マイクロメッシュを用いた 三次元電場構造型 μ-PIC の開発

神戸大学 越智 敦彦、本間康浩、桂華 智裕、 故島陽太、守谷健司、道前武 1. Introduction 2. Test operation of prototype 3. Summary 日本物理学会 2007 年春季大会 26 Mar. 2007

Introduction

Mesh • Micro pixel chamber ( m -PIC) – Position resolution ( - 100 m m) – Timing resolution ( < 100ns) – High rate capability ( > 10 7 c/sec/mm 2 ) • With micro mesh – Higher gain in stable operation (>10 4 )

400

m

m

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 • 10 4-5 • Reduction of positive ion distribution across detection volume – ~ 1% (simulation)

Applications

• Replacement of m -PIC with GEM – Real time imaging device for • X-ray • Gamma-ray • Charged particle • Neutron • etc.

• TPC – Low ion diffuse • No gating method needed

Prototype test

• Micro mesh was mounted on m -PIC – Supported by plastic film / nylon wire • Support structure is future tasks – Distance between m -PIC and wire • About 300 m m – Micro mesh is connected to HV controller • Operation gas – Ar:C 2 H 6 = 90:10

Micro mesh mounted on m -PIC by hand.

Size of m -PIC = 3cm x 3cm.

Efficient area using mesh = 2mm x 3cm Micro scope pictures for same place (different focus point) 0.5mm

Test parameters

• Only signal pulses (gain) were measured – Gain dependency on Drift Plane • Anode voltage (=Va) • Mesh voltage (=Vm) • Drift voltage (=Vd) Mesh

10

m

m

Cathode

100

m

m 10

m

m

Anode Vd Vm 信号 Va

Gain curve (Va, Vm dependence)

Gain 16000 14000 12000 10000 8000 6000 4000 2000 0 no mesh Vm=0V Vm=-50V Vm=-100V Vm=-150V 420 430 440 450 460 470 480 490 500 Va [V] • Vd-Vm = 100V (Vd=2kV for no mesh plot) • Gas: Ar(90%)+C2H5(10%) • Source: Fe55 (5.9kV)

Collection efficiency problem

• Collection efficiencies for electrons – Depend on Vd-Vm … smaller is better Gain Without Mesh Va=450V Gain Va=450V With mesh (Vm=0V) Vd [-V] Vd [-V]

Current status of development

• Came up with the new idea  m -PIC with micro mesh • Prototypes were made and tested – Gas multiplicity of it is more than 3 times – Gain of 2 x 10 4 were attained • With prototype mesh (distance is about 300 m m) – More studies are needed for tuning up the parameters • Simulation studies  Keika will talk

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 m -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 m -PIC