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T.Takahashi, Hiroshima Conf., 2004
Application of CdTe for the NeXT mission
Tadayuki TakahashiISAS / JAXA, Japan
NeXT mission
~2010-
T. Takahashi, K. Nakazawa, S. Watanabe, G. Sato, T. Mitani,T. Tanaka, K. Oonuki, K. Tamura, H. Tajima, M. Nomachi, Y. Fukazawa, M. Kokubun and the HXI/ SGD team
HXI & SGD
X-ray
X-ray
T.Takahashi, Hiroshima Conf., 2004
100 keVCdTe/CZT detectors
• Wide band gap (Eg:1.5 eV, e:4.4 eV)⇒ Allows room temperature operationHigh resistivity ~ 109-11 Wcm
• High Z semiconductor (ZCd = 48, ZTe = 52), r=5.9 g/cm3
• Poor charge transport properties (recombination and trapping)• Crystal NON-Uniformity and Size
-> Significant Progress in 1990’s(see review by Takahashi & Watanabe, IEEE NS48, 4, 950, 2001)(see Poster by G. Sato, CZT detectors for the Swift mission)
VERY
ATT
RACTI
VE
CdTe vs CZT(CdZnTe) : advantages/disadvantages
T.Takahashi, Hiroshima Conf., 2004
Recent Achievement
-20 deg (Amptek’s discrete Amp) Digital Movie of Analog Clock (by ACRORAD)
CdTe single crystal (ACRORAD)
5cm
200 micron
Room Temperature
ISAS
ISAS
Advantage
T.Takahashi, Hiroshima Conf., 2004
Gamma-ray40 layer CdTe Stack (Watanabe et al. 2002)
137Cs
FWHM2.1 keV
662keV
Takahashi et al., IEEE N.S. 48, 3(2001)
Medical application (see poster by ACRORAD)ISAS ISAS
Prof. Hayashi, Chiba U.
T.Takahashi, Hiroshima Conf., 2004
Total weight : 1700 kg
The NeXT MissionSuper Mirror ( 0.5-80 keV )
Hard X-rayImager
focal length12 m
30’’ HPD
E>10 keV
NeXT Mission Proposal, ISAS, 2004
Nagoya U./ISAS
T.Takahashi, Hiroshima Conf., 2004
Wide band X-ray Imager- A solution for the detector
to cover 0.3 - 80 keV -
Shield & Window
Transparent X-ray CCDX-ray
Hard X-ray
CdTe Pixel Detector
BGO Active ShieldSi Strip Detector(Option)
APDHXI
SXI
X-ray CCD for soft X-ray
CdTe pixel for Hard X-ray
(Takahashi et al. NIM A 436 , New Astronomy Reviews, 48, 2004)
NeXT Mission Proposal, ISAS, 2004
T.Takahashi, Hiroshima Conf., 2004
CdTe Hard X-ray Imager (HXI)
• CdTe PixelGoal
2cm
3cm 6 arcmin
3 arcmin
Thickness : 0.5mm-1.0mmDetector Area : 2cm x 3cmPixel size: 250 µm x 250 µm
WXICCD(see Poster by Tsuru et al.)
CdTe0.5mm
1mm
Si-CCD0.3mm
BGO w APD(see PosterbyKataoka/Fukazawa)
T.Takahashi, Hiroshima Conf., 2004
Bump Technologyfor the CdTe pixel detector
CdTe
ASIC
underfill
50 micron
ISAS&MHI patent applying(Takahashi et al. IEEE NS. 2001)
X-ray/Gamma-ray
Electrode
CdTe/CdZnTe
ASIC Support board
• In/Au stud bump•Good for CdTe/CZT material (soft)• Mechanical support by under-fill• Thermal Cycle (-55 deg …+125 deg)
200µm pixels(ISAS/Bonn U.)
Stud bump
T.Takahashi, Hiroshima Conf., 2004
What we need is…
2mm
2dim version(200µm pitch)
16x16
12x12
CdTe Pixel DetectorVLSI based on deep submicron CMOSTechnology
(a) Low Noise (ENC ~50 e- RMS at 0pF)
(b) Low Power (~0.2 mW/pixel) (c) Self Trigger Capability (d) Low Rate
ISAS/SLAC w KEK, LBNL
Tamura et al. 2004
Tajima et al. 2004
Front end analog ASIC for Spectroscopy
T.Takahashi, Hiroshima Conf., 2004
Demonstration of the “NeXT” Technology
• Use CdTe (from ACRORAD) instead of CZT
• Use Caltech ASICs (Capacitor Array: analog output, PI F.Harrison)
• Use ISAS/MHI bump technology for hybridization
• High Uniformity and Good Low-energy Responseachieved by CdTe single crystal
pixel size: 580 µm x 580 µmhybrid size : 1.3 cm x 2.5 cmpower : 50 µW/pixelOonuki et al. 2004
T.Takahashi, Hiroshima Conf., 2004
Soft Gamma-ray Detector (SGD)Narrow FOV Compton Telescope on the NeXT
~40 cm
600 DSSDsTotal Area 15,000 cm2
75 CdTe PixelsTotal Area 3,125 cm2
Ultra-Low Background Soft Gamma-ray DetectorStack of Double-sided Si strips
High Resolution
CdTe pixels
Well-typeBGO Active shield
T.Takahashi, Hiroshima Conf., 2004
Narrow FOV Compton Telescope
DSSD 0.5mm thick, 400 micron pitch 24 layersCdTe Pixel Wall, 5-6 mm thick, 1-2 mm pitch
• Semiconductor : High E & Pos. Resolution• Si : low Z : Scatterer• CdTe : High Z : Absorber
• Narrow FOV : γ-ray comes from FOV• Energy Range : 80 keV - 1000 keV
SGD
€
E2 =(E1+ E2)
1+(E1+ E2)(1− cosθ)
mec2
And gets rid of most of background includingthe internal background (activation).
(Takahashi et al. SPIE 4851,1228 2003; New Astronomy Rev. 2004)
Select two hits events andaccept only if
T.Takahashi, Hiroshima Conf., 2004
Narrow FOV Compton Telescope
DSSD 0.5mm thick, 400 micron pitch 24 layersCdTe Pixel Wall, 5-6 mm thick, 1-2 mm pitch
• Semiconductor : High E & Pos. Resolution• Si : low Z : Scatterer• CdTe : High Z : Absorber
• Narrow FOV : γ-ray comes from FOV• Energy Range : 80 keV - 1000 keV
SGD
€
E2 =(E1+ E2)
1+(E1+ E2)(1− cosθ)
mec2
And gets rid of most of background includingthe internal background (activation).
(Takahashi et al. SPIE 4851,1228 2003; New Astronomy Rev. 2004)
Select two hits events andaccept only if
T.Takahashi, Hiroshima Conf., 2004
DSSD1. High resolution Silicon Strip detector
(w Hamamatsu, see Poster by Fukazawa et al.)2. Low Noise ASIC (ISAS/SLAC/IDEAS)
1. VA32TA (2002)
2. VA64TA_LP (2004)0.2 mW /channel
0
200
400
600
800
1000
12002x10
241Am
59.5 keV
Energy [keV]
13.9 keV
17.6 keV
21.0 keV
26.3 keV
0 10 20 30 40 50 60 70
ΔE =1.5keV(FWHM)
25mm/400micron pitch
Uno etal., 2003
3-layers ISAS
T.Takahashi, Hiroshima Conf., 2004
Highly uniform CdTe detector with a new ASIC
ISAS & SLAC
Pixel size 2 mm x 2 mm : 64 pixel
Co57: 122 keV
T.Takahashi, Hiroshima Conf., 2004
Some Test Results
Azimuth Scattering Angle (deg) (deg)φ
0 50 100 150 200 250 300 3500
20
40
60
80
100
120DATA 43±3 %
(deg)φ0 50 100 150 200 250 300 350
0
50
100
150
200
250
300
350
EGS4.4 MC 41±2 %
CdTe pixel detector
DSSD
θ
Mitani et al. IEEE NS, 2004
Compton Imaging by 122 keV γ-ray (Tanaka et al. SPIE, 2004)
Two sources
T.Takahashi, Hiroshima Conf., 2004
Same Flux from the sourceCase for High Background & Low BackgroundAfter background subtraction
High Background
Low Background
Compton Mode5x5 unit option
Total Effective Area(Photo Abs Only +Compton)
Gamma-ray Sensitivity of the NeXT5x5 option
Super Mirror + WXI (SXI + HXI)
SGD
NeXT Mission Proposal, ISAS, 2004
T.Takahashi, Hiroshima Conf., 2004
Summary• CdTe
– High Resolution/High Uniformity materialnow available;
– Still need R&D for >100 cm^2• Crystal• Readout• Hybridization
• NeXT Mission– High Energy X-ray/Gamma-ray mission– CdTe plays VERY important role
• Hard X-ray Imager• Gamma-ray Compton Camera for soft gamma-rays
• High Energy Astrophysics detector would also beimpossible without ASICs.