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Radiation Work Discussion at CMS Week Workshop - October 2, 2019

Discussing radiation challenges and solutions for Muon systems at the CMS Week Workshop, highlighting the need for a common approach, radiation hardness, rate capability, and more. Presented findings are a starting point for future work.

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Radiation Work Discussion at CMS Week Workshop - October 2, 2019

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  1. Phase-2 Radiation discussion GEM Workshop Oct 2 2019 Piet Verwilligen – INFN Bari Disclaimer: this is not an overview of work done but instead provides a starting point for discussion and work to be done CERN, Oct 2 2019

  2. https://indico.cern.ch/event/836166/ Let’sroll: Radiation WS during CMS Week Sophie Mallows (BRIL) Frank Hartmann (Upgrade Coord) • Huge work, notonly for usbutalso for the entireMuon community… • … need a common approachamong the differentMuonsystems • Need to scrutinizeeach part along the detection-trigger-readoutchain: • Rate capability of the detector • Radiationhardness of detector & front-end electronics • Availablebandwidth to sendhits to trigger • Combinatorics in EMTF / Segmentreconstruction • …

  3. https://indico.cern.ch/event/839944/ Why?HGCAL steadilyimproves design • V.3.7.18.0 reducedmaterial budget (reducedabsorptionlength • V.3.7.19.1 new envelope & supportstructure • More improvements to come ? Ourref: MU TDR (2016): OK! • Reduced dose 60 < R < 70 cm (innermostetapartition) • Slightlyhigher dose for R > 90 cm • ok for us, butthey do notwant to ask time and again …and want to knowwhatlimitswe can stand…

  4. https://cds.cern.ch/record/2283189/files/CMS-TDR-016.pdf Rate Capability • Mostrecentestimates: Muon Upgrade TDR (2016); howeverFlukasimulation with old HGCAL geometru (reuse of HE absorber) • Max hit rate (5E34 or 7.5E34 ?): 1.5kHz/cm2 (GE1/1) – 50kHz/cm2 (ME0)

  5. https://cds.cern.ch/record/2021453/files/CMS-TDR-013.pdf Rate Capability • Howeverwe do nothavemargin on rate capability right now! --- tests and R&D needed! • Standard GEM Foils: HV filter 10k-2.2nF-100k + 10MOhm for each HV segment (40) • Sustainedoperation: more efficientsparkprotection with 100kOhm – 1MOhm instead of 10kOhmbut V = IR thereforehigherfilterresistorswillresult in highervoltagedrop and hencelower rate-cap Irradiation of full chamber (2019) GE1/1 TDR (2012): Local irradiation Claim: 100MHz/cm2 Reality: 10kHz/cm2 Measured up to 400 kHz/cm2 Disclaimer:result 2B scrutinized by GEM DPG: e.g. assumes for conversion of bkg-rate to bkg-inducedcurrentthatallbkgparticles produce MIP-likesignal. Finalresultmight be worse.

  6. https://indico.cern.ch/event/836166/ Rate Capability • Furthermoreletusnotforgetthatthisissimulation! • Background simulationismuchimproved in the past 5 years, butstill no perfect data-mc agreement: cfr. GEM slice-test: up to 50% differenceat high eta! RoumyanaHadjiiska – Muon System Background

  7. RadiationHardness • Requirement for allmaterialsused for Chamberconstruction & FE Electronics • Cfr: Barrel RPC sufferleaks due to ageing of gaspipeexposed to non-negligible HF-concentration • Materials for chamberconstructiontested by Jeremie (PhDthesis) – believe OK • Electronicsreviewed for GE1/1 TDR, CMS TP, MU TDR – but I wouldleaveit to exp! • VFAT3 rad hard (100Mrad = 1MGy) max dose expected ME0 < 100kGy • I believeothercomponents are radhardaswell: FEAST, OH, … • What are the margins? Trigger BW / Trigger Combinatorics ? • Bandwidth of hits out of ME0: needdedicatedanalysis to understandmargins • a.f.a.i.k. ME0 segmentsneveradded to EMTF, so for Combinatoricswe are blind! • More studies are needed: more manpower & experiencedguidance welcome What else?

  8. Last word? • I seeit a little bit problematicthatweshouldgivenumbersatwhichourtechnology breaks down... • I seethis once more as a push to accepthigherradiationlevelswithoutgoodmotivation. • I believethat for the longivity of the GEM detectors we are on the safe side: our detectors are tested for several C/cm^2 expected to be accumulated over the HL-LHC period • limits on the particlerates come rather from the readoutpoint of view (rate capability) and the increasingcombinatorics in L1 Trigger logic • Howeveracceleratedradiationtests are not 100% reliable and oneshouldalwaystry to keep the accumulatedchargeaslowaspossible, for instancesee the efforts in the past of the CSC to fine-tune the gain in eachchamber to avoidtoo high gain (and charge) and the efforts of the DT colleagues to work atlower HV workingpoint to reduce the gain in the tubes.  • Therefore I am more in favour of givingnumbers to BRIL that are for example just 20 or 30% more thanwhatweexpect from previoussimulations. In the end, they just want to have an alarm. RoumyanaHadjiiska – Muon System Background

  9. Study HGCAL scenarios Work performed February – May 2019 Wooijn Jang, Yechan Kang, Piet Verwilligen CERN, Oct 2 2019

  10. Introduction • Changes in HGCAL to accomodate electronicshaslead to a reduction of number of absorberlayers in Back Hadronic from 12 to 10 layers • resulting in an effectivereduction of the totalabsorberthickness of 10 to 9 • First approach: reduce density of HGCAL steel to have 9 totalthickness - CMSSW_10_4_0 • Second approach: improved HGCAL geometryavailablenow - CMSSW_10_6_0_pre3 Upgrade TP Reduced

  11. Studiesperformed on «ReducedDensity HGCAL» in CMSSW_10_4 • Expected: due to reduction with 1 interactionlengthweexpect 30% lessshowercontainment more • Expected: no impact on muonfake rate (dominated by  decay in flight in tracker; ifdecay in calorimeters, willarriveanyway in muonsystem, independently of number of of HCAL • Observed: 200PU MinBias sample: 20% (avg)-30% (max) increase in simhits, digis & rechits in detectors behind HGCAL: ME0, GE1/1, ME1/1; • Increase 30-35% of segmentsin ME0, ME1/1 • Impact on muon reco after ID and PT cutsminimal Offline seems OK • Impact on trigger due to increasedcombinatoricsisdangerous • Observed: 0PU PionGun sample: no increase of fake rate

  12. ME0 Segments CMSSW_10_4_0 CMSSW_10_6_0_pre3 15% more segments in updated HGCAL 30% more segments in reducedHGCAL Strange dropsateta 2.2 & 2.5 resolved, curve issmoother and reflectsbetter reality! Segmentincreaseconfirmed (howeveronly 10%) likelyonly due to increase in muons However CSC keepsseeing 30% increase in segments in ME1/1! (seenext slide)

  13. CMSSW_10_6_0_pre3 CSC Segments ME1/2 ME1/1 30% more segments in reducedHGCAL 30% more segments in reducedHGCAL 30% segmentincreaseseen in CMSSW_10_4_0 confirmed in CMSSW_10_6_0_pre3

  14. CMSSW_10_6_0_pre3 GEM Hits 20-30% more digis, increaseconstant over wholeetarange 20-30% more background hits (e,p,K,) 15% more hitsTrend seen in ME0 not confirmed 20-30% hit increaseseen in CMSSW_10_4_0 confirmed in CMSSW_10_6_0_pre3

  15. Summary • 30% segmentincrease in ME1/1 and 20-30% hit increase in GE1/1 confirmed with more detailedHGCalgeometry • For ME0 initial 30% increaseseen in CMSSW_10_4_1 waslowered to 15% increase in more detailedHGCalgeometry • Inclusion of HGCalservices in Barrel-Endcap gap • Due to inclusion of the back flange (verticalshield) thatwasmissingbefore Lessonslearnt • GEANT helpedus to do a quickstudysincewehad no personsworking on FLUKA, neithercould BRIL giveusquickly an estimate of the fluxes • Howeverthiswas don in emergency mode and on best-effortbasis • Changes in GEANT geometry are implementedslowly and wecannotaffordthisresources intensive work for every epsilon change • Need to get back manpower on FLUKA • Waiting for v.3.7.19.1 to be in the webtool: • https://cms-project-fluka-flux-map-paas.web.cern.ch/

  16. Back Up CERN, Oct 2 2019

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