M.Bhuyan, S.D.Kalmani, N.K.Mondal, S.Pal, Deepak Samuel, B.Satyanarayana and R.R.Shinde Gouranga Kole, Chiraag Lala and Kanishka Rawat

PERFORMANCE OF GAS SEALED RPCS

M.Bhuyan, S.D.Kalmani, N.K.Mondal, S.Pal, Deepak Samuel, B.Satyanarayana and R.R.Shinde

Gouranga Kole, Chiraag Lala and Kanishka Rawat

B.Satyanarayana, TIFR, Mumbai INO Collaboration Meeting, Madurai January 23-26, 2011

Requirement of gases in ICAL

GasAvalanch

e(%)

Streamer

(%)

Maximum(%)

Volume(L)

Density(g/L)

Weight(Kg)

Cost(Rs/Kg)

Argon 0.0 30.0 30.0 58,503 1.784 104.4

R134a 95.5 62.0 95.5 186,234.6 4.25 791.5

Isobutane 4.3 8.0 8.0 15,600.8 2.51 39.16

SF6 0.2 0.0 0.2 390 6.164 2.40

Total number of RPCs in ICAL = 3 150 64 = 28,800Total gas volume = 28,800 184cm 184cm 0.2cm = 195,010 litresFor example: One volume change/day with 10% gas top-up in a re-circulating schemeApproximate running gas cost = Rs 30,000/day (R134a from Mafron)


Motivation for this study Recycling of gas mixture for reduction of gas

cost and complying with environmental regulations.

Further reduction in the operating cost of ICAL in the long run without compromising on the detector efficiency and performance.

Study contamination and formation of radicals in the gas mixture flowing through the RPCs.

These kind of studies do not seem to have been performed by other researchers.


The first studyOne 1m×1m RPC (called AB13) was sealed on

February 5, 2010. Its operating parameters such as strip rate and current were monitored 24×7, along with laboratory temperature and

relative humidity. After 130 days of

uninterrupted operation, the gas

inside RPC was analyzed using a

Residual Gas Analyzer (RGA)


Lab temperature & noise rate


Noise rates of 8 strips


Lab temperature & current


RGA analysis - 1

40

332

0 69

28

RGA spectra was collected with background of Argon.


RGA analysis – 228

33

69

83

Removing the background Argon spectra, major fragment was at mass no. 28


RGA analysis - 333

69

8351

Removing the air background , major fragment was at mass no. 33


Summary of RGA RGA spectra

contains nearly 50% air and 3% water vapour.

RPC AB13 was sealed for 130 days.

Amount of air accumulated ~1000ml.

Therefore, the leak rate ~8ml/day.

Major fragments of pure gases


Sealed gas test for C217 stack

Stack of 12 1m×1m RPCs L0, L4 and L11 were used as reference Other RPCs sealed on April 27, 2010

Summary of the study

Sl. no

Layer No

RPC Name

Sealing date

Gas flow restarted

No of days sealed

1 L00 AB06 -------------- -------------- --2 L01 AB07 27-Apr-10 19-Jul-10 833 L02 AB10 27-Apr-10 19-Jul-10 834 L03 AB11 27-Apr-10 31-May-10 345 L04 AB09 -------------- -------------- --6 L05 IB02 27-Apr-10 19-Jul-10 837 L06 AB02 27-Apr-10 29-May-10 328 L07 AB01 27-Apr-10 29-May-10 329 L08 AB03 27-Apr-10 19-Jul-10 8310 L09 AB04 27-Apr-10 29-May-10 3211 L10 AB12 27-Apr-10 28-May-10 3112 L11 AB08 -------------- -------------- --


Reference and sealed RPC

0

20

40

60

80

100

120

140

160

28-Mar 12-Apr 27-Apr 12-May 27-May 11-Jun 26-Jun 11-Jul 26-Jul 10-Aug

Cu

rren

t (n

A)

AB06_+ve AB06_-ve

0

50

100

150

200

250

300

350

400


Cu

rren

t (n

A)

AB04_+ve AB04_-ve

A

B

A= RPC Sealed for 32 days B = Gas flow restarted

Reference RPC


RPCs sealed for 83 days

0

50

100

150

200

250

300

350

400


Cu

rren

t (n

A)

AB07_+ve AB07_-ve

0

50

100

150

200

250

300


Cu

rren

t (n

A)

IB02_+ve IB02_-ve

A

A

B

B


Comparison of leaky RPCs

0

50

100

150

200

250

300

350

21-Feb 23-Mar 22-Apr 22-May 21-Jun 21-Jul 20-Aug 19-Sep 19-Oct

Str

ip R

ate

(H

z)

L00

L06

L05

A

B

C

A = Sealed (L05, L06) B = Flow started (L06) C = Flow started (L05)


Repair of leaky RPCs

Pressurise the chamber to 20-30mm water column.

Look for the leak. Locate the leaks using gas

sniffer. Plug the leaks with glue. Redo the above till all the

leaks are plugged.


Summary of sealed gas testLayer RPC

Id Test L rate I end I begin I I rate R end R

begin R R rate

(Days)(mm/hr)

(nA) (nA) (nA)(nA/day)

(Hz) (Hz) (Hz)(Hz/day)

0 AB06 (Ref) TBD - - - - - - - -

1 AB07 83 TBD 241 38 203 2.4 416 15 401 4.8

2 AB10 83 1.3 190 19 171 2.1 505 30 475 5.7

3 AB11 34 12 262 47 215 6.3 377 81 296 8.7

4 AB09 1 72 - - - - - - - -

5 IB02 83 TBD 120 68 52 0.6 100 40 60 0.7

6 AB02 32 TBD 302 69 233 7.3 377 37 340 10.6

7 AB01 32 TBD 266 67 199 6.2 344 45 299 9.3

8 AB03 83 TBD 182 21 161 1.9 256 52 204 2.5

9 AB04 32 TBD 355 55 300 9.4 1067 70 997 31.2

10 AB12 31 10 492 46 446 14.4 934 31 903 29.1

11 AB08 (Ref) 12 - - - - - - - -


Conclusions Different rate of change of strip rate and

current with time may be attributed to different leak rate for different RPCs.

With proper sealing condition, the detector can run for at least one month, once filled, reducing the cost by factor of 30.

The gas can be recovered efficiently with more contaminants by reusing the same gas for longer period of time.

All the RPC parameters have come back to their earlier values after reflowing fresh gas through RPCs.


Tracking efficiency & Multiplicity (L0,L04,L11)

70

75

80

85

90

95

100

23-Mar 22-Apr 22-May 21-Jun 21-Jul 20-Aug 19-Sep

Eff

icie

ncy

(%)

EFF_X0

EFF_X4

EFF_X11

0

1

2

3


Mu

ltip

licit

y

MULT_X0

MULT_X4

MULT_X11


Tracking efficiency & Multiplicity (L3,L6,L7,L9)

0

1

2

3


Mu

ltip

licity MULT_X3

MULT_X6

MULT_X7

MULT_X9

80

85

90

95

100


Eff

icie

ncy

(%)

EFF_X3

EFF_X6

EFF_X7

EFF_X9


Tracking Efficiency & Multiplicity (L1,L2,L5,L8)

0

1

2

3


Mu

ltip

licit

y MULT_X2

MULT_X5

MULT_X8

MULT_X1

70

75

80

85

90

95

100


Eff

icie

ncy

(%)

EFF_X2

EFF_X5

EFF_X8

EFF_X1


Documents

M.Bhuyan, S.D.Kalmani, N.K.Mondal, S.Pal, Deepak Samuel, B.Satyanarayana and R.R.Shinde Gouranga Kole, Chiraag Lala and Kanishka Rawat