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Traditional techniques for Resistive Gaseous Detectors

Bari, RCGD19, May 13-14 2019. Traditional techniques for Resistive Gaseous Detectors. Paul Colas, CEA/ Irfu,Université Paris Saclay. Surface resistivity. R = r L/S : bulk resistivity Metal : 10 -6 - 10 -5 W .cm Insulator >10 17 W .cm. S. L. R = r L/ wt Flat layer: t small

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Traditional techniques for Resistive Gaseous Detectors

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  1. Bari, RCGD19, May 13-14 2019 Traditionaltechniques for ResistiveGaseous Detectors Paul Colas, CEA/ Irfu,Université Paris Saclay

  2. Surface resistivity • R = r L/S • : bulkresistivity • Metal : 10-6 - 10-5W.cm • Insulator >1017W.cm S L R = r L/wt Flat layer: t small Square L=w Surface resistivity R= r/t Units : Ohm per square t w Paul Colas -Resistive coatings

  3. Measurement techniques (1) Cut a long band of resistive. Holditboth ends withconductive adhésive on an insulating surface, measure the resistance and divide by the number of squares L/w. Paul Colas -Resistive coatings

  4. Measurement techniques (2) Circular probe (for example ETS model 803B) Measure the resistancebetween 2 rings Paul Colas -Resistive coatings

  5. Measurement techniques (3) Four-point probe Necessary for uniformitymeasurements, but might scratch the layer Paul Colas -Resistive coatings

  6. ResistivityMeasurements • Resistivitymeasurement protocole definedand reproducible, usingcircular probe and square ‘Ochi’ probe for plain coating • And ‘square counting’ for resistivestrips • under Microscope AIDA 2020, 4th annual - P. Colas

  7. ResistivityMeasurements • Resistivitymeasurement protocole definedand reproducible, usingcircular probe and square ‘Ochi’ probe for plain coating • And ‘square counting’ for resistivestrips • under Microscope Lowerresistivity DLC-coated foil for T2K TPC AIDA 2020, 4th annual - P. Colas

  8. Improvement of stripquality • Problem 1 : ink spreads sothatstripwidthislargerthanwhatis on the mask • Problem 2 : Staticelectricity and dustdegrade the stips Solution: adapt the mask to fine enough pitch to compensate Solution : Discharge the base foil and work in a dust-free environment AIDA 2020, 4th annual - P. Colas

  9. Resistiveinks Screen printing : 60x60 cm² meshstretched on a robustAluminum frame. Ink from ESL Europe Company, 100 KΩ/□ (ESL RS12115) and 1 MΩ/□ (ESL RS12116). Need to be mixed with a solvent before use.

  10. Improvement of stripquality • Problem 3 : unstable high resistivity (pressing at 12 bar at ELVIA for NSW takes the 400 kOhm/sq made in Japan to 800 kOhm/sq). Solution : after 11 trial productions spread fromFeb. 2018 to October 2018, a process to makehomogeneous production wasdetermined: • Humidity control • Improvement of the clean room • 1 Mohmpaste + 10 to 30% of 100 kOhm + 5% of neutralpaste (insulating) + a few drops of solvant, careful mix and immediatescreen-printing. • Pressing at 7 bar at ELVIA. • The resultis more uniformthan DLC, at 3.4+-0.2 Mohm/sq AIDA 2020, 4th annual - P. Colas

  11. Use of resistivecoatings in detectors • Stabilization of gain and protection of electronics • Charge spreading • Chip protection • Potentialdegradingfor E-fieldshaping Protection diodes, resistorsand capacitors no longer needed : thissavesspace on the FE boards 25 cm 14 cm 3,5 cm 2,8 cm

  12. ResistiveBulkMicromegas October 2007: resistivebulks for HL-LHC (SLHC) (became ATLAS MAMMA, and later NSW)

  13. June 2010 measurements

  14. Applications of resistivecoatings: spark mitigation • The avalanche charge iskeptlocally for some time • This lowers the potentiallocally • This in turnlowers the gain and avoid the Ratherlimit to beattained • Moreover, as the charge goes to groundthrough a resistance, thislimits the currentthrough the preamplifiers, protectingthem • You canalso pattern resistors in your PCB (Rui de Oliveira, Max Chefdeville) Paul Colas -Resistive coatings

  15. Different sparking behaviours of standard and resistive detector: Resistive R3(@wide beam,15KHz): Standard SLHC2(@10KHz): S. Wu SLHC2: HV=400 V (Gain ~3000): current when sparking < 0.4 mA voltage drop< 5% R3: HV=410 V (Gain ~3000): current when sparking < 0.2 mA voltage drop<2%

  16. Chip protection in Gridpix • A single spark kills a TimePix chip • High current, hot plasma -> destroys circuit • A sufficiently thick SiProt layer reduces and softens the sparks • How protection works? • Allows charge to stay over the pad, lowering the local potential • Limits the current thru the amplifier • Protects mechanically • Avoids points, smoothens the surface? • Any damage to the signal? • Amplitude loss? • Charge sharing with neighbouring pads? • Short-circuit of the amplifiers • Introduces dead time? Paul Colas -Resistive coatings

  17. Chip protection in Gridpix Rneighb = r L/el = r/e for square pads For 10 µ aSi, r=1011W.cm, R=1014W/square Rthru = r e/Ll ~ 0.04 1014W Rneighb/Rthru = L2/e2 e<<L to avoid spreading the charge by side conductivity. The charge preferentially escapes thru the pad, but with an extremely high resistance. L l e R neighbour R thru Cneighb = er e0 Le/l = er e0 /e for square pads Cthru = er e0 Ll/e (note er ~11 for Si) The influence acts preferentially thru the pad if L>>e Paul Colas -Resistive coatings

  18. L l e R neighbour 1/Cneighbourw R thru 1/Cthruw Also Rthru >> 1/Cw to leave the induced signal (OK with 1011W.cm within 3 orders of magnitude for 10 ns signals) Equivalently, RC time constant >> 10ns The signal is fully capacitive Paul Colas -Resistive coatings

  19. Resistivematerials in use or to bedevelopped • Sheldal film + cermet (Al Si) (Madhu Dixit) • Resistivepaste or ink(Carbon-loadedepoxyresine) (Rui de Oliveira, Imad Laktineh, Nick Lumb, José Répond) • Spray of carbonpowder in glue (G. Mikenberg) • KaptonwithDiamond-likeCarbon by sputtering (seeAtsuhiko Ochi’s talk) • Amorphoussilicon, HydrogenatedA-Si (Nicolas Wyrsch)SiNi(SiNx) • Carbon-loadedPolyimide • ResistivepastesRutheniumDioxide(Michael M. Steeves,Electronic Transport Properties of Ruthenium and RutheniumDioxideThinFilms

  20. Charge sharing in a TPC

  21. Pad Responsefunction 2D distribution : Charge fraction vs Xpad-Xtrack Fit a parameterization to the profile, for instance: Use the Pad ResponseFunction to obtain the trackpostion in eachpadrowfrom the charge fraction Re-fit the track and iterate

  22. Residuals of the fittedtrack (afteriterations) Take the geometricalmeanbetweenresolutionincluding and excluding the hit in question to get an unbiasedresult

  23. Position resolution Constant termsqrt(z) diffusion contribution Constant term = 60 µm with 3mm pads! (1/50th pad witdth) dE/dx resolution 4.8% resolution for nominal tracklength (192 hits) Conclusion : Beam test shows that the high performances are preserved in the new scheme

  24. Uniformity of the charge spreading Widthparameter of the PRF (mm) s = sqrt(2t/RC)

  25. Diamond DLC Graphite Whatis DLC? • Diamond-likeCarbon • Properties • Electric : resistive • Mechanical : hardness, anti-corrosion protection, solidlubricant • Applications in MPGD • Charge spreading anode: deposited on an insulatingsubstratemakes a continuousresistive-capacitive network, evenlyspreading the charge, improving point resolution by allowing a barycenterbetween pads or strips • Anti-spark protection (O(1 to 10 or 100) MW/). Needsseveral microns to get to lowenoughresistivity for T2K (400 Kohm/sq) • Other applications • Fuel cellbattery component Amorphouswith H, both sp2 and sp3 sp3bounds sp2bounds

  26. Two fabrication techniques • Sputtering : use an argon plasma to vaporize a graphite target • BE-sputcompany in Kyoto (contact by Atsuhiko Ochi). Successfullyproducedresistivity in the range 0.4-several 10 Mohmper square. • Plasma Assisted ion deposition : use a methane plasma in a high E field to depositcarbon on the substrate. Deposition rate 5-10 µ/hour. Need ~2 microns for 400 Kohm/sq (T2K requirement) • PAI company in Kyoto (contact by Takeshi Matsuda)

  27. With the PIA technique, bulkresistivitybelow 10-2W.cm requirestemperatures in excess of 350 °C Bulkresistivity (Ohm.cm) T (°C)

  28. PAI first test for 400+/-200 KW/sq On HN kapton PC+MZ, 2018/6/25 107KW/sq 120KW/sq 430KW/sq 205 KW/sq 94KW/sq Scratches from the 4-point probe 4-point probe measurement : 103.6 150KW/sq 102KW/sq 315KW/sq 445KW/sq 150KW/sq 116KW/sq 150KW/sq First test : the coatingis not uniformenough. Will tryagainwith APICAL (etchablepolyimide)

  29. Uniformity of DLC resistivity by sputtering Same pattern for each horizontal lines, vertical iso-resistivitylines BE-sput, 7 foils measured at CERN with ‘Ochi probe’ for T2K-ND280 upgrade

  30. RATE CAPABILITY Resistivelayers slow down the detector, as the charge remainssome time on the anode. Theydegradeslightly the rate capability. Simulation by J. Galan D. Attié et al., JINST (2013), ‘A piggybackMicromegas’ For 10 MW, thereis a 20% gain drop at 100 kHz/cm2 Paul Colas -Resistive coatings

  31. Use of resistivesheets for TPC Field cages Replace set of conductive rings interconnected by resistors by a continuouslyresistivevessel to degrade the potential Application to cryogenicTPCs(strongdependence of the resistivitywith T and potentialdifference) R. Berner et al., ‘First Operation of a Resistive Shell Liquid Argon Time Projection Chamber - A new Approach to Electric-Field Shaping’, Instruments2019, 3(2), 28

  32. CONCLUSIONS There are many applications of resistivecoatings in MPGDs. Theycanimprove the operationstabilityand the resolution of detectors. In the future, wewillneed more materialsand more patterning ‘Wallpaper’ ASIP photo-cell (EPFL/MIT)

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