Water Tank

as the Outer Muon Veto

Mingjun Chen

2006-06-10@IHEP

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Outline

Past work As the muon veto MC simulation Future Plan

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Schematics of a water tank.

Material of water tank ： PVC Size ： 1m×1m×13m Shape of two ends ： Winston Cone Inner wall covered by 1070D Tyvek and Al film with 90% reflectivity 8-inch photomultipliers installed in two ends as the photons’ collectors Clean de-ionized water (>10MΩ·cm) is used A simple water purification system with 0.1μm filter

We built a water tank prototype:

Middle point of water tank is set as the origin of coor

dinate system

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Water Tank

Prototype

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Position Dependent Response of the Water Tank

The muons vertically pass through the prototype at the different positionsX is the distance from the trigger counters to the PMT at right

Effective absorption length of the water tank: 5.74+/-0.29(m)

Energy Res. 7%/Sqrt(E(GeV))

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Angular Dependent Response of the Water Tank

The track lengths of all data points are normalized to 1m

at x=0.5mMuons pass through the prototype with different angles

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Elevation:

Use water tank as the muon veto

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Two 8-inch PMTs

Al Mirror Reflector

16m

Top View:

Tyvek

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Advantages of Water Cherenkov DetectorCompared with RPC and plastic scintillator

Good detection efficiency(about 100% theoretically )

Not sensitive to the natural radioactivity of Daya Bay’s rock

Simple machine( the tanks immersed in water) Very low cost ( Use water as the media)

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MC simulation

To study the detection efficiency of Cherenkov photons

Based on GEANT4 and including the detailed optical model

The parameters of optical model come from the MC simulation program of the prototype

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Some parameters of MC simulation program:

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Nu

mb

er of D

etected p

ho

toelectro

ns

(m)

X is the incident position of the vertical mouns

10 muon run @1Gev

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Future Plan on the prototype:

Look for new reflector instead of Tyvek For example: reflective paint

Two PMTs installed in each end of water tank Redesign the optics collection system of two

ends ☺Use lens system

Better water purification system