Development of Hard X-ray Detectorwith GEM

Shoji Uno (KEK)M. Sekimoto, T. Murakami, T. Uchida (KEK)

T. Koike (Tokyo University of Science)M. Kuroishi (Shinshu University)KEK Detector Technology Project

MPGD2009 　Crete, Greece12 June 2009

GEM foils made by Japanese company

• New method (plasma etching) was tried in several years ago. – Not chemical etching (CERN) – M. Inuzuka, et al., NIM A 525(2004) 529-534

• Laser + Plasma – To reduce sparks– T.Tamagawa, et al., NIM A560(2006) 418

• It is convenient for us to make new types of GEM foils.– Fine pitch/small hole : 50m/30m

• Better resolution Cosmic X-ray polarimeter• RIKEN

– Thicker/thinner : 100(150)m/ 25(12)m • Higher gas gain : a part of my talk

– S.Uno, et al., NIM A581 (2007) 271• Higher transparency : Gating grid for TPC

– Coated GEM• Boron : Neutron detection • Gold : Hard X-ray my talk• CsI : Hamamatsu Sekiya’s talk

10cm

10cm

Scienergy Co., Ltd. (Japanese company)http://www.scienergy.jp/

Ar-CO2

P10

Triple GEM with 50mt

Single GEM with 100mt

100mmt GEM : Hole diameter 70m (90m)Pitch 140m

Double GEM with 100mt GEM 70m

Thickness(m)

VGEM1

(V)VGEM2

(V)Sum(V)

Gain Comments

100/100 557 557 1114 1.3x104

100/100 579 579 1158 4.3x104

100/100 651 506 1157 5.4x104

100/50 675 375 1050 4.8x104 Stable

100/50 650 400 1050 5.0x104 Stable

Triple 390 × 3 1170 3.0x104

Diameter:90m for 100mt GEM :70m for 50mt GEM

Combination of different thickness GEM

Hard X-ray detector• Hard X-ray can even penetrate a thick iron plate and a concrete

block. Therefore, it is useful for non-destructive inspection in industrial purpose.

• Usually, Xenon gas has been used for detection of X-ray.

• But, efficiency is not so high for hard X-ray ( >~60keV).

• Solid converter (Gold) is used for detection of hard X-ray.

• Range of produced electron is very short. Gold layer should be thin. Then, many thin gold layers are necessary to get higher efficiency.

Gold plated GEMto get higher efficiency

for hard X-ray with higher energy

Au 　 3m Cu 　 1m

Polyimide 　 50m

X-Rays

Electrons

Standard GEM+Gold Plating

141keV γ-ray

0.00

0.05

0.10

0.15

0.20

0.25

0.30

0.00 0.05 0.10 0.15

Electron Energy (MeV)

Rel

ativ

e In

tens

ity

8

Simulation Study

Energy spectrum in gas volume for produced electron in gold layer

0

5

10

15

20

25

30

0 10 20 30 40 50

Number of GEMs

Eff

icie

ncy(

%)

9

Optimization of Gold thickness

0.0

0.2

0.4

0.6

0 5 10 15 20 25

Thickness of Gold Layer (m)

Effic

ienc

y (%

)

Photon Energy: 141keV

1m

2m

3m

4m

5m

10m

Simulation

Chamber structure

Au-GEM3m

2mm

2mm

Readout board X-Y strip0.8mm pitch 120+120

Multiplication

X-ray conversion layersEffective gas gain ~ 1

Gas:Ar-CO2(70-30)

Ground

100mt GEM1mm1mm1mm

1mm

1mm

　 50mt GEM

Drift planeAu 3m

0

1

2

3

4

0 1 2 3 4 5

Number　of　Au-GEM

Rel

ativ

e V

alu

e

11

Experimental result

57Co （ 122keV ）

Thickness of Gold Layer: 3mon both surfaces

Gold coated GEMC

oun

tin

g ra

te (

rela

tive

val

ue)

GEMChamber

• I/F– One HV cable– Five LV cables– One Ethernet cable

• Electronics– Four ASIC boards– One FPGA board

• FE2007 ASIC– By Y. Fujita (KEK)

• Data transfer and Control through Ethernet– SiTCP ( by T. Uchida)– Using Note-PC

Present Detector System

Low Voltage

Electronics

Note PC

Ethernet

Detector size 150mm×150mm×510mm

High Voltage

Compact and Portable System T.Uchida et. al., "Prototype of a Compact Imaging System for GEMdetectors," was published on IEEE TNS 55(2008)2698.

0

0.2

0.4

0.6

0.8

0 20 40 60 80 100 120 140

Photon Energy (KeV)

Rel

ativ

e In

tens

ity

X-ray irradiation test

• Medical X-ray Generator

– Voltage 　 120kV

– Current 　 1mA 0

200

400

600

800

1000

1200

0 1 2 3 4 5

(mA)管電流値

(kHz)

計数

率

Current (mA)

Cou

ntin

g ra

te (

kHz)

Energy Spectrum

Data Taking Rate

Without filterWith Mo 0.3mmt

Max. rate1.1MHz

2D Image for Hard X-ray

Clear 2D image could be seen.

96mm96

mm

Pinhole （ 0.5mm ） Irradiation time:100sec

0.8mm

0.8m

m

Iron Plate and Bars• On the Detector

1. Grid (Laminate structure of Lead and Aluminum)

To reduce scattering X-Rays 2. Iron plate : 10mm thickness 3. Four bars with different diameter

0.4mm2mm

0.9mm4.2mm

Iron Platewith holes

9mm 8mm 7mm

6mm 5mm 4mm

3mm 2mm1mm

Depth:

Iron plate with 10mm thickness Hole diameter : 6mm

Iron Bars inside Concrete

Thickness of Concrete :10cmIrradiation Time : 100sec

9~10mm 6mm 15~17mm

Four types of Iron Barsbefore molding

Concrete sample with Iron Bars

10cm

Summary• Japanese company (Scienergy Co., Ltd.) can produce various

GEM foils.

• Flexible 100mt GEM is effective to get higher gas gain for single GEM structure.

• Gold coated GEM foils were manufactured.

– Higher efficiency was obtained with more GEM foils.

• A prototype of hard X-ray detector with gold coated GEM was

constructed.• Performance study was done with X-ray generator.

– Clear 2D image could be seen.

– Hard X-ray could be observed through the thick iron plate with 10mm thickness.

– Iron bars could be seen inside concrete block.