TPC 　 PAD 　Optimization

Yukihiro Kato (Kinki Univ.)

1. Motivation2. Simple Monte Carlo simulation3. PAD response4. PAD response for two tracks5. Summary & Plan

Motivation ･ We are planning to use TPC with MPGD(Micro pattern Gas Detector) as a main tracker. ･ Advantage of MPGD

-- small E×B effect -- detect real electron with small spread　　　　 -- large gain (103-104) ･ Candidates of readout for TPC are GEM and Micromegas.

Study of PAD optimization!!

･ To achieve the fine spatial resolution and the two track separation on the TPC.･ Need fine pixel read out pad to achieve above items? 　

PAD shape & size

　･ σRφ= ~150μm (drift distance: 0~235cm)　･ 2 hit separation = ~2mm

　･ # of channel (12M channel @ 1mm ×1mm PAD)　･ Read out method (analog or digital etc.)

What determine the PAD shape?

Optimization of PAD by Simple Monte Carlo simulation

Estimate PAD shape & size by Monte Carlo Simulation.--- Using the detailed simulation(Geant4) is better way to optimized PAD shape.--- We start the PAD optimization using simple Monte Carlo simulation.

Simple simulation can optimize PAD size as first step. ･　 The electron generated along a track drift to MPGD. 　 → The electrons amplified by MPGD reach the PAD. ･ We estimate the number of electrons in PAD with various PAD sizes.

Simple Monte Carlo simulation

(1) Primary electron cluster is generated along a track.(2) Making the primary+secondary electron clusters.(3) Drift the electrons to GEM with dispersed by Diffusion .(4) Distributed the electrons at closest GEM hole.(5) GEM holes amplify the electrons.(6) Move the electrons to PAD with dispersed by Defocusing.(7) Counting the # of electron on each PAD.

Today’s results takes into account the effect (3) and (6).(First step of the very simple simulation) --- Gas diffusion constant: CD = 80μm/√cm (TDR gas, 3T) --- Defocusing : σ= 100μm --- GEM gain = 103

PAD response

･ Shape of PAD is a rectangle (1cm×0.15, 0.5, 1.0, 2.0 mm) ･ Generate Single primary+secondary

electron at a fix point. (# electron of the cluster is 100) ･ Making the distribution of electron

in the PAD and estimate the σ.

(PAD width : 150 μm ）

PAD response

PAD response(PAD width: 500 μm ）

PAD response

(PAD width : 1mm ）

PAD response

(PAD width : 2mm ）

PAD response for two tracks

･ Shape of PAD is a square.

･ The distance of two track is 2mm.

Both track pass through 45°

for X , Y-axis.

･ Generate electrons along a track

(# electron is 100/cm)

･ Making the distribution of electron

in the PAD and estimate the σ.

PAD response for two tracks(Drift distance is 235cm)

PAD response for two tracks(Drift distance is 235cm)

PAD response for two tracks(Drift distance is 235cm)

PAD response for two tracks(Drift distance is 20cm)

PAD response for two tracks(Drift distance is 20cm)

Summary & Plan

　･ Just started the PAD shape & size optimization by simple Monte Carlo simulation. ･ The size of electron dispersing due to the diffusion

of the drift gas. TDR gas is not good for MPGD/TPC.　･ Complete the simple simulation and find the good

PAD shape & size. ･ Further study – using the detailed simulation.