Development of GEM at CNS Hideki Hamagaki Center for Nuclear Study University of Tokyo

Contents of This Presentation What is GEM How to make GEM Plasma etching and its improvement Test of gain variation GEM application GEM-TPC HBD X-ray detector with Xe gas Summary and outlook Improve GEM performance and stability Applications 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

MICRO PATTERN GAS DETECTOR 研究会 ＠京大 What is GEM Gas Electron Multiplier Developed at CERN by Sauli et al. Foil of Kapton with Copper coated at both sides typical: Kapton 50mm, Copper 5mm with holes: typical: pitch 140mm, and 70mmf Electron multiplication in the strong field inside the holes typical voltage between the two Copper foils = 300 ~ 550V 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

Characteristics of GEM simple structure with lost cost material low mass multiple stacking  high gain less risk of severe sparks/breakdown S.Bachmann et al, NIM A438 (1999) 376 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

How GEM is or will be used COMPASS experiment@CERN tracking chambers near beam-pipe high rate ~150 kHz low mass & high resolution Possible applications Time Projection Chamber PHENIX, STAR, TESLA, JLC, … UV photon detector with CsI photocathode Gas Cherenkov counter: e.g. PHENIX HBD X-ray detection Cosmology  T. Tamagawa’s talk Biology/Medical applications 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

MICRO PATTERN GAS DETECTOR 研究会 ＠京大 How to make GEM step1 put proper masks to the copper foils step2 wet etching of masked copper foils step3 make holes to the Kapton foil wet etching --- CERN GEM laser etching --- persued by T. Tamagawa plasma etching --- persued by us (CNS) hybrid of the above --- persued by us (CNS) 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

MICRO PATTERN GAS DETECTOR 研究会 ＠京大 Plasma Etching Method A method different from CERN Fuchigami Micro has expertise on this inherent gain variation in CERN GEM our suspicion is on the hole shape CERN-GEM CNS-GEM 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

Characterstics of CNS-GEM Low resistance or sparks at low HV in the beginning  aging surface roughness small residues Similar gain to CERN-GEM Lower breakdown point than CERN-GEM 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

Improvement of CNS-GEM CERN-GEM Earlier breakdown cleaning process surface roughness due to over-hung of Copper edges Succeed to reduce over-hung Still breakdown at lower HV This is only crucial for high HV operation, needed for CF4 gas CNS-GEM 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

MICRO PATTERN GAS DETECTOR 研究会 ＠京大 Test of Gain Variation gain measurement with Fe55 source gain of CNS-GEM seems to stabilize in shorter time After the first try, gain seems to stabilize much sooner, as long as GEM is kept inside the chamber Need further work condition; temperature, oxygen, moisture, … simultaneous comparison Blue : CERN-GEM（Gas : flow） Black: CNS-GEM（Gas : noflow） Red: CNS-GEM(Gas: flow) 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

MICRO PATTERN GAS DETECTOR 研究会 ＠京大 GEM-TPC; motivation Need of 3D-tracking device durable under high particle density and high rate at RHIC position resolution, two-track separation, energy measurement Expected advantage of GEM small ion feedback; no need of gating grid simple structure flexible readout configuration 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

MICRO PATTERN GAS DETECTOR 研究会 ＠京大 GEM-TPC prototype Tested at KEK-PS two types of readout pads rectangular & chevron type 1.09 mm x 12 mm charge-sensitive pre-amp 1 ms time-constant readout with 100 MHz FADC 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

Performance of GEM-TPC (I) Position resolution z direction x direction resolution gets worse with increase of drift length diffusion effect magnitude depends on gas species P10 Ar+C2H6(30%) CF4 Electric field (V/cm) Drift velocity (cm/ms) Diffusion (T)@1cm (mm) (L)@1cm Ar(90%)+CH4(10%) 130 5.5 570 360 Ar(70%)+C2H6(30%) 390 5.0 320 190 CF4 8.9 110 80 R : P10 chevron B : P10 rect. Y : Ar+C2H6 rect. G : CF4 chevron 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

Performance of GEM-TPC (II) 36 mm of P10 gas drift length = 85mm Energy loss measurement P10: s(55Fe;5.9 keV) = 11 % Ne(primary) ~ 222 for 5.9keV X-ray in P10  ~1.7 times larger than statistical estimate obtained energy loss is as expected for various particles with different momentum Beam rate effect no change up to 5000 cps/cm2 good enough for HI applications further studies may be needed Z direction R : P10 chevron B : P10 rectangular 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

MICRO PATTERN GAS DETECTOR 研究会 ＠京大 Hadron Blind Detector UV photon detector with CsI cathode CF4 gas radiator Ne(Cherenkov) > Ne(ionization) development at Weizmann Institute Use to measure low mass electron pairs at RHIC Rejection of Dalitz pairs and external conversion pairs 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

MICRO PATTERN GAS DETECTOR 研究会 ＠京大 Summary and Outlook How to improve GEM performance and stability improve etching procedure cleaning procedure after etching use wet etching (cleaning) to smoothen the surface washing out small residues choice of material base: insulator  resistive plastics prevent gain variation due to charge up Copper  Aluminum low mass, long radiation length 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大

Summary and Outlook (cont.) X-ray detector with Xe gas for medical/biological use; two versions 2D radiation dose monitor taking advantage of simple structure, and flexible configuration precise 2D tomography started development of a custom ADC chip with Tanaka’s group at NIAS 12/27/2018 MICRO PATTERN GAS DETECTOR 研究会　＠京大