1. WG2 session summary M. Chefdeville RD51 collaboration meeting 7-10 October 2010, Bari, Italy 1

2. Session agenda Emphasis on operation in argon at low temperature (3 talks) – GEM/Micromegas/GridPix MAMMA collaboration presentations (2 talks) – Status report and spark study Application with neutrons – GEM for neutron beam diagnostic High rate application – Micromegas for COMPASS – Proposal of an experiment at a pp collider 2

3. The double phase argon LEM-TPC, D. Lussi 3

4. Large Electron Multiplier – 1000/500/800 um thickness/diameter/pitch Two dimensional projective anode – 10x10 cm2 with 3 mm readout pitch – Spark protection and preamplifier Gas purification system – Cool down phase – filling – recirculation – 1 volume / 48 h – best purity achieved [O2]eq < 0.6 ppb The double phase argon LEM-TPC, D. Lussi Made @ CERN workshop 4

5. Test setup @ CERN The double phase argon LEM-TPC, D. Lussi 5

6. Cosmic tracks – X/Y correlation -> Q sharing close to 1 – Extraction field scan: attachment and time smearing < 1 kV/cm – Landau MPV @ ≠ voltages -> max gas gain ~ 30 – dQ/dx VS time -> e- life-time & [O2]eq The double phase argon LEM-TPC, D. Lussi Alternative charge readout: Micromegas (A. Delbart) 6

7. Robustness test of Bulk Micromegas @ low T – Max. voltage of at decreasing temperature (1300 V@-196° C) – After drying out detector at 80° C for 1 night gas gain curve was lower than before bath High pressure gas gain measurement @ Room T – Former Hellaz exp. Chamber – No particular gas purification system – 241 Am alpha source + ORTEC readout of mesh – Gain max of 500 @ 3.5 bar with 50 um micro-Bulk First test of Micromegas in double phase liquid Ar, A. Delbart 7

8. Goal: operation & gas gain measurement with a Bulk-Micromegas 1D readout with 32 strips (3.1 mm pitch) -> modified PCB (CERN workshop) 2 bulk done with 128 and 100 um gap First test of Micromegas in double phase liquid Ar, A. Delbart 8

9. Measure gain @ various voltages (10 fC/strip expected for MIP) Fields of 42, 46, 47 kV/cm, gain of 1,3, 4 Steep transition from stable to unstable conditions Signal loss while increasing drift field (250-750 V/cm) not observed First test of Micromegas in double phase liquid Ar, A. Delbart 42 kV/cm 46 kV/cm 47 kV/cm 9

10. The maximum gain is low and may be due to the very high purity of Argon (which is demanded for charge drift in liquid) Such a low gain could be suitable for neutrino applications but higher gains (>100) are needed for dark matter search But these are the first tests and further improvements and studies are planned (thinner bulk gaps, micro-bulk, …) First test of Micromegas in double phase liquid Ar, A. Delbart 10

11. DARWIN: European R&D project for bi-phase missing mass/energy detectors With InGrid TPC: – detection of single, individual electrons essential: granularity and the very small source capacitance at pixel input – high (95 %) single electron efficiency – accurate X, Y and Z (timing) precision – potentially: (UV) photon detector First operation of GridPix low temperature, H. van der Graaf 11

12. First operation of GridPix low temperature, H. van der Graaf 12

13. TimePix proved to work at -100 °C, confirmed at -73 °C, -160 still to be tested Maximum gas gain of 200 – Might not be a problem with a new TimePix with preamplifier optimized for low temperature application (noise of 20 e- ?) New collaboration with Rubbia group at CERN – Construct support structure to place GridPix inside the Cryostat (-186 °C) – First test to check the suitability of detector’s electronical components Detect scintillation light signal with GridPix – CsI layer on grid First operation of GridPix low temperature, H. van der Graaf 55Fe in pure argon, HVgrid = 350 V P = 1 bar T = -70 C at NLR cryostat gain: ~ 200 ! 13

14. MAMMA: Muon Atlas MicroMegas Activity – High rate application -> avoid sparks or make detector spark-proof – High resistive coating may solve the sparking issue Test in high intensity beam of detector with different resistive coatings (2009) – Preliminary results Preparation of next test beam & resistive Bulk characterization – Gain stability and spark topology studies Characterization of resistive Micromegas for MAMMA, D. Attie 14 Requirements: High rate capability (≤ 10 kHz.cm-2) Spatial resolution ~100 µm (θ ≤ 45 °) Radiation hardness and good ageing properties Time resolution ~few ns Level1 triggering capability Large surface

15. Strong attenuation of spark current and voltage drop Spatial resolution of 80 um (1 mm pitch strip) Low cluster size value Characterization of resistive Micromegas for MAMMA, D. Attie 15 2009 TB preliminary results

16. Setup for the next TB – Increase cluster size with higher diffusion gas (Ar/CF4/iso 95/3/2 -> Ar/iso 98/2) – More detector with smaller strip pitch (0.5 mm) First characterisation with 55Fe source – Gas gain measurements & energy resolution – Charging up effects & model comparison 16 Characterization of resistive Micromegas for MAMMA, D. Attie

17. Sparking study in resistive detectors with an alpha source – Measure voltage drop through a 1 MOhms resistance on 4 adjacent strips and apply threshold 17 Characterization of resistive Micromegas for MAMMA, D. Attie

18. In some configuration the resistive coating is able to contain or even suppress the spark signal Ready for the next beam test at Cern to determine in high rate condition operation the efficiency of the various resistive Micromegas. 18 Characterization of resistive Micromegas for MAMMA, D. Attie R14, Resistive strips 300 kΩ/ □ R17, Joerg like Standard Bulk

19. New results with “Joerg” chambers: R11,R12,R13 – Small 100 x 100 mm 2 chamber with 100 mm long strips and 250 µm strip pitch, 360 strips in total Characteristics: – Resistive strips connected to the ground – Thin insulating layer between of the resistive and readout strips – AC coupling of signals – Sparks are neutralized through the resistive strips to the ground 19 Micromegas progress report, V. Polychronakos

20. Laboratory tests with X-tube and 55Fe quanta 20 Micromegas progress report, V. Polychronakos

21. Test in a neutron beam – First plots showed at previous collaboration meeting – New results on spark rate R11 worked fine in a neutron flux of up to 1.5 x 10 6 n/cm 2 s Despite sparks, no HV breakdown, no dead time Measured three Ar:CO 2 gas mixtures, 93:7 looks very interesting, with a spark rate almost a factor 5 lower than for 80:20 21 Micromegas progress report, V. Polychronakos

22. Test in a high intensity hadron beam R11, R12, R13, and P3 chambers were tested in +120 GeV pion beam intensities 40 kHz & 5 kHz in two Ar:CO 2 mixtures, 85:15 and 93:7 Main goals: – Study HV and current behavior of resistive and non-resistive chambers in a hadron beam – Measure performance (spatial resolution and efficiency) of resistive chambers – Study performance of long strips (0.4 m & 1m, non-resistive) A few million of events are being analyzed 22 Micromegas progress report, V. Polychronakos Event display: Timing at angle 40°

23. Micromegas progress report, V. Polychronakos MM readout chip design BNL chip features Data Driven System with Peak Amplitude and Time Detection: on-detector zero suppression Neighbour-channel enabling circuitry: high thresholds without losing small amplitudes Able to provide Trigger Primitives for on- detector track finding logic Based on existing chip developed a few years ago for a TPC application Appropriate for a variety of detectors (mMegas, TGC, TPC, GEM, etc.) requiring amplitude and time measurement

24. Example of test of BNL chip with Micromegas On-chip zero suppression: only channels that exceed a predefined trigger threshold, plus the two neighbouring ones are analyzed and read out Simulation Micromegas progress report, V. Polychronakos

25. Next steps – Proceed with full-size prototype (CSC size) First version is under design Readout with APV25 chip and RD51 readout system Test in H6 foreseen in October – Multi-plane full-size prototype design will start this fall BNL electronics should be available Could install a test chamber in ATLAS during 2012 shut down 25 Micromegas progress report, V. Polychronakos

26. nGEM Detectors for the SPIDER neutron facility, G. Croci Fast neutron beam diagnostic Interaction of deuterium ions of 100 keV with the beam dump: – D + D -> 3 He + n(2.45 MeV) detect any variation of the deuterium beam intensity with 1 ns & 20 mm reso. SPIDER beam divided into 16 groups of 5*16 beamlets of 20x22 cm2 Beam dump 2 layers of CuCrZn alloy interleaved with water Place detector behind to measure neutrons flux 26

27. nGEM detectors Triple GEM detector – dimensions : 35.2 cm x 20 cm – 3 mm/ 1 mm / 2 mm/ 1 mm gaps Pads readout with 16*10 = 160 pads of 20 x 22 mm 2 Al or Cu Cathode equipped with a polyethene (CH 2 ) layer used to convert neutrons into protons Gas mixture Ar/CO 2 70%/30% FE Electronics: CARIOCA (open to other counting chip solution) 27 nGEM Detectors for the SPIDER neutron facility, G. Croci The Al layer thickness is optimized in order to stop all the protons that are not normally emitted 60 keV deposited in the gas

28. nGEM Detectors for the SPIDER neutron facility, G. Croci Previous measurements in beam At Frascati Neutron Generator Detector divided into 2 halves – One sensitive to 2.5 MeV neutrons (DD reaction) – One sensitive to 14 MeV neutrons (DT reaction) Readout Anode : 128 readout pads 6x12 cm 2 organized in a matrix 16x8 On-going and future tests Gamma test @ Frascati now Neutron TB in November 16 nGEM detectors should be produced in order to equip all the beam dump, total area of about 1.5 m 2  2012 The final detector will be HV powered using the new HV GEM module 28

29. Proposal for a high rate experiment with MPGD readout, D. Kaplan Fixed target experiment to study CP-violation of hyperons particles Use Fermilab anti-proton beam and existing apparatus after Tevatron shut down (2011?) 29

30. Status report of the Micromegas R&D for COMPASS at Saclay, M. Vandenbroucke Pixelized center for COMPASS 40x40 cm2 Bulk Micromegas 2560 channels read out by APV chips In COMPASS since end August 2010 with comparable performance with “old” Micromegas 30 APV tunning Parameters – Preamplifier feedback current – Shaper powering current – Shaper feedback current Optimization between noise, amplitude and time occupancy of the APV signals

31. Status report of the Micromegas R&D for COMPASS at Saclay, M. Vandenbroucke Gain measurements Mesh and strip readout Measure that resistive detectors have lower gain – Not yet understood Further studies will continue with the October RD51 test beam on SPS 31 PS/T11 test beam, Aug. 2010 COMPASS/CLAS12 – 6x10 cm2 Bulk detectors – 144 strips with 400 um pitch – Read out by AFTER (T2K) Investigation of different protection schemes GEM pre-amplification Resistive layers Low energy beam Study influence of hadron energy Analysis on-going

32. Last slide Thanks to the speakers for their contributions Thanks you all for your attention