Multi-channel Detector
Readout Integrated Circuits
with ADCs for X-ray and
Gamma-ray Spectroscopy in
Space
Sindre Mikkelsen1, Dirk Meier1, Jahanzad Talebi1, Suleyman Azman1, Gunnar Mæhlum1
1Gamma
Medica-Ideas (Norway) AS
Monday, September 6th 2010, 15:00 – 15:30
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AMICSA 2010
Abstract
We 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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AMICSA 2010
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
•
•
•
3
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
Picture:
JAXA
GM-I supplies ROICs for 2 instruments: HXI, SGD
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Space Application (2)
BepiColombo MMO
Picture: JAXA
GM-I supplies ROICs for the MPPE instrument.
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Astro-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), but
transparent for hard X-rays (>30keV)
– 1 layer of double-sided CdTe detector detects hard
X-rays (20keV...80keV)
– BGO well is active shield
•
The Soft Gamma-ray Detector (SGD) is a
– non-focusing soft gamma-ray, 10—600 keV
•
•
6
– narrow-FOV Compton telescope, rejects
background radiation
GM-I delivers the Read Out Integrated Circuits for the
Silicon and CdTe detectors
BepiColombo MMO MPPE
• Single sided strip detector
• Measure High Energy Particle energy to
investigate the the structure and dynamics of the
Mercury's magnetosphere.
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JAXA /
KIPAC
[Watanabe,
vertex 2009]
Design criteria
• ASTRO-H SGD (VATA450), launch 2014:
– Very low power
– Medium DNR
• ASTRO-H HXI (VATA461), launch 2014
FOXSI (VATA451), launch 2011:
– Low noise, medium power
– Low DNR
• BepiColombo MPPE (VATA460), launch Aug. 2013:
–
–
–
–
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Low power
High DNR
Medium noise
Large temperature range
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and
Radiation Detector Principle
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VATA-ASIC Basic Functionality
Functionality
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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
Configuration
Four distinct modes
of operation:
in
In0
Ch0
trig
a
a
Ch0 ADC
out
In63
trig
a
a
in
Ch63
Ch1 ADC
trig
a
a
Ch63 ADC
out
CM
Bias Network
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I/O
out
BackEnd
Ch1
Front – End
Calibration
in
ADC
In1
–
–
–
–
Initialization
Acquisition (FE)
Conversion (ADC)
Readout (BE)
ASIC FE Channel Architecture
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The VATA PRINCIPLE
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ADC Architecture
+
-
+
A in 1
-
A in 6 3
+
13
1 0 b it A D C
la tc h
10
D ig ita l
d e la y
1 0 b it A D C
la tc h
10
D ig ita l
d e la y
1 0 b it A D C
la tc h
10
1 0 b it
co u n te r
V o lta g e ra m p
-
D ig ita l
d e la y
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Do 0
Do 1
D 0 63
CM
d e te cto r
A in 0
CM
• 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 converted
Back-End Architecture
Internal control
signals
ADC 0
10
+
+
ADC 63
10
+
-
CM
14
10
Digital threshold
generator
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Multiplexer
Digital
comparators
-
Control IO
-
Control Interface
ADC 1
10
• Digital data
reduction
• Output data
format:
– Status bits
– Trigger
map
– ADC data
VATA-ASIC Extended Functionality
Function
15
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)
VATA450
VA32TA6
JAXA / KIPAC [Watanabe et al., Vertex 2009]
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Data taken by JAXA / KIPAC
Test results – Energy Spectroscopy (2)
VATA451 (low noise)
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
JAXA / KIPAC [Saito et al.,, SPIE 2010]
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Test results (3)
VATA460 (HDR)
Measurements performed by Takashima et al, JAXA.
Energy [keV]
Threshold of Noise
Energy measurement Thresh-hold
Temperature[degree]
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Energy Resolution
(FWHM)
Test results (4)
VATA460 (HDR)
Energy [keV]
Measurements performed by Takashima et al, JAXA.
Energy Resolution (FWHM)
Under CC-on
Energy Resolution (FWHM)
under CC-off
Noise level under CC-on
Noise level under CC-off
Temperature[degree]
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Radiation Tolerance and Latch-up
• 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 latchup immunity.
• Initial SEL tests have been
performed, and the design has
passed these.
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.
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Radiation test of VATA460
Gain
Noise
Radiation test by 6MeV/n He.
Measurements performed by Takashima et al, JAXA.
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Legacy of GM-I ASICs in Space
Selection 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.
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•
STEREO/PLASTIC (launched Oct. 2006, http://stereo.sr.unh.edu/): A.B. Galvin et al.,
•
SWIFT/Burst Alert Telescope (launched Nov. 2004): L.M. Barbier, F. Birsa, J. Odom, S.D.
•
AMS (AMS-01 launch 1998, AMS-02 launch 2011): B. Alpat, ”Alpha Magnetic
•
CREAM (balloon experiment, launch Dec. 2004): M.G. Bagliesi, C. Avanzini, G.
•
•
•
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-
“The Plasma and Suprathermal Ion Compositioin (PLASTIC) Investigation on the STEREO Observatories”, Space Science Reviews,
136, 1-4, April 2008.
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.
Spectrometer (AMS02) Experiment on the International Space Station ISS”, Nucl. Sci. Tech. 14, 3, 2003.
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.
Ray and Gamma-Ray Spectroscopy in Space”, Proceedings of AMICSA 2008.
AMICSA 2010
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 Specifications
Parameter
Number of Input Channels
•VATA450/451
•VATA460/461
Comment
Readout for 32/64 pixels
64
32
Input charge dynamic range
•VATA450
•VATA451
•VATA460
•VATA461
±16
±1.6
±72
±5.5
TP slow (VATA450/451//460/461)
TP fast
3/ 3/ 2/ 3.5
0.6/ 0.6/ 0.3 / 0.6
Power consumption
•VATA450
•VATA451
•VATA460
•VATA461
27
Value
0.25
1.16
0.336
1.28
Charge (fC), linear range. Some of the
ASICs have much higher saturation range
at higher non-linearity.
µs. Default settings.
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
Detector Capacitance
5-7
Optimization value (pF).
Detector Leakage Current
10pA
Optimization value. VATA460 has been
designed to tolerate up to 36nA.
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Baseline noise and noise slope. At default
bias values.