マイクロメッシュを用いた 高増幅率型 μ-PIC の開発 Development of  -PIC using micro mesh 1. Introduction 2. Test operation of prototype 3. Simulation studies 4. Summary 神戸大学 越智 敦彦、桂華 智 裕 Kobe Univ. Atsuhiko Ochi, Tomohiro Keika

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

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 attain safely 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 300  m –Micro mesh is connected to HV controller Operation gas –Ar:C 2 H 6 = 90:10

0.5mm Micro scope pictures for same place (different focus point) Micro mesh mount 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 100  m Drift Plane Cathode Anode 信号 Vd Va Mesh Vm

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 Mesh With mesh (Vm=0V) Va=450V Vd [V] 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 –More studies are needed for tuning up the parameters Simulation studies  Keika will talk There are many issue to study –How to hold the mesh on detector? –Optimization of geometries and operation voltage? –2 dimensional readout and larger detection area –We have to get the budget for this project !!! There is no budget about this project yet !!