Design and Construction of a GEM-TPC Prototype for R&D Purposes

Transcription

1 Design and Construction of a GEM-TPC Prototype for R&D Purposes 2003 IEEE NSS - Satellite Workshop on Micro-Pattern Detectors for Time Projection Chambers Portland, Oregon (USA) October, ) 1,2) 1) J. Kaminski, S. Kappler, B. Ledermann, 1) 2) 2) T. Müller, L. Ropelewski and F. Sauli 1) Institut für Experimentelle Kernphysik, Karlsruhe University (Germany) 2) CERN, EP Division, Geneva (Switzerland)

2 Outline 4 Introduction 4 Design of the COMPASS Triple-GEMs 4 Design & Construction of the GEM-TPC Prototype 4 Design Requirements 4 Overview 4 Choice of Materials 4 Field Cage and Drift Cylinder 4 Multi-GEM Endcap 4 Performance Tests 4 Summary & Outlook

3 The Gas Electron Multiplier (GEM) Principle of Operation The GEM foil + Kapton foil of 50mm, two-side copper-clad (5mm each) + Perforated with a high density of holes (etched in a photolithographic process, typically p=140mm, D=70mm, d=60mm) + High voltage on electrodes (~0.4kV) + Fieldlines from the volume above the GEM are strongly compressed into the holes: -> Proportional Gas Amplification

4 The Gas Electron Multiplier (GEM) Multi-GEM Detectors Principle + Parallel plate detector with one or more GEMs inserted Example: + Triple-GEM detector as used in the Small-Area-Tracker (SAT) of the COMPASS experiment at CERN Features + Amplification in several stages grants stable operation (low discharge prob.) + Separation of gas amplification and readout stage gives high flexibility in the design of the readout pads / strips 3mm 2mm 2mm 2mm ionizing particle drift cathode GEM GEM GEM readout PCB electric field readout electronics

5 The COMPASS Triple-GEMs Small Area Tracking (SAT) with GEM Detectors Overview + Active area 31x31cm2 + Radiation length 7.19 o/oo only + Ar-CO2 (70:30) + 2D microstrip readout Common Muon Proton Apparatus for Structure and Spectroscopy COMPASS SAT + 20 GEM Detectors installed + Since 2001 very successful operation in the experiment Performance + Fully 2D efficient at G= sx = 45mm, st = 15ns + Aging test up to >7mC/mm2

6 The COMPASS Triple-GEMs Final Detector Design Design NIM A 490 (2002) => minimize risk due to discharges! 307mm 2 + Active area 31x31cm +Triple-GEM detector + Standard Geometry GEM-foils, segmented on one side into 12 sectors (plus central disk) + 3 GEMs powered by resistive voltage divider and operated at asymmetric gain distribution NIM A 479 (2002) D Readout, 2x768 strips 400mm pitch, 70 & 350mm width + Rigid support with Nomex honeycomb and Vetronite skin + Total thickness 15mm

7 The TPC Prototype Design Requirements Study Prospects + Electron drift properties in various gases + Ion feedback suppression + Performance in strong magnetic fields + Tracking studies R&D Aspects + Easy replacement / modification of: a) Gas amplification stage b) Readout PCB c) Front-end electronics + Robust design, but with moderate material budget + Irradiation with X-rays and low-energy b-rays must be possible? Practical / Technical Requirements + Easy mounting / dismounting + Only well known, non-outgassing materials facing the gas volume + Readout PCB and FEE on ground potential

8 The TPC Prototype Design Overview Drift cylinder + Inner diameter d = 20cm + Length l = 25cm and l = 12.5cm + Irradiation windows foreseen Field cage + Double-layer layout + Validated up to 12kV Endcaps + Detector can be equipped with different MPGD-types or micro pad designs

9 Field Cage and Drift Cylinder Design Field Cage + Double-layer technology + 3mm wide rings with 4mm pitch + Resistive voltage dividers outside the counting gas in order to avoid: - Distortions of the electric field - Heating of the counting gas - Possible outgassing of the resistors - Metallic tips due to soldering Drift cathode + 10mm Stesalite with round holes (as irradiation windows) + 125mm Kapton + 18mm copper

10 Field Cage and Drift Cylinder Design Schematic view of the layers outside All components glued with ARALDIT AY HD 991 Field cage foil + 2x18mm copper rings on 125mm Kapton + 60 (59) rings with p = 4mm, w=3mm + offset between the two layers 2mm + Kapton guarantees gas tightness inside 50mm copper 150mm Ferrozell 3mm Honeycomb 350mm Ferrozell 125mm Kapton foil 161mm field cage foil Two resistive voltage divider chains + 10MW Resistors (BC Components,. -5 MBB0207, 1% tolerance, temp. coeff / K) + Total resistivity 294MW + Dissipation 10kV

11 Multi-GEM Endcap Design Gas amplification + Multi-GEM structure on PVC pillars + 10x10cm2 active area + Number of GEMs and gaps flexible + Field correction plate (copper on 2mm thick G10) + Possibility to add grids oids v a e t a l p ction ide e s r t r u o o c d d l l e e i Fi ctric f e l e e h t f so ture distortion uared) GEM struc the (sq field plate GEMs field plate gas inlet GEMsPCB micropad readout Micropad Readout PCB field plate field plate HV HV

12 Micropad Readout PCB Design Readout PCB + Passivated copper on G10 + HV feed-through for GEMs field plate GEMs field plate Micro pads + Rectangular shape x12.5mm pitch Micropad Readout PCB HV Pitch adapter + 1:2 pitch adapter + FEE mounted directly to the PCB a) b) c) 1.27mm ->2.54mm

13 The TPC Prototype Choice of Materials For parts in contact with or close to high voltage electrodes only HV proofed materials were admitted. + Copper and passivated copper + Stainless steel + Kapton + PVC pillars + Stesalite + G10 NIM A 490 (2002) All materials facing the gas volume were selected with respect to their outgassing properties. NIM A 350 (1994) Glue ARALDIT AY HD O-ring for sealing Materials facing the gas volume Cathode Endcap Drift Cylinder Multi-GEM Endcap Assembly glue Sealing Copper Kapton G10 Copper Stainless steel Kapton Copper (passivated) Stainless steel Kapton PVC Stesalite G10 ARALDIT AY HD 991 O-ring

14 The TPC Prototype Current Setup Gas amplification stage 2 + Double-GEM, 10x10cm + No gating grid Readout PCB micro-pads, 1.27x12.5mm + Pitch adapter to 2.54mm Readout electronics Provided by LBNL, Berkeley (USA ) + Modified version of the STAR-TPC electronics + Pseudo-Gaussian pulse shape, 180ns peak time, 180ns fwhm + Signal sampling rate 19.7 MHz (50.86ns per time slice)

15 The TPC Prototype Performance Tests System checks a) Drift velocity Measurement of drift velocity excludes distortions of the electric field and impurities in the gas due to leaks b) Energy resolution Good energy resolution with 5.9keV X-rays after 25cm drift distance, thus no impurities in the gas which could cause electron-attachment

16 The TPC Prototype Performance Tests Beam Test + Operation in a hadronic beam at the CERN PS in Summer 2003 Setup in T11 beam line + + 3Gev p beam, parallel to pads + Double-GEM, 2mm gaps + ET=2.5kV/cm, EI=3.5kV/cm + UGEM,1 = UGEM,2 + 10V Ar-CH4-CO2 (93:5:2) Ar-CO2 (70:30) Drift field 0.24 V/cm 0.31 kv/cm Drift velocity 4.55 cm/ms 0.70 cm/ms t withou ld! ie f c i t e magn

17 The TPC Prototype Performance Tests Efficiency scan Spatial Resolution in x ( p = 1.27mm ) efficiency [%] TESLA TDR gas, 6cm drift Ar-CO 2 (70:30), 13cm drift effective gain Fully efficient. G > residuals s [mm] (without track error) Ar-CO 2 (70:30, 0T) TDR gas (0T) drift distance [cm] down to s = 1.27mm pitch

18 The TPC Prototype Performance Tests Efficiency scan Spatial Resolution in x ( p = 1.27mm ) efficiency [%] TESLA TDR gas, 6cm drift Ar-CO 2 (70:30), 13cm drift effective gain residuals s [mm] (without track error) More results in session T17: A GEM-TPC Prototype with Low-Noise highly integrated Front-End Electronics for Linear Collider Studies Tuesday, 16:15, Timberline Room (JB) Ar-CO 2 (70:30, 0T) TDR gas (0T) drift distance [cm]

19 Summary & Outlook 4 GEM readout of TPCs is investigated for a number of future particle-physics experiments 4 The design of and experience with the Triple-GEM detectors for the Small-Area-Tracker (SAT) of COMPASS offers a solid basis for the design of GEM-TPCs 4 Considering study prospects, R&D aspects and practical requirements, a prototype TPC has been designed and constructed: 4 Double-ring layout field cage 4 Currently equipped with Multi-GEM plus pads readout 4 Materials selected with respect to outgassing properties 4 Detector validated in performance tests and in hadronic particle beams (=> session T17)