application of cdte for the next missiontakahasi/download/takahashi-hiroshima-2004.pdf ·...

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


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


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


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.


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


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)



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)


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


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


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


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


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


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


Highly uniform CdTe detector with a new ASIC

ISAS & SLAC

Pixel size 2 mm x 2 mm : 64 pixel

Co57: 122 keV


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


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



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.


Angular ResolutionDoppler broadening will limitultimate angular resolution.

0

2

4

6

8

10

0 1 2 3 4 5

Energy resolution (keV)

An

gu

lar

reso

luti

on

(deg

) E=0.1 MeVE=0.2 MeVE=0.5 MeV

By Tajima, 2003

application of cdte for the next missiontakahasi/download/takahashi-hiroshima-2004.pdf ·...

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