Characterization of RPC Operation with Eco-Friendly Gas ...
Transcript of Characterization of RPC Operation with Eco-Friendly Gas ...
Characterization of RPC Operation with
Eco-Friendly Gas Mixtures
Summer Student: Stefano Ghislandi
Department: EP-DT-FS Fluidic system
Supervisors: Guida Roberto, Mandelli Beatrice, Rigoletti Gianluca
August 20th, 2019
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Introduce myself
Name: Stefano Ghislandi
Country: Italy
University: Universita degli Studidi Milano-Bicocca, Italy
My studies: I’m a graduatedphysics student. Now I’mattending particle physics mastercourses.
My project here at CERN is about testing RPC performances with neweco-friendly gas mixtures, in order to reduce the greenhouse gasemissions coming from particle detectors.
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What are greenhouse gases?
A Greenhouse gas (GHG) is a gas that irradiates thermal energy, it contributesto cause the greenhouse effect.
⇓ How to estimate emissions?
Global Warming Potential (GWP): index of the energy absorbed by an emitted gasrelative to CO2 whose GWP is 1.
RPC system have the highest LHCGHG emissions.
RPC standard gas mixture (ATLAS,CMS):
- 95.2% C2H2F4, also called R134a(GWP 1430);
- 4.5% iC4H10 (GWP 3.3);
- SF6 (GWP 22800).
The European Union has adopted legislative acts to control emissions from fluorinatedgreenhouse gases.The CERN has a strategy to reduce GHG emissions from particle detectors includingthe use of new Eco-Friendly gas mixtures.
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RPC (Resistive Plate Chambers)
HV
Ionizing particle
Readout strips
Foam
External frame
Polycarbonate spacer
Insulating layer
Bakelite sheet
Gas mixture
Main parameters:
• Efficiency;
• Streamer probability;
• Deposited charge;
• Time resolution (FWHM of the timedistribution);
• Cluster size (Number of consecutive stripsfired);
How it works:
• Intense and constant electric fieldbetween the two bakelite sheet;
• Suitable gas mixture flowed inside;
• When a particle passes through, itproduces primary ionization electronswhich start a multiplication;
• The produced charge reaches thebakelite sheets inducing a signal on thereadout strips.
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Setup at lab256
GAS MIXING RACK● Can mix up to 6 different gases;● With MFC can measure precisely the
gas flow.
RPCs SETUP● 2 scintillators used as trigger for cosmics
muon;● 2 bakelite RPCs single gap (2mm).
GAS ANALYSIS● Gas chromatograph and mass
spectrometer (GCMS);
ACQUISITION SETUP● Digitizer V1730 (2Vpp, 500 MS/s,
14 bit);● Coincidence measures system.
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Reference measurements
GOALTest RPCs performances using new
gas mixtures with eco-friendlycomponents.
⇒ Measures with standard mixturesneeded as reference.
[Ongoing] HFO instead of R134a longterm stability measurements are givingfirst promising results.
[Ongoing] NOVEC gases instead ofSF6 (current work);
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Setup at GIF++
The high-luminosity LHC (HL-LHC), with the increasing luminosity, will producehigher particle background.
⇓At Gamma Irradiation Facility (GIF++), located in H4 beam line in EHN1, studies of
long term detector response under high irradiation condition.
Measure of long term aging for 2 RPCswith HFO standard mixture (ATLAS,CMS), irradiated with:
• 13.2 TBq source of 137Cs (662 keVgamma);
• Up to 100 GeV muon beam.
Previous measures showedcurrents raise and sensibledrop of performances
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Chamber recovery
Studies of RPCs recovery at lab256; different flux and voltage conditions.
To evaluate the improving conditions of RPC:
Recovery index := ∆currents
Time[days]
• High raise of current few days laterthe irradiation;
• Currents lower with time;
• Better recovery indexes for higherflows and voltages;
• Weak dependence on temperatureand pressure.
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Reco
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x [
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ays]
Voltage 4000Voltage 5000Voltage 6000Voltage 7000Voltage 8000Voltage 9000Voltage 9800
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Comparison of analysis software (1/2)
I’ve also taken into account two different signal analysis script comparing theiralgorithms and outputs:
1. Read and study the algorithms;2. Adapt them to receive the same input data;3. Compare the outputs trying to deeply understand their differences;4. Modify one of the two script including the pros of the other one and solving
issues.
3000 3050 3100 3150 3200 3250 3300Sample number [2ns]
8280
8290
8300
8310
Volta
ge [A
DC]
Event for script A and not for script B
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Comparison of analysis software (2/2)
3000 3050 3100 3150 3200 3250 3300Sample number [2ns]
8100
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8300
Volta
ge [A
DC]
SignalScript A upper integration boundaryBaselineScript B charge upper boundary
Cluster size script A = 7 7
Cluster size script B = 1 7⇓
Corrected algorithms
Computed charge script A = 3.8pC
Computed charge script B = 7.7pC
⇓Not compatible calculation
⇓Corrected bugs and modified algorithm
thresholds.
3000 3050 3100 3150 3200 3250 3300 3350 3400Sample number [2ns]
7600
7700
7800
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8300
Volta
ge [A
DC]
strip1strip2strip3strip4strip5strip6strip7
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