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Development of GEM detectors for a large acceptance ф meson spectrometer

Development of GEM detectors for a large acceptance ф meson spectrometer. Yosuke Watanabe K.Utsunomiya, K.Ozawa, Y.Komatsu, S. Masumoto, T. Sato K. Aoki A ,H.Enyo A , S. Yokkaichi A T. Gunji B , H. Hamagaki B , Y. Hori B , T.Tsuji B M. Sekimoto C

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Development of GEM detectors for a large acceptance ф meson spectrometer

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  1. Development of GEM detectors for a large acceptance ф meson spectrometer Yosuke Watanabe K.Utsunomiya, K.Ozawa, Y.Komatsu, S. Masumoto, T. Sato K. AokiA,H.EnyoA, S. YokkaichiA T. Gunji B,H. Hamagaki B, Y. Hori B, T.Tsuji B M. Sekimoto C University of Tokyo, RIKENA, CNSB, KEK C,

  2. Outline • J-PARC E16 experiment • GEM tracker • Setup • Result of beamtests • Further improvement • Summary

  3. J-PARC E16experiment p Detection of φmeson mass spectrum modificationin nuclear matter φ 30 GeV J-PARC E16 KEK –PS E325 2 times better resolution 100 times more statistc sM=11MeV, <1.25 sM=5MeV, <0.5 Systematic study -Momentum dependence -Nuclear size depencence Mass modification exist

  4. E16 spectrometer • How to 100 times more statistic? ×10 beam intensity × 5 acceptance × 2 cross section New spectrometer GEM Required ability for the tracker -100μm position resolution with high rate events(5kHz/mm2)

  5. GEM(Gas Electron Multiplier) • Our GEM (made in Japan) 10cm • schematic view 4 μm Copper • Hole size : 70 -90 μm • Pitch: 140 μm • Most of the applications use 50 μm GEM. 70~90μm Kapton 50μm 100 μm LCP 140μm

  6. GEM Chamber • Collect ionized electrons • (Drift gap) • Length • Electric field • Chamber set up and parameters １ 2 • Amplify electrons • setup1: 50μm GEM × 3 • setup2: 50μm GEM+100μm GEM 3 • 2 D strip read out • 700μm pitch

  7. Test configuration First test Second test 2mm 2mm 2mm 2mm 2mm good effective gain

  8. Analysis procedure Hit position determined by Silicon Strip Detector(SSD) GEM SSD SSD Events Q3 Q4 Q2 beam Q1 Q5 X1 X2 X3 X4 X5 differencemm Hit position determined by GEM chamber Center Of Gravity -Multiple scattering -Tracking Accuracy Position resolution

  9. Test result • Required performance incident angle position resolution : 100μm incident angle : 0 – 30 degree Drift gap Achieved our goal ! Better resolution for inclined beam The effect of multiple scattering and tracking accuracy is subtracted

  10. Further improvement • Worse resolution for Second test • Estimate of the number of electrons in drift gap. • collection efficiency: • probablity for an electron in drift gap to be collected and multiplied Drift gap Improve collection efficiency A setup with 3mm drift gap may get as many Nprimary x collection as the first test

  11. Better collection efficiency with narrow drift gap • εcollection= εcollection(GEM geometry, EGEM/ Edrift) EGEMshould be stronger Edriftshould be weaker disadvantage Setup with three layers of 50μm GEM • The collection efficiecy of the first test with three layers of 50μm GEM is also bad.. + stronger EGEM smaller hole - less optical transparency The setup with current design of GEM has 2~3 times better collection efficiency.and 2 times larger gain (preliminary results)

  12. Summary • Developing of GEM tracker for E16 experiment is under way • We achieved100 resolution for 0 degree beam. • Narrower drift gap leads to better resolution for tilted track. • We obtained better collection efficiency with smaller hole GEM • Another beam test will be performed at the end of the next month.

  13. Back ups

  14. Beam test setup 20cm Fuji @ KEK Kakuriken@Tohoku SSD (silicon Strip Detector) 2 GeV electron ~5Hz 600MeV positron ~100Hz scintilator GEMchamber 40cm • Read out circuits for GEM pre-amplifier post-amplifier charge sensitive ADC(v792) • Trigger ←Scintillators

  15. Remaining issues 2 • What if collection efficiency = 100% ? simulation position resolution (μm) Not enough for our goal • How to deal with it ? (To be tested) incident angle (degree) • Narrower drift gap (1mm,2mm) • Use arrival timing information

  16. Estimation of collection efficiency • Fit with simulation • Make primary and secondary electrons • primary : poisson • secondary: NIM simulation experiment Collection efficiency • Amplify those electrons • Polya distribution(θ~0-5) Add noise

  17. Test @ laboratory 90Sr 3mm experiment 50μmGEM×3 12cm simulation Pad read out scintilater 3cm Estimate the collection efficiency by comparing with simulation

  18. Analysis procedure GEM SSD SSD ratio Xi – XSSD mm Q3 Q4 Q2 Qi/Q Q1 hit Q5 Hit position determined by GEM chamber X1 X2 X3 X4 X5 Xi Center Of Gravity -Multiple scattering -Tracking Accuracy position resolution XGEM – XSSD mm

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