AMICSA 20101

Multi-channel Detector Readout Integrated Circuits

with ADCs for X-ray and Gamma-ray Spectroscopy in

SpaceSindre Mikkelsen1, Dirk Meier1, Jahanzad Talebi1, Suleyman Azman1, Gunnar Mæhlum1

1Integrated Detector Electronics AS

Monday, September 6th 2010, 15:00 – 15:30

AMICSA 20102

AbstractWe 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 in this article belong to the VATA family with integrated analog-to-digital converters (ADCs) for fully digital readout of x-ray and gamma-ray detectors. The VATAs are ideal for the readout of cadmium zinc telluride (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 shaping circuits and level comparators for triggering and address encoding. Each channel contains a Wilkinson ADC that generates a 10-bit digital word proportional to the amplitude of the input pulse. Upon interaction of radiation in the sensor the VATA delivers digital signals proportional to the energy of the photon as well as a digital address corresponding to the point of interaction. The power dissipation is as low 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 are Compton cameras based on silicon pads and strips, CdTe pixels and pixels, and APDs with BGO scintillators. ASTRO-H will help to study the evolution and structure of the universe. ASICs of the same family are also under test for one instrument in the Mercury Plasma Particle Experiment (MPPE) on board of the BepiColombo mission to Mercury and for the FOXSI rocket experiment. This article describes the VATA architecture and presents results from tests in the lab.

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Introduction

A Family of recently developed Multi-Channel Radiation Detector Readout ASICs.• Radiation Energy Spectroscopy• Radiation Imaging

The ASIC family is at the moment being utilized for the following 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

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Space Application (1)ASTRO-H

GM-I supplies ROICs for 2 instruments: HXI, SGDGM-I supplies ROICs for 2 instruments: HXI, SGD

Picture: JAXA

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Space Application (2)BepiColombo MMO

GM-I supplies ROICs for the MPPE instrument.GM-I supplies ROICs for the MPPE instrument.Picture: JAXA

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Astro-H, BepiColombo (Astro-H, BepiColombo (HXI, SGD, MPPE)HXI, SGD, MPPE)

• The Hard X-ray Imager (HXI) The Hard X-ray Imager (HXI)

– 4 layers of double-sided silicon strip detectors 4 layers of double-sided silicon strip detectors (DSSD) absorbs soft X-rays (<30keV), but (DSSD) absorbs soft X-rays (<30keV), but transparent for hard X-rays (>30keV)transparent for hard X-rays (>30keV)

– 1 layer of double-sided CdTe detector detects hard 1 layer of double-sided CdTe detector detects hard X-rays (20keV...80keV)X-rays (20keV...80keV)

– BGO well is active shield BGO well is active shield

• The Soft Gamma-ray Detector (SGD) is a The Soft Gamma-ray Detector (SGD) is a

– non-focusing soft gamma-ray, 10—600 keVnon-focusing soft gamma-ray, 10—600 keV

– narrow-FOV Compton telescope, rejects narrow-FOV Compton telescope, rejects background radiationbackground radiation

• GM-I delivers the Read Out Integrated Circuits for the GM-I delivers the Read Out Integrated Circuits for the Silicon and CdTe detectorsSilicon and CdTe detectors

• BepiColombo MMO MPPEBepiColombo MMO MPPE• Single sided strip detectorSingle sided strip detector• Measure High Energy Particle energy to Measure High Energy Particle energy to

investigate the investigate the the structure and dynamics of the the structure and dynamics of the Mercury's magnetosphere. Mercury's magnetosphere.

JAXA / KIPAC [Watanabe, vertex 2009]

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Design criteria

• ASTRO-H SGD (VATA450), launch 2014:– Very low power – Medium DNR

• ASTRO-H HXI (VATA461), launch 2014 and 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

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Radiation Detector Principle

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VATA-ASIC Basic FunctionalityFunctionality Concept

Input: Readout of 32/64 radiation sensors/electrodes/strips/pixels

32/64 parallel & independent inputs channels, current input

Signal processing• amplitude spectroscopy• simultaneously and independent

32/64 x analog signal processing: • charge sensitive amplifiers CSAs, • Semi-Gaussian shapers, • Discriminators•10 bit ADC (integrating)•Digital signal processing

Data sparsification •Analog amplitude discriminators to identify events•Digital data processing to minimize data output

Output: Delivers•Asynchrounous trigger signal•Digitized amplitude and pixel address

The trigger is set immediately after first crossing of amplitude threshold. Digital data is read out synchrounously by the system.

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ASIC TL architecture

Four distinct modes of operation:– Initialization

– Acquisition (FE)

– Conversion (ADC)

– Readout (BE)

Bias Network

Cal

ibra

tion

Fro

nt

– E

nd

In0

In1

In63

a

trig in Ch0

a

trig in Ch1

a

trig in Ch63

AD

C

ADC out

a Ch0

ADC out

a Ch1

ADC out

a Ch63

Bac

k- E

nd

CM

Configuration

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ASIC FE Channel Architecture

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The VATA PRINCIPLE

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ADC Architecture

• 32/64 channels converted in parallel

• Integrating single slope ADC (”Wilkinson”)

• 10 bit resolution• 10MHz conversion clock

speed• 1mW/channel power

consumption default, tunable between 0.5-2mW

• 6 bit programmable offset correction

• Common mode calculation• Termination of conversion

phase when all channels have been convertedV

olta

ge

ra

mp

10

bit

cou

nte

r CM

d

ete

cto

r

Ain 0

Ain 1

Ain 63

Digital delay

+

-

10 bit ADC latch

10

Digital delay

+

-

10 bit ADC latch

10

Digital delay

+

-

10 bit ADC latch

10

Do 0

Do 1

D0 63

CM

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Back-End Architecture

• Digital data reduction

• Output data format:– Status bits– Trigger

map– ADC data

Dig

ital

com

para

tors

Mul

tiple

xer

Con

trol

Inte

rfac

e

Digital threshold generator

10ADC 0

10ADC 1

10ADC 63

+

-

+

-

+

-

10CM

Internal control signals

Con

trol

IO

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VATA-ASIC Extended FunctionalityFunction Implementation

User can adjust •internal bias values•adjust all thresholds individually•enable or disable channels, adjust gain, adjust power/noise, test individual channels

progammable configuration register

Internal calibration pulse generation Individual channels can be tested through a digital interface

Combine several ASICs ASICs can be Daisy-chained for serial read-out, control and configuration

Compensate change of external temperature Differential signals

Compensate large detector leakage current current compensation network

Electrostatic Discharge (ESD) protection Customized diodes at the inputs, optimized for low noise

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ASIC Layout

JAXA / KIPAC [Watanabe, vertex 2009]

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Test results – Energy Spectroscopy (1)VATA450 (low power)

JAXA / KIPAC [Watanabe et al., Vertex 2009] Data taken by JAXA / KIPAC

VA32TA6 VATA450

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Test results – Energy Spectroscopy (2)VATA451 (low noise)

JAXA / KIPAC [Saito et al.,, SPIE 2010]

Noise (ENC)

VATA450 59 +14 e/pF

VATA451 27 +6.6 e/pF

VATA460 179 +16 e/pF

VATA461 34 + 5.5 e/pF

ASIC measurements, by GM-I

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Test results (3)VATA460 (HDR)

Threshold of Noise

Energy Resolution (FWHM)

Energy measurement Thresh-hold

En

ergy

[k

eV]

Temperature[degree]

Measurements performed by Takashima et al, JAXA.

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Test results (4)VATA460 (HDR)

Energy Resolution (FWHM)Under CC-on

Energy Resolution (FWHM)under CC-off

Noise level under CC-off

Noise level under CC-on

Temperature[degree]

En

ergy

[k

eV]

Measurements performed by Takashima et al, JAXA.

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Radiation Tolerance and Latch-up

Reference: 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 of Front-end Electronics for Belle SVD Upgrades”, IEEE, Proc. Nucl. Sci. Symp. Conf. Rec. 2000, Vol. 2, 9/213 – 9/216.

• The most sensitive structures have been tested for radiation tolerance

• ASIC fabricated in 0.35um CMOS process with epitaxial layer.

• ASIC fabrication process has been choosen for good radiation tolerance and latch-up immunity.

• Initial SEL tests have been performed, and the design has passed these.

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Radiation test of VATA460

Radiation test by 6MeV/n He.Measurements performed by Takashima et al, JAXA.

Gain Noise

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Legacy of GM-I ASICs in SpaceSelection of most known missions:• AGILE (launched April 2007). Two different ASICs for the ST instrument and

the SuperAGILE instrument: Luigi Pacciani, Ennio Morelli, Alda Rubini, Marcello Mastropietro, Geiland Porrovecchio, 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 and CdZnTe Spectral Measurements”, IEEE, Trans. Nucl. Sci. 46(1), 7, 1999.

• AMS (AMS-01 launch 1998, AMS-02 launch 2011): B. Alpat, ”Alpha Magnetic Spectrometer (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-end electronics 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.

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Single-event Upset (SEU)

• All configuration registers are implemented with majority vote flip-flops, with 3 storage cells.

• Automatic error correction• Upsets are flagged externally using the trigger

line. • Occurence of SEU events is flagged in the

output data stream.

Reference: Samo Korpar, Peter Krizan, Sasa Fratina, ”SEU Studies of the Upgraded Belle Vertex Detector Front-End Electronics”, Nucl. Instr. Meth., A 511 (2003) 195–199.

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Summary

• We developed a family of X-ray and Gamma detector Read Out ASICs, suitable for a number of space missions.

• Main achievements are.– Reduced power dissipation– Low noise– High level of integration

• Other applications include:– Nuclear medicine – Security applications– High energy physic

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Acknowledgments

We would like to thank our colleagues at JAXA and Kavli/Stanford for good collaboration, and for allowing us to use their test results in this presentation.

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Appendix: Performance SpecificationsParameter Value Comment

Number of Input Channels•VATA450/451•VATA460/461

64

32

Readout for 32/64 pixels

Input charge dynamic range•VATA450•VATA451•VATA460•VATA461

±16

±1.6

±72

±5.5

Charge (fC), linear range. Some of the ASICs have much higher saturation range at higher non-linearity.

TP slow (VATA450/451//460/461)

TP fast

3/ 3/ 2/ 3.5

0.6/ 0.6/ 0.3 / 0.6

µs. Default settings.

Power consumption•VATA450•VATA451•VATA460•VATA461

0.25

1.16

0.336

1.28

Power consumption per channel (mW), nominal bias settings. Acquisition mode.

Electronic noise of CSA•VATA450•VATA451•VATA460•VATA461

59 e + 14e / pF

27 e + 6.6e / pF

179 e + 16e /pF

34 e + 5.5e /pF

Baseline noise and noise slope. At default bias values.

Detector Capacitance 5-7 Optimization value (pF).

Detector Leakage Current 10pA Optimization value. VATA460 has been designed to tolerate up to 36nA.