Micro Pixel Chamber 4 - PowerPoint PPT Presentation

大面積 Micro Pixel Chamber の開発 4 京都大学 永吉 勉 谷森 達、窪 秀利、身内 賢太朗、 竹田 敦、折戸 玲子、植野 優、 高田 淳史、岡田 葉子 MIT Oleg Bouianov, Helsinki Univ. Marina Bouianov of Technology 日本物理学会年次大会 @ 九州大学 2004 年 3 月 27 日

Contents • Micro Pixel Chamber • Simulation study � Electron collection ( � net gas gain) � Electric field ( � discharges) • Large area detector • Summary

Micro Pixel Chamber ( µ -PIC) • PCB technology • Pixel electrode • 2D readout 100 µ m • 400 µ m pitch electrodes • 256 anodes and 10cm 256 cathodes Detection area = 100cm 2

Performances 0.5mm slits Gas gain Max: 1.6 × 10 4 ) 0 1 / 10 4 0 ) 0 9 2 ( / H 6 0 8 C 2 ( / r H 6 A C 2 / r A 10 3 position resolution 620 400 σ =120 µ m Anode voltage [V] Max: 1.6 × 10 4 Gas gain Stable: ~6000 Length along the edge [mm]

Next development MIP Current status • Max gas gain >10 4 • Stable operation ( >1 month) @ gas gain ~ 6000 ~4 electrons / anode Next step Tracking of • Stable operation @ gas gain > 10 4 MIPs • Detection area = 30 × 30cm 2 Simulation study for optimization of the electrode

Simulation µ -PIC … 3D structure Maxwell & Garfield Dielectrics • Maxwell – 3D structure – Finite element method • Garfield – Electron drift – Gas multiplication Field Expected MAXWELL GARFIELD map performance

Dependence on Electron collection substrate thickness 1.0 Thin substrate � low efficiency Fraction collected current µ -PIC � small signal Drift end points 0.5 Efficiency Efficiency ~ 40% > 90% 0.2 0 10 100 Substrate thickness [ µ m] - - - - (-) 5 µ m thick 200 µ m thick (+)

Damaged electrodes Discharge of MSGC 10 µ m ~ Limit of MSGC ~ (anode) E [kV/cm] ~200kV/cm @ cathode edge 200 (cathode) 10 µ m Damaged electrode 100 (anode) 0 Nagae et al., Field emission NIM A 323 (1992) 236 e- x To avoid discharge: anode cathode Low electric field High field � field emission @ cathode edge … one of the discharge mechanisms

Dependence on Electric field substrate thickness 350 Dangerous!! Thickness Thin substrate … E field [kV/cm] 5 µ m •High electric field 100 µ m @ cathode edge 200 µ m Discharge •Low electric field 100 @ anode top Low gas gain Safe!! r O Substrate should be THICK. anode cathode ( > 100 µ m) (600V) (GND)

Maximum gas gain 10 7 1000 Experiment Current status V lim [V] M lim � V lim = 600V (Thickness=100 µ m) E ~ 200kV/cm 600 10 4 @cathode edge 300 V lim for each thickness 10 � M lim Thickness = 150 µ m 100 150 200 Substrate thickness [ µ m] � M lim > 10 5

30 × 30cm 2 µ -PIC 9 µ -PICs on 1 substrate � Single 30 × 30cm 2 detector is feasible. Center 17 × 17cm 2 � very small offset ~17cm Edge region � thermal expansion ~30cm should be corrected

Summary • Micro Pixel Chamber ( µ -PIC) – Gas gain >10 4 (max) – Position resolution ~ 120 µ m • Optimization of the electrode structure – 3D simulation using Maxwell & Garfield – Thicker substrate (150 µ m) � gas gain >10 5 • Next development – 30 × 30cm 2 area detector – 150 µ m thick substrate gas gain >10 5 High quality electrode in near future