADC dataDigitalcomparatorsMultiplexerControlInterfaceDigital thresholdgenerator10ADC 010ADC 110ADC 63+-+-+-10CMInternal controlsignalsControlIO
AMICSA 201015VATA-ASIC Extended FunctionalityFunction ImplementationUser can adjust•internal bias values•adjust all thresholds individually•enable or disable channels, adjust gain,adjust power/noise, test individual channelsprogammable configurationregisterInternal calibration pulse generation Individual channels can be testedthrough a digital interfaceCombine several ASICs ASICs can be Daisy-chained forserial read-out, control andconfigurationCompensate change of external temperature Differential signalsCompensate large detector leakage current current compensation networkElectrostatic Discharge (ESD) protection Customized diodes at the inputs,optimized for low noise
AMICSA 201019Test results (3)VATA460 (HDR)Threshold of NoiseEnergy Resolution(FWHM)Energy measurement Thresh-holdEnergy[keV]Temperature[degree]Measurements performed by Takashima et al, JAXA.
AMICSA 201020Test results (4)VATA460 (HDR)Energy Resolution (FWHM)Under CC-onEnergy Resolution (FWHM)under CC-offNoise level under CC-offNoise level under CC-onTemperature[degree]Energy[keV]Measurements performed by Takashima et al, JAXA.
AMICSA 201021Radiation Tolerance and Latch-upReference: H.Aihara, M. Hazumi, H. Ishino, J. Kaneko, Y. Li, D.Marlow, S. Mikkelsen, D. Nguyen, E. Nygaard, H. Tajima, J. Talebi,G. Vamer, H. Yamamoto, and M. Yokoyama, ”Development ofFront-end Electronics for Belle SVD Upgrades”, IEEE, Proc. Nucl.Sci. Symp. Conf. Rec. 2000, Vol. 2, 9/213 – 9/216.• The most sensitive structureshave been tested for radiationtolerance• ASIC fabricated in 0.35umCMOS process with epitaxiallayer.• ASIC fabrication process hasbeen choosen for goodradiation tolerance and latch-up immunity.• Initial SEL tests have beenperformed, and the design haspassed these.
AMICSA 201022Radiation test of VATA460Radiation test by 6MeV/n He.Measurements performed by Takashima et al, JAXA.Gain Noise
AMICSA 201023Legacy of GM-I ASICs in SpaceSelection of most known missions:• AGILE (launched April 2007). Two different ASICs for the ST instrument andthe SuperAGILE instrument: Luigi Pacciani, Ennio Morelli, Alda Rubini, Marcello Mastropietro, GeilandPorrovecchio, Enrico Costa, Ettore Del Monte, Immacolata Donnarumma, Yuri Evangelista, Marco Feroci, Francesco Lazzarotto,Massimo Rapisarda, Paolo Soffitta, “SuperAGILE Onboard Electronics and Ground Test Instruments”, Nucl. Instr. Meth. A 574, 2,2007, 330-341.• STEREO/PLASTIC (launched Oct. 2006, http://stereo.sr.unh.edu/): A.B. Galvin et al.,“The Plasma and Suprathermal Ion Compositioin (PLASTIC) Investigation on the STEREO Observatories”, Space Science Reviews,136, 1-4, April 2008.• SWIFT/Burst Alert Telescope (launched Nov. 2004): L.M. Barbier, F. Birsa, J. Odom, S.D.Barthelmy, N. Gehrels, J.F. Krizmanic, D. Palmer, A.M. Parsons C.M. Stahle, J. Tueller, “XA Readout Chip Characterization andCdZnTe Spectral Measurements”, IEEE, Trans. Nucl. Sci. 46(1), 7, 1999.• AMS (AMS-01 launch 1998, AMS-02 launch 2011): B. Alpat, ”Alpha MagneticSpectrometer (AMS02) Experiment on the International Space Station ISS”, Nucl. Sci. Tech. 14, 3, 2003.• CREAM (balloon experiment, launch Dec. 2004): M.G. Bagliesi, C. Avanzini, G.Bigongiari, A. Caldarone, R. Cecchi, M.Y. Kim, P. Maestro, P.S. Marrocchesi, F.Morsani, R. Zei, “Front-endelectronics with large dynamic range for space-borne cosmic ray experiments”, Nucl. Phys. Proc. Suppl.172:156-158, 2007.• GRIPS (balloon experiment, launch 2012).• CALET, (launch 2013). To be installed on the ISS.• ASIM (approved for ISS): S. Mikkelsen et al., ” A Low Power and Low Noise Multi-Channel ASIC for X-Ray and Gamma-Ray Spectroscopy in Space”, Proceedings of AMICSA 2008.
AMICSA 201024Single-event Upset (SEU)• All configuration registers are implementedwith majority vote flip-flops, with 3 storagecells.• Automatic error correction• Upsets are flagged externally using the triggerline.• Occurence of SEU events is flagged in theoutput data stream.Reference: Samo Korpar, Peter Krizan, Sasa Fratina, ”SEU Studies ofthe Upgraded Belle Vertex Detector Front-End Electronics”, Nucl. Instr.Meth., A 511 (2003) 195–199.
AMICSA 201025Summary• We developed a family of X-ray and Gammadetector Read Out ASICs, suitable for a numberof space missions.• Main achievements are.– Reduced power dissipation– Low noise– High level of integration• Other applications include:– Nuclear medicine– Security applications– High energy physic
AMICSA 201026AcknowledgmentsWe would like to thank our colleagues at JAXAand Kavli/Stanford for good collaboration, andfor allowing us to use their test results in thispresentation.
AMICSA 201027Appendix: Performance SpecificationsParameter Value CommentNumber of Input Channels•VATA450/451•VATA460/4616432Readout for 32/64 pixelsInput charge dynamic range•VATA450•VATA451•VATA460•VATA461±16±1.6±72±5.5Charge (fC), linear range. Some of theASICs have much higher saturation rangeat higher non-linearity.TP slow (VATA450/451//460/461)TP fast3/ 3/ 2/ 3.50.6/ 0.6/ 0.3 / 0.6µs. Default settings.Power consumption•VATA450•VATA451•VATA460•VATA4610.251.160.3361.28Power consumption per channel (mW),nominal bias settings. Acquisition mode.Electronic noise of CSA•VATA450•VATA451•VATA460•VATA46159 e + 14e / pF27 e + 6.6e / pF179 e + 16e /pF34 e + 5.5e /pFBaseline noise and noise slope. At defaultbias values.Detector Capacitance 5-7 Optimization value (pF).Detector Leakage Current 10pA Optimization value. VATA460 has beendesigned to tolerate up to 36nA.