R05-5

High Energy and Position
Resolution CdTe DiodeDouble-Sided Strip Detectors
Shin Watanabe (ISAS/JAXA)
Shin’ichiro Takeda1
Goro Sato1
Kouichi Hagino1,2
Tamotsu Sato1,2
Yuto Ichinohe1,2
Shinya Saito1,2
Taro Fukuyama1,2
Masayuki Ohta1
Hirokazu Odaka1
Motohide Kokubun1
Tadayuki Takahashi1,2
Yoshikatsu Kuroda3
Kei Genba3
Mitsunobu Onishi3

1: ISAS/JAXA
2: University of Tokyo
3: Mitsubishi Heavy Industry Ltd.

the 18th International Workshop on Room-Temperature
Semiconductor X- and Gamma-ray Detectors, Oct. 25 2011

Introduction
High Precession Astrophysics Observation
Hard X-ray / Gamma-ray Imaging Spectrometers
Requirements•a few hundred micrometer position resolution•FWHM 1--2 keV or 1% energy resolution
ASTRO-H(2014)

CdTe Diode Double-sided Strip Detectors• large area and fine position resolution with relatively
small number of readout channels• simple• low power consumption• 1 dim. ASIC (2 dim. ASIC is difficult)
ASTRO-H Hard X-ray Imager(HXI) [focal plain imager of hard X-ray mirrors]

CdTe DSD for ASTRO-H HXIASTRO-H HXI Flight Model Design

3.4 cm wide CdTe diode device (Al/CdTe/Pt type) [ACRORAD]
250 µm strip pitch, 200 µm wide strip electrodes
128 strips on each side, imaging area 3.2 cm x 3.2 cm, 0.75 mm thickLSI (VATA chip)
We have developed with GM-IDEAS (Norway).
VATA460/461

S/H
ChargeinCSA

Slow-shaper
τ〜2-4 μs

To Common
mode detector

Discriminator+−Digital
delay

Discriminator

1010 bit
ADC
latch+−Digitalcomparator

32 units

10

Fast-shaper
τ〜0.6/1.2 μs

Triggerout+−VssMultiplexer

ADC partVdd10TA part

VA part
HoldVoltageramp

10 bit global
counter
DigitalthresholdThreshold
ADC
dataFixed delay•32ch signal processing•CSA and two Shapers(Spectroscopy & Trigger)•Internal ADC (Wilkinsontype)•Data suppression(only hitch data are output)•Inside Common mode
Noise Calculation•only Digital I/O

Low Power Consumption: 0.3 mW/ch or 1 mW/ch (selectable)
Good Noise Performance: 41 e- ( 0 pF), 77 e- (6 pF, 10 pA) [designed]
110 e- (10 pF, 10 pA) [measured]Spectroscopy Performance
Pt side–20ºC, Bias 250V
1 hit events
histe2_000

22000

Al strip side (+H.V.)

241Am Spectra

histe2_001

14000~1.6 keV FWHM
@ 60 keV

20000

18000

Pt strip side ( 0 V)
tail:small µτ of hole

12000

~1.2 keV FWHM
@ 13.9 keV

10000

16000

14000
8000

larger input capacitance

12000

X/γ-ray

10000

6000

8000
4000

6000
4000

2000

2000
001020304050

Energy[keV]

6070001020304050

60

Energy[keV]7080

Imaging
RI

Shadow Image

241Am 60 keV gamma-ray Image

Slit
CdTe DSD
100 μm800 μm

100 μm800 μmImaging
Shadow Image

CdTe DSD(count/mm2)

Slit

241Am 60 keV gamma-ray Imagey (mm)

RI

100 μm800 μm

100 μm800 μmx (mm)Imaging
Shadow Image

CdTe DSD(count/mm2)

Slit

241Am 60 keV gamma-ray Imagey (mm)

RI

100 μm800 μm

100 μm800 μmx (mm)Imaging
Shadow Image

CdTe DSD(count/mm2)

Slit

241Am 60 keV gamma-ray Imagey (mm)

RI

100 μm800 μm

100 μm800 μmx (mm)By using one hit/ two hits information, sub-strip position resolution was achieved.

Application1: Coded Mask Camera

1m

Swift BAT
INTEGRAL IBIS
4 mm pitch

fine pitch imager & mask≈8 cm
250 µm pitch

5.0 mmvery Compact Cameras
newly designed fine pitch coded mask

(50 µm thick Ni + 2-3 µm gold plating)
46.75mm x 8 layers
400 µm pitch, 350 µm square holes
Random pattern (a part of Swift BATmask pattern)

46.75 mm0.40 mm pitch
0.35 mm hole

Coded Mask Camera Imaging
point-like RI

30cm
Mask
CdTe DSD

8cm

241Am 60 keV peak[mm]

151050-5-10-15-15-10-5051015[mm]2D-gaussian fitting

sigma = 0.8 mm -> 9.0 arcmin

Reconstruction
cross correlation photon tagging

Coded Mask Camera Imaging
point-like RI

30cm

Reconstruction
cross correlation photon tagging

Mask
CdTe DSD

8cm

241Am 60 keV peak
15[mm]

1.513 mm

10500.5
0-0.5-1-5566.5

3 mm-10-15-15

5.5-10-505

1015[mm]

2D-gaussian fitting

sigma = 0.8 mm -> 9.0 arcmin

77.58

Coded Mask Camera Imaging
point-like RI

30cm

Reconstruction
cross correlation photon tagging

Mask
CdTe DSD

8cm

Y+0.5 mm

241Am 60 keV peak[mm]

151.51.5

110.5

0.5

00-0.5-0.5-1-13 mm

1050-5566.5

3 mm-10-15-15

5.5-10-5051015[mm]2D-gaussian fitting

sigma = 0.8 mm -> 9.0 arcmin

77.5

85

5.5

66.5

7

7.5

8

Coded Mask Camera Imaging
point-like RI

30cm

Reconstruction
cross correlation photon tagging

Mask
CdTe DSD

8cm

Y+0.5 mmY+0.2

241Am 60 keV peak
[mm]

15

1.5

1.5

110.5

0.5

00-0.5-0.5-1-13 mm

1050-5566.53 mm-10-15-15

5.5-10-5051015[mm]2D-gaussian fitting

sigma = 0.8 mm -> 9.0 arcmin

77.5855.5

66.5

77.58

Coded Mask Camera Imaging
point-like RI

30cm

Reconstruction
cross correlation photon tagging

Mask
CdTe DSD

8cm

Y+0.5
Y+0.2 mmY+0.1

241Am 60 keV peak
[mm]

151.5

1.5

1

1

0.5

0.5

00-0.5-0.5-1-13 mm

1050-5566.53 mm-10-15-15

5.5-10-5051015[mm]2D-gaussian fitting

sigma = 0.8 mm -> 9.0 arcmin

77.5

85

5.5

66.5

77.58Coded Mask Camera Imaging
point-like RI

30cm

Reconstruction
cross correlation photon tagging

Mask
CdTe DSD

8cm

Y+0.5
Y+0.2 mmY+0.1

241Am 60 keV peak
[mm]

15

1.5

1.5

1

1

0.5

0.5

00-0.5-0.5-1-13 mm1050-5

56

6.5

7

7.5

85

5.5

66.5

77.5

3 mm

-10-15-15

5.5-10-505

1015[mm]

2D-gaussian fitting

sigma = 0.8 mm -> 9.0 arcmin0.1 mm position determination-> ~1 arcmin

8Application2: Compton Camera
CdTe DSD high energy resolution & fine position resolution
Ideal Compton Camera Detectors
Si/CdTe Semiconductor
Compton Camera

Double-sided Si Strip
Detectors (same design)
Stacking Compactly
stack pitch 5.4 mm( 5 layers )Gamma-ray Imaging Performanceot monitor

Compton Imaging
356 keV
511 keV
662 keVRadio Isotope
1 m distance

SimultaneousMulti-RI Imaging

56 keV, 2.3 MBq, 1.2m )Details:
R09-1 T. Takahashi’s talkMIC5-7 S. Takeda’s talk

Summary• CdTe Diode Double-sided Strip Detectors (ASTRO-HHXI model)• CdTe Diode Devices , Al / CdTe /Pt type
• 250 µm strip pitch, 128 strips / side,• 3.2 cm x 3.2 cm imaging area, 0.75 mm thick• VATA LSI• Good Spectral Performance• FWHM 1.2 keV @ 13.9 keV, FWHM 1.6 keV @ 60 keV• Imaging Performance• Sub strip position resolution• Applications• compact coded mask cameras• Si/CdTe semiconductor Compton cameras