To uncover hotspots of radiation
with a Si/CdTe Compton Camera--Recovering from the tragedy -Tadayuki Takahashi, Shin Watanabe,
Shin’ichiro Takeda, Yuto Ichinohe
Institute of Space and Astronautical Science (ISAS),JAXA&Hiro Tajima
Solar-Terrestrial Environment Laboratory, Nagoya U.
&Yoshikatsu Kuroda, Hiroshi Ikebuchi,
Kei Genba, Daisuke Matsuura
International X-ray Observatory

ASTRO-H

Mitsubishi Heavy Industry

ASTROCAM7000HS

1. Effects caused by the nuclear accident at Fukushima
2012/June 22-28
Radiation Level

http://radioactivity.nsr.go.jp

Cs134/137 Bq/m3Quick removal of dust with radioactive
materials (decontamination) is essential
HSTD9, 2013

2

3. Our Challenges, since the first e-mail in April/2011

2011

2012

2013
Demonstration
Type (2012)

Earth Quake
March11 Aug/11-12

3.2. CC EM1 データ処理の流れと実験セットアップ

ProtoType(2011)
HSTD9, 2013

Commercial
ASTROCAM-7000HS

17A-H SGD
Type (2011)
図 3.2: SGD CC EM1 実機

3

4. Requirments for “Gamma-Camera” in Fukushima

counts

1. Spectral Resolution (need to identify 134-Cs, 137-Cs : ~3%)
2. Image (Larger FOV is better)
3. Angular Resolution (a few degrees)
Spectrum taken in
4. Efficiency (Shorter exposure is better)
Fukushima
5. Portability
6. Availability(People in Fukushima
really need thiskind of device, now.)

HSTD9, 2013

134-Cs(605 keV)
137-Cs(662 keV)
134-Cs(796+802 keV)

energy [keV]4

5. Our technology - Si/CdTe Compton Camera Back-Projection to the Sky(x1, E1)

θComptonscattering

Six2
CdTe
x3

(x2, E2)

Photo absorptioncosθ = 1 − me c2!

11−E2 E1 + E2"

Si and CdTe are the best match to realize semiconductor based Compton
Camera (Si/CdTe Compton Camera)( Takahashi et al. 2001 ,2002,
Watanabe et al. 2005,
Si : Good scatterer←High σCompton/σPhotoAbs Ratio
Takeda et al. 2012)
CdTe : Good absorber←High stopping power.
HSTD9, 20135

5. Our technology - Si/CdTe Compton Camera Angular Resolution (ARM)(x1, E1)

θComptonscattering

Six2
CdTe
x3

(x2, E2)

Photo absorptioncosθ = 1 − me c2!

11−E2 E1 + E2"

Si and CdTe are the best match to realize semiconductor based Compton
Camera (Si/CdTe Compton Camera)( Takahashi et al. 2001 ,2002,
Si : Good scatterer←Low Doppler Effect (Low Z)
HSTD9, 2013

Watanabe et al. 2005,Takeda et al. 2012)
64 mm

5. Our technology - Si/CdTe Compton Camera -3.

2cm32 mm

Large FOV (180x180 deg)
10 times larger thanexisting gamma cameras
Good Energy resolution(2.2 % @ 662 keV)

HSTD9, 2013

Six20.5 mm
thick

CdTex30.7 mm
thick5. Our technology - Si/CdTe Compton Camera Key Technology - High Resolution CdTe Imager +Low work function
metal (In or Al)

Schottky barrier
1. Thin device (0.5 – 2.0 mm)
p-CdTe2. Schottky diode
Takahashi et al. 1998
3. Guard ring–with ACRORAD• Extremely low leakage current
Full charge collection• High bias voltage(NO TAIL)Best spectra we presented 10 years ago.

0.26 keV(FWHM)@6.4keV(3x3 mm, 1 mmt)
HSTD9, 2013

2.1keV (FWHM)
0.32%@662 keV(2x2 mm, 0.5 mmt)
8

5. Our technology - Si/CdTe Compton Camera - High energy/position resolution & high uniformity are quite important.
250 micronpitch strips
for both side2 x 128 = 256 channels(<<128*128=16,384)

Al-electrode side (+HV)
Pt-electrode side (GND)

φ3 mm hole
100 µm width slit
800 µm pitch
φ2 mm hole

bad strips(open)[mm]

Al-strip (+)(Schottky barrier)

3.2 cm-20degApplied bias: 250 V
ΔE: 1.7-1.9 keV at 60 keV (FWHM)
Low threshold: 5 keV[mm]

HSTD9, 2013(a)Watanabe et al., 20119(b)6. Angular Resolution of a Si/CdTe Compton Camera
Doppler effect in Si limits the angular resolution

Doppler

Si : ΔE = 1.6 keV
CdTe: ΔE/E = 1%Si: 400μm DSSD
CdTe: 1.4 x 1.4 mm pixel

1 deg
Takeda et al. 2008
10HSTD9, 2013

7. Performance of the first prototype

133Ba

HSTD9, 2013

137Cs

22Na

11

7. Performance of the first prototype
137-Cs (662 keV)730

Ѯminclination anglem

Only 20 % down
@ 80 degCompton camera= 80 deg= 60 deg= 40 deg= 20 deg

Large FOV of ~2π str., Angular resolution 3.8 deg
HSTD9, 2013

Takeda et al.
(2012)
12

8. Demonstration in Fukushima - Part 1Si/CdTe Compton Camera went to Fukushima.
134Cs

134Cs

569 keV605 keV
137Cs

662 keV

134Cs

795 + 802 keVEnergy [keV]

Optical image takenwith a fish-eye lens
HSTD9, 2013

Select lines,directly emitted from Cs, to avoid
scattered component13

8. Demonstration in Fukushima - Part 1Contour on
the Backprojection
Image

An image shot by the Ultra-Wide-Angle
Compton Camera showing the intensity (flux)
distribution of gamma rays of 605, 662, 796, and802 keV directly emitted from Cesium-134 and137. Red is high intensity while blue is low.

Intensity

Significance3 sigma
HSTD9, 2013148. Demonstration in Fukushima - Part 1BackProjection
PeakPoint Spread Function
for a point source

BackProjection
Tail

Extracted
Point Source

Takeda et al.
(2013)
HSTD9, 201315

8. Demonstration in Fukushima - Part 1Contour on
the Back projection
Image

An image shot by the Ultra-Wide-Angle
Compton Camera showing the intensity (flux)
distribution of gamma rays of 605, 662, 796, and802 keV directly emitted from Cesium-134 and137. Red is high intensity while blue is low.

Intensity

Significance

40 度

30 µSv/

HSTD9, 2013180 deg(back ground 〜3 µSv/h)16

8. Demonstration in Fukushima - Part 1Contour on
the Backprojection
Image

An image shot by the Ultra-Wide-Angle
Compton Camera showing the intensity (flux)
distribution of gamma rays of 605, 662, 796, and802 keV directly emitted from Cesium-134 and137. Red is high intensity while blue is low.

Intensity

Significance

30 µSv/h

HSTD9, 201317

9. Further Improvements✤ Higher sensitivity (Shorter Exposure)✤ Portability

Use the design of
the ASTRO-H SGD Compton Camera• 0.6 mm thick Si Pixel + 0.75 mm thick CdTe Pixel• 3.2 by 3.2 mm pixel size for Si and CdTeFirstDemonstration
Type (2011)

see Watanabe’s talkin this session

30 times higher sensitivity

ASTRO-Hに搭載される軟ガンマ線検出器

10 times higher sensitivity(reasonable price)）x2
HSTD9, 2013

Supported by the JST Program“development of systems and technology for advanced measurement and analysis” (2012-) 18

9. Further Improvements (Same design as the ASTRO-H SGD Compton Camera)
hist1_387

5 cm

Si Pixel (Pad) detector

9000

241Am

8000
7000
6000

FWHM 1.1 keV

5000@59.5 keV

4000
3000
2000
1000
050

100

150

200

250

CdTe Pixel (Pad) detector

see Watanabe’s talkin this session
HSTD9, 2013

35057Co2500• 32 layers of Si(~2 cm in total)• 8 layers of CdTe
• 2 layers of side CdTe

300

FWHM 1.7 keV
2000@122 keV

1500

1000

500

00100

200300400500

600

700

19

Vast Improvements

10. Vast Improvements (Same design as the ASTRO-H SGD Compton Camera)

CC EM1 データ処理の流れと実験セットアップ

1710 cm※First Prototype (2012) took 5 min.

Still very comact
137-Cs, 2.7 MBq @ 1 m

10 sec !

図 3.2: SGD CC EM1 実機

出器にかけられたバイアス電圧に従って検出器内を移動し、その結果電極にアナログ電荷誘起される。この電荷信号を、我々が SGD 専用に開発してきた低ノイズ同時多チャンネ
出し ASIC (SGD-ASIC) を用いて読み出す [38][39]。
4 に、SGD-ASIC の回路構成を示す。各ピクセルに誘起された電荷信号は、64 チャンネル
れ別のプリアンプに入力され、電圧信号が後段の二つのシェーピングアンプに渡される。
時定数 600ns 程度の速いシェーピングアンプ (ファストシェイパー) であり、トリガーをる。そのトリガーを受け、CC FPGA が適当なディレイの後に時定数 数µs 程度の遅いピングアンプ (スローシェイパー) にサンプルホールド信号を送る。ホールドされた波高ィルキンソン型の ADC [40] によって AD 変換され、マルチプレクサによってシリアル信て読み出される。の ASIC の中でここまで行われた後それぞれのシリアル信号は、8 ASIC ずつ (Si, CdTem)、あるいは 6 ASIC ずつ (CdTe-Side)、CC FPGA によってデイジーチェーンで読み出
1 。CC FPGA・検出器のバイアス電圧の制御やデータ取得は、MIO (Mission I/O) ボーじて行う。ASTRO-H 衛星では次世代衛星共通通信規格である SpaceWire [41] を採用しため、MIO ボードから出力される LVDS (Low Voltage Differential Signaling) 形式の信igabit Ethernet に変換し、ノートパソコンを用いて制御を行う。の実験セットアップを図 3.5 に示す。コンプトンカメラ、HV モジュール、DC-DC コン、そして MIO ボードはアルミケースによって一つにまとめられ、冷凍機の中に収納され凍機の外側にあるのは電源ボード、SpW-GbE、PC と、温度、露点のモニタである。冷凍機

Efficiency 0.03 cps/MBq @ 137-Cs, 1m→1.1 cps/MBq @ 137-Cs, 1m

EM1 には全部で 208 個の ASIC がある。これらの ASIC はグループ分けされており、データ取得やレジス定をするときに、そのグループごとに一つのシリアルデータが読み出される。これらのデータはグループ内のASIC を順番に直列に通過する。このようなデータ通信方式をデイジーチェーンという。

HSTD9, 201320

10. Vast Improvements (ASTRO-H SGD type)
We can learn a lot
from the real detector
hithitSequence 1Sequence 2DSSD

Ex. Scattering Sequences[φl t]

Multi Hit Analysis

122CdTe

[φl t]
1

Multi Hit Analysis Included
Si (1hit) + CdTe (1hit) event only

Ichinohe et al.
(2013)
HSTD9, 201321

12. ASTROCAM-7000HS (Our technology goes to the market)

on Camerabution

es havegheveloped

adioactiveveterials

nergym137

 SpecificationsDimensions
View Angle

Radiation Visualization Camera Specifications

 Overview

MHI

445L x 340W xISAS/JAXA*
235H and(mm)Mitsubishi Heavy Industries haveVisualization of radiation distribution

Dimensions

445L x 340W x 235H (mm)developed a camera using cutting-edge, highresolution radioactive sensor technology developedfor the ASTRO-H* satellite.

View Angle<detection efficiency depending on
angular positions>

180 degrees (ultra-wide)<detection efficiency depending on
visible light image is overlapped with a radioactive
angular positions>Aimage
into one display.
High
Approximately
8 䡚direction
13kg resolution(Camera UnitOnly)
Capability of measuring radioactive

180 degrees (ultra-wide)

Approximately 8 䡚 13kg
(Camera Unit Only)

Weight< depending on specifications>Power Source

AC100V䡚240V and Battery

OperatingTemperature

0 to 40 degrees Celsius< depending on specifications>

Storage
Temperature

0 to 50 degrees CelsiusPower SourceIdentificationof radioactive materials
AC100V䡚240Vand Battery

Operating
Humidity

35 to 80%
(Non-condensing)OperatingTemperature

0 to 40 degrees Celsius

Weightenergy bands

The system is capable of measuring the energybands of Sodium22, Cobalt60,
Iodine131,Barium133, Cesium134, Cesium137
and others.

Auxiliaries
Minimum Configuration

Camera Controller Box,
Laptop PC,
Maximum
Configuration
Visualization
SoftwareAll specifications may be changed without notice

Storage
Temperature Commercial
Model
0 to 50 degrees
CelsiusSi

Operating
Humidity

35 to 80%
(Non-condensing)

Auxiliaries

Camera Controller Box,
Laptop PC,
Visualization Software Field Test Example

Detected Radioactive Spots

CdTeᵰᵿᶂᶇᶍᵿᶁᶒᶇᶔᶃᴾᶇᶋᵿᶅᶃᴾᶓᶑᶇᶌᶅᴾᶓᶊᶒᶐᵿᵋᶕᶇᶂᶃᴾᵡᶍᶋᶎᶒᶍᶌᴾᶁᵿᶋᶃᶐᵿ ίᵡᶍᶓᶐᶒᶃᶑᶗᴾᶍᶄᴾᵨᵟᵶᵟὸ

ᵡᵿᶋᶃᶐᵿᴾᵳᶌᶇᶒAll specifications may be changed without noticeHSTD9,Field
Test Example2013

 Laboratory Test Example(using commercial model)

Detected Radioactive Spots22ᵠᵿᵋᵏᵑᵑᵡᶑᵋᵏᵑᵕ

12. ASTROCAM-7000HS (Our technology goes to the market)
StatusOperation

Nucleid137-CsSpectrum133-Ba22-Na

Light Curve

HSTD9, 2013

Mode12. ASTROCAM-7000HS (Our technology goes to the market)
Performance
137-CsAngular Resolution(ARM)

662 keV
ΔE/E = 2.2 % (FWHM)

5.4 ° (FWMH)

Pixel size (~3 mm) is optimized to get required angular resolution
HSTD9, 201324

14. Summary1) Space science missions require cutting edge technology due to its highscientific requirements (e.g. X-ray Satellite ASTRO-H)
2) We are now able to access all the technologies which are necessary to
make the next-generation CdTe-based gamma-ray imager (ASTRO-H Hard Xray Imager & Soft Gamma-ray Compton Camera)3) Si/CdTe Compton camera has been demonstrated in
Fukushima as a “Gamma Camera” with high angularresolution (a few degrees at ~600 keV).
The camera meets the requirements.
3D Imaging is possible by multiple pointing.
JAXA ASTRO-H

HSTD9, 2013

4) Our technology hasbeen transferred to theindustry.
“Ultra-wide angleCompton Camera” is now
commercially AVAILABLE.

MHIASTROCAM 7000HS
25A. Appendix
1) Space science mission requires cutting edge technology due to its highScientific Requirements
2) We are now able to access all the technologies which are necessary to makethe next-generation CdTe-based gamma-ray imager (ASTRO-H HXI&SGD)
3) Our Si/CdTe Compton Camera can be applied to various fields.
One example is...
4) Still needfurther eﬀorts
to reach the final
goal.

thyroidskull

spineadrenallumbarfemur

genitals

See presentation by Takeda, today (MIC 5-7)HSTD9, 2013

Takeda et al. 201126

3D Imaging
Stereoscopic Observation of Mouse（ISAS/JAXA, Gunma U.,JAEA）
Yamaguchi et al (2009)
Suzuki et al (2013)
Radiology. 2013 Jun;267(3):941-7.
doi: 10.1148/radiol.13121194. Epub 2013 Feb 15.

27

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

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

or Cool Environment

511 keVP. Luke (2006)

Takahashi and Watanabe (2000)