1. GEM, Micromegas detector production. detector’s dynamic range detector’s dynamic range Rui De Oliveira Catania 24/11/2011 24/11/20111Rui De Oliveira

2. CERN PCB Workshop 24/11/2011Rui De Oliveira2 18 persons Building :1000 sqr meters Making PCBs since 1960 -PCB -Rigid -Flex -Flex-rigid -Micovias -fine line (15um) -large size (up to 2m) -Thick film Hybrids -Thin film Hybrids -Chemical milling -Cu, Fe, Al, Au, Ag, W, Mb, Ti, Cr, Ni -MPGD -GEM/thinGEM/THGEM/RETHGEM -MSHP/Cobra -MICROMEGA/ Bulk/ Micro-BULK -RES BULK -Resistive MSGC -Low mass circuits -Multilayer flexes with aluminum strips -embedded heat sinks (carbon, graphite, metals, diamon) -Embedded components -passive -Active

3. GEMGEM Large size situationLarge size situation Detector without spacersDetector without spacers MicromegasMicromegas Large size situationLarge size situation X/Y and U/V/W readoutX/Y and U/V/W readout Ionization range and detector’s dynamicsIonization range and detector’s dynamics The problemThe problem Possible solutionsPossible solutions 24/11/20113Rui De Oliveira OUTLINE

4. 24/11/2011 Rui De Oliveira 4 GEM Foil Present size 1.2m x 0.6m Future max size 2m x 0.6m Std pattern 140um pitch/70um holes

5. 24/11/2011 Rui De Oliveira 5 Base material : Polyimide 50um + 5um on both sides Polyimide : Apical NP from company Kaneka (Japan) Supplier of the copper clad material : Nippon Mining (Japan) GEM double mask Vs GEM single Mask Same base material Hole patterning in Cu Polyimide etch Bottom electro etch Second Polyimide Etch Limited to 40cm x 40cm due to Mask precision and alignment Limited to 2m x 60cm due to Base material Equipment Double maskSingle mask

6. 24/11/2011Rui De Oliveira6 GEM Double mask Vs GEM single Mask Similar patterns, similar behavior, same material. Angles can be adjusted in both structure (Typ value : 70um copper hole, 50um polyimide hole) Steeper angles gives lower gain but also lower charging up

7. COMPASS (CERN) 7 GEM double mask examples LHCb-Muon trigger (CERN) TOTEM (CERN) Window Drift electrode GEM stack Pad Plane Support & Media-Distribution Cooling Support & LV- Distribution Front-End Electronic Shielding Cover & Read-out Plane STAR experiment (US) 24/11/2011Rui De Oliveira Present double mask production quantities : around 500 GEMs/ year in average Max size: 40cm x 40cm

8. 8 GEM Single mask examples KLOE – Cylindrical 3 GEM Detector GEM 800mm x 500mm Read-out 2D : 800mmx 500mm CMS RPC possible upgrade GEM 1.1m x 500mm Present production rate : 100 Gem /year (1.2mx0.6m) Expected rate for 2012 : 250 GEM/Year/technician 24/11/2011Rui De Oliveira

9. GEMGEM Large size situationLarge size situation Detector without spacersDetector without spacers MicromegasMicromegas Large size situationLarge size situation X/Y and U/V/W readoutX/Y and U/V/W readout Ionization range and detector’s dynamicsIonization range and detector’s dynamics The problemThe problem Possible solutionsPossible solutions 24/11/20119Rui De Oliveira

10. No spacers in active area Assembly time ½ hour for 10cm x 10cm detector (1 technician) 2 hours for 1m x 0.6m detector (1 technician) No gluing, no soldering Re opening possible GEM exchange possible Full detector Re-cleaning possible No intermediate test New GEM stretching method (NS2) advantages: 24/11/201110Rui De Oliveira

11. No spacer self stretching structure 24/11/2011Rui De Oliveira11 15mm Readout connector O-ring GEM attaching structure (4 pieces defining gaps) Drift electrode Free to slide External screws to adjust stretching GND gluing

12. 24/11/2011Rui De Oliveira12 30cm x 30cm

13. 24/11/2011Rui De Oliveira13 FRAME GEM HV DIVIDER DRIFT BOARD CLOSED DETECTOR Screws O-ring HV BNC Connector Gas connectors Read-out connectors

14. GEMGEM Large size situationLarge size situation Detector without spacersDetector without spacers MicromegasMicromegas Large size situationLarge size situation X/Y and U/V/W readoutX/Y and U/V/W readout Ionization range and detector’s dynamicsIonization range and detector’s dynamics The problemThe problem Possible solutionsPossible solutions 24/11/201114Rui De Oliveira

15. 24/11/201115 PCB lamination Mesh deposit lamination development Rui De Oliveira Large Micromegas Largest size produced: 1.5m x 0.6m Limited by equipment BULK Technology DUPONT PC 1025 coverlay BOPP Meshes SERITEC stretching

16. 16 Fine segmentation 1cm², thickness 8mm for ILC Hadronic calorimetry Tested in the RD51 1 kHz beam Bulk Micromegas ILC DHCAL first m 2 LAPP Annecy 24/11/201116Rui De Oliveira Pad read-out large TPC Neutrino detector 10 sqr meter in service T2K experiment Japan

17. Atlas CSC replacement project 24/11/2011Rui De Oliveira17 MPGD Vs Wire chambers -Faster -no need for fancy gases -lower cost -robust 1.2m x 0.6m

18. Resistive Bulk MicroMegas structure 24/11/2011Rui De Oliveira18

19. 24/11/2011 Rui De Oliveira 19 Resistive strip process PCB -Good resistor uniformity -Easy to clean -Thermally robust Read-out strips or pads Copper lamination layer Resistive inverse patterning Resistive layer deposition Copper stripping

20. 24/11/2011Rui De Oliveira20 Atlas CSC replacement project Double sided Board Resistive strip deposit Bulking Test before closingClosing

21. GEMGEM Large size situationLarge size situation Detector without spacersDetector without spacers Compact HV dividerCompact HV divider MicromegasMicromegas Large size situationLarge size situation X/Y and U/V/W readoutX/Y and U/V/W readout Ionization range and detector’s dynamicsIonization range and detector’s dynamics The problemThe problem Possible solutionsPossible solutions 24/11/201121Rui De Oliveira

22. Resistive strips Bulk MicroMegas resistive anode and 2D readout 24/11/2011Rui De Oliveira We have produced : X/Y read-out U/V/W read-out Grounded mesh detectors 22

23. 24/11/2011Rui De Oliveira23 X/Y read-out U/V/W read-out

24. GEMGEM Large size situationLarge size situation Detector without spacersDetector without spacers Compact HV dividerCompact HV divider MicromegasMicromegas Large size situationLarge size situation X/Y and U/V/W readoutX/Y and U/V/W readout Ionization range and detector’s dynamicsIonization range and detector’s dynamics The problemThe problem Possible solutionsPossible solutions 24/11/201124Rui De Oliveira

25. 24/11/2011Rui De Oliveira25 Normal situation in a detector for HEP: Detectors are looking for one type of particles for example: Muons Usually the main concern is rate, multiplicity, accuracy in time and position All the parameters : gain, gas etc … are tune for one type of particle Some hadrons can come and pollute the measurement Different techniques have been developed to avoid this pollution creating Sparks based on resistive layers (RPC,Micromegas,TGC) The idea is to reduce, in time and amplitude, the spark But it is impossible to get any information from heavy ionizing particle In fact you have to choose what you want to see.

26. Problem : How to see an event like this in a TPC? Bragg peak of 62 MeV proton Beam acquired with a water-tank system and a Markus chamber ionization chamber at CATANA facility 24/11/2011Rui De Oliveira26 In the same detector you need in theory a high gain to see the first part of the curve and a low gain at the end.

27. Case 1 24/11/2011Rui De Oliveira27 Set the detector gas gain at a low value In this area the signal to noise ratio Will be OK In this area the gain will be to low Lot’s of noise

28. Case 2 24/11/2011Rui De Oliveira28 Set the detector gas gain at a high value Sparks In this area the Signal to noise ratio will be OK

29. GEMGEM Large size situationLarge size situation Detector without spacersDetector without spacers Compact HV dividerCompact HV divider MicromegasMicromegas Large size situationLarge size situation X/Y and U/V/W readoutX/Y and U/V/W readout Ionization range and detector’s dynamicsIonization range and detector’s dynamics The problemThe problem Possible solutionsPossible solutions 24/11/201129Rui De Oliveira

30. 24/11/2011Rui De Oliveira30 MM principle of operation

31. 24/11/2011Rui De Oliveira31 End of the curve means sparks Sparks mean reaching Raether limit Raether limit is not in theory an amount of electrons but a charge density The higher the field The higher the charge density The gas is playing a big role For a given set up the Raether Limit is a constant and usually In the range of 10^6 – 10^7 electrons

32. 24/11/2011Rui De Oliveira32 Dynamics : -primary ionization define Max gain (Raether limit) For a given set up -Ex: blue curve The detector is set at a gain of 10^4 for good S/N ratio Event creating 2 x more time electrons  ok Event creating 10 x more time electrons  spark A detector reaching high gains can have large dynamics Be careful with plots  primary ionization?

33. GEM principle of operation 24/11/2011Rui De Oliveira33 Amplification Diffusion Sharing between holes Amplification

34. Triple GEM 24/11/2011Rui De Oliveira34

35. Triple GEM 24/11/2011Rui De Oliveira35 Why not 4 layers?

36. MM/GEM 1 mm MM/GEM 2 mm PPP Gain MM Gain MM+GEM discharge rate in low momentum hadron beam: 36 => A GEM pre-amplification reduces the discharge rate by at least a factor 10 G. Charles et al., NIM A648 (2011), 174 Rui De Oliveira MM+GEM 24/11/2011

37. Rui De Oliveira37 Possible directions to improve the dynamic range: Decrease the maximum fields in the amplifying gaps Multiply the amplifying layer Increase the gaps between the amplifying layers Choose a gas increasing diffusion You have to fight against Raether limit  10^6 to 10^7 local charges

38. 24/11/2011Rui De Oliveira38 Goods and bads of multiple amplification stages: It Lowers the gain at each stage High diffusion between the stages dilute charges and avoid reaching Raether limit It gives the possibility at each stage to amplify again It reduces the spacial resolution It need a high diffusion gas It needs larger gaps between amplification layers It means also higher voltages The structures will anyway have to support some sparks (MM ok, GEM be careful) (Adding resistive protection can help) It probably requires an electronics with a high dynamic range or non linear amplification

39. GEM single mask process is stable -Ramp up the production -Increase the size to 2m x 0.6m -Reduce the prices Large Protected Micromegas -Process nearly stabilized -increase the size to 2m x 1m Measuring Bragg peak probably needs a multiple stage gas amplification detector Conclusions and next steps 24/11/201139Rui De Oliveira

40. 24/11/2011Rui De Oliveira40 Thank you