Micropattern Gas Detectors Oleg Bouianov, M.I.T. Cambridge KEK, Tsukuba, 21 February 2004 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge Outline Introduction to micropattern gas detectors. MSGC, GEM, MICORMEGAS, MSHP. 3D simulations of gas detectors. Limitations of micropattern detectors. Imperfections of detector fabrication. µPIC, MDOT. New materials and fabrication methods. MIPA. Trends in micropattern detector development. 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Processes in Gas Detectors Ionisation Charge Transport Charge Multiplication Signal Formation -0.015 -0.01 -0.005 0.02 0.04 0.06 0.08 0.1 x 10 -5 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

History and introduction to micropattern gas detectors 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

MWPC: Multi-Wire Prop. Chamber Georges Charpak Nobel Prize in Physics 1992 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Limitations of MWPC F.Sauli, APS-DPF2000 Counting rate is limited by space charge to ~104 Hz/mm2 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge Aging of MWPC Anode wire deposits 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

MSGC: Micro-Strip Gas Chamber A. Oed, NIM A 263 (1988) 351. Drift electrode 200 µm Anode strip Glass support Back plane Cathode strips 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge MSGC vs MWPC 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge MSGC Dimensions 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge MSGC: Discharges FULL BREAKDOWN MICRODISCHARGES F.Sauli, IEEE NSS 2002 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge MSGC: Discharges F.Sauli, IEEE NSS 2002 For detection of minimum ionizing tracks a gain ~ 3000 is needed In presence of heavily ionizing particles background, the discharge probability is large ON EXPOSURE TO a PARTICLES 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge Aging of MSGC R. Bouclier et al, NIM A381(1996) 289 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge MICROMEGAS Thin-gap parallel plate chamber Y. Giomataris et al, Nucl. Instr. and Meth. A376 (1996) 29 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge MICROMEGAS 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

GEM: Gas Electron Multiplier F.Sauli, CERN 1997 GEM Dimensions 45μm 75 μm 140 μm 50 μm Copper Kapton 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge GEM operation Particle traversing the detector volume Ionization Drift of primary charges Avalanche multiplication 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge Cascaded GEM GEM #1 GEM #2 -0.015 -0.01 -0.005 0.02 0.04 0.06 0.08 0.1 x 10 -5 Pad readout 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Cascaded GEM: Simulated Strengths of simulations: Each electron and ion can be individually traced. Nano-scale study of all major processes. 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Features of GEM-based Detectors Flexibility. Charge multiplication and signal formation are separated Gas gain can be optimised by cascading GEMs Freedom in selecting a signal readout geometry Only signal due to electrons is seen. Ion feedback suppression. Inexpensive to manufacture in large area. High-rate operation. Gain uniformity over large detector areas. Stability at high gas gains (cascaded). 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Micro-Hole and Strip Plate (MHSP) A cross between MSGC and GEM J.M. Maia et al., IEEE Trans. Nucl. Sci. NS-49 (3) (2002) 875 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge MHSP Operation hv photocathode Features: Double-stage amplification Low ion feedback Low UV photon feedback cathode mesh 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

3D Simulation of Gas Detectors 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Why 3D Simulation? 2D: Electric field lines 3D: Field strength 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Why 3D Simulation? 2D: Avalanche 3D: Avalanche and charge sharing 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge Simulation Flow Simulation Tools Maxwell FEM 3D Electric Field Simulator Garfield 3D drift chambers simulation Heed gas ionisation by particles Magboltz electron transport properties in gas mixtures Maxwell Garfield 3D Geometry Model Generate Data Charge Transport Magboltz Mesh Generation Gas Data Track Particle Field Calculation Heed Ionisation Data 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

FEM Modelling of e-Field 3D Detector Model Mesh Generation FEM Field Calculation 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

GEM Simulation Studies 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Early effort on GEM simulations Setting up simulation environment (1999). Validation and comparison with published measurement results. O. Bouianov et al., “Progress in GEM simulation”, Nuclear Instruments and Methods in Physics Research A, 450 (2000), 277-287. Study of charge losses. O. Bouianov et al., “Foil geometry effects on GEM characteristics”, Nuclear Instruments and Methods in Physics Research A, 458 (2001), 698-709. Study of gas gain instabilities. O. Bouianov et al., “Charging-up effects in the gas electron multiplier”, Research reports B24, Laboratory of Computational Engineering, Helsinki University of Technology, 2001, ISBN 951-22-5413-1. 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge Studied geometries (a) cylindrical (b) biconical (c) conical 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge Detector modelling Minimisation of detector volume for various hole distribution patterns: (a) hexagonal (b) rectangular 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Study of charge transport in GEM 3D model of GEM. E-field calculation. Gas properties. Primary charge generation. Propagation of charges (with or without diffusion). 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Deposition of charges (losses) 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Modelling of dielectric charging 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Modelling of dielectric charging Distribution of electric potentials in GEM: initial modified by charging 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Comparison with measurements The alteration of the effective gas gain: measured (dots) and simulated (solid curve). R. Bouclier et al., Nucl. Instr. and Meth. A, 396 (1997), 50. time constants 1/ 2 =6 total equivalen resistance R≈150∙109 Ω 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Typical characteristics of gaseous micropattern detectors 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Shortcomings of gaseous micropattern devices discharges at high count rates and gains low effective gas gain space-charge effects time-dependent gain variation (dielectric charging) slow response due to ions gain non-uniformity across detector area aging limited energy resolution (>20% E/E FWHM) … 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Discharges in micropattern detectors A. Bressan et al, NIM A 424 (1999) 321 Systematic study of discharges by F.Sauli at CERN. Irradiation: high-rate soft X-rays + heavily ionizing alpha particles. All single-stage micropattern detectors show similar limitation due to discharges at a gain of few thousand. 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Imperfections of detector fabrication Fabrication process limitations: Layer-to-layer registration Photolithography errors Isotropic etching process Electrode shape errors (undercut) Dielectric shape errors 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge GEM: close look CERN Imperfections of wet etching and RIE. CERN Fuchigami Co 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Modelling of realistic structures The effect of MPGD fabrication imperfections has been studied. 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Modelling of realistic structures Smoother electrode structure. Twofold decrease of the field strength. 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Fabrication techniques: a comparison of results 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

MDOT: Micro – Dot Chamber A remarkable detector with high gain and low discharge rate Metal electrodes on silicon: microelectronic fabrication process S. Biagi et al, Nucl. Instr. and Meth. A361 (1995) 72 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge MDOT performance No discharges observed at high rates with alphas up to the gains 2104 A. Bressan et al, NIM A 424 (1999) 321 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

µPIC: Micro Pixel Chamber New micrpattern detector Developed at Kyoto University Similar to MDOT PCB technology Discharges at gains of few thousand. A. Ochi et al., Nucl. Instr. and Meth. A 471 (2001) 264. 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge µPIC vs MDOT µPIC MDOT Technology Advanced PCB Microelectronic Electrode thickness 10 µm ~ 1 µm Feature tolerances > 10 µm ~ 0.5 µm Performance average exceptional Reasons for different performance: Technology imperfections? … T.Nagayoshi, Kyoto group 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

New Materials and Manufacturing Technologies 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Scale-up: “macropattern” LC TPC R&D: LEM or Macro-GEM “Macro-GEM” structure is manufactured and its performance studied at MIT/LNS. Macro-GEM geometry Hole pitch 2.5 mm Max. hole diameter 1.2 mm Min. hole diameter 0.6 mm Copper thickness 50 m Dielectric thickness (G10) 150 m 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Microstructure detectors Scale-down Microstructure detectors 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Photoplastics for MEMS Polyimide Low aspect ratio (< 3:1) ~80 m thick SU-8 epoxy PR – popular material for MEMS microfabrication High UV transparency High aspect ratio (>10:1) Straight walls > 500 m thick spin coated 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Microfabrication with photoplastics Spin coating SU-8 process 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Examples of SU-8 microstructures 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Molding of metal structures Results in precise metal shapes with smooth surfaces. 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Early attempts to produce gas detectors with MEMS techniques 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge MSGC type structures M. Key CNM, Barcelona 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

MIPA: Micro-Pin Array Uses new materials and fabrication processes Matrix of individual needle proportional counters P. Rehak et al, IEEE Trans. Nucl. Sci. NS-47(2000)1426 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

SU-8 Radiation Hardness M. Key CNM, Barcelona 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge Not a Conclusion 1928 1988 2000 G e n r a t i o s f g u d c 3 rd generation 2 nd generation 1 s t g e n r a i o 4 × 10 2 3 D e t c o r s l u i n , m 5 50 500 S g d a v 1 st gene- ration 2 nd gene- ration 3 rd gene- ration 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge

Oleg Bouianov, M.I.T. Cambridge Thank you … 21 Feb 2004 Oleg Bouianov, M.I.T. Cambridge