AMICSA 2010 1

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

1Integrated Detector Electronics AS

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

AMICSA 2010 2

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.

AMICSA 2010 3

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

AMICSA 2010 4

Space Application (1)

ASTRO-H

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

Picture:

JAXA

AMICSA 2010 5

Space Application (2)

BepiColombo MMO

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

AMICSA 2010 6

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

– 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.

JAXA /

KIPAC

[Watanabe,

vertex 2009]

AMICSA 2010 7

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

AMICSA 2010 8

Radiation Detector Principle

AMICSA 2010 9

VATA-ASIC Basic Functionality Functionality 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.

AMICSA 2010 10

ASIC TL architecture

Four distinct modes

of operation:

– Initialization

– Acquisition (FE)

– Conversion (ADC)

– Readout (BE)

Bias Network

Cali

bra

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

Ba

ck-

En

d

CM

Configuration

AMICSA 2010 11

ASIC FE Channel Architecture

AMICSA 2010 12

The VATA PRINCIPLE

AMICSA 2010 13

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 converted

Vo

lta

ge

ra

mp

10

bit

co

un

ter C

M

de

tecto

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

AMICSA 2010 14

Back-End Architecture

• Digital data

reduction

• Output data

format:

– Status bits

– Trigger

map

– ADC data

Dig

ita

l

co

mp

ara

tors

Mu

ltip

lexe

r

Co

ntr

ol In

terf

ace

Digital threshold

generator

10ADC 0

10ADC 1

10ADC 63

+

-

+

-

+

-

10CM

Internal control

signals

Co

ntr

ol IO

AMICSA 2010 15

VATA-ASIC Extended Functionality

Function 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

AMICSA 2010 16

ASIC Layout

JAXA / KIPAC [Watanabe, vertex 2009]

AMICSA 2010 17

Test results – Energy Spectroscopy (1)

VATA450 (low power)

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

VA32TA6 VATA450

AMICSA 2010 18

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

AMICSA 2010 19

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.

AMICSA 2010 20

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

erg

y [

keV

]

Measurements performed by Takashima et al, JAXA.

AMICSA 2010 21

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.

AMICSA 2010 22

Radiation test of VATA460

Radiation test by 6MeV/n He.

Measurements performed by Takashima et al, JAXA.

Gain Noise

AMICSA 2010 23

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.

• 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.

AMICSA 2010 24

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.

AMICSA 2010 25

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

AMICSA 2010 26

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.

AMICSA 2010 27

Appendix: Performance Specifications

Parameter 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.