1 daya bay collaboration meeting, ihep, beijing, aug. 1-3, 2007 test opera gas mixture on ihep rpc...
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1Daya Bay collaboration meeting, IHEP, Beijing, Aug. 1-3, 2007
Test OPERA gas mixture on IHEP RPC w/ 8m long strip
C. Lu
Princeton University
2Daya Bay collaboration meeting, IHEP, Beijing, Aug. 1-3, 2007
Why OPERA RPC gas mixture?
OPERA RPC gas mixture:
Ar/R134A/Isobutane/SF6 (75.4/20/4/0.6)
Their test results:
Efficiency plateau Single’s rate
Notice very low HV used, plateau starts at 5400V! Also good plateau length!
Very low single’s rate, 17Hz/m2, 100 times lower than what we expect for Daya Bay RPC!!
Larger amount of Ar, less R134A, save gas cost.
3Daya Bay collaboration meeting, IHEP, Beijing, Aug. 1-3, 2007
Test on IHEP RPC with 8m long strip readout
ADC peak spectrum, calibration curve:
V(mV)=0.181*ADC(ch)+9.88
4Daya Bay collaboration meeting, IHEP, Beijing, Aug. 1-3, 2007
… Test on IHEP RPC
Efficiency plateau curve: Dark current:
5Daya Bay collaboration meeting, IHEP, Beijing, Aug. 1-3, 2007
Streamer induced signal after the buffer
HV = 5800V, 100mV/div, 80ns/div
6Daya Bay collaboration meeting, IHEP, Beijing, Aug. 1-3, 2007
…Streamer induced signal after the buffer
HV = 6200V, 100mV/div, 80ns/div
7Daya Bay collaboration meeting, IHEP, Beijing, Aug. 1-3, 2007
More R&D on OPERA gas mixture
The single's rate of OPERA RPC underground is remarkably low: 17Hz/m2 (NIM A572(2007)177), that means the intrinsic noise rate is extremely low, it is almost 2 orders of magnitude lower than the ordinary RPC performance.
Private communication with Alberto Garfanini of OPERA RPC group confirms the condition for them to get such low noise rate:
•Trigger threshold is 40mV;
•The rate is obtained with self-triggering scheme, w/o any other triggers, thus reveals the intrinsic noise rate of the RPC.
•Gas mixture used is a premixture of Ar/C2H2F4/iso-C4H10/SF6 (75.4/20/4/0.6%);
•Gas flow rate is 5 volume changes/day;
Alberto mentioned that with this gas mixture the after pulses are a bit higher, probability is a factor of two respect to our previous mixture 48/48/4 - babar, Santonico ....
8Daya Bay collaboration meeting, IHEP, Beijing, Aug. 1-3, 2007
… More R&D on OPERA gas mixture
• Flow rate influence on the single’s rate;
• After pulse study, how serious it will affect the random noise rate?
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