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東大 CNS における GEM の基本動作特性の研究 Measurement of basic properties of GEM at CNS, Univ. of Tokyo

東大 CNS における GEM の基本動作特性の研究 Measurement of basic properties of GEM at CNS, Univ. of Tokyo. Yorito Yamaguchi CNS, Univ. of Tokyo. Outline. Introduction Setup for Measurements Basic properties of Standard-GEM P/T dependence, Gain Stability, V GEM dependence Development of 150 m m-GEM

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東大 CNS における GEM の基本動作特性の研究 Measurement of basic properties of GEM at CNS, Univ. of Tokyo

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  1. 東大CNSにおけるGEMの基本動作特性の研究Measurement of basic properties of GEM at CNS, Univ. of Tokyo Yorito Yamaguchi CNS, Univ. of Tokyo MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  2. Outline • Introduction • Setup for Measurements • Basic properties of Standard-GEM • P/T dependence, Gain Stability, VGEM dependence • Development of 150mm-GEM • Feature of 150mm-GEM • Electric field, Gain, Multiplication factor, Gain Stability • Summary MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  3. CERN SciEnergy Co., Ltd Etching technique wet etching dry etching The cross section of a hole Cylindrical Bi-conical Hole shape Introduction A new type of GEM was successfully developed using a dry etching technique. • Basic properties were measured to evaluate the performance of SciEnergy-GEM. • P/T dependence, Gain Stability ,VGEM dependence. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  4. Setup for Measurements • ED = 0.5kV/cm • ET = EI • DVT = DVI = DVGEM • Moisture % < 10ppm MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  5. Measurement of basic properties • P/T dependence of Gain • Gain Stability • VGEM dependence of Gain MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  6. Ar/CO2 Ar/CH4 P/T Dependence of Gain ① Longitudinal axis : Gain Horizontal axis : P/T [Torr/K] Range : 2.50~2.65 It was observed that Gain decreases exponentially as P/T increases. A change of 1% in P/T value causes a gain variation of 9% (Ar/CH4) and of 11% (Ar/CO2). MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  7. P/T Dependence of Gain ② • Base point in Gain • P=760.0Torr • T=300.0K • P/T=2.533 [Torr/K] Both results of SciEnergy-GEM and CERN-GEM are in good agreement with the unique exponential function. The results with different P/T can be normalized to the same condition using the obtained function. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  8. Gain Stability ① Known problem in gain stability It was reported that gain of CERN-GEM increases (or decreases) as a function of illumination time. A. Orthen et al., NIM A 512 (2003) 476 Possible reason • Due to shape of a GEM hole • Charge up of the insulator surface inside the hole. • Due to nature of insulator • Due to surface conditions • Measurement condition • VGEM is kept constant during the measurement. • Rate of signals is 3Hz for all measurements. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  9. Without charge-up Gain Stability ② All results are normalized to the condition of P/T=2.533 [Torr/K] using the obtained relation between Gain and P/T. • Gain variation • SciEnergy-GEM • within 0.5% (both case) • CERN-GEM • Increase 15% (Ar/CH4) • Increase 45% (Ar/CO2) MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  10. Gain Stability ③ SciEnergy-GEM has a much better gain stability than CERN-GEM. Electric field inside a GEM hole 10mm from hole edge Drift direction of electron CERN-GEM SciEnergy-GEM • The electric field near the hole edge is distorted due to a bulge of a insulator for CERN-GEM. • Probability of charging-up is higher for CERN-GEM than SciEnergy-GEM. E [V/cm] VGEM=350V MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  11. VGEM Dependence of Gain • SciEnergy-GEM can attain 20% (Ar/CH4) and 50% (Ar/CO2) higher gain than CERN-GEM at the same VGEM. • SciEnergy-GEM has larger effective area in multiplication than CERN-GEM. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  12. Development of 150mm-GEM • Feature of 150mm-GEM • Electric field of 150mm-GEM • Gain of 150mm-GEM • Multiplication factor • Gain Stability MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  13. Feature of 150mm-GEM The dry etching technique can allow to fabricate a thicker GEM (Thick-GEM) than Standard-GEM (insulator thickness:50mm). • 150mm-GEM is comparable to a triple layer structure of Standard-GEM with respect to the total length of a hole. Advantage of 150mm-GEM 150mm-GEM is expected to multiply electrons more effectively than triple layer structure of Standard-GEM. • Larger effective path length for multiplication • Less effect of transmission efficiency Structure of 150mm-GEM 140mm • Cu(8mm) + LCP(150mm) + Cu(8mm) • f = 70mm • hole pitch = 140mm • LCP:Liquid Crystal Polymer 150mm 70mm MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  14. Electric Field of 150mm-GEM Electric field through the hole center VGEM/50mm=250V/50mm • 150mm-GEM VGEM=750V • 100mm-GEM VGEM=500V • Standard-GEM (50mm) VGEM=250V • The electric field of Thick-GEM is much stronger than that of Standard-GEM. • Especially, 150mm-GEM reaches plateau for about 50mm. a>0 150mm-GEM should have a better multiplication ability than Standard-GEM. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  15. Tamagawa-san’s result • (Gain100mm-GEM)3/2 Gain Magnification Ratio at 300V/50mm Standard-GEM 30 1.0 1.0 x103 3.6 x102 100mm-GEM 1.3 x103 3.9 x104 150mm-GEM Gain of 150mm-GEM Gain for Standard-GEM is obtained by triple GEM structure. • 150mm-GEM had a continuous discharge at 270V/50mm.(Gain~4000) Ar(70%)/CO2(30%) 150mm-GEM can attain much higher Gain than Standard-GEM at the same VGEM/50mm. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  16. Multiplication Factor Simulation results of the transmission efficiency is used. • 150mm-GEM (M150):eT150=0.17 • 100mm-GEM (M1003/2):eT100=0.34 • Standard-GEM (M503):eT50=0.24 EI is stronger than for Standard-GEM and 150mm-GEM. As expected from the electric field inside a hole, 150mm-GEM has the highest multiplication factor. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  17. Gain Stability of 150mm-GEM • The rate of signals = 2.5Hz • VGEM=230V Ar(90%)/CH4(10%) • Gain of 150mm-GEM is stable within 1.0% for 9 hours. • 150mm-GEM has a good gain stability as well as Standard-GEM MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  18. Summary • The basic properties have been measured to evaluate the performance of SciEnergy-GEM. • Gain decreases exponentially as P/T increases. • A change of 1% in P/T value causes a gain variation of 9% (Ar/CH4) and of 11% (Ar/CO2). • SciEnergy-GEM has a much better gain stability than CERN-GEM. • Probability of charging-up is higher for CERN-GEM because of a distortion of electric field near the hole edge. • SciEnergy-GEM can attain higher gain than CERN-GEM at the same VGEM. • 150mm-GEM has been fabricated successfully using dry etching. • Electric field of 150mm-GEM is much stronger than that of Standard-GEM. • 150mm-GEM has much higher gain and multiplication ability with a good gain stability than a triple layer structureofStandard-GEM. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  19. Back up MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  20. Applications • We are developing some detectors using GEMs. • GEM-TPC • S.X. Oda et al., NIM A 566 (2006) 312 • Photon detector • Hadron Blind Detector (HBD) installed in PHENIX@RHIC. • Please hear Ozawa-san’s talk (15:15~ in tomorrow session). • Neutron Counter • Development is now on going. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  21. Relation between Gain and P/T From the equation of state, The expected relation between Gain and P/T should be exponential. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  22. Simulation of GEM structure • Aim of study • To understand the behavior of electrons inside a GEM hole qualitatively and quantitatively. • To search for optimum GEM structure. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  23. VGEM=350V Bi-conical Cylindrical Potential Distribution of GEM hole The electric field inside the GEM hole was calculated using Maxwell 3D. • The calculation was carried out for two type of GEM. • Bi-conical (CERN-like) • Cylindrical (SciEnergy-like) Potential distributions are very similar in both cases. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  24. Electric Field inside GEM hole Drift direction of electron Hole center 10mm from hole edge Although there is little difference between them at hole center, the electric field of Bi-conical near the hole edge is distorted due to a bulge of a insulator. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  25. ions electrons Simulation of Avalanche • The avalanche inside a GEM hole was simulated using Garfield. • The calculation results from Maxwell 3D are the inputs to Garfield. • Avalanche simulation ware carried out with two methods. • True path integration • Projected path integration • Ar/CO2 (70:30) was used at P=760.0Torr, T=300.0K. Gain can be defined as a following equation. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  26. Gain Behavior of Electrons Created point of electron Number of created electron Lost point of electron GEM • There is a significant difference in multiplication near the hole edge. • SciEnergy-GEM has better multiplication ability than CERN-GEM. • More than 70% of secondary electrons are absorbed by the lower electrode of GEM. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  27. Gain • Most of electrons created near the hole edge are absorbed by electrode. • There is not a big difference in gain as seen in multiplication factor. Simulation results are qualitatively consistent with measured result, but they are quantitatively inconsistent. It is needed to improve the calculation method in multiplication inside a GEM hole. MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  28. Setup for Measurements of 150mm-GEM • ED = 0.5kV/cm • DVI = DVGEM/3 MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

  29. Gain of 150mm-GEM (Ar/CH4) MPGD Workshop in Saga (Yorito Yamaguchi, CNS, Univ. of Tokyo)

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