hep.uni-freiburg.detalkskircherGasMeetingTalk.ppt

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					         Atlas MDT ageing test

                Sven Kircher
                  04.04.01
            University of Freiburg



•Goal of MDT ageing test
•Setup
•Results of ageing tests
•Test of single components & cleaning agents
                     Goal of MDT ageing tests

Single Tubes                                       MDT Operating Point
•Number : 380000                                   •Drift gas: Ar-CO2 (93-7)
•Length : up to 6m                                 •Gas gain: 2*104
                                                   •HV: 3080V

Rates :                                            Goal :
high γ and n Background
 Countrates up to 300Hz/cm                        Lifetime > 0,6 C/cm




                                                 Ar-CO2 „Baseline Gas“
                                                 Ar-CH4-N2-CO2 „R&D Gas“

04/04/01               Sven Kircher, University of Freiburg                    2
     Differences between Ar-CH4-N2-CO2 und Ar-CO2
                             700

                                         ArCO2
                             600
                                         Ar-CH4-N2-CO2
                             500
           Driftzeit in ns




                             400


                             300


                             200


                             100


                              0
                                   0,0               0,5                  1,0    1,5
                                                           Radius in cm




                             Drift Properties
                             •Ar-CO2 (93-7)
                                 •non linear  not stable against (p, T, E)
                                 •slower  höhere Okkupanz

04/04/01                                  Sven Kircher, University of Freiburg         3
                 Ageing Setup in Freiburg
                            Title:
                            Aufbau_1_5.eps
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           • 80 individual tubes
           • Active zone 2.5 - 8cm
           • 4 different irradiation rates (4 distances)
           • 2 different gas flows (2 & 20 h/vol. ex.)
           • 2 different gas mixtures
04/04/01            Sven Kircher, University of Freiburg                4
                   Purity of Components
Gas    Quality       Impurities   Price/Bottle
Ar 5.0 99.999% CnHm<1ppm, Air<10 65 CHF
CO2 4.5 99.995% CnHm<1ppm, Air<10 250 CHF
H2O double distilled              10 CHF ???



  Gas system:                                              Never tested
  • All tubes stainless steel                               for Atlas
  •All vales without O-rings or grease
  •No circulation of gas

04/04/01            Sven Kircher, University of Freiburg                  5
                                             Effect of H2O in the drift gas
        Ar-CH4-N2                                  Ar-CH4-N2-CO2                                                        Ar-CO2
                                                                                         Title:
Title:                                             Title:                                ../mn_simulmess 93_7ma00.drif tmax .eps
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../nim_simulmess datc ha_00.m ax.eps               ../nim_simulmess newgas_00.max.eps    HIGZ Vers ion 1.23/07
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                                       H2O in drift gas desired because of
                                       •Mechanical stability of plastic over long time
                                       •Electrical stability


 04/04/01                                         Sven Kircher, University of Freiburg                                             6
                                    Examples of dying tubes in Ar-CH4-N2-CO2
Title:                                                                        Title:
/us ers/us e/atlas/of fline/mutage/results/besorg/tube                        /us ers/us e/atlas/of fline/mutage/results/besorg/tube
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 04/04/01                                                Sven Kircher, University of Freiburg                                          7
             Dependence on Voltage in Ar-CH4-N2-CO2
       Title:
       ../ps files /ageing_hv q_d.eps
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                Q:= Total Charge/Length = Charge until 70%-Level
                Equal Colors = identical parameters except Voltage

                         Strong HV-Dependence of Lifetime Q
04/04/01                                  Sven Kircher, University of Freiburg   8
                    Dependence on Rate in Ar-CH4-N2-CO2
       Title:
       ../ps files /ageing_rateq_d.eps
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                Q:= Total Charge/Length = Charge until 70%-Level
                  Equal Colors = identical parameters except rate

                          Strong rate-dependence of lifetime Q
04/04/01                                  Sven Kircher, University of Freiburg   9
    Dependence on irradiation zone in Ar-CH4-N2-CO2
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       ../ps files /ageing_leadq_d.eps
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         Q:= Total Charge/Length = Charge until 70%-Level
      Equal Colors = identical parameters except irradiation zone

                          Strong irradiation zone dependence of lifetime Q
04/04/01                                  Sven Kircher, University of Freiburg   10
                                      Dependence on gas flow in Ar-CH4-N2-CO2
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                           4000                                                                Merlin-along2-tube10-12.eps
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                                                                                               pasc hhof @pcf rhl with x mgr
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 Total Charge Q in mC/cm




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                           3000                                                                other ty pes of printers.




                           2000




                           1000
                                                     Errorbars are 40% of Total Charge



                              0
                                  0            200                   400                 600
                                                  Gas Flow in ml/h




                                      Q:= Total Charge/Length = Charge until 70%-Level
                                      Equal Colors = identical parameters except gas flow

                                             Strong gas flow dependence of lifetime Q
04/04/01                                                           Sven Kircher, University of Freiburg                           11
                                   Dependences of lifetime in Ar-CH4-N2-CO2
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../ps files /ageing_hv q_d.eps
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                                                          Total Charge Q in mC/cm
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                                                                                    2000




                                                                                    1000
                                                                                                              Errorbars are 40% of T otal Charge



                                                                                       0
                                                                                           0            200                    400                 600
                                                                                                           Gas Flow in ml/h




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                                                          Strong dependence of the lifetime
                                                          Q on HV, rate, flow and irr. zone
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                                                          Extrapolation to Atlas-Operating
                                                          Point (600cm, 300Hz/cm, 3130V)
Title:
                                                          not possible
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                                                          “Perfect ageing test”:
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                                                          full length, design gas                                                                        X5
                                                          flow and higher rate &
                                                          HV
  04/04/01                                   Sven Kircher, University of Freiburg                                                                             12
           Dependence of lifetime in Ar-CO2 93-7
                 Ar-CO2 (90-10) :
                    •Number: 47 Tubes                      •Source: 137Cs (660 keV)
                    •HV: 3400V, 3440V                      •Rate: 1,8 kHz/cm
                    •Irradiation Zone: 3,4 m

                      • 100% efficient after 0,6 C/cm

  =0
 (no sign of     Ar-CO2 (93-7) :
   ageing)          •Number: 21 Tubes           •Source: 241Am (60 keV)
                    •HV: 3400V, 3500V           •Rate: 0,8–12,5 kHz/cm
                    •Irradiation Zone: 2,5 – 8 cm

                     100% efficient after 1,3 C/cm (avr.)
                      one tube 4,8 C/cm


04/04/01            Sven Kircher, University of Freiburg                         13
                     Noise in Ar-CO2 93-7
X5-1998:
3 out of 48 tubes became noisy during the ageing experiment
No explanation found
FR-2000
13 out of 16 tubes noisy before start of any experiment
Reason most likely dirt from production

Aleksa-1998
M. Aleksa investigated location of noise
Source believed to be very localized spots in the tube
Another hint on dirt

           Cleanliness during production and in gas system
           is of paramount importance for LHC
04/04/01             Sven Kircher, University of Freiburg     14
                    Ageing tests of components
Mass test : Build tubes with final components & cleaning agent
   •HP (cleaning agent for tubes used by producer)
   •Acetone / Isopropanol (cleaning agent for tubes not used these days)

„Bubblertests“ : Put a lot of one component in the gas flow
   • EPDM (O-ring)
   •Apiezon (vacuum grease)
   •URON B3 (cleaning agent for brass tubes)
   •Pocan (gas jumper material)

                                                               Expectation :
                 Apiezon                                       Ar-CO2
    EPDM
                                                               No ageing
                                                               Ar-CH4-N2-CO2
                                                               Same Lifetime

04/04/01                Sven Kircher, University of Freiburg                15
                           Results of component tests
 Mass test
                Ar-CO2 : No ageing seen

                Ar-CH4-N2-CO2 :
                •Clear dependence on cleanliness in general found
                    (Acetone better than uncleaned)
                •No significant difference between Acetone and HP
 Bubbler test




                Ar-CO2 : EPDM, Apiezon, URON B3
                   •No ageing seen (all charges above 0,6 mC/cm)
                Ar-CH4-N2-CO2 : Apiezon, Pocan (Bubbler with strong g-Source)
                   •Pocan-Test a : 180 vs. 122 mC/cm (1,6 sigma)
                   •Pocan-Test b : 282 vs. 215 mC/cm (0,6 sigma)
                   •Apiezon-Test : 245 vs. 215 mC/cm (0,2 sigma)

                   Small effect                                Pocan-Test the only
                   with Pocan                                   one with g-source
04/04/01                       Sven Kircher, University of Freiburg                  16
                                Conclusion

                     Ar-CO2 93-7 is ageing resistant



                  Avoid impurities to keep this property



           Make gas system as simple and clean as possible !!!




            Only Pocan was tested with a radioactive source


04/04/01                Sven Kircher, University of Freiburg     17
           Ways to measure the drift tube efficiency
                                                                                     300


1.) Current (every 30m)
                                                                                     200
                                                                                                                              Mean




                                                     Entries
2.) Count Rate (every 30m)                                                           100




3.) Mean Pulse Height (every 3d)                                                       0
                                                                                           80      280          480         680         880
                                                                                                              ADC-Channel



4.) Ageing (∼ 4 times in a MDT-live)                                                 300




                                                      Mean Pulse Height in ADC-Chn
            ADC (irradiated )                                                        250

 ageing :                        66 %                                              200
           ADC ( NotIrradiated )
                                                                                     150


                                                                                     100                                 Not
                                                                                      50                              Irradiated
                                                                                                Irradiated
           No effects from electronics                                                 0
                                                                                            0        50               100         150         200
                                                                                                         Position along Wire in mm


04/04/01              Sven Kircher, University of Freiburg                                                                                    18

				
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