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Advancements in Large Area GEM Detectors: 11th Pisa Meeting

Collaboration on micropattern gas detectors, procedures, measurements, performance, and future applications at CERN and LNF.

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Advancements in Large Area GEM Detectors: 11th Pisa Meeting

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  1. 11th Pisa Meeting on Advanced Detectors La Biodola, 26.05.09 Activity of CERN and LNF Groups on Large Area GEM Detectors Danilo Domenici INFN - LNF

  2. LNF and CERN in RD51 Collaboration • LNF and CERN groups work together within the RD51 Collaboration: Development of Micro-Pattern Gas Detectors Technologies • WG1/Task1: Technological Aspects and Development of New Detector Structures / Large Area GEM Detectors • Installed and working detectors: • 20 31x31cm2 Triple-GEM in COMPASS NIM A490 (2002), 177 • 40 14.5cm  Triple-GEM in TOTEM NPPS 172 (2007), 231 • 24 20x24cm2 Triple-GEM in LHCb NIM A494 (2002), 156 • Need for Large-Area GEM • Present size limitation: ~450x450mm2 • Width of raw material (457mm roll) • Alignment precision of double-mask procedure

  3. Standard Double-Mask Procedure Starting raw material: 50μm Kapton foil with 5μm Copper clad Photoresistcoating , Double Mask are laid down and exposed Double side metal etching Double side kapton etching. The hole has bi-conical shape

  4. New Single-Mask Procedure Starting raw material: 50μm Kapton foil with 5μm Copper clad Photoresist coating, Single Maskare laid down and exposed Hole is opened with top side metal etching and kaptonetching Bottom side metal etching. Top side metal is preserved with CathodicProtection technique Back to kaptonetching for 30 sto get cylindrical shaped hole Eventual quick metal etching to form the rim

  5. Hole Geometry 5um Cu 70 STD GEM 50 70 5um Cu NEW GEM 70 65 5um Cu

  6. Nearly Cylindrical Holes TOP Kapton TOP Sparking voltage 700 V in air BOT BOT Kapton

  7. X-Ray Measurements Single-GEM chamber layout 4 mm Drift Gap 2 mm Induction Gap Current readout • Single-GEM readout in current mode • 2 identical chambers have been tested with X-rays: • 1 with single-mask foil • 1 with standard foil • Flushed on the same gas line and irradiated with front and side openings of the gun GAS: Ar/CO2 70/30

  8. X-Ray Measurements Electron Transparency 80% at 0 Field: larger Optical Transparency due to larger diameter VGEM = 400V Ed= 1.5kV/cm

  9. X-Ray Measurements Ion Feedback VGEM = 400V Ed= 1.5kV/cm

  10. X-Ray Measurements Charge Sharing Equal Sharing Field highly dependent on New-GEM orientation 4.6kV/cm 5.7kV/cm VGEM = 400V Ed= 1.5kV/cm 5.2kV/cm

  11. X-Ray Measurements Gas Gain G60-70 / Gstd = 0.67 G70-60 / Gstd = 0.80 Additional 10  20 V needed to operate at the same Gain as Standard GEM

  12. Simulation: Drift Lines 75–55 95–55 55–55 55–75 55–95

  13. Simulation: Field Intensity 95–55 75–55 55–55 55–75 55–95

  14. Future Applications CERN TOTEM Upgrade LNF KLOE Upgrade

  15. TOTEM Large Prototype • Idea of upgrade for T1 tracker (now Cathode-strips Wire chamber) • Discs of 2 x 5 chambers, back to back, allow to cover all the surface Large Triple-GEM prototype (~ 2000 cm2) obtained from two 66x33cm2 foils

  16. Splicing GEM heat pressure Foils are spliced over a narrow seam using an adhesive flexible kaptoncoverlayer (25µm thick) Efficiency with X-rays ( 0.5mm collimator)

  17. Manufacturing of Prototype Stretching and framing the spliced single mask gem foils Making the honeycomb base plane and top cover

  18. Manufacturing of Prototype Gluing the cathode to the honeycomb frame Final assembly of all frames

  19. Performance Energy Resolution with 8.9keV X-rays σE/E = 9.5% Rate Capability up to 1MHz/mm2 Triple-GEM Gain in Ar/CO2 preliminary hole geometry Effective Gain Voltage Sum (V)

  20. Cylindrical Triple GEM Read-out Anode 2 mm GEM 3 2 mm GEM 2 2 mm GEM 1 3 mm Cathode Induction Transfer 2 Transfer 1 Conversion & Drift KLOE2 Inner Tracker • 5 independent tracking layers 15 to 25cm from IP to improve vertex reconstruction • σrφ= 200 µm and σZ= 500 µm spatial resolutions with XV strips-pads readout • 700 mm active length • 1.5% X0total radiation length in the active region with Carbon Fiber supports •  300 x 352mm prototype with Std GEM has been assembled and tested Realized as an innovative Cylindrical-GEMdetector

  21. Manufacturing the Prototype 960 mm 352 mm 1 2 3 Full sensitive and Ultra-light detector Distribution of epoxy on foil edge 3 spliced foils ~1000mm long Cylindrical mould in vacuum bag Cylindrical GEM foil Cylindrical Cathode with annular fiberglass support flanges 5 4

  22. Performance Efficiency ε = 99.6% Performance measured at PS testbeamwith GASTONE digital Readout Electronics (INFN-Bari) and external Drift Tubes Tracking System Spatial Resolution (GEM)=(250µm)2 – (140µm)2  200µm

  23. Large Planar Prototype Cathode PCB 70x30 cm2 Triple-GEM planar detector with Single-mask foils for quality and uniformity test GEM1 GEM2 GEM3 1.5x2.5 cm2 pad readout PCB

  24. Tooling and Simulations Meters With the usual 1 kg/cm, finite element simulation (ANSYS) indicates a maximum gravitational+electrostatic sag of the order of 20 μm Load Cells Jaws A very large tensioning toolhas been designed. The frame gluing will be performed by using the “vacuum bag” technique, tested in the construction of the CGEM

  25. RD51 Testbeam Facility WG7: Common Test Facilities • H4 beam-line at SPS: 150GeV pions • Goliath Magnet: dipole field up to 1.5T in a ~3x3x1m2 • Semi-permanent setup for RD51 users • First test June 21st – July 6th • CERN: Large-GEM prototype • LNF: XV readout and BField RD51 setup Beam direction Goliath magnet

  26. Conclusions • A change of the GEM production procedure has been driven by the wide request of Large Detectors by the GEM community • A new Single-Mask and Cathodic Protection etching technique has been tuned, allowing for foils as large as 450x2000mm2 • The short size limitation, due to the definite width of the raw-material, can be overcome by splicing more foils together • A Single-Mask 10x10cm2 foil has been tested with X-rays in a Single-GEM detector readout in current mode. Results show slight difference with the standard GEM • LNF and CERN groups are developing Large-GEM detectors for future applications: TOTEM upgrade and KLOE upgrade • Other possible applications are Super-LHC Detector upgrades (LHCb TT and Muon), Screening for homeland security and PET scanners

  27. SPARES

  28. Cathodic Protection An example of active corrosion protection CP is a technique to control the corrosion of a metal surface by making it work as a cathode of an electrochemical cell. Used to protect ship hulls and oil pipes 0V +3V +3V Resist layer to protect back part from the bath Bottom electrode at +3V is chemically etched Bath at +3V Top electrode at ground is electrically protected

  29. Single-Mask Etching Isotropic metal etching Resist layer Opening of the hole, but unwanted angles in the copper Over-etching of the copper Going back to Polyimide etching for 30 sec The hole become cylindrical

  30. Helium-Isobuthane

  31. X-Ray Measurements Relative Gain vs GEM Voltage Single-GEM Edrift = 1.5 kV/cm Eind = 5 kV/cm

  32. X-Ray Measurements Normalized gain vs VGEM Triple-GEM 40V Data normalized to previous Absolute gain measurements with Ar/CO2 70/30 Fields: Ed=1.5 – Et1=2.5 – Et2=3.0 – Ei=5.0

  33. 2-D Readout Circuits Both views can be readout from the 2 ends of the circuit: suitable for a cylindric geometry without dead spaces 650 µm pitch V strips Orthogonal XY 650 µm pitch X strips

  34. Readout studies: 2-D strips Cluster multiplicity studies on the first two XY chambers Gast1: induction gap 2 mm Gast2: induction gap 1 mm

  35. Readout studies: B-Field Simulation of effects of a Magnetic Field (B=0.5T) on a Triple-GEM Ar/CO2=70/30 <α>L~ 8o 9o 9mm 1.2mm He/i-C4H10=90/10 <α>L~ 3o 4o 0.6mm

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