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Forward endcap ECL, pure CsI upgrade

Forward endcap ECL, pure CsI upgrade. Peter Kri ž an University of Ljubljana and J. Stefan Institute. 18th Open collaboration meeting, KEK, June 20, 2014. At this meeting reports on APD tests Read out electronics Radiation hardness studies Shielding MC studies Background Funding

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Forward endcap ECL, pure CsI upgrade

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  1. Forward endcap ECL, pure CsI upgrade Peter Križan University of Ljubljana and J. Stefan Institute 18th Open collaboration meeting, KEK, June 20, 2014

  2. At this meeting reports on • APD tests • Read out electronics • Radiation hardness studies • Shielding • MC studies • Background • Funding • Future plans

  3. Reminder: forward endcap ECL upgrade Upgrade a part of the forward endcap ECL (~8 rings) CsI(Tl)  pure CsI Photodiode • photopentodeprevious B2GM • APD

  4. Photopentode studies: Canada Photopentode with preamp and voltage divider, mounted on a CsI crystal Calibrated with gamma sources (Cs137, Na22) noise 71keV Tests with cosmic rays: 39 MeV average energy loss Fast/total component = 0.55 85 pe/MeV for 100ns integration

  5. Photopentode studies: Italy Beam pipe BTF LNF Frascati ElectronicsSystem Horizontal Finger CsI Pure e- Vertical Finger SCOPE & & Logic Trigger 100 MeV electrons Noise: ~200 keV

  6. APD: Hamamatsu LAAPD  A. Rossi Hamamatsu S8664-1010, 10x10 mm2 active area, 2 sensors per crystal Default working gain: G=50, operated at G=200 (a special selection of G=165 APDs receveid in May) Cosmic ray tests: mean deposition 30 MeV Waveform sampling (scope) Noise (ENE), with software shaping: ~ 1 MeV Noise (ENE), with CSP shaper: ~ 1.6 MeV Temperature dependence: -4.3% 1/K

  7. APD: Excelitas APD  R. de Sangro Excelitas C30739ECERH-­2 5.6 x 5.6 mm2 active area • Highgain • Verylowdarkcurrentandcapacitance • QE about 30% at 315nm • Small area Test set-up: CsI with 4 sensors IndvidualAPDs: noise ~2 MeV Sum offour: noise ~1 MeV

  8. Read-out electronics  P. Branchini Preamplifier APD HV/bias control system Preamplifier + HV/biassupply Designed to workbothwith • APDs • photopentode Testedwithbothsensortypes Preparationof a sufficientnumberofchannelsfor the Octoberbeam test with a 4x4 matrix

  9. Radiation hardness  S. Fiore Irradiationwithphotonsat Calliope, fastneutronsat Tapiro Exposure to full Belle II expectations Studiesof: Pure CsI crystalsfromdifferentmanufacturers • Amcrys, SICCAS, Optomaterials (newItalianproducer) Transverselighttransmission: 50-55% forAmcrysandOptomaterials, 18% SICCAS Scintillationproperties • lightyieldandlightyielduniformity: OptomaterialsslightlybetterthanAmcrys

  10. Radiation hardness  S. Fiore Irradiationwithgammas at Calliope, fastneutronsat Tapiro Studiesof: APDs • Excelitas, considerableradiationdamage: lossof QE byfactorof 3 (at 315nm) at 10**13 n/cm2 = 5x full Belle II exposure (maincomponentprobablydue to a damageof the protection resin) Opticalcouplingmaterials: • opticalgrease OK • epotekdrop at 315nm

  11. Backgrounds after 9th campain  S. de Jong Shield design  A. Beaulieu Main component still RBB, while it was Touschek in Belle…

  12. Structure  A. Beaulieu Studying challenges we will be facing if photopentodes are used photosensors. Some ideas of the clearance between PMT’s and existing cooling structure

  13. Canadian plans  C. Hearty Continue work on pure CsI • Preamp finaldesign; preliminary design of faraday cap, cabling, mechanical connection to crystal • Characterization of photopentode/preamp performance: gain, linearity, noise factor, short and long-term stability, lifetime. Establishing a case for the upgrade • Background studies • Important to understand our sensitivity to imperfections in collimation or other accelerator parameters;estimateinjection background. • Contribute to BEAST: test background simulations; dominated by Touschek and Coulomb in Phase I. • Software: the most convincing physics case would make use of Belle II backgrounds, simulation, reconstruction and physics tools;theseare not currently adequate for the task. Responding to backgrounds and radiation damage in CsI(Tl) • RadiationhardnesstestsofCsI(Tl) • Calibrationmethodswithrecorded data, dvancedcalibrationmethodsofdamagedcrystals

  14. Organisation, funding Pure CsI task force (C. Cecchi, C. Hearty, P. Križan, A. Kuzmin, K. Miyabayashi, I. Nakamura, M. Roney) A lot of progress in the R+D, regularly reported at the ECL meetings Photo-sensorchoice (photopentodevs APD): all data will be availableby the endofOctober (beam test of a matrixof pure CsI crystalswith APD readout) A formal proposal of the upgradeis being prepared forthe EB. Canadian,Italian andRussiancollaborators applied for funding

  15. Canadianfunding • Reviewersrequested a demonstrationof a clearphysicscase to proceed to the next step in the capitalfundingapplication(~5 MUSD) • MC study* of B -> taunu, K nunuwascarried out bytaking Belle II backgroundsandBaBaranalysis effectof the upgradeonlymarginalassuming nominal backgrounds (+ 3x Touschekand 3x Coulomb) (summary at http://kds.kek.jp/getFile.py/access?contribId=0&resId=1&materialId=slides&confId=15776) • Canadiangroupsfeltthatthey do not have a strongenoughcase, andhaveabandoned the applicationforcapitalfunding (duemidJune); nextpossibility in 2 years (maybe) • Theywant to continuetheir R+D efforts (regulargrant)  backupslide • Major changefor the pure CsI project *Hybrid MC study (Belle II backgroundssuperimposed on BaBar MC, analysis)

  16. How to proceed? Do we indeed need a partial upgrade? Yes One of the main tasks for ECL is to determine the Eextra in missing energy studies – one of our main advantages over LHCb hermeticity • We need a robust detector that can handle potentially considerably higher background levels than we currently simulate (Belle experience: background in ECL dominated by Touschek and injection backgrounds; in MC we assume perfect collimators for Touschek screening, no injectionbackground) • Scaling Belle backgrounds to Belle II (TDR) showed a 25% increase in significancefor B taunuforanupgradedforwardencap ECL. • Radiation dose: expect a factor of two loss in light yield at the end of the experiment, for some crystals this could be even much worse. 

  17. L/L0 after 1/ab at Belle fixed theta, best and worst modules fixed theta, modules along phi What happens when 400 rad  up to 10 krad?

  18. CsI(Tl) radiation hardness studies Relative light yield decrease: -DL/L0 Carried out at BINP in 1995  D.M. Beylin, Nucl. Instrum. Meth. A541 (2005) 501-515

  19. L/L0 after 50/ab at Belle II, extrapolated from Belle ? 400 rad  up to 10 krad -DL/L0 400 10 krad 

  20. Motivationfor a partial upgrade, continued • Strong deterioration requires at least a complicated time dependent calibration; some partsof the detectormight be evendead. • Rad damageof the photodiodeswillincrease the noise, complicate the calibration, andcouldcauseinstabilities in the read-out chain. • Pile-up ofsignalscouldbecome a seriousissuewith a decreasedlightyield • Requirementsto have analarm system for a high dose in the endcap ECLcouldmake machine tuning more difficult (wewould not be ableto explore a part of the phasespaceofmachineparameters)

  21. Action plan -Continue R+D on all relevant issuesfor the pure CsI upgrade(crystals, photodetectors, electronics, mechanics, MC withrelaxedcollimators) -Seek additional capitalfunding (at present: Italyand a fundingrequest in Russia) -Modify ECL TDR to make it clear that Belle II wants atleast a partial forward endcap upgrade, and make it clear that we haveone plan, i.e. to use pure CsI. The read-out sensor choice still needssome more R+D before the decision can be made.Smallmodification, neededforfurtherfundingrequests.  backup -Evaluatethe performance of the CsI(Tl) modulesafter receiving a veryhighdose. Plan endorsedby EB yesterday.

  22. Summary -Considerableprogress in photosensorsandelectronicsR+D -Beam test of a 4x4 matrixequippedwithHamamatsuAPDsanddedicatednewelectronicsscheduledforOctober -SlowcontrolsystemuSOP is underdevelopemnt -Backgroundstudiesandstudiesofcalorimeterperformance in highbackgroundenvironment: some finished, some underway -Seekingadditional capitalfunding -Evaluatethe performance of the CsI(Tl) modulesafter receiving a veryhighdose.

  23. Backup slides

  24. TDR, very minor update Motivation for the TDR update: make it clear that Belle II wants at least a partial forward endcap upgrade, and make it clear that we have one plan, i.e. to use pure CsI. The read-out sensor choice still needs some more R+D before the decision can be made. Modification proposal: Leave most of the ECL chapter untouched (barrel, electronics) 9.3 Performance… : modify a few sentences on the expected backgrounds and their impact on the endcap performance 9.5 Endcap upgrade chapter • The introduction paragraphs of this chapter are completely rewritten to take intoaccountthatwenowhave a baselineoption. • Pure CsI chapter: more orlessuntouched, updatewith some R+D • Other considered options: leave in as subsections (BSO, PWO-II)

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