1. Development of micromegas for the ATLAS Muon System Upgrade Jörg Wotschack (CERN) MAMMA Collaboration Arizona, Athens (U, NTU, Demokritos), Brandeis, Brookhaven, CERN, Carleton, Istanbul (Bogaziçi, Doğuş), JINR Dubna, MEPHI Moscow, LMU Munich, Naples, CEA Saclay, USTC Hefei, South Carolina, Thessaloniki Work performed in close collaboration with CERN/TE-MPE PCB workshop (Rui de Oliveira) Lots of synergy from the RD51 Collaboration

2. Outline  The ATLAS Muon System upgrade  The micromegas technology  Making micromegas spark-resistant  Performance & ageing studies  Two-dimensional readout structure  Towards large-area micromegas chambers  First data from ATLAS  Next steps Frascati, 7 Dec 2011Joerg Wotschack (CERN)2 Not covered: electronics

3. The MAMMA *) R&D activity  Using the micromegas technology to build muon chambers for the ATLAS upgrade was first suggested in an ATLAS Muon Collaboration brainstorming meeting back in 2007 by I. Giomataris (CEA Saclay)  By this time MMs had been successfully used in several experiments at very high rates (COMPASS, NA48) but the largest chambers did not exceed 0.4 x 0.4 m 2  Profiting from the know-how of the CERN PCB workshop, the first prototype chamber, 0.4 x 0.5 m 2 in size, was built still in 2007; it worked very nicely  2008/2009 we convinced ourselves of the excellent performance of MMs and their potential for large-area muon detectors  2010 was dedicated to making micromegas spark resistant  2011 the first resistive large-area chambers successfully built and tested Frascati, 7 Dec 2011Joerg Wotschack (CERN)3 *) Muon ATLAS MicroMegas Activity

4. The ATLAS Muon System Upgrade Phase I (2018) Frascati, 7 Dec 2011Joerg Wotschack (CERN)4

5. Count rates *) in the ATLAS Muon System at √s = 14 TeV for L = 10 34 cm -2 s -1 Frascati, 7 Dec 2011Joerg Wotschack (CERN)5 Small Wheel Rates in Hz/cm 2 Rates at inner rim 1–2 kHz/cm 2 *) ATLAS Detector paper, 2008 JINST 3 S08003

6. Rates: measurement vs simulation Frascati, 7 Dec 2011Joerg Wotschack (CERN)6 Measured and expected count rates and in the Small Wheel detectors Data correspond to L = 0.9 x 10 33 cm -2 s -1 at √s = 7 TeV Rate in Hz/cm 2 as a function of radius in the large sectors Ratio between MDT data and FLUGG *) simulation (CSC region not shown) *) FLUGG simulation gives rates about factor 1.5 – 2 higher than old simulation

7. At least two reasons for new Small Wheels  Small Wheel muon chambers were designed for a luminosity of L = 1 x 10 34 cm -2 s -1 The rates measured today are 2–3 x higher than estimated All detectors in the SW will be at their rate limit at L >1 x 10 34 cm -2 s -1  Eliminate fakes in high-p T (> 20 GeV) triggers Currently over 95 % of forward high p T triggers are fake (removed at LV2) Use tracks in SW as LV1 confirmation Requires pointing precision of 1 mrad Frascati, 7 Dec 2011Joerg Wotschack (CERN)7 Today 2018

8. Small Wheel performance requirements  Rate capability 15 kHz/cm 2 (L ≈ 5 x 10 34 cm -2 s -1 )  Efficiency > 98%  Spatial resolution ≤100  m (Θ track < 30°)  Good double track resolution  Trigger capability (BCID, time resolution ≤ 5–10 ns)  Radiation resistance  Good ageing properties Joerg Wotschack (CERN) 8 Frascati, 7 Dec 2011 All requirements can be met with micromegas

9. 2.4 m ATLAS Small Wheel upgrade proposal *) Frascati, 7 Dec 2011Joerg Wotschack (CERN)9 CSC chambers Today: MDT chambers (drift tubes) + TGCs for 2 nd coordinate (not visible) Equip the Small Wheels with 128 micromegas chambers (0.5–2.5 m 2 )  Combine precision and 2 nd coord. measurement as well as trigger functionality in a single device  Each chamber comprises eight active layers, arranged in two multilayers  Each layer with two coordinates with 0.5 and 1.5 mm strip pitch  2M readout channels  a total of about 1200 m 2 of detection layers *) other candidates: combined systems sMDT+TGC and sMDT+RPC

10. The micromegas technology Frascati, 7 Dec 2011Joerg Wotschack (CERN)10

11. -800 V -550 V Micromegas operating principle  Micromegas (I. Giomataris et al., NIM A 376 (1996) 29) are parallel- plate chambers where the amplification takes place in a thin gap, separated from the conversion region by a fine metallic mesh  The thin amplification gap (short drift times and fast absorption of the positive ions) makes it particularly suited for high-rate applications  The price to pay is time resolution, e.g., compared to RPCs Joerg Wotschack (CERN)11 The principle of operation of a micromegas chamber Frascati, 7 Dec 2011 Conversion & drift space Mesh Amplification Gap 128 µm (few mm)

12. Micromegas as µTPC  Wide drift region (typically a few mm) with moderate electric field of 100–1000 V/cm  Narrow (100 µm) amplification gap with high electrical field (40–50 kV/cm); a factor E m /E d ≈70–100 is required for full mesh transparency for electrons  With drift velocities of 5 cm/µs (or 20 ns/mm) electrons need 100 ns for a 5 mm gap  By measuring the arrival time of the signals a MM functions like a TPC  => Track vectors for inclined tracks Frascati, 7 Dec 2011Joerg Wotschack (CERN)12

13. An established technology  Micromegas were (and are) used successfully over the last 10 years, e.g., in the COMPASS experiment as vertex chambers in a high-rate muon beam  12 planes with dimensions 400 x 400 mm 2  Strip pitch: 360 µm; 1024 channels/plane  Superb performance in high rates (>100 kHz/cm 2 ) Spatial resolution ≈70 µm; time resolution 9 ns  T2K near-detector as TPC readout  72 chambers of 350 x 360 mm 2  ‘Mass production’ using bulk micromegas technique Frascati, 7 Dec 2011Joerg Wotschack (CERN)13

14. Pillars (  ≈ 300 µm) The bulk-micromegas* technique PCB Photoresist (64 µm) r/o strips Mesh *) I. Giomataris et al., NIM A 560 (2006) 405 The bulk-micromegas technique, developed at CERN, opens the door to industrial fabrication Frascati, 7 Dec 2011Joerg Wotschack (CERN)14

15. Bulk-micromegas structure Frascati, 7 Dec 2011Joerg Wotschack (CERN)15 Standard configuration  Pillars every 2.5 – 10 mm  Pillar diameter ≈300 µm  Dead area ≈1–2%  Amplification gap 128 µm  Mesh: 350 wires/inch  Wire diameter 20 µm Pillars (here: distance = 2.5 mm)

16. Early performance studies (2007-2009)  All initial performance studies were done with ‘standard’ micromegas chambers  We used different gas mixtures, initially Ar:CF 4 :iC 4 H 10 (88:10:2, 95:3:2), moved later to Ar:CO 2 (80:20, 85:15, 93:7)  The chambers were read out with the ALTRO chip (up to a maximum of 64 channels) and the ALICE Date readout system (Thanks to H. Muller and ALICE!)  End 2010 we switched to a new readout electronics (APV25, 128 ch/chip) and a new ‘Scalable Readout System’ (SRS) developed by H. Muller et al. in the context of RD51 Frascati, 7 Dec 2011Joerg Wotschack (CERN)16 P1 (40 X 50 cm 2 ), H6 Nov 2007

17. 2008: Demonstrated performance Frascati, 7 Dec 2011Joerg Wotschack (CERN)17  Standard micromegas (P1)  Safe operating point with efficiency ≥99%  Gas gain: 3–5 x 10 3  Very good spatial resolution 250 µm strip pitch σ MM = 36 ± 7 µm Ar:CF 4 :iC 4 H 10 (88:10:2) (MM + Si telescope) X (mm) y (mm) Inefficient areas

18. Conclusions by end of 2009  Micromegas (standard) work  Clean signals  Stable operation for detector gains of 3–5 x 10 3  Efficiency of 99%, limited by the dead area from pillars  Required spatial resolution can easily be achieved with strip pitches between 0.5 and 1 mm  Timing performance could not be measured with the ALTRO electronics  However: sparks are a problem for LHC operation  Sparks lead to a partial discharge of the amplification mesh => HV drop & inefficiency during charge-up  The good news: no damage on chambers, despite many sparks Frascati, 7 Dec 2011Joerg Wotschack (CERN)18

19. 2010: Making MMs spark resistant  Tested several protection/suppression schemes  A large variety of resistive coatings of anode  Double/triple amplification stages to disperse charge, as used in GEMs (MM+MM, GEM+MM)  Settled on a protection scheme with resistive strips  Tested the concept successfully in the lab ( 55 Fe source, Cu X-ray gun, cosmics), H6 pion & muon beam, and with 2.3 MeV and 5.5 MeV neutrons Frascati, 7 Dec 2011Joerg Wotschack (CERN)19

20. The resistive-strip protection concept Frascati, 7 Dec 2011Joerg Wotschack (CERN)20

21. Large number of resistive-strip detectors tested  Small chambers with 9 x 9 cm 2 active area  Large range of resistance values  Number of different designs  Gas mixtures  Ar:CO 2 (85:15 and 93:7)  Gas gains  2–3 x 10 4  10 4 for stable operation Frascati, 7 Dec 2011Joerg Wotschack (CERN)21 R16 R16, first chamber with 2D readout

22. Small resistive-strip detectors Frascati, 7 Dec 2011Joerg Wotschack (CERN)22

23. Frascati, 7 Dec 2011Joerg Wotschack (CERN)23 Detector response

24. Sparks in resistive chambers  Spark signals (currents) for resistive chambers are about a factor 1000 lower than for standard micromegas (spark pulse in non-resistive MMs: few 100 V)  Spark signals fast (<100 ns), recovery time a few µs, slightly shorter for R12 with strips with higher resistance  Frequently multiple sparks Frascati, 7 Dec 2011Joerg Wotschack (CERN)24 R GND = 45 MΩ R strip = 5 MΩ/cm R GND = 20 MΩ R strip = 0.5 MΩ/cm

25. Performance in neutron beam  Standard MM could not be operated in neutron beam  HV break-down and currents exceeding several µA already for gains of order 1000–2000  MM with resistive strips operated perfectly well,  No HV drops, small spark currents up to gas gains of 2 x 10 4 Frascati, 7 Dec 2011Joerg Wotschack (CERN)25 Standard MMResistive MM

26. Spatial resolution & efficiency for R12 (250 µm strips) Analysis of data taken in July 2010 Frascati, 7 Dec 2011Joerg Wotschack (CERN)26 Resistive strip chambers are fully efficient (≈98%)over a wide range of gains Spatial resolution with 250 µm strip: ≈30 µm with Ar:CO 2 (93:7), even better with 85:15 Inefficiency compatible with area of mesh support pillars (d=2.5 mm)

27. R11 rate studies Frascati, 7 Dec 2011Joerg Wotschack (CERN)27 Clean signals up to >1 MHz/cm 2, but some loss of gain Gain ≈ 5000 ATLAS rates

28. Test beam Nov 2010 Frascati, 7 Dec 2011Joerg Wotschack (CERN)28 Four chambers with resistive strips aligned along the beam NEW: Scaleable Readout System (SRS) – RD51 (H. Muller at al.) APV25 hybrid cards

29. APV25 data – two track example Frascati, 7 Dec 2011Joerg Wotschack (CERN)29 Strip (0.25 mm) Time (25 ns) Integrated charge

30. Frascati, 7 Dec 2011Joerg Wotschack (CERN)30 R11 R12 R13 R15 Time bins (25 ns) Charge (200 e - ) Strips (250 µm pitch) v e ≈ 4.7 cm/µs

31. Frascati, 7 Dec 2011Joerg Wotschack (CERN)31 R11 R12 R13 R15 Delta ray Time bins (25 ns) Charge (200 e - )

32. Inclined tracks (40°) – µTPC Frascati, 7 Dec 2011Joerg Wotschack (CERN)32 R12 R11 Time bins (25 ns)Charge (200 e - ) v e ≈ 2 cm/µs

33. … and a two-track event Frascati, 7 Dec 2011Joerg Wotschack (CERN)33 R11 R12 Time bins (25 ns) Charge (200 e - ) v e ≈ 2 cm/µs

34. Ageing Frascati, 7 Dec 2011Joerg Wotschack (CERN)34

35. Ageing studies  Micromegas have shown excellent ageing properties in the past, no long-term effects were observed  However, no results are reported so far for MMs with resistive coating  We have started an ageing test campaign at CEA Saclay that involves high-rate exposure of resistive chambers to few MeV X-rays and thermal neutrons Frascati, 7 Dec 2011Joerg Wotschack (CERN)35

36. Long-time X-ray exposure  A resistive-strip MM (R17a) has been exposed at CEA Saclay to 5.28 keV X-rays for 12 and 21 days. In parallel, an ‘identical’ chamber (R17b) was measured without being irradiated continuously, in the 2 nd period.  Accumulated charge: 765 + 918 mC/4 cm 2 (>20 years of sLHC) Frascati, 7 Dec 2011Joerg Wotschack (CERN)36

37. Exposure to thermal neutrons  R17a was then moved to the Orphee reactor at Saclay and has been under radiation from 7 – 17 Nov 2011  Neutron flux is ≈0.8 x 10 9 n/cm 2 /s with energies of 5–10 x 10 -3 eV  Total exposure on-time: 40 hrs equivalent to ≈20 years LHC at 5 x 10 34 cm -2 s -1 (including a safety factor of 3)  Detector response perfectly stable over full duration of irradiation Frascati, 7 Dec 2011Joerg Wotschack (CERN)37

38. Two-dimensional readout & other structural issues Frascati, 7 Dec 2011Joerg Wotschack (CERN)38

39. 2D readout (R16 & R19)  Readout structure that gives two readout coordinates from the same gas gap; crossed strips (R16) or xuv with three strip layers (R19)  Several chambers successfully tested Frascati, 7 Dec 2011Joerg Wotschack (CERN)39 x strips: 250/150 µm r/o and resistive strips y: 250/80 µm only r/o strips PCB Mesh Resistivity values R G ≈ 55 MΩ R strip ≈ 35 MΩ/cm Resistive strips x strips y strips R16

40. R16 x-y event display ( 55 Fe γ) Frascati, 7 Dec 2011Joerg Wotschack (CERN)40 R16 x R16 y Charge (200 e - ) Time bins (25 ns) Strips (0.25 mm)

41. R19 with xuv readout strips  x strips parallel to R strips  u,v strips ±60 degree Frascati, 7 Dec 2011Joerg Wotschack (CERN)41 R strips v strips u strips x strips Mesh  Tested two chambers with same readout structure (R19M and R19G) in a pion beam (H6) in July  Clean signals from all three readout coordinates, no cross-talk  Strips of v and x layers well matched, u strips low signal, too narrow  Excellent spatial resolution, even with v and u strips σ = 94/√2 µm

42. Chamber construction simplifications  Mesh  Mesh stretching over large-area is possible but complicates the production process  Mesh HV insulation requires special attention, work intensive  Mesh segmentation is difficult to achieve, dead areas, labour intensive  Two variants tried  Replace the mesh with a GEM foil (works, but not pursued further, does not really simplify anything)  Connect the mesh to ground and the R strips to HV  Readout structure Frascati, 7 Dec 2011Joerg Wotschack (CERN)42

43. Inverting the HV connection scheme  Instead of connecting the mesh to HV, we connected in R20 the R strips to HV and the mesh to ground (A. Ochi)  Simplifies considerably the detector production  Clean signals, good energy resolution  High gain  Little charge-up  Good high-rate performance Frascati, 7 Dec 2011Joerg Wotschack (CERN)43 PCB Resistive Strips (+HV) Copper readout strip Insulator Mesh Drift electrode (-HV) Works very well, all recent detectors were built along these lines R20

44. Performance of R20 (inverted HV) Frascati, 7 Dec 2011Joerg Wotschack (CERN)44 G≈10000 G≈5000 55 Fe γ (5.9 keV) Ar:CO 2 93:7 Signal drop: 5 % (compared to 10–15% for R11, R12,…) 8 keV Cu X-rays Signal drop compatible with HV drop over resistive strips (0.5–1 GΩ)

45. Simplifying the readout board  Instead of two or three layers of readout strips on one side of the PCB we placed the readout strips on the two sides of the PCB  PCB thickness 0.8 – 1 mm  Signals capacitively coupled across the PCB  No through holes; connectors on both sides of the PCB  Avoids multi-layer PCBs  Leads to major simplification of production and cost reduction  Concept has been successfully tested in R21  Optimization of charge sharing ongoing Frascati, 7 Dec 2011Joerg Wotschack (CERN)45

46. Towards large-area MM chambers Frascati, 7 Dec 2011Joerg Wotschack (CERN)46

47. Assembly of 1 st large resistive MM in March 2011  Size: 1.2 x 0.6 m 2  2048 circular strips  Strip pitch: 0.5 mm  8 connectors with 256 contacts each  Mesh: 400 lines/inch  5 mm high frame defines drift space  O-ring for gas seal  Closed by a 10 mm foam sandwich panel serving at the same time as drift electrode Frascati, 7 Dec 2011Joerg Wotschack (CERN)47 Dummy PCB

48. Cover and drift electrode Frascati, 7 Dec 2011Joerg Wotschack (CERN)48

49. Drift electrode HV connection Frascati, 7 Dec 2011Joerg Wotschack (CERN)49 HV connection spring for drift electrode O-ring seal Al spacer frame

50. Chamber closed  Assembly simple, takes a few minutes  Signals routed out without soldered connectors Frascati, 7 Dec 2011Joerg Wotschack (CERN)50

51. Chamber in H6 test beam (July 2011) Frascati, 7 Dec 2011Joerg Wotschack (CERN)51 Large resistive MM R19 with xuv readout (seen from the back)

52. Experience with large (1.2 x 0.6 m 2 ) MM  The large MM with resistive strips and 0.5 mm pitch has been successfully tested in July and November in the H6 beam Frascati, 7 Dec 2011Joerg Wotschack (CERN)52 Event display showing a track traversing the CR2 chamber under 20 degree Hit map showing the beam profile (top) and charge spectrum (bottom)

53. The 2 nd large resistive chamber  Chamber completed end of Nov 2011  Employs the new HV scheme with mesh on ground potential and resistive strips on +HV Frascati, 7 Dec 2011Joerg Wotschack (CERN)53

54. Cosmic tracks in the two large MMs (I) Frascati, 7 Dec 2011Joerg Wotschack (CERN)54

55. Cosmic tracks in the two large MMs (II) Frascati, 7 Dec 2011Joerg Wotschack (CERN)55

56. Micromegas in ATLAS cavern Frascati, 7 Dec 2011Joerg Wotschack (CERN)56

57. Four resistive MMs installed behind last muon station Frascati, 7 Dec 2011Joerg Wotschack (CERN)57 R11 R12 R13x R16xy Trigger (strips) DCS mmDAQ DCS mmDAQ Laptop in USA15 ≈120 mm R16

58. Collision data and cavern background  The chambers operated from April to November 2011  Most of the time collision data were recorded with a stand-alone trigger  In a few fills we recorded several 10 M events with a random trigger  For each trigger the detector activity was measured for 28 time bins of 25 ns, i.e. 700 ns (accepted 500 ns) over a total area of 2 x 81 cm 2  Measured background rate: 2.7–3 Hz/cm 2 at 10 34 cm -2 s -1 About a factor 3 lower than the background rate measured in the nearby EOL MDT Frascati, 7 Dec 2011Joerg Wotschack (CERN)58

59. Frascati, 7 Dec 2011Joerg Wotschack (CERN)59 ATLAS cavern Collision track

60. Two types of background events Photon ? Neutron ? induced nuclear break-up Total charge: 1700 ADC counts Total charge: >10000 ADC counts Frascati, 7 Dec 2011Joerg Wotschack (CERN)60

61. Conclusions Frascati, 7 Dec 2011Joerg Wotschack (CERN)61

62. What have we learned so far ?  Micromegas fulfil all of the Small Wheel requirements  Excellent rate capability, spatial resolution, and efficiency  Potential to deliver track vectors in a single plane for track reconstruction and LV1 trigger  We found an efficient spark-protection system that is easy to implement; sparks are no longer a show-stopper  MMs are very robust and (relatively) easy to construct (once one knows how to do it)  Large-area resistive-strip chambers can be built … and work 62Frascati, 7 Dec 2011Joerg Wotschack (CERN)

63. What next?  We are working on a detector of 1.2 x 0.5 m 2 with four active planes and two-coordinate readout in each plane; to be installed in the winter shutdown in ATLAS on the Small Wheel  Install a small detector (MBT0) in front of the end-cap calorimeter as prototype for a replacement of the Minimum Bias Scintillator trigger detector  Build a 1 m wide chamber (possible after the completion of the upgrade of the CERN PCB workshop, early 2012 ?)  Move to industrial processes for  Resistive strip deposition  Mesh placement … and build a full-size module0 for the Small Wheel in 2012 Frascati, 7 Dec 2011Joerg Wotschack (CERN)63

64. Proposal for Micromega chamber positioning in CSC region of Small Wheel HO side sector 9 and services routing Micromegas chamber Routing of services Frascati, 7 Dec 2011Joerg Wotschack (CERN)64

65. What next?  We are working on a detector of 1.2 x 0.5 m 2 with four active planes and two-coordinate readout in each plane; to be installed in the winter shutdown in ATLAS on the Small Wheel  Install a small detector (MBT0) in front of the end-cap calorimeter as prototype for a replacement of the Minimum Bias Scintillator trigger detector  Build a 1 m wide chamber (possible after the completion of the upgrade of the CERN PCB workshop, early 2012 ?)  Move to industrial processes for  Resistive strip deposition  Mesh placement … and build a full-size module0 for the Small Wheel in 2012 Frascati, 7 Dec 2011Joerg Wotschack (CERN)65

66. MBT0 : Double gap chamber with x and u (v) readout strips Chamber position Routing of services Frascati, 7 Dec 2011Joerg Wotschack (CERN)66

67. What next?  We are working on a detector of 1.2 x 0.5 m 2 with four active planes and two-coordinate readout in each plane; to be installed in the winter shutdown in ATLAS on the Small Wheel  Install a small detector (MBT0) in front of the end-cap calorimeter as prototype for a replacement of the Minimum Bias Scintillator trigger detector  Build a 1 m wide chamber (possible after the completion of the upgrade of the CERN PCB workshop, early 2012)  Move to industrial processes for  Resistive strip deposition  Mesh placement … and build a full-size module0 for the Small Wheel in 2012 Frascati, 7 Dec 2011Joerg Wotschack (CERN)67

68. Thank you ! for your attention... Frascati, 7 Dec 2011Joerg Wotschack (CERN)68

69. Backup slides Frascati, 7 Dec 2011Joerg Wotschack (CERN)69

70. Spark rates in neutron beam (R11)  Typically a few sparks/s for gain 10 4  About 4 x more sparks with 80:20 than with 93:7 Ar:CO 2 mixture  Neutron interaction rate independent of gas  Spark rate/n is a few 10 -8 for gain 10 4  Larger spark rate in 80:20 gas mixture is explained by smaller electron diffusion, i.e. higher charge concentration Frascati, 7 Dec 2011Joerg Wotschack (CERN)70

71. Frascati, 7 Dec 2011Joerg Wotschack (CERN)71 A tentative Layout of the New Small Wheels and a sketch of an 8-layer chamber built of two multilayers, of four active layers each, separated by an instrumented Al spacer for monitoring the internal chamber deformations

72. Sparks in 120 GeV pion & muon beams  Pions, no beam, muons  Chamber inefficient for O(0.1s) when sparks occur  Stable, no HV drops, low currents for resistive MM  Same behaviour up to gas gains of > 10 4 Frascati, 7 Dec 2011Joerg Wotschack (CERN)72 Gain ≈ 10 4 Gain ≈ 4000 8000

73. Homogeneity and Charge-up  No strong dependence of effective gain on resistance values (within measured range)  Systematic gain drop of 10–15% for resistive & standard chambers; stabilizes after a few minutes  Charge-up of insulator b/w strips ? Frascati, 7 Dec 2011Joerg Wotschack (CERN)73 R ≈ 45 MΩ R ≈ 85 MΩ

74. Replacing the mesh by a GEM foil GEM is simply placed on 128 µm high pillars on the resistive strips Frascati, 7 Dec 2011Joerg Wotschack (CERN)74 1. Stripped GEM foil (lower Cu layer removed)  R19G, successfully used in test beam in July  Works well, no striking difference to 19M (with micromesh)  High rate looks OK 2. Standard GEM foil  Works similarly as R19G  Did not find with this configuration a HV setting to profit from gain in GEM  Fragile, sparks in GEM destroyed GEM 3. Stripped GEM foil (upper Cu layer removed)  Did not find good operating point  Works as MM but problems with GEM transparency Effort not pursued any further

75. Trigger & readout  New BNL chip: 64 channels; on-chip zero suppression, amplitude and peak time finding  Trigger out: address of first-in-time channel with signal above threshold within BX  Data out: digital output of charge & time for channels above threshold + neighbour channels  Trigger signals and data are driven out through one (same) GBTx link/layer (one board/layer)  Trigger: track-finding algorithm in Content-Addressable Memory (or in FPGA) in USA15; latency estimated 25–32 BXs (of 42 allowed)  Small data volumes thanks to on-chip zero-suppression and digitization Frascati, 7 Dec 2011Joerg Wotschack (CERN)75

76. Trigger/DAQ Block Diagram 76Frascati, 7 Dec 2011Joerg Wotschack (CERN) GBTx Gigabit Tranceiver Chipset being developed at CERN, will combine Data, TTC, DCS on a single fiber GBTx Gigabit Tranceiver Chipset being developed at CERN, will combine Data, TTC, DCS on a single fiber

77. BNL chip specifications (prelim.) 64 channels/chip (preamplifier, shaper, peak amplitude detector, ADC)  Real time peak amplitude and time detection with on-chip zero suppression  Simultaneous read/write with built-in derandomizing Buffers  Peaking time 20–100 ns; dynamic range: 200 fC  Fast trigger signal of all and/or groups of channels  Rate: 100 kHz  SEU tolerant logic A similar older BNL chip (with longer integration time and smaller rate capability) has been tested with our MMs and is working well Frascati, 7 Dec 2011Joerg Wotschack (CERN)77