TPC Gas Studies with MP-TPC

Document Sample
TPC Gas Studies with MP-TPC Powered By Docstoc
					              TPC Gas Studies
               with MP-TPC
                    (cosmic ray test)

                                  Ryo YONAMINE
                                   KEK Master Student




MP-TPC:
Multi-Prototype-TPC(small test chamber)
MP-TPC was manufactured at MPI.
INTRODUCTION
R&D on 3D gasous tracker for ILC


Under international collaboration for LC-TPC,
Asia group is investigating the performance of GEM-TPC

        Small prototype TPC study
           TU-TPC(@Tsinghua Univ.), MP-TPC(@KEK)


       Large prototype TPC study
          We are preparing for GEM panels for the large prototype(LP1).

          Tsinghua Univ. provided PC boards for the GEM panels.



In this report, I will talk about gas optimization for GEM-TPC.
                                                                                        cosmic ray
Why gas optimization ?                                            cosmic-ray Trigger Counter

                     TPC priciple                          GEM
                                                             +
                                                       Read-out Pads       Drift Volume


                     PC                      Flash ADC             Y
                                                                          X
                              Raw Data
                               • Charge                                    Z          Efield
                               • Pad ID
                               • DriftTime                             cosmic-ray Trigger Counter
                                                         • trigger signal
 Process from generation to detection of signals
        Ionization            Gas molecules are ionized along tracks of incident particles.
                              The generated clusters of electrons drift toward the
  Drift & Diffusion
                              endplate by E-field while diffusing.
   Amplification               Amplification with GEM
    (    further Diffusion)

        Detection               12 rows of 32 Readout Pads ( Pad Size 6.3mm×1.27mm )


 The chamber gas plays important roles for measurement of track position.
BACKGROUND
  of OUR STUDY
CF4 gas mixtures for LC-TPC


Ar-CF4 gas mixtures are spotlighted as chamber gas for LC-TPC.

        ADVANTAGE
          CF4 makes       τ (mean free time) longer
              With B-field diffusion gets smaller.

        CONCERN
           CF4 has a strong electron affinity.


         Electron attachment might be a problem.


   We have to study CF4 gas mixtures for GEM-TPC.
 WHAT WE
WANT TO DO

 To make sure whether Ar-CF4 gas mixtures is a
 good gas for GEM-TPC.
 To make sure the validity of GARFIELD/Magboltz
 simulation by comparing to measured data.


In order to achieve these goals,
        we have to measure the following parameters.
   Drift Velocity v
   Diffusion coefficient CD
   Effective number of electrons Nef f
   ( Nef f is the parameter which is related to spacial resolution. )
                  MP-TPC




Superconductive
  Magnet(1T)
Trigger Counter
                                      PreAmp



                       Drift Region
     Field Cage H.V.
                                         Digitizer




                               MPGD
Trigger Counter
                                      PreAmp



                       Drift Region
     Field Cage H.V.
                                         Digitizer




                               MPGD
                                                                                 Drift Time Distribution

   HOW TO ANALIZE




                                                                                # of events
     TPC DATA
                                                                                                Drift Time
         Pad ID
         Drift Time                   •Reconstruct Hit-position by
                                      charge centroid method                                  TPC
         Charge                       •Reconstruct tracks
                                                                          Maximum drift length =
                           Event Reconstruction                               Maximum drift time ×           v
                                           Drift Time Distribution
Pad Response vs Drift Length               PadRespose vs Drift Length
                                           Resolution vs Drift Length
    σPR2




                                           x Resolution vs Drift Length
                        Drift Legth
                                                                          v    CD Nef f
                                           σX
Charge




         Read-Out Pad

Pad Response                                             Drift Legth
                                                                                                                Time Distribution

 SAMPLE RESULTS                                                                                                                         1000

                                                                                                                                           800
Ar-CF4-isoC4H10(95:3:2) E=200[V/cm], B=0[T]
                                                                                                                                           600

                                                                                                                                          400

                                                                                                                                          200

                                                                                                                                                0
                                                                                                                                                    0     500 1000 1500 2000 2500 3000 3500 4000 4500

                                                  Pad Response
                                                             Width of pad response (All row)

                                                                           8
                                                              !2 [mm 2]
                                                                                              GEM, Ar:CF4:iC4H10(95:3:2),200V, 0T,#=±2 °,"=±3°, V_GEM=250V   $2= 3.68 / n.d.f.= 5
                                                                           7
                                                                                              CD= 311 ± 7.47 [µ m / cm ], ! PR (0)= 552 ± 43.1 [µ m]
                                                               PR



                                                                           6

                                                                           5
                                                                                                                                                   !2 = !PR (0)2 + C2 z
                                                                                                                                                                    D
                                                                           4

                                                                           3

                                                                           2

                                                                           1

                                                                           00                 50                    100                      150              200             250

                                                                                                                                                         Drift distance [mm]
xResolusion
             0.8
   !x [mm]




                    GEM, Ar:CF4:iC4H10(95:3:2),200V, 0T,#<2°, "<3°,V_GEM=250V             $2= 5.61 / n.d.f.= 6
             0.7
                    CD/ N eff = 61 ± 1.37 [µ m / cm ], ! 0 = 110 ± 7.69 [µ m]
             0.6

             0.5
                                                                           2
                                 !2 = !2 + CD/ N eff
                                       0
                                                                                z
             0.4

             0.3

             0.2

             0.1

              00   50                    100                         150                200                       250

                                                                                    Drift distance [mm]
                                                                                                                Time Distribution

 SAMPLE RESULTS                                                                                                                         1000

                                                                                                                                           800
Ar-CF4-isoC4H10(95:3:2) E=200[V/cm], B=0[T]
                                                                                                                                           600

                                                                                                                                          400

                                                                                                                                          200

                                                                                                                                                0
                                                                                                                                                    0     500 1000 1500 2000 2500 3000 3500 4000 4500

                                                  Pad Response
                                                             Width of pad response (All row)

                                                                           8
                                                              !2 [mm 2]
                                                                                              GEM, Ar:CF4:iC4H10(95:3:2),200V, 0T,#=±2 °,"=±3°, V_GEM=250V   $2= 3.68 / n.d.f.= 5
                                                                           7
                                                                                              CD= 311 ± 7.47 [µ m / cm ], ! PR (0)= 552 ± 43.1 [µ m]
                                                               PR



                                                                           6

                                                                           5
                                                                                                                                                   !2 = !PR (0)2 + C2 z
                                                                                                                                                                    D
                                                                           4

                                                                           3

                                                                           2

                                                                           1

                                                                           00                 50                    100                      150              200             250

                                                                                                                                                         Drift distance [mm]
xResolusion
                                                                                                                                                                                                                   Pad response (Region 3)

             0.8
   !x [mm]




                                                                                                                                                                                                         i
                                                                                                                                                                                      Normalized charge: Q / Σ Q
                    GEM, Ar:CF4:iC4H10(95:3:2),200V, 0T,#<2°, "<3°,V_GEM=250V             $2= 5.61 / n.d.f.= 6                                                                                                        1




                                                                                                                                                                                                         i
             0.7
                                                                                                                                                                                                                    0.8
                    CD/ N eff = 61 ± 1.37 [µ m / cm ], ! 0 = 110 ± 7.69 [µ m]
             0.6
                                                                                                                                                                                                                    0.6

             0.5
                                                                           2                                                                                                                                        0.4
                                 !2 = !2 + CD/ N eff
                                       0
                                                                                z
             0.4
                                                                                                                                                                                                                    0.2

             0.3
                                                                                                                                                                                                                      0
                                                                                                                                                                                                                      -6    -4     -2        0   2    4      6

             0.2                                                                                                                                                                                                                 x Track - xCenter of Pad [mm]



                                                                                                                                                                                    Charge Distribution
             0.1

              00   50                    100                         150                200                       250

                                                                                    Drift distance [mm]
                           GARFIELD/Magboltz
                           (Drift Velocity & Diffusion Constant)
                                  (ploted by Ishikawa-san)


RUN SUMMARY
Data taking conditions                                               E[V/cm]



        Gas                  E-field [V/cm]                         B-field [T]
                                                                        0
Ar-CF4-isoC4H10(95:3:2)    100(diffusion minimum)                       1
                                                                        0
Ar-CF4-isoC4H10(95:3:2)           130                                   1
                                                                        0
Ar-CF4-isoC4H10(95:3:2)           165                                   1
                                                                        0
Ar-CF4-isoC4H10(95:3:2)           200                                   1
                                                                        0
Ar-CF4-isoC4H10(95:3:2)    250(velocity maximum)                        1
      ※We need little isobutane(isoC4H10) to get enough gain.
               Results of
                                                       preliminary
              Drift Velocity

          8



          7
[cm/!s]




          6

                                               GARFIELD (95:3:2)
          5                                    MEASURED(95:3:2) 0T
                                               MEASURED(95:3:2) 1T

          4

                   100         150             200        250
                                     E[V/cm]
                Results of                           preliminary
           Diffusion Coefficient
       400



       300
[!m/"cm]




                 GARFIELD (95:3:2) 0T
       200       MEASURED (95:3:2) 0T
                 GARFIELD (95:3:2) 1T
                 MEASURED (95:3:2) 1T

       100




                  100          150             200      250
                                     E[V/cm]
Electron Attachment I                                                                    preliminary
    ~Drift Region~
                                                                    ADC counts example for each bins
ADC counts vs Drift Length                                                    Charge sum vs Z position (All rows)

                                                                                  2000
    Charge sum vs Z position (All rows)                                           1800
                                                                                  1600

                       3000                                                       1400
    ! Qtrack (ADC counts)




                                                                                  1200
                                  cosmic-ray (V      =250V)                       1000
                                                   GEM
                       2500                                                       800
                                                                                  600
                                                                                  400

                       2000                                                       200
                                                                                    0
                                                                                         500   1000 1500 2000 2500 3000
                                                                                                     Σ Q track (ADC counts)

                       1500


                       1000

                                                                                  Maximum
                            500
                                                                                   Point

    too                       0       50     100     150         200        250
   small                                                   Drift Distance [mm]
  events
                                     No problem about attachment in the drift region.
Electron Attachment II
~Amplification region~
Since it is difficult to measure directly Electron Attachment from
amplification region, we checked effective number of seed electrons(Nef f ).
 Nef f can be calculated from spacial resolution plot.

                      0.8
            !x [mm]




                             GEM, Ar:CF4:iC4H10(95:3:2),200V, 0T,#<2°, "<3°,V_GEM=250V            $2= 1.98 / n.d.f.= 5
                      0.7
                             CD/ N eff = 66.2 ± 2.95 [µ m / cm ], !0 = 66.4 ± 27.1 [µ m]
                      0.6

                      0.5
                                                                                    2
                                           !2 = !2 + CD/ N eff
                                                 0
                                                                                        z
                      0.4

                      0.3

                      0.2

                      0.1

                       00
   Ar-CF4-isoC4H10(95:3:2) E=200[V/cm] B=0[T]
                 50      100     150    200                                                                     250

                                                                                            Drift distance [mm]

   example                          CD = 303 ± 5
   Ar-CF4-isoC4H10(95:3:2)
      E=200[V/cm], B=0T
                               CD
                               Nef f
                                     = 66 ± 3                             }          Neff ~ 21 ± 2 (※P5 ~22)
Theoretical Caluculation
 of Spacial Resolution
analytical theory(without angle effect)                           |θ|=0° |Φ|=0°

                0.8
    !x [mm]




                                            0T
                0.7

                0.6

                0.5

                0.4

                0.3                                                       1T

                0.2
                                                                                    3T
                0.1                                                                 3.5T
                                                                                    4T
                 0
                      0       500          1000        1500        2000        2500
              induction gap + transfar gap = 14 [mm]          Drift distance [mm]
 Ar-CF4-isoC4H10(95:3:2)
 E= 200[V/cm], Neff = 22
Conclusion
    Our measured data provide good agreement with
        GARFIELD/Magboltz simulation in v , CD .
    Electron attachment is small enough.
      ( Nef f is enough big as well as P5.)


 Ar-CF4-isoC4H10(95:3:2) is a good gas for LC-TPC.

     As for this study, this gas mixture seems to
           have rather good performance.

NEXT STEP
   Ar-CF4-isoC4H10(96:3:1), Ar-CF4(97:3)
   Theoretical caluculation included angular effect
BACK UP
                   1T                                               0T
Graph                                           Graph

    0.8                                             0.8

    0.7                                             0.7

    0.6                                             0.6

    0.5                                             0.5

    0.4                                             0.4

    0.3                                             0.3

    0.2                                             0.2

    0.1                                             0.1

        00   50   100   150   200   250                 00     50   100   150   200   250




                   Blue: HodoScope Effect + Diffusion Effect
                   Red: only Diffusion Effect
                                                               Ar-CF4-isoC4H10(95:3:2) E=200[V/cm]
    Width of pad response (All row)

                8
    !2 [mm 2]

                             GEM, Ar:CF4:iC4H10(95:3:2),200V, 0T,#=±2 °, "=±3°, V_GEM=250V   $2= 6.45 / n.d.f.= 10
                7
                             CD= 303 ± 5.08 [µ m / cm ], ! PR (0)= 574 ± 32 [ µ m]
     PR




                6

                5
                                                                                  !2 = !PR (0)2 + C2 z
                                                                                                   D
                4

                3

                2

                1

                00           50                    100                      150              200               250

                                                                                        Drift distance [mm]




(                                                                  )           σP RF = 480[µm]
    (                                 )                                        σP RF = 440 ± 40[µm]
Full theory             0.8




              σx [mm]
                        0.7

                        0.6

                        0.5

                        0.4

                        0.3

                        0.2

                        0.1

                          0
                              0   500   1000   1500        2000        2500

                                                      Drift distance [mm]




Asymptotic    σx [mm]
                        0.8



 formula
                        0.7

                        0.6

                        0.5

                        0.4

                        0.3

                        0.2

                        0.1

                         0
                              0   500   1000   1500        2000        2500

                                                      Drift distance [mm]




              Ar-CF4-isoC4H10(95:3:2)
              E=200[V/cm], Neff = 22
What is Neff ?
¯
x : Charge centroid                ˜
                                   x : True position of cluster at the begining
i : Label of electron in a cluster xi : position of i-th electron
Gi : Gain of i-th electron                           ∆xi : diplacement of i-th electron
     ˜
xi = x + ∆xi
         N                               N
         i=1 Gi xi                       i=1 Gi ∆xi
¯
x=        N
                         ˜
                        =x+                N
          i=1 Gi                           i=1 Gi
                                                                       probability of gain fluctuation
               ∞                  N
                            ¯                                                Gi            Gi
   x ˜
P (¯; x) =          PI (N ; N )              d∆xi PD (∆xi ; σd )        d    ¯        PG   ¯ ;θ
             N =1                 i=1
                                                                             G             G
             probability of ionization      probability of diffusion                   N
                                                                                       i=1 Gi ∆xi
                                                                     ¯ ˜
                                                                  ×δ x − x −             N
                                                                                         i=1 Gi


                                                                                  2
                                                         2    1             G                      1
 2
σx
 ¯   =        d¯P (¯; x)(¯ − x)
               x x ˜ x ˜                      2
                                                      σd                    ¯          ≡    2
                                                                                           σd
                                                              N             G                   Nef f

				
DOCUMENT INFO
Shared By:
Categories:
Tags:
Stats:
views:6
posted:9/19/2011
language:English
pages:24