Aging studies of Micromegas prototypes for the HL-LHC Summary and update

1. Agingstudies of Micromegasprototypesforthe HL-LHCSummary and update D. Attie, J. Derre, E. Ferrer-Ribas, J.Galan, A. Giganon, Giomataris, T. Giron de Faucher, F. Jeanneau, R. de Oliveira, P. Schune, J. Wotschack onbehalf of MAMMA collaboration

2. OUTLINE There are two similar resistiveprototypesavailable of which one has beensubjecttodiferentirradiationtests … Thenature of theradiationis 1. X-raygenerator 2. Lowenergyneutronbeam 3. Intense gamma source 4. Alphairradiation

3. X-raygeneratorirradiation 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 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 X-ray exposure in a small active area region of 4 cm2. RD51 miniweek November 2011

4. X-raygeneratorirradiation 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.

5. X-raygenerator: Relativegainbefore,during and aftersecondirradiationperiod Measurementsat different position wereperformedbyusing a maskwithseveralequi-distantholesoverthe active region of the detector. Normalizedgainmeasurements show therelativecompatibilitywith position. Theexposedregiondoesnot show a considerable changerespecttothe non-exposedregions. Exposed detector R17a NON Exposeddetector R17b

6. Neutronagingtests at Orphee reactor. High intensitythermalneutronirradiationhad place at C.E.A. Orphee reactor. Severalneutronresearchlinesavailable. Neutron flux : ~8.108n/cm2/sec Neutronenergy : 5 to 10 meV Detector emplacement at Orpheereactor Neutron guide

7. Detector activationafterneutronexposure After a short irradiation period the detector is quickly activated and takes long time to deactivate. The activation rate measuredsaturates and reaches a limit of about 250kHz whichdoes not increasewithexposures longer than 2 hours. After 5 minutes neutron exposure After a period of 2 hoursexposure

8. Detector aginghistoryduringneutrontests. Neutron flux at the level of CSC in ATLAS ~3.104 neutrons/cm2/s 10 yearsatHL-LHC (=> x10.107sec) with a security factor : x3 At the HL-LHC, wewillaccumulate 1,5.1013 n/cm2 AtOrpheewe have ~8.10^8 n/cm2/sec so in 1 hourwe have : 8.108x 3600 ~ 3.1012n/cm2/hourwhichis about 2 HL-LHC years (200 daysyear).

9. HL-LHC expected gamma flux LHC -nominal condition- prediction (from Background task force, ATL-GEN-2005-001) • For LHC (L = 1034 cm-2 s-1): • Hottest region for gamma (E> 30 keV) in muon spectrometer is in forward CSC region: • ~18 kHz/cm2 = 1.8 104 Hz/cm2 • For 10 years of HL-LHC (assuming 1 y = 107 s): • x5 Lumi increase • x3 security factor • x10 year • Total of time equivalent: 1.5 109 sec • In hottest region ~2.7 1013 gamma / cm2during 10 years of HL-LHC exposure

10. COCASE. Gamma irradiationfacility at CEA Saclay (Cobalt decay emits two gammas together: one at 1.33 MeV + one at 1.17 MeV) COCASE (IRFU) • Source activity in summer 2005: • 17 Cu ~ 630 G.Bq = 6.3 1011 Hz • Minimum distance ~10 cm, ~30 deg. half-ang. • Mid of January 2012, (~6.5 y later, T1/260Co ~ 5.27 y), • 268 G.Bq (cf. R.C.) => 2.7 1011 decay / s • If at 50 cm from cobalt source: • Solid angle ~ 3.1 104 cm2 • 8.7 106 decay / cm2 / sec x 2 ~ 1.7 107 gamma /cm2 /sec • Need 1.55 106 sec = 430 hours = 17.9 days • At 20 cm from cobalt source (reduce by (5/2)2 ) => 2.87 days (Atlas hottest region ~2.7 1013 gamma / cm2for 10 years of HL-LHC)

11. COCASE gamma rayfacility: Installation and irradiationmonitoring • Source de Cobalt 60 placed at 50cm from the source: • 2 gammas à 1.33Mev et 1.17 MeV • 2.7.1011désintégrations/s 20 days of exposure for 10 yearsof HL-LHC A temperature control system kept the room at constant temperature. Gamma exposure between 22nd of March and 11th of April (2012). Total exposure time : 480 hours Total integrated charge : 1484 mC Mean mesh current : 858.4 nA

12. Gamma irradiation: Relativegainbefore and afterirradiation Measurementsat different position wereperformedbyusing a maskwithseveralequidistantholesoverthe active region of the detector (Samemaskusedalongalltheagingtests). 9 Holes mask used Fe55 source calibrations at different hole positions Gain profile measured at the 9 reference points Detector transparency

13. Alphairradiation: Relativegainbefore and afterirradiation Alpha source installed inside the chamber and centered just on top of the drift grid. R17a detector irradiated with an alpha Alpha spectrum Rate = 3000Hz Mesh = 450V Drift gap = 0.5cm Gain profile before and after irradiation Mesh current during alpha irradiation Mesh = 540V Gain ~ 15000

14. Sumarizing Conclusions Two X-ray irradiation periods had place at the detector in two different regions with a charge generation equivalent to 5 years of HL-LHC each. Several neutron irradiation periods had place at Orphee reactor, corresponding to the equivalent 10 years of HL-LHC. Gamma rays illumination by using a high intensity Cobaltum source, 10 years HL-LHC equivalent. A preliminar test with an alpha source to produce streamer like conditions has been done. Future tests could be performed with controlled amounts of Radon in the detector. Perhaps long term ageing set-up? Long periodageing are kept in mind.

15. Back-up slides Conclusions

16. COCASE gamma rayfacility: Description COCASE service is provided by a 60-Co source Of 500 mGy/h which emits gammas at 1.1MeV and 1.7 MeV. Detector was placed at 50 cm from the source at an equivalent flux of 1.7 107 gammas/cm2/s

17. X-raygenerator. Second X-rayexposure (October 2011) Secondirradiationperiodhad place at a differentregion of thedetector Testswere re-taken in ordertoverifytheresultsobtained. Moreover, duringthesecondagingperiodthesecond detector (R17b) isconnected in parallel(withoutbeingexposed), and itisusedto do gain control measurementstocross-checkthegainchangescomingfrompossibleenviromentaleffectson gas mixture. Additionaly, in thissecondperiod, control gainmeasurements in theexposed detector (R17a) were done at different positions, before and aftertheirradiation. Acumulatedcharge : 918 mC in 21.3 effectivedays.

18. Somepictures at thelab

19. Futureagingtestsextension • Planning for longer and softer exposure • Pros : more reliability • Cons : X-ray generator will be busy and could be useful for further/alternative characterization • Strip linear resistive during irradiation (going on now at neutron beam) • Single event read-out (APV/T2K) + mesh signal (during aging) • DAQ to be prepared • Slow control (gas pressure-flow and enviromental temperature) • Slow control to be developed • A good estimation to retake these tests using APV + Slowcontrol • Middle march? • Data analysis. • Future aging data, pulse shape properties and homogeneity over the detector active area • Different configurations a t neutron beam (basic Geant4 simulation)