Development and study ofGlass Resistive Plate Chambers

Satyanarayana BheesetteRoll number: 04412701

Supervisors

Prof Raghava Varma, IIT Bombay

Prof Naba Mondal, TIFR Mumbai

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Plan of the presentation

Introduction Principle of operation of a glass RPC Overview of the field Our prototype designs and fabrication RPC gas mixtures and gas system Cosmic ray muon telescope Data acquisition system Preliminary results RPC aging problem Future work plan

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Introduction

Neutrinos are one of the fundamental particles of matter. Electrically neutral and were initially thought to be mass less. Three types or flavors (eof neutrinos known.

Recent evidence indicates that neutrinos have mass and also experience mixing among these flavors.

Neutrino oscillations can explain the discrepancy between theory and observations about its flux; can be used to estimate its mass.

Pioneering experiments at the KGF underground laboratories. Formation of Indian Neutrino Observatory (INO) collaboration. Feasibility studies for setting up of a neutrino experiment in India

is in progress.

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Proposed INO detector

Magnetised iron calorimeter

Iron

RP

C

140

laye

rs

RPC dimension: 3m X 2m

No of chambers: 11K

No of channels: 220K

No of TDC channels: 3K

35KTons

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Principle of operation of a RPC

Two 2mm thick float glassesSeparated by 2mm spacers

2mm thick spacer

Glass plates

Graphite coating on the outer surfaces of glasses

Pickup strips

V-I model

Each discharge locally deadens the RPC. The recovery time is approximately

l

A

A

lRC

s 2)10 x (8.85 x 4 x )10 x ( -1210

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Our prototype designs: Single gap

Gas inlet

HV terminals

Graphite coat

Gas outlet

Spacer

Two versions

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Our prototype designs: Double gap

Double gap RPC for better detection efficiencies

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Jigs for RPC fabrication

A glued RPC

Resistivity measurement jig

A finished small area RPC

RPC fabrication jig

Glue and dispensers

Glass handlers

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Gas mixing and flow control unit

Gas mixing unit

Flow monitor

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P1P2

P3

P4P5

P6

Glass RPC under test

Muon Trigger =654321 PPPPPP

Schematic of Cosmic ray muon trigger

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Cosmic ray muon telescope setup

Mounting structure for flexible and precise telescope alignment

Paddle alignment detail

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Schematic of data acquisition system

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Data acquisition system electronics

NIM CAMAC

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V-I characteristics

Small RPC Large RPC

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Typical RPC pulse profile

RPC pulse

Muon trigger

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Noise rate and efficiencies

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Charge performance

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Timing performance

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Charge-time linearity

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RPC aging problem

Drop in efficiency, increase in noise rate and chamber current seen after a few weeks of continuous operation

Reports in the literature (Monolith, Belle etc)

Moister contamination in Freon gas, the culprit?

Use of SF6 instead of Freon preferred

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Controlled humidity test

Carlo Gustavino et al, LNGS

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AFM images of damaged electrodes

2scans 10scans

Damaged electrodes

Damaged electrodes

Raw glass

Raw glass

¶ 500nm structures of 100nm thick seen in the images

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SEM image of damaged electrode

6scan 2scan

Damaged electrode Fluorine: 38%

Raw glass Fluorine: 4%

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Future work plan

Systematic study of RPC stability problemFabrication of more large area RPCs and studiesDetailed studies on timing, spatial resolution, cross-talkOptimization of detector gas composition INO prototype detector; needs about 16 large area RPCsPerformance studies of prototype detector; comparison

of results with those from simulation studiesRPC Parameter inputs for electronics and data

acquisition system designFull pledged RPC device simulations

Backup slides

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RPCs of modern designs

Multi gapHybrid RPC Micro RPC

Applications in HEP research

Cosmic ray experiments: EAS-Top, Cover-Plastex, Argo, Auger

Accelerator based experiments: Belle, Babar, Star, Harp

Future experiments: Alice, ATLAS, CMS, LHCb

Medical applications etc

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Telescope stability monitoring

100000

120000

140000

160000

180000

200000

220000

240000

260000

280000

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16

Time, Hours

Tele

scop

e pa

ddel

rat

es

P1

P2

P3

P4

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Preliminary cross-talk measurements

Gas Mixture Tele window

(mm)Cross talk (%)

62:8:30 10 6.8

62:8:30 15 6.7

62:8:30 20 6.2

57:8:35 20 6.5

52:8:40 20 5.9

46:8:46 20 6.3

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Recovery of a damaged RPC

Purging with pure Argon at high flow rate.

Bubbling pure Argon through pure ethyl alcohol.

Bubbling pure Argon through 3% Ammonia solution for 24 hours with high voltage off.

Recovers efficiency and brings down noise rate.