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

Ghislandi Stefano EP-DT Summer Student presentation 1 / 10

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.


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.


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.


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.


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);


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


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.

19/07/1219/07/13

19/07/1419/07/15

19/07/1619/07/17

19/07/1819/07/19

19/07/2019/07/21

19/07/2219/07/23

19/07/2419/07/25

19/07/2619/07/27

19/07/28

Date

0.15

0.10

0.05

0.00

0.05

0.10

0.15

0.20

Reco

very

inde

x [

A / d

ays]

Voltage 4000Voltage 5000Voltage 6000Voltage 7000Voltage 8000Voltage 9000Voltage 9800


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


Comparison of analysis software (2/2)

3000 3050 3100 3150 3200 3250 3300Sample number [2ns]

8100

8150

8200

8250

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

7900

8000

8100

8200

8300

Volta

ge [A

DC]

strip1strip2strip3strip4strip5strip6strip7


characterization of rpc operation with eco-friendly gas

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