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 神戸大学 越智 敦彦、桂華 智 裕 Kobe Univ. Atsuhiko Ochi, Tomohiro Keika 3 rd MPGD Saga Univ. 26/Jan/2007

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 be attained 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 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 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 –Gain of 2 x 10 4 were attained With prototype mesh (distance is about 300  m) –More studies are needed for tuning up the parameters Simulation studies  Keika will talk

Optimization of parameters for μ-PIC with micro mesh MPGD 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. Anode Cathode micromesh Height Optimization for detector parameters Structure Operation voltage 3D simulation

About simulation software Maxwell3D 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 mesh 100μm 200μm 500μm or Height of micro mesh Cathode Anode Polyimide Height 100μm 200μm 500μm

Effect using micro mesh No micro mesh (Va=450V) Micro mesh 100μm (Va=450V,Vm=-100V) Micro mesh Color display of electric field Anode

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. Gas gain of μ-PIC without micro mesh is

Supply voltage to micro mesh 赤： Mesh100um 青： Mesh200um 緑： Mesh500um Gain 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

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=-400V Distance from the subtrate to micro mesh 100μm 200μm 500μm Electric field We had better lower the electric field near micro mesh to prevent electric discharge.

Collection efficiency Terminal 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 10 4 with micro mesh (Va=450V, Vm=-400V, Distance=500um) : 2.0 x 10 5 Results Gas gain get more increased But 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