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Resistive Micromegas Ageing tests

Resistive Micromegas Ageing tests. D. Attie , J. Derre, E. Ferrer-Ribas, J.Galan , A. Giganon, I. Giomataris, F . Jeanneau , J . Manjarres, P. Schune. Ageing tests description.

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Resistive Micromegas Ageing tests

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  1. ResistiveMicromegasAgeingtests D. Attie, J. Derre, E. Ferrer-Ribas, J.Galan, A. Giganon, I. Giomataris, F. Jeanneau, J. Manjarres, P. Schune

  2. Ageingtestsdescription Themain idea istoproofthecapability of detectorsmade of new Micromegastechnologytooperate in long data takingperiods. Ageingtests are beingcarriedout in CEA Saclaybyusing 2 type of radiation. X-raysradiation-> Simulate detector chargeoperationforlong time equivalentperiod Neutronradiation-> proofinvariability of detector material properties and ageingdueto nuclear interaction. X-rayexposureresultsready, and satisfactory. The X-rayageingstudyincludes Characterization of X-raygunrate and spectrumnature. Determiningtheexpectedequivalentintegratedchargeat the HL-LHC during 5 years. Estimation of exposure time requiredtovalidatethe detector forlongoperating times. Detector characterizationbefore and afterexposure. X-rayspectrumisdeterminedby3 parameters, electroncurrent (mA), aceleratingvoltage (kV), and cathodecomposition.

  3. Resistiveprototypes (2D readout) Tworesistiveprototypes (R17) weresenttoSaclayforperformingageingtests Geometrical properties Bulk Mesh Strip pitch/width for all: 250 µm/150 µm Top layer ( Resistivestrips): 35 µm thick Insulation(coverlay):60 µm Ystrips (90 degrees to R strips): 9 µm Cu Insulation(FR-4):75 µm Xstrips (same direction as R strips): 9 µm Cu Resistance to GND: 80-140 MOhm Resistancealongstrips: 45-50 MOhm/cm 17A Resistance to GND: 60-100 MOhm Resistancealongstrips: 35-40 MOhm/cm 17B 128 um Both detectors show similar gain properties Re-characterized at CEA for different gas mixtures Coverlay Y readout FR-4 Xreadout

  4. X-rayguncharacterization : Lowintensity and wellcollimated X-raygunspectrum Throughcollimator 0.5 mm diameter Area = 0.2 mm2 55Fe source mainpeak 5.96 keV Sets up ADC gain 82.67 ADCs/keV E = 5.96keV Double gaussian fit for X-ray gun sets up main peak energies and rates.

  5. X-rayguncharacterization : Usingcopperlayer 5 layers of 3M copper tape (35um/layer) are usedtoscreenthegenerated X-rays and produce fluorescence in thecopper. Thecoppertransmissionallowsusto determine the original rate at 8keV. Thesamemask as in theageingexposurewasused (4cm2 square). The attenuated rate at the 8keV peak is related with the original rate at the detector at around the 8keV peak. Rate measurements attenuated with Copper If the original rate around 8keV is considered constant the integrated transmission factor is resulting 43 kHz/mm2/keV/mA at 8keV resulting 43 kHz/mm2/keV at 8keV Original rate (before reaching gas volume)

  6. Ageingtests : X-rayexposure Detector operatedin data takingconditions Gas mixture : Argon + 10% CO2 Gas Flow = 0.5 l/h Gain3000 HVm = 540V HVd =790 V X-raygeneratorset-up at 10 kV 5 mA Equivalentchargegeneratedduring 5 yearsHL-LHC Wi (Argon+ 10% CO2) = 26.7 eV Gain = 5000 MIP deposit in 0.5 cm drift = 1248.5 eV Charge per iteration = 37.4 fC Expectedrate at the HL-LHC : 10kHz/cm2 5 years of HL-LHC operation (200days X year) Total detector chargegeneratedduring HL-LHC operationisestimatedto be 32.5 mC/cm2 X-ray exposure in a small active area region of 4 cm2.

  7. Ageingtests : X-rayexposure Detector gainwasnotdegraded at thearea of X-rayexposure Duringthe X-rayageing test itwasgenerated a total charge of Qageing = 765mC in 4cm2, during a total exposure time of Texposure = 11days 21 hours And therefore, the total chargeto be generated at the HL-LHC during 5 yearswith more than a factor 5 of security factor.

  8. Detector characterization : Dependencywith position A maskwith 9 holeswaspreparedto do gainmeasurements at different positions. Thegain and therate are monitored at eachhole. Forthatthesourceiskeptalways at thesamerelative position. One axis seemsto be more stablethantheother. Possibleinfluencefromtheresistivestripsorientation?

  9. Detector characterization : Dependencywith position Axis U Axis V . . . . . . . . 1 9 1 . . . . . . . . HV1 HV2 HV1 HV2 9

  10. Detector characterization : Influence of rate in detector gain Measurements at different rates were taken by attenuating the X-ray gun with several copper layers. The X-ray generator is set-up at HV = 11.5 kV and increasing current from 0.4 mA to 21.8 mA to generate the different rates. Rate and gain are estimated using the 8keV peak from copper.

  11. Conclusions We can conclude there is no damage or ageing due to the operation of the detector for an equivalent charge to the generated in thHL-LHC. First results are positive. Misterious gain evolution during ageing tests. Fabrication charge trapping and during operation is released? Resistive plane voltage offset affecting the effective amplification field, and that’s why we observe improvement? Homogeneity with position, grounding? We could not use APV connectors for proper grounding. Gain dependency with rate reveals no more than 80% loss for rates up to 10kHz Further ageing tests with neutrons will proof the detector operation due to the material degradation, and secondaries produced by neutrons; recoils, material activation, high ionizing events due to hadronic interaction.

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