マイクロメッシュを用いた高増幅率型 μ-PIC の開発

Development of -PICusing micro mesh

1. Introduction2. Test operation of prototype3. Simulation studies

神戸大学　　越智 敦彦、桂華 智裕Kobe Univ. Atsuhiko Ochi, Tomohiro Keika

3rd MPGD workshop @ Saga Univ. 26/Jan/2007

400m

Mesh

Introduction

• Micro pixel chamber (-PIC)– Position resolution ( - 100m)– Timing resolution ( < 100ns)– High rate capability

( > 107c/sec/mm2)

• With micro mesh– Higher gain in stable

operation (>104)

Effect using micro mesh

• Higher Electric field around the anode– Vertical direction against

detection flat– Without increase of e-field

near cathode edge Higher gas gain will 　

be attained safely• 104-5

• Reduction of positive ion distribution across detection volume

Applications

• Replacement of -PIC with GEM– Real time imaging device for

• X-ray• Gamma-ray• Charged particle• Neutron• etc.

• TPC– Low ion diffuse

Prototype test• Micro mesh was mounted on -PIC

– Supported by plastic film / nylon wire• Support structure is future tasks

– Distance between -PIC and wire• About 300m

– Micro mesh is connected to HV controller

• Operation gas– Ar:C2H6 = 90:10

0.5mm

Micro scope picturesfor same place(different focus point)

Micro mesh mounted on -PIC by hand.Size of -PIC = 3cm x 3cm.Efficient area using mesh = 2mm x 3cm

Test parameters

• Only signal pulses (gain) were measured– Gain dependency on

• Anode voltage (=Va)• Mesh voltage (=Vm)• Drift voltage (=Vd)

10 m

10 m100m

Drift Plane

Cathode

Anode 信号

Vd

Va

MeshVm

0

2000

4000

6000

8000

10000

12000

14000

16000

420 430 440 450 460 470 480 490 500

no meshVm=0VVm=-50VVm=-100VVm=-150V

Gain curve (Va, Vm dependence)

• Vd-Vm = 100V (Vd=2kV for no mesh plot)• Gas: Ar(90%)+C2H5(10%)• Source: Fe55 (5.9kV)

Va [V]

Gain

Collection efficiency problem

• Collection efficiencies for electrons– Depend on Vd-Vm … smaller is better

Without MeshWith mesh (Vm=0V)

Va=450V Va=450V

Vd [-V] Vd [-V]

Gain Gain

Current status of development

• Came up with the new idea -PIC with micro mesh

• Prototypes were made and tested– Gas multiplicity of it is more than 3 times– Gain of 2 x 104 were attained

• With prototype mesh (distance is about 300m)

– More studies are needed for tuning up the parameters

• Simulation studies Keika will talk

Optimization of parameters for μ-PIC with micro mesh

2007.1.26-27 MPGD workshop

@Saga Univ.

Kobe Univ.M2 　 Tomohiro Keika神戸大学　桂華　智裕

マイクロメッシュ μ-PIC の最適動作パラメーターの探索

Simulation Study

Parameters

•Height of micro mesh

•Mesh Voltage (Vm)

•Drift Voltage (Vd)

（ Anode Voltage is fixed ）We optimize the height of micro mesh using a simulation.

AnodeCathode

micromesh

Height

Optimization for detector parameters

•Structure

•Operation voltage3D simulation

About simulation softwareMaxwell3D

Garfield

3D field simulator made by Ansoft Co. America

•Make a 3D structure geometry•Calculate electromagnetic field using a finite element method (FEM) (Supported by Cosmic Ray Group at Kyoto Univ.)

2D・ 3D field simulator made by CERN

•Feed maps made by Maxwell3D to Garfield

•Calculate electromagnetic field , gas gain and so on.

Geometry drawing

We compare the three patterns.

Micro mesh100μm

200μm

500μm

or

or

Height of micro mesh

Cathode

Anode

Polyimide

Height

100μm200μm500μm

Effect using micro mesh

No micro mesh (Va=450V)

Micro mesh 100μm (Va=450V,Vm=-100V)

Micro mesh

Color display of electric field

AnodeAnode

Comparison of the results by Maxwell3D and by observed value

How to calculate gas gain•Calculated using the first Townsend coefficient•Collection-efficiency•No space-charge effect, ion-electron recombination

Focus: increasing or decreasing trend of the results

（ Va=450V,Vd=-5000V ）→It is the comparative data.

4102.2

Gas gain of μ-PIC without micro mesh is

Supply voltage to micro mesh

赤：Mesh100um

青：Mesh200um

緑：Mesh500um

Gai

n

4102.2

Select these parameters to compare the electric field near micro mesh.

条件： Va=450V,Vm-Vd=100V

Dependences of gas gain on Anode Voltage and Height of micro mesh

Dependences of gas gain on Anode Voltage and Height of micro

mesh

赤：メッシュ 100um

Vm=0V,Vd=-100V

青：メッシュ 200um

Vm=-100V,Vd=-200V

緑：メッシュ 500um

Vm=-300V,Vd=-400VDistance from the subtrate to micro mesh

100μm

200μm

500μm

Ele

ctri

c fi

eld

We had better lower the electric field near micro mesh to prevent electric discharge.

Collection efficiencyTerminal points of electron on the electrode plane or micro mesh.

Vm=0V Vm=-200V

Anode:37%

No-Anode:3.6%

Mesh:60%

Anode:37%

No-Anode:21%Mesh:41%

Study for the optimization using a 3D simulation.

(Qualitative interpretation)Gain dependency on voltage of mesh  Vm increase Collection efficiency decrease

Estimation of electric field near the micro mesh  Most desirable fields were obtained in wider (500um) case In typical case, gain using micro mesh is quite greater than symple u-PIC.  simple u-PIC (Va=450V, Vd=-5000V(10mm) ） : 2.2 x 104

 with micro mesh (Va=450V, Vm=-400V, Distance=500um) : 2.0 x 105

Results

Gas gain get more increasedBut

Gain rise

Future prospects

• How to hold the mesh on detector?– How to keep the flatness of the mesh?– Wire or leg?– Insulations are attached with micro mesh or -PIC?

• Optimization of geometries and operation voltage?– Collection efficiency ↑ 　 and gas gain 　↑– To get consistency of simulation and measurement

• 2 dimensional readout and larger detection area– With amplifiers and data acquisition system

• We have to get the budget for this project !!!– There is no budget about this project yet !!

• We need more than 5M JPY to make new design of -PIC