COSMIC RAY MUON DETECTION USING COSMIC RAY MUON DETECTION USING SCINTILLATION COUNTERSCINTILLATION COUNTER

AND AND WAVELENGTH SHIFTING FIBERSWAVELENGTH SHIFTING FIBERS

ARUNODAYA BHATTACHARYA VSRP-2009,TIFR,MUMBAI 6/7/09

•Motivation•Tools used•Experimental setup•Data collection•Analysis of data•Results•Future Plans

Topics coveredTopics covered

MotivationMotivation

• Scintillator detectors are used for detecting muons in many High energy physics experiments like the CMS experiment. In this experiment they have a geometry of four wavelength shifting fibers in each scintillator tile for trigger generation.

• But tiles are big, so difficult to localize muon event on the tile.

• If we read each fiber independently then we may improve our trigger condition.

• For this we need a reference for determining muon position on scintillator.

• To independently determine the position of the muon, Resistive Plate Chambers (RPC) are used in the INO lab.

• Photomultiplier tubes are used as read-outs for the optical fibers.

MuonsMuons

• Fundamental charged particles-LEPTONS

• One unit of charge

• Produced by decay of pions

• Mean life time=2.2μsec.

• Mass is 210 times the mass of electron.

Construction of PaddleConstruction of Paddle• Paddle=Scintillator+optical fibers+Photomultiplier tube

• Organic (plastic) scintillator – polyvinyl toluene

• Light is produced when charged particle passes through it

• We use four wavelength shifting fibers embedded in the scintillator to transmit light to the Photomultiplier tube.

• Wavelength shifting fibers are spliced with clear low attenuation optical fibers at the end of the tile to avoid signal loss.

• Initially all four fibers are coupled to one PMT .

• In the second stage of the experiment each fiber is read out separately to study light collected by single fiber.

PMT

SCINTILLATOR

30cmx30cmx1cm

SCINTILLATOR

30cmx30cmx1cm

4 PMT

s

Photomultiplier tube and BasePhotomultiplier tube and Base

198.9K

21R7

6

Dy7

199.8K

1

R8

8

Dy8

199.7KR9

4.7nF

0.01uF

7

Dy9

198.8KR10

17

Dy10

198.5KR11

Dy11

16C5

R12

Dy12

2

+HT

0.01uF

198.6K

15 SIGNAL

Focussingelectrode

198.4kR13

Dy1

Cathode

198.5kR14

Dy2

R2

3

198.7KR1

R15

4.7nF

Dy3

14

Anode

249K

R16

Dy4

0.01uF

4

C6

1K

C1

R3

13

0.01uF

820K

10C2

R4

5

Dy5

199K

Bleeder resistance=3.32M Ohms

C3

R5

12

Dy6

50k

268K

C4

R6

4

MAIN PADDLE

21

22.5cm

24.5cm

DELAY

COINCIDENCE

COINCIDENCE

3FSCALAR

SCALAR4-Fold

23.5cm

Dimensions:

Pad.1=20cmx2cmx1cm

Pad.2=20cmx5cmx1cm

Pad.3=30cmx20cmx1cm

Pad.4=30cmx20cmx1cm

Operating voltage of PMT and Noise RateOperating voltage of PMT and Noise Rate

SCALAR

Efficiency=(4F/3F)X100 %

NIM

DISC.

Vth= -30mV

3-Fold

VARIATION OF EFFICIENCY AND NOISE RATE OF PADDLE

0

20

40

60

80

100

120

1000 1200 1400 1600 1800 2000

Applied voltage(v)

Eff

icen

cy(%

)

0

20

40

60

80

100

120

140

160

Noi

se ra

te

EFFICIENCY NOISE RATE

1650V

RESISTIVE PLATE CHAMBERS

Independent measurement required to confirm “MUON” event

• Gas filled detector

with glass electrodes• Gas composition

Freon=95.15%

Isobutane=4.15%

SF6=0.34%• Resistivity of

glass=10^(12)cm• Width of pickup

strips=2.8cm

1m

1m

10kV is applied between glass plates.!

Charge particle produces an avalanche in the gas which induces signal on pick-up strips.

V-I Characteristic of RPCV-I Characteristic of RPC

Equivalent circuit of RPC

V-I CHARACTERISTIC OF RPC

0

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0 1000 2000 3000 4000 5000 6000

Applied voltage(V)

Curr

ent(n

A)

Operating voltage

Final Experimental setupFinal Experimental setup

GIVE THE STACK DIAGRAM!!!

17

27

GEOMETRY ALIGNMENT OF THE SCINTILLATOR ON THE RPC LAYER02

21

X-STRIP NUMBER

28

20

Y-S

TRIP

NU

MB

ER

20212223

16 15

19

1419

24

22

25SCINTILLATOR

23 18

26

RPC LAYER02

RPC is triggering our paddle!

Trigger Generation And Analysis of the OutputTrigger Generation And Analysis of the Output

RPC STACK

12LAYERSSCINT.

PADDLE

ADC

GATE

INPUT

DATA ACQUISITION SYSTEM

RPC DATA

X-Y POSITIONOF MUONPROCESSED DATA

COMPUTER CONSOLE

8-Fold TRIGGER

ANALOG

PULSE

C

A

M

A

C

B

U

S

ADC OUTPUT

DELAY

COMPUTER CONSOLE

Signal attenuation due to delay cablesSignal attenuation due to delay cables

• Paddle pulse is delayed for coincidence with the RPC trigger• Gate width =53.4nsec.• Net delay imparted = 198nsec.• Percentage decrease in paddle pulse height=58%

RPC TRIGGER

PMT PULSE

Histogram of ADC Output

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90000

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ADC output

Co

un

ts

Histogram of ADC output

0

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6000

7000

8000

0 5 10 15 20 25 30 35 40 45 50 55 60 65 70

ADC output

Co

un

ts

Pedestal peak

Muon signal distribution

Change over to Single FiberChange over to Single Fiber

• Three out of four optical fibers are cut from the PMT cookie.

• Only one fiber is connected to PMT now.

• Paddle is aligned again on the RPC stack as done earlier.

• We want a synchronized run of the Data Acquisition System of RPC and ADC.

We did not get any muon signal distribution with single fiber.

This has happened due to the attenuation because of long cables!!!

Histogram of ADC output

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10 20 30 40 50 60 70 80

ADC counts

Co

un

ts

Pedestal peak

No muon signal !!!

• Since muon signal is very weak, we used “STORAGE OSCILLOSCOPE”

• Initially we studied with four fibers.

Ch.2

Ch.1Paddle Pulse

8F RPC Signal

Ch.2 TRIGGERS

WE AVOIDED DELAYING PADDLE PULSEAND HENCE

THE ATTENUATION

Ch.1

STORAGE

OSCILLOSCOPE

Major Problems to solve:Major Problems to solve:

• We need to synchronize the Data Acquisition System of RPC and ADC or storage oscilloscope .This can be done by lowering the trigger rate from the RPC.

• We need to somehow find a solution to avoid the attenuation of the paddle pulse.

Trigger rate from RPC is higher than the sampling rate of the storage oscilloscope. So, we can’t correlate the data corresponding to x-y position of muon and their pulse height.

Future workFuture work

• Since signal attenuation is difficult to avoid, we will amplify the PMT signal by charge amplifiers and obtain good pulse height.

•We will reduce the trigger rate from the RPC to achieve a correlation between the x-y position of the muon and the corresponding pulse height from the scintillator.

ACKNOWLEDGEMENTACKNOWLEDGEMENT

Prof.Sudeshna Banerjee

B.S.Satyanarayana

L.V.Reddy

And all the lab members!

Thank You!

Graph between ADC output and Signal and Pedestal counts

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ADC counts

freq

.of p

edes

tal+

padd

le

0

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6000

8000

10000

12000

14000

freq

. of p

edes

tal

pedestal+paddlepedestal

Graph between ADC output and Signal and Pedestal counts

0

1000

2000

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4000

5000

6000

7000

10 15 20 25 30 35 40 45 50 55 60 65 70

ADC counts

freq

.of p

edes

tal+

padd

le

0

2000

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6000

8000

10000

12000

14000

freq

. of p

edes

tal

pedestal+paddlepedestal

X- (mm)

y

(mm)

Muon signal

distribution

Pedestal

distribution

Scintillator tile area We expected larger

ADC count in the tile area!!!!

Maybe there is a mismatch between DAQ system of RPC and ADC!!!

ADC Count plot

!Problem needs to be figured out!

Plateau curve and Noise Rate

GEOMETRY ALIGNMENT

4

MAIN PADDLE

21

22.5cm

23.5cm

24.5cm

3F

1,2,3,4=PADDLES

4F

D=DISCRIMINATOR = -3OmV

S1

S=SCALAR

11615

2

S2

D11

S3

D3 DELAY

2 D2

3

D4

MAINPADDLE

1

23

4

Dimensions:

Pad.1=20cmx2cmx1cm

Pad.2=20cmx5cmx1cm

Pad.3=30cmx20cmx1cm

Pad.4=30cmx20cmx1cm

VARIATION OF EFFICIENCY AND NOISE RATE OF PADDLE

0

20

40

60

80

100

120

1000 1200 1400 1600 1800 2000

applied voltage(v)

Eff

ice

nc

y(%

)

0

20

40

60

80

100

120

140

160

no

ise

ra

te

EFFICIENCY NOISE RATE

1650V

Graph between ADC output and Signal and Pedestal counts

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20000

30000

40000

50000

60000

70000

80000

90000

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10 15 20 25 30 35 40 45 50 55 60 65 70

ADC counts

freq

.of

ped

esta

l+p

add

le

0

2000

4000

6000

8000

10000

12000

14000

freq

. o

f p

edes

tal

pedestal+paddlepedestal

With four fibers going to one PMT

Graph between ADC output and Signal and Pedestal counts

0

1000

2000

3000

4000

5000

6000

7000

10 15 20 25 30 35 40 45 50 55 60 65 70

ADC counts

freq

.of

ped

esta

l+p

ad

dle

0

2000

4000

6000

8000

10000

12000

14000

freq

. o

f p

ed

esta

l

pedestal+paddlepedestal

Plateau curve and Noise Rate

GEOMETRY ALIGNMENT

4

MAIN PADDLE

21

22.5cm

23.5cm

24.5cm

Dimensions:

Pad.1=20cmx2cmx1cm

Pad.2=20cmx5cmx1cm

Pad.3=30cmx20cmx1cm

Pad.4=30cmx20cmx1cm

1650V

VARIATION OF EFFICIENCY AND NOISE RATE OF PADDLE

0

20

40

60

80

100

120

1000 1200 1400 1600 1800 2000

Applied voltage(v)

Eff

icen

cy(%

)

0

20

40

60

80

100

120

140

160

Noi

se r

ate

EFFICIENCY NOISE RATE

268K

2 9 .7 8 V

R 8

1

198.9KR 9

0 . 0 1 u F

6

4 . 7 n F

D y7

199.8K

0 . 0 1 u F

R 10

2 9 .5 0 V8

D y8

199.7K

17

492.6V

R 1

7

D y9

R 11198.8K

2 9 .8 1 V16

D y10

R 12198.5K

2

0 . 0 1 u F

D y11

C 51 5

D y12

3 9 .7 5 V

+ H T

R 13198.6K

2 9 .7 5 VSI G N A L

R 2 R 14

F ocussingelectrode

198.4k

2 9 .7 7 V3

D y1

R 15

C athode

198.5k

2 9 .8 9 V

4 . 7 n F

D y2

0 . 0 1 u F

R 16

198.7K

2 9 .7 5 V

R 3

D y3

14

C 1

A node

249K

2 9 .8 1 V

R 4

D y4

4

C 2

C 6

1K

2 9 .7 6 V

R 5

13

C 3

5 0 k

820K

10

2 9 .7 2 V

R 6

5

D y5

C 4

199K

B le e de r re s is ta nc e = 3 .3 2 M O hm s

2 9 .7 1 V

R 7

12

Dy6

21

Bleeder circuit of PMT base

LAYE R 00

1

PADDLE

G A T E

ADC

RPC

1 82T R IG G E R

DISCRIMINAT OR; -20mV T HRE SHOLD

1 82

1 82

8F

1 82

1 82

LAYE R 01

DE LAY

CA

MA

C B

US

LAYE R 02

5.2ns ec ./m of c able

DEL A Y

LAYE R 03

LAYE R 04 1

2345

6789

LAYE R 05

1 82

1 82

LAYE R 06

1 82

LAYE R 07

1 82

PC

Study of Muon pulses using RPC trigger

Histogram of Pulse height of the Paddle pulses

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Pulse height(mV)

Cou

ntTotal sample 11310

Magnified scale histogram of pulse height

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Pulse height(mV)

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un

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Total sample 2114

Result with Single Fiber

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8 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40 42 44 46 48 50 52 54 56 58 60

ADC counts

Cou

nts

Histogram of ADC output

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ADC counts

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nts

Count Rate Of The Paddle Constructred

0123456789

-80 -70 -60 -50 -40 -30 -20

Discriminator voltage(mV)

Coun

t rat

e(pe

r sec

ond)