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A comparative study of mixed irradiated silicon strip sensors 19 th RD50 Workshop 21.11 . – 23.11.2011. Florian Petry , Robert Eber T. Barvich , F. Bögelspacher , W. de Boer, A. Dierlamm , A. Kornmayer , Th. Müller, P. Steck. Ingredients for the study. Introduction Sensors
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A comparative study of mixed irradiated silicon strip sensors 19th RD50 Workshop 21.11. – 23.11.2011 Florian Petry, Robert Eber T. Barvich, F. Bögelspacher, W. de Boer, A. Dierlamm, A. Kornmayer, Th. Müller, P. Steck
Ingredientsforthestudy • Introduction • Sensors • Mixed irradiationscheme • Annealingprocedure • ALiBaVameasuremets • Results • Charge collection • Signal tonoiseratio • Leakagecurrent • Summary
Sensor overview • Sensor thickness: 300µm • 5 sensorsofeach material
Irradiation • Mixed irradiationwithprotonsandneutrons • Chose 5 fluencemixturescorrespondingto 5 different radii in the CMS Tracker after 3000fb-1 • Irradiation with Protons in Karlsuhe • ZAG: Cyclotron, 23MeV protons • Irradiation withneutronsin Louvain-la-Neuve • Neutron generationbyshootingdeuterons on Betarget • 1 steponlyneutronirradiation
Annealing • Logarithmicannealingstepstoobserve • shortterm (beneficial) annealing • longterm (reverse) annealing M.Moll, phdthesis, Hamburg, 1999
Parameterisationofchargecollection Beneficialannealing Reverse annealing Stabledamage
Measurement • Measurement Setup: 2 ALiBaVastations in Karlsruhe • 90Sr source • Signal • Signal tonoiseratio • Leakagecurrent • Temperature: -20°C (-30°C) • Voltage 0V – 1000V • Cuts • Seed: S/N > 5 • Neighbour: S/N > 2 • Total error on measurements: 2.5% • Error on irradiatedfluence > 10% The smallALiBaVastation Sensor Scintillator DB HV Pre-cooling
Measurement Results Parameters T = -20°C V = 900V
Charge collection • P-type materialscollectmorechargethan n-type materials • FZ-n • showshighestdependence on annealing time • Large drop in chargecollection after 10d@RT (reverseannealing) • Onlysmalldependenceofchargecollection on annealing time forothermaterials Increasingfluence P N P N
Charge collection • 1.8*1015neq/cm2 • FZ-p showslargestchargecollection • Charge multiplicationfor large annealing (charge > 24000 e-) • MCz: almostnodependence on annealingtime • 1.2*1016neq/cm2 • FZ-n: Nosignalathighestfluencefor all annealingsteps • FZ-p: rise in signalforlongannealingtime • MCz-p sensordidn‘tworkforfirstannealingstep • MCz-n: nosignalat T= -20°C Increasingfluence MCz-n T= -30°C
Charge Collectionoverview Max: 15k/40k Max: 24k Max: 22k Max: 10k MCz-n T=-30°C No Signal at T=-20°C
Signal to Noise P N 1. All quitegood 3. p isbetterthan n 2. Same range FZ-n drops out 4. Lowerlimit, seedcut > 5
Charge multiplication • Signal increases after Annealingof >100d@RT • Signal tonoiseratiodoesn‘tdecrease • Large increaseofleakagecurrent
Charge collection / multiplication • Landau-Gauß-Fit broadensverymuch • Peak isshiftedtohighervalues • Not a MIP signalanymore usualdistribution
Charge collection / multiplication • MPV cannotbedeterminedverywell FZ-p + MCz-p T=-20°C MCz-n T=-30°C
Charge Collection / Signal to Noise Summary 15d 337d Charge multiplication CC S/N T= -30°C MCz-n
LeakageCurrentSummary 15d 337d Charge multiplication
Neutron only / mixedirradiation N-type • Mixed irradiationF = 4.6*1014neq/cm2 • F(p) = 0.8*1014neq/cm2 • F(n) = 3.8*1014neq/cm2 • Neutron onlyirradiation • F(n) = 4.0*1014neq/cm2 MCz FZ • Neutron onlyirradiation: • FZ-n hassmallersignalthanMCz-nsimulatedby M. Huhtinen NIMA 491, 194-215, 2002 • Mixed irradiation: • Noimprovement in CC due tomixedirradiationG. Casseet al. Vertex2008:036, 2008
Summary • P-type materialsshowedhigherchargecollectionandsignaltonoise • FZ-p performancemostinteresting • Charge multiplicationonlyseenwith FZ-p F > 1*1015neq/cm2, A > 100d@RTManufacturerMicron • Highestleakagecurrent • FZ-n showedlargestdependence on annealing time • Not usableat high fluences • Charge collectionofMCzmaterialsdoesnot annealverymuch • MCz-n is not workingat T= -20°C at F=1.2*1016neq/cm2 • Additional differencesbetween n-type and p-type materials due tomanufacturer? • Comparetootherstudies: Charge multiplicationstudy, HPK
Thanksforyourattention • Diplomathesisof F. Petry (IEKP-KA/2011-27) • Will bepublishedsoon: • http://www-ekp.physik.uni-karlsruhe.de/pub/web/thesis/iekp-ka2011-27.pdf