NDIP08

Recent Advances
on CdTe/CdZnTe detectors
For High Energy PHOTON
Tad Takahashi
Institute of Space and Astronautical Science (ISAS)
Japan Aerospace eXploration Agency (JAXA)
andUniv. of Tokyo

Acknowledgement : Z. He(Michigan), P.Luke (LBNL), F. Harrison(Caltech),
O. Limousin(CEA), C. Szeles (eV), R. Ohno(ACRORAD), J. Matteson (UCSD)
T.Takahashi

Outline

NDIP08• Demand and CdTe/CdZnTe• Recent Progress on technology• Crystal and ASIC

• X-ray Imager• Pixel & Strips• Gamma-ray Detector• Coded Mask /PET• Compton Camera• Summary/Future Prospects
T.Takahashi

NDIP08

Demands
Need Detector Material which can be used as
an alternative to Si (in terms of Efficiency)
an alternative to Ge (in terms of Operating Temperature)

Good Energy Resolution similar to Ge (0.2%@662keV)
High Efficiency, above 10 keV upto 1 MeV
Position resolution a few hundred micron
A detector can be operated at room temperature

In the field of
Medical Application
Homeland Security
Astronomical Observation
Seems to be very diﬃcult and would need

another 10 to 20 years for the ﬁnal answer

3T.TakahashiNDIP08

All next generation telescopes need a Hard-X camera
above 10 keV, where Si becomes transparent

To take a photo ofSuperNova explosionin hard X-ray

NuSTAR Small Explorer
Two hard X-ray (6 - 79 keV) focusing telescopes-39d30m

Launch August 2011
-40d00m17h16mNeXT Mission(JAPAN)

Launch 201317h14m17h12mSimbol-X(ASI/CNES)

4

Launch 2014

T.Takahashi

NDIP08

With Newly developed
Hard X-ray Mirror

Nagoya U.
Mirror
Detector
10-20 mT.Takahashi

CdTe/CdZnTe seem to be the only candidate
at least, at this moment• High Z semiconductor

NDIP08100 keV(ZCd = 48, ZTe = 52), ! =5.9 g/cm3• Room Temperature Operation

or Cool Environment

511 keVP. Luke (2006)

Takahashi and Watanabe (2000)
T.Takahashi

NDIP08

Slow mobility/ short lifetime of carriers
are a bit problem for CdTe/CdZnTe"

Signal is Depth Dependent

cathodecathode'+'!#1%(-%(+43!"#$%&'!
hh2mmeheanode$%+'-%(+4"(%&'eanode"2)*+,'-$'./$#-&'0'(&,-%(-#$'-.(#'1"!#.%(-&'0#$We now know how to handle this Charge
Collection Issue (Coplanar Grid/Cross Strip etc.)
For the case of thin detector, and with high bias
voltage (400 V/0.5mm), can collect full charge.

Thick vs Thin approaches, I’ll explain later

Takahashi and Watanabe (2000)
T.Takahashi

CdTe/CdZnTe seem to be the only candidate
at least, at this moment

NDIP08Because, they’ve already shown good performance

CdTe/ACRORAD

Thin CdTe diode at -20 deg
137Cs

662keVFWHM
2.1 keV
0.3 %260 eV
at 6.4 keV

CdZnTeNuSTAR/Caltechepoxy
gold stud

ASIC
Takahashi et al. 2005

T.Takahashi

NDIP08

CdTe/CdZnTe Commercial Products
AmptekAXION CdTe dental panoramic digital imaging system

aguila (US)X-ray Spectrometer

Radiation-Threat-Detector

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CCD
Scintillator
CMOS

CdTe
CMOS

Courtesy of AJAT (Finland)

T.Takahashi

Commercial Products

NDIP08Hard X-ray Imager

Integrated type1 dim Imager (30cm)

100 micron pitch

AJAT, Finland

T.Takahashi

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Technologies
Crystal&ASIC
T.Takahashi

Who makes CdTe/CdZnTe Crystal?

NDIP08From a review talk by P.J. Sellin (2005)

T.Takahashi

Recent Advances on Technologies
ACRORAD (JAPAN)

Large Single Crystal

NDIP08

1st Large Scale CdTe Camera in Space (INTEGRAL)
Travel Heater Method(THM)

Careful treatment of
post heating

Very uniform wafer

Quartz ampoule
CdTe poly crystal
Te-rich Cl-doped
Cd-Te solvent
Heater unit

CdTe single
crystal seed

THM

Cl-doped CdTegrown single crystal

T.Takahashi

Recent Advances on Technologies

NDIP08eV Products (High Pressure Bridgman and improved method)

Large Crystal

SWIFT !-raysatellite (2004-)
2m1m

CdZnTe 4x4x2mm

T.Takahashi

NDIP08

Recent Advances on Technologies
REDLEN
succeeded to make CZT by THM
Large Single Crystal

662 keV 1. 18% (7.8 keV, FWHM)
without additional signal correction)

IR imagevery small Te
precipitate/inclusion

Chen et al. JAP, 2008

2 x 2 x 1.05 cm3monolithic pixel
pixel size 2.46 mm

T.Takahashi

NDIP08

We need ASIC :If you need CdTe/CdZnTe imaging detectors
VAanalog outTAVdd

Levelsensitive
Discriminator

S/HCharge
Integrator Semigaussian(preamp.) “slow” shaper

Spectrum

Multiplexer

Semigaussian“fast” shaper

Monostable(fixed width)

VssTrigger
OutADC

Need 50 e- at 0pF for both cases

Photon Counting

T.Takahashi

NDIP08

Hard X-ray Camera
For photons

above 10 keV
below 100 keV
T.Takahashi

NDIP08

CdTe Photon-counting imager using XPAD chip

0.7 mm thick CdTe
20 kpixels (130!m x 130!m)2 ms/frame 106 photons/pixel

Basalo et al. , NIMA 2008

T.Takahashi

CdZnTe Imager with Spectroscopic Capability NDIP08
Prototype (for HEFT)

for NuStar Satellite
Flat Image
non-uniformity of the image comesfrom CZT, not from ASIC

0.5mm pitch, 2mm thickTwo hybrids: 24 x 48

32 x 32 array, 0.6 mm pitch
2 mm thick CdZnTe

CSAtoADC
16 capacitors

T.Takahashi

CdZnTe Imager with Spectroscopic Capability NDIP08
Prototype (for HEFT)

for NuStar Satellite
Flat Image
non-uniformity of the image comesfrom CZT, not from ASIC

0.5mm pitch, 2mm thickTwo hybrids: 24 x 48

5 mm CdZnTe, 800 V, 1C
Single pixel 155Eu
900 eV FWHM @ 86 keV

counts32 x 32 array, 0.6 mm pitch
2 mm thick CdZnTe

E F. Harrison, 2008

T.Takahashi

CdTe Imager with Spectroscopic Capability

NDIP08for Simbol-X Satellite! HED: mosaic of 64 independent CdTe (Al/CdTe/Pt) cameras! Caliste 64: first prototype of detection unit
241Am spectrum at -10°C, 500V with thesingle events of the 64 pixels!

See A. Meuris’ talk in this session

0.66 keV fwhm @ 13.94 keV
0.84 keV fwhm @ 59.54 keV

Large Area Hard X-ray Imager

NDIP08

ISAS/JAXA

Large Area 1024 pixel CdTe Array(pixel size 1.4 x 1.4 mm2)5 cm

0.5 mm thickNDIP08

X-ray Imager

Allow us to study where in the leaf
absorb which kind of metal(multi-tracer imaging)

140 keV69-80 keV

99mTc

201Tl

Fine Pitch CdTe Strips

NDIP08Previously

1) Diﬃcult to make strips on the barrier
electrode (In) for CdTe diode.

2) Wire-bond does not work on CdTe.
With new electrode material

on CdTe (Al as anode/Pt as cathode)we have succeeded to make ﬁne pitch
Double Sided Cross Strip detector

ASIC
wire-bonding

strip pitch 100-400 micron
ceramic board with through holes
In/Au stud bump
CdTe
ASIC

strip electrodewire-bonding

NDIP08

Results(imaging)
Shadow Imagevarious RIs(241Am, 133Ba, 57Co)–20ºC, 500V biasnut(M2)washer(M3)
14060

100
100
140120

50
50

120
80
80
100

40
40

100
80
60
60
80

y [ch]nut(M3)

81keV
31keV
60keV
122keV

spectra

30
30

60
60
40
40solder2020(0.6mm)

40
40
20
20
20
20

1010
241Am
133Ba
57Co

00
00

1010202030
40
30
40
[ch]
xx [ch]50506060!x~400!m Imaging Spectroscopy !!

00

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Gamma-ray
above 100 keV

T.Takahashi

CdTe & CdZnTe detectors for gamma-ray
Thick Approach

NDIP08Energyat room temperature

P.Luke (LBNL)

T.Takahashi

Gamma-ray Detector

Cross Strip CdZnTe

NDIP08For a Large NIH Program 1 mm spatial resolution, ~2% energy resolution at 511 keV
Depth Correction

by using Cathode/AnodeInfo.

NIH Grant #R01CA120474

511keV
3.1 % FWHM

Edge on geometry
Eff. of 86 % for 511 keV
by 4cm CZT

by C. Levin of Stanford,and J. Matteson et al.
2008
California Breast Cancer Research Program, CBCRP Grant Number 12IB-0092

T.Takahashi

Gamma-ray Detector

NDIP08Mini Coded Mask (cross strip CZT)DGAS specs:!- Image a 5 mCi source at >5 m in less than 10 sec,and localize it to <10 degrees!- Energy band of 40 - 250 keV!- Better than 10% energy resolution at 122 keV

Redlen CZTJ. Matteson &Aguila Tech., 2008
supported by HSRAPA
T.Takahashi

NDIP08

CdTe & CdZnTe detectors for gamma-ray

Thin Approach
Concept!

AmptekXR-100T-CdTe-STACK

Area 5 x 5 mm

Thickness 2.25 mm(three layers)
Full Charge Collection (No Tail)-> Stack thin CdTe layers
to get high efficiency.

Watanabe, TT et al. 2002

40 layer = 20 mm thick CdTe

T.Takahashi

Gamma-ray Detector

CdTe PET (1st Result)
Achieved Spatial Resolution< 1mm

NDIP08

Tohoku Univ.

Array of 1mmX1mmX5mm
5120 CdTe BAR

Edge on geometry
Press Release by K. Ishii,
Tohoku Univ., Japan

BrainRat

Mouse
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Gamma-rayCompton Camera
for High Sensitivity
Imaging
T.Takahashi

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Gamma-ray Detector

CdZnTe Compton Camera (Thick)
Z. He et al. Michigan U. (2008)• Cathode/Anode Ratio (Depth Info)• Timing Measurement (Drift Time)( Multiple Interaction/ Depth Info)

2!2!1.5 cm3= 6 cm3 CZT(eV Products)
ASIC front-end(Gamma-Medica-Ideas AS)

T.Takahashi

NDIP08

Room-temperature
handheld CdZnTe !-ray
imaging spectrometerswith energy resolution ~1% FWHM at 662 keV

T.Takahashi

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Demonstration of !-Ray Imaging using a Single
1.5"1.5"1 cm3 CZT Detector (FOV=4pi)
Accidentally
Detected a 10 !C 137Cs source next door90deg
Systematicerror shouldremain constantangular resolution ~10 degrees at 667 keV
T.Takahashi

NDIP08

Gamma-ray Detector

Si/CdTe Compton Camera (Thin)!"#"$%&%'()*+,-.'/012%345'6"44%7'"&'!"#$'
89%:'%;#413"<1$'=-3"5'*%4%&61#%>?)"@%44A@%':A44'B&%'A@'013'@C%'&%$&A<D%'2%"&B3%2%$@'0312'EFF'G%H'@1'IFF'G%HJ

Concept (Takahashi et al. SPIE 2003).
Narrow FOV (field-of-view)
Compton camera.
Compton kinematics tosuppress backgrounds%&'&('&)"*+')",&-"'*('.%-*/"0"012'&A$6%'A@'A&'41:'K'2"@%3A"4'"$7'212%$@B2'10'%4%6@31$'"31B$7'@C%'$B64%A'A&'&2"44'-L'M%&&'"N%6@%7'O5'P1##4%3'
Q31"7%$A$R

D'EF&<34''+*5"0('67'89:';;'<=&->'%&'?&@"+
A'+*5"0('67'89B:';;'<=&->'C)$"'?&@"+

T.Takahashi

NDIP08

Gamma-ray Detector

Si/CdTe
ComptonCamera!"#$#$%&'.//%0$1%23-45%+36*7$%89:.%"$;*$$+<=>?%"$;%@A1Z
CdTe Side
47.4

47.4,-%&%'()$*+X

14.4

DSSDs

CdTe Bottom!"#$%&%'()$*+energy

Compton250
cone.//%0$1200150

source direction

10050

Angular resolution ~3 degrees at 511 keV00()*+',*-'$-*./-0111-23-45567

100

200

300

400

500

600

T.Takahashi

Si/CdTe Compton Camera

NDIP08Good performance for both
multiple and diffuse
sources. Large FOV andgood energy resolution

ISAS, 2008!"#$%!"&$%'()*+,)-+.-)/0-1222-34-56678

T.Takahashi

Summary/Future Prospects

NDIP08

1. CdTe and CdZnTe are now in the phase ofreal application.
2. Large and Thin CdTe wafers are widely used forthe commercial products of hard X-ray camera
3. Photo Counting Detector(109-1010 photons/pixel /s)would be the next step.
4. For gamma-ray detection, Thick approach andThin approach both work.
5. Homeland Security and Medical Imaging boost thedevelopment
6. Space missions are always one step ahead interms of technological requirements, which is good.
T.Takahashi