Transcript Mesh - SAGA-HEP

マイクロメッシュを用いた
高増幅率型μ-PICの開発
Development of m-PIC
using micro mesh
神戸大学
越智 敦彦、桂華 智裕
Kobe Univ. Atsuhiko Ochi, Tomohiro Keika
1. Introduction
2. Test operation of prototype
3. Simulation studies
3rd MPGD workshop @ Saga Univ. 26/Jan/2007
Introduction
Mesh
• Micro pixel chamber (m-PIC)
– Position resolution ( - 100mm)
– Timing resolution ( < 100ns)
– High rate capability
( > 107c/sec/mm2)
• With micro mesh
– Higher gain in stable
operation (>104)
400mm
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 m-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 m-PIC
– Supported by plastic film / nylon wire
• Support structure is future tasks
– Distance between m-PIC and wire
• About 300mm
– Micro mesh is connected to HV controller
• Operation gas
– Ar:C2H6 = 90:10
Micro scope pictures
for same place
0.5mm
(different focus point)
Micro mesh mounted on m-PIC by hand.
Size of m-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)
Drift Plane
Vd
Mesh
Vm
10 mm
Cathode
100mm
Anode
10 mm
信号
Va
Gain curve (Va, Vm dependence)
Gain
16000
14000
12000
no mesh
Vm=0V
Vm=-50V
Vm=-100V
Vm=-150V
10000
8000
6000
4000
2000
0
420
430
440
450
460
470
480
490
500
• Vd-Vm = 100V (Vd=2kV for no mesh plot)
• Gas: Ar(90%)+C2H5(10%)
• Source: Fe55 (5.9kV)
Va [V]
Collection efficiency problem
• Collection efficiencies for electrons
– Depend on Vd-Vm … smaller is better
Gain
Va=450V
Without Mesh
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 104 were attained
• With prototype mesh (distance is about 300mm)
– More studies are needed for tuning up the
parameters
• Simulation studies
 Keika will talk
Optimization of parameters
for μ-PIC with micro mesh
マイクロメッシュμ-PICの
最適動作パラメーターの探索
2007.1.26-27 MPGD workshop
@Saga Univ.
Kobe Univ.M2 Tomohiro Keika
神戸大学 桂華 智裕
Simulation Study
Optimization for detector parameters
•Structure
3D simulation
•Operation voltage
micromesh
Parameters
•Height of micro mesh
•Mesh Voltage (Vm)
•Drift Voltage (Vd)
（Anode Voltage is fixed）
Height
Cathode
Anode
We optimize the height of micro
mesh using a simulation.
About simulation software
Maxwell3D
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.)
Garfield
2D・3D field simulator made by CERN
•Feed maps made by Maxwell3D to Garfield
•Calculate electromagnetic field , gas gain and so
on.
Geometry drawing
Height of micro mesh Micro mesh
100μm
Cathode
Polyimide
or
200μm
or
500μm
Anode
We compare the three patterns.
Height
100μm
200μm
500μm
Effect using micro mesh
Micro mesh
Anode
Anode
No micro mesh
(Va=450V)
Micro mesh 100μm
(Va=450V,Vm=-100V)
Color display of electric field
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
Gas gain of μ-PIC without micro mesh is
2.2 10
4
（Va=450V,Vd=-5000V）
→It is the comparative data.
Dependences of gas gain on Anode
Voltage and Height of micro mesh
Gain
条件：Va=450V,Vm-Vd=100V
2.2 104
Supply voltage to micro mesh
赤：Mesh100um
青：Mesh200um
緑：Mesh500um
Select these parameters
to compare the electric
field near micro mesh.
Dependences of gas gain on
Anode Voltage and Height of micro
meshWe had better lower the
500μm
200μm
Electric field
100μm
electric field near micro
mesh to prevent electric
discharge.
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
Distance from the subtrate to micro mesh Vm=-300V,Vd=-400V
Collection efficiency
Terminal points of electron on the electrode plane or micro
mesh.
Vm=0V
Anode:37%
No-Anode:3.6%
Mesh:60%
Vm=-200V
Anode:37%
No-Anode:21%
Mesh:41%
Results
Study for the optimization using a 3D simulation.
(Qualitative interpretation)
Gain dependency on voltage of mesh
Vm increase
Gain rise
Collection efficiency decrease
But
Gas gain get more increased
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
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