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Summary of MM meeting at CEA Saclay , 25/26 Jan 2010

Summary of MM meeting at CEA Saclay , 25/26 Jan 2010. Some selected topics. CLAS12 and Compass Damien Neyret. H4 (RD51) test beam run in fall 2009 in magnetic field Discharge studies (10 prototypes, different meshes) Resistive layers, GEM foils pre-amplification Charge spreading

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Summary of MM meeting at CEA Saclay , 25/26 Jan 2010

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  1. Summary of MM meetingat CEA Saclay, 25/26 Jan 2010 Some selected topics

  2. CLAS12 and CompassDamien Neyret • H4 (RD51) test beam run in fall 2009 in magnetic field • Discharge studies (10 prototypes, different meshes) • Resistive layers, GEM foils pre-amplification • Charge spreading • Preliminary results • compatible with old Compass studies (D. Thers et al.) • very small differences between classic MM and bulk • no impact of magnetic field on discharge rate so far • promising results from MM+GEM detector • further studies to be done: resist and MM+GEM with high and low intensity hadrons, performances with magnetic field, time resolutions

  3. Damien Neyret, slide 8

  4. Damien Neyret, slide 8

  5. SebastienProcureurSimulation of the spark rate in a Micromegas detector with Geant4 • Geant4 simulation of MM in hadron beams

  6. SabstienProcureur Spark rate estimate and experiment • Tool will be useful to optimize detector design • Still some doubts about reliability of simulation at low energies

  7. Detectors in test Non-Resistive Resistive Beam 1 mm 0.25 mm 1 mm X X Y X Y Shuoxing WuAnalysis on November test beam • Standard bulk detectors (2 M Ω/☐) • Resistive Kapton: R3 & R4 (250 M Ω/☐) • Resistive paste: R5 (400K Ω/☐) • Resistive strips: R6 (Few tens of kΩ/☐) • Resistive pads: R7 • Segmented one: S1

  8. Shuoxing Wu Sparking behaviors of R6&S1: eight sparking six sparking five sparking four sparking three sparking two sparking one sparking R6: 400K Ω/ Resistive strips (paste) S1:

  9. Shuoxing Wu Detector performance at same gas gain (~3000)(preliminary):

  10. Shuoxing Wu Conclusion and outlook: • Resistive coating is a successful method to reduce the micromegas spark rate and limit the change in mesh voltage and current. • Good spatial resolution<100mm can be reached with a resistive strip coating detector of 1mm pitch. • High efficiency (>98%) can be achieved with resistive strip coating micromegas detector, and efficiency drops less than 4% when increasing the beam intensity from 5KHz to 40KHz . • The definition of real ‘spark’ needs to be discussed. • R&D and studies will continue inside the MAMMA collaboration (next beam test in 6 months)

  11. Esther FerrerRibas Topology of sparks: tests in the laboratory Esther Ferrer Ribas, Arnaud Giganon, Yannis Giomataris, Fabien Jeanneau • Compare in exactly the same conditions (sameelectronicchain) • Amplitude of the spark (charge released) • Dead time 24th-25th January 2010, Sparkworking Meeting Saclay

  12. Esther FerrerRibas Measuring sparks: The Chain Am241 ORTEC 142B Oscilloscope C = 1.5 pF MM detector HTmesh R1 5.6 KΩ R2 5.6 KΩ C = 470 pF

  13. Examples of pulses Esther FerrerRibas STANDARD RESISTIVE

  14. Amplitude – charge considerations Esther FerrerRibas • Standard case: the wholemeshiscompletelydecharged Qtot= Cdet × VmeshCdet = 600 pF, Vmesh= 400 V Ne = Qtot / qe = 24 × 104pC/ qe ~ 1.5 × 1012 Ne ~ 1.5 × 1012 • With the measured pulses in the resistive case: VPA ~ 8 V , C= 1.5 pF GainPA = 450 mV/pC Ne ~ 2 × 1010 To becontinued • In a systematicway and with all types of resistive detectors… • Need a lower gain PA to avoid saturation in the standard pulses • It seemsthat the released charge in a resistive detector is ~1000lower than in a standard one • Dead time probably a high gain as well • Carefulanalyis of the pulses isneeded. Study and understand the differentregimes • <

  15. Status of test beam data analysis … with emphasis on resistive coating studies Progress and questions Jörg Wotschack, CERN

  16. R5 • Similar to R3 but with more robust resistive layer and different technique (Rui’s talk) • R ≈ 5 kΩ Mesh Resistive paste Insulator ≈ 50 µm PCB 1mm x 0.15 mm pad Jörg Wotschack, CERN

  17. R5 spectra Gain = 5000 10000 S3 (570 V) Jörg Wotschack, CERN

  18. R5: first observations • First measurements of R5 (55Fe source) • Sparking starts at HVmesh ≈ 560 V • Large currents (several µA) • Large HV drop (100–200 V) • R5 signal ≈2 x S3 signal • For comparison: R3 signal ≈ 0.8 x S3 signal • Charge resolution much worse than for S3 (and R3); escape peak not well separated Jörg Wotschack, CERN

  19. TwostagesmMega Doublemesh (Dmesh) orGem asoptionsfor Preamplificationgap

  20. Gainvs. HVonthemMega and Gem Gain vs. HV on the mMega and Dmesh

  21. Max. gainvs. HVGemorDmeshforFe55andAlpha

  22. Paris 25-01-10 Resistive protections Rui de oliveira Rui De Oliveira

  23. Rui De Oliveira

  24. Structure test 3 Microvia Pad : 150um x 1.5mm 40um kapton >1kv breakdown voltage Copper Strip 0.1mm x 100mm 1 mm resistor More than 1kv breakdown Voltage 5Kohms (Omegaply in future) Rui De Oliveira

  25. Mesh -500V charge Gas 130um Strip 0.1mm x 10cm PCB 3mm 0 ohms c2 c3 c1 c4 GND R1 R3 C1 : 200pF ? Decoupling capacitor for readout C2 : in the range of 5pF Parasitic capacitor mesh to strip C3 : in the range of 1.5pF Parasitic capacitor strip to GND C4 : in the range of 1nF Parasitic capacitor mesh to GND R1 : 1Mohms ? Resistor to discharge strip R2 : 10 Ohms ? Limiting resistor for spark current Rui De Oliveira

  26. Normal operation Z2 -400V Z1 charge 0 ohms c2 c3 c1 c4 GND R1 R3 -In normal operation the induced charge will be split between Z1 and Z2 -Maximum charge will flow through Z1 if Z1<<Z2 -Z2 = (C2 serial C4)//C3 we forget R1 which is high compared to the capacitors -Z2= C2//C3 because C2 serial C4 is close to C2 -C1 min should be 10 x C2//C3 : 10x 6.5pf  65pf min  200pf good choice -to capture the maximum of charge :Z1 should be as low as possible Rui De Oliveira

  27. sparks -500V spark Z1 0 ohms c2 c3 c1 c4 GND R1 R3 -In spark mode the current will be mainly define by C4 and Z1 - Z1 at 1Ghz is: ZC1 + R3 -C1=200pF  3 Ohms at 1Ghz and 100 Ohms at 10Mhz -Peak current : 500V/13ohms = 39A during a few ns (170 A without R3) 500V/110 =4.5A during 100ns -the average current is in this case around 0.7uA (1.5uA without R3) -Up to 10 lines should be sparking at the same time looking at the currents measured Rui De Oliveira

  28. -400V signal Strip 0.1mm x 10cm pad 0 ohms c2 c3 c5 c4 c6 GND R1 -In normal operation the induced charge will be split between C5 and C6 (on both sides capacitors are virtually grounded) -C6 is in the range of 0.01pf and C5 0.1pf -R1 should be higher than C5 at any frequency but low enough to keep high rates (5K for test 3) Rui De Oliveira

  29. -400V signal Strip 0.1mm x 10cm pad 0 ohms c2 c3 c5 c4 c6 GND -In case of spark C4 will be discharged through C5 (1k Ohms @ 1Ghz, 100k@10Mhz) It will create a peak current of 500V/1k=0.5 A during a few ns +500V/100K= 5mA during 100ns (0.1A with R1=5K) the average value is in this case in the range of 3nA (R1=50K) and 10nA (R1 =5K) Here also many pads should be sparking at the same time (up to 4uA measured) (500 pads have an area of 15mm x 15mm) R1 Rui De Oliveira

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