performance of gas sealed rpcs

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 - 140

332

0 69

28

RGA spectra was collected with background of Argon.


RGA analysis – 228

33

6983

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

020406080

100120140160

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

Cur

rent

(nA

)

AB06_+ve AB06_-ve

050

100150200250300350400


Cur

rent

(nA

)

AB04_+ve AB04_-veA

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


Cur

rent

(nA

)

AB07_+ve AB07_-ve

0

50

100

150

200

250

300


Cur

rent

(nA

)

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

Strip

Rat

e (H

z)

L00L06L05

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)

707580859095

100

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

Effic

ienc

y (%

)

EFF_X0EFF_X4EFF_X11

0

1

2

3


Mul

tiplic

ity MULT_X0MULT_X4MULT_X11


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

0

1

2

3


Mul

tiplic

ity MULT_X3MULT_X6MULT_X7MULT_X9

80

85

90

95

100


Effic

ienc

y (%

)

EFF_X3EFF_X6EFF_X7EFF_X9


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

0

1

2

3


Mul

tiplic

ity MULT_X2MULT_X5MULT_X8MULT_X1

70

75

80

85

90

95

100


Effic

ienc

y (%

)

EFF_X2EFF_X5EFF_X8EFF_X1

performance of gas sealed rpcs

Documents

gas topup

reduction of gas cost

days b

studyrecycling of gas

total gas volume

rga analysis

rga spectra

sealed rpcb