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Gunnar Lindstroem University of Hamburg

The WODEAN Project present status. Gunnar Lindstroem University of Hamburg. Reliable detection of mips S/N ≈ 10 reachable with. Experimental request Detector property. Proton-proton collider Energy: 2 x 7 TeV Luminosity: 10 34 Bunch crossing: every 25 nsec Rate: 40 MHz

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Gunnar Lindstroem University of Hamburg

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  1. The WODEAN Projectpresent status Gunnar LindstroemUniversity of Hamburg WODEAN workshop, Vilnius 02/03 June 07

  2. Reliable detection of mips S/N ≈ 10 reachable with Experimental requestDetector property Proton-proton collider Energy: 2 x 7 TeV Luminosity: 1034 Bunch crossing: every 25 nsec Rate: 40 MHz pp-collision event rate: 109/sec (23 interactions per bunch crossing) Annual operational period: 107 sec Expected total op. period: 10 years LHC properties period of 10 years low dissipation power atmoderate cooling Silicon pixel and microstrip detectors meet all requirements for LHC How about future developments? LHC-Challenge for Tracking Detectors employing minimum minimum detectorthickness material budget High event rate excellent time- (~10 ns) & high track accuracy & position resolution (~10 µm) Silicon Detectors: Favorite Choice for Particle Tracking Example: Large Hadron Collider LHC, start 2007 • Proton-proton collider, 2 x 7 TeV • Luminosity: 1034 • Bunch crossing: every 25 nsec, Rate: 40 MHz • event rate: 109/sec (23 interactions per bunch crossing) • Annual operational period: 107 sec • Expected total op. period: 10 years LHC properties Experimental requests Detector properties Reliable detection of mips S/N ≈ 10 High event rate time + positionresolution: high track accuracy~10 ns and ~10 µm Complex detector design low voltage operation in normal ambients Intense radiation field Radiation tolerance up to during 10 years 1015 hadrons/cm² Feasibility, e.g.large scale availability 200 m² for CMSknown technology, low cost ! Silicon Detectors meet all Requirements ! WODEAN workshop, Vilnius 02/03 June 07 Intense radiation field Radiation tolerance up to throughout operational 1015 1MeV eq. n/cm²

  3. LHC ATLAS Detector – a Future HEP Experiment Overall length: 46m, diameter: 22m, total weight: 7000t, magnetic field: 2T ATLAS collaboration: 1500 members principle of a silicon detector: solid state ionization chamber micro-strip detectorfor particle tracking 2nd general purpose experiment: CMS, with all silicon tracker! For innermost layers: pixel detectors WODEAN workshop, Vilnius 02/03 June 07

  4. Main motivations for R&D on Radiation Tolerant Detectors: Super - LHC 5 years 10 years 2500 fb-1 500 fb-1 • LHC upgradeLHC (2007), L = 1034cm-2s-1f(r=4cm) ~3·1015cm-2 • Super-LHC (2015 ?), L = 1035cm-2s-1f(r=4cm) ~1.6·1016cm-2 • LHC (Replacement of components)e.g. - LHCb Velo detectors (~2010) - ATLAS Pixel B-layer (~2012) • Linear collider experiments (generic R&D)Deep understanding of radiation damage will be fruitful for linear collider experiments where high doses of e, g will play a significant role.  5 CERN-RD48 CERN-RD50 WODEAN workshop, Vilnius 02/03 June 07

  5. Radiation Damage in Silicon Sensors Two types of radiation damage in detector materials: Bulk (Crystal) damagedue to Non Ionizing Energy Loss (NIEL - displacement damage, built up of crystal defects – I. Increase of leakage current (increase of shot noise, thermal runaway) II. Change of effective doping concentration(higher depletion voltage, under- depletion) III. Increase of charge carrier trapping(loss of charge) • Surface damagedue to Ionizing Energy Loss (IEL)- accumulation of charge in the oxide (SiO2) and Si/SiO2 interface – affects: interstrip capacitance (noise factor), breakdown behavior, … ! Signal/noise ratio = most important quantity ! WODEAN workshop, Vilnius 02/03 June 07

  6. Deterioration of Detector Properties by displacement damage NIEL Point defects + clusters Dominated by clusters Damage effects generally ~ NIEL, however differences betweenproton&neutron damage important for defect generation in silicon bulk WODEAN workshop, Vilnius 02/03 June 07

  7. Radiation Damage – Leakage current with time (annealing): 80 min 60C Increase of Leakage Current …. with particle fluence: • Leakage current decreasing in time (depending on temperature) • Strong temperature dependence: • Damage parameter  (slope in figure)Leakage current per unit volume and particle fluence •  is constant over several orders of fluenceand independent of impurity concentration in Si can be used forfluence measurement Consequence:Cool detectors during operation! Example: I(-10°C) ~1/16 I(20°C) WODEAN workshop, Vilnius 02/03 June 07

  8. …. with time (annealing): Short term: “Beneficial annealing”Long term: “Reverse annealing” - time constant depends on temperature:~ 500 years (-10°C)~ 500 days ( 20°C)~ 21 hours ( 60°C) Radiation Damage – Effective doping concentration Change of Depletion Voltage Vdep (Neff) …. with particle fluence: „Hamburg model“ “Type inversion”: Neff changes from positive to negative (Space Charge Sign Inversion) before inversion afterinversion p+ n+ n+ p+ Consequence:CoolDetectors even during beam off (250 d/y)alternative: acceptor/donor compensation by defect enginrg.,e.g. see developm. with epi-devices (Hamburg group) WODEAN workshop, Vilnius 02/03 June 07

  9. Summary • Silicon Detectors in the inner tracking area of future colliding beam experiments have to tolerate a hadronic fluence of up to Feq = 1016/cm² • Deterioration of the detector performance is largely due to bulk damage caused by non ionizing energy loss of the particles • Reverse current increase (originating likely from both point defects and clusters) can be effectively reduced by cooling. Defect engineering so far not successful • Change of depletion voltage severe, also affected by type inversion and annealing effects. Modification by defect engineering possible, for standard devices continuous cooling essential (freezing of annealing) • Charge trapping is the ultimate limitation for detector application, responsible trapping centers widely unknown, cooling and annealing have little effects WODEAN workshop, Vilnius 02/03 June 07

  10. Outline for a correlated project • Main issue: charge trapping, the ultimate limitation for detector applications in future HEP experiments source for trapping so far unknown! Maximum F to be tolerated: 1.5E+16 n/cm². • Charge trapping: independent of material type (FZ, CZ, epi) and properties (std, DO, resistivity, doping type). not depending on type of irradiating particles and energy (23 GeV protons, reactor neutrons), if F normalised to 1 MeV neutron equivalent values (NIEL). In contrast to IFD and Neff there are almost no annealing effects (in isothermal annealing studies up to 80C). • Correlated project:use all available methods: DLTS, TSC, PITS, PL, trecomb, FTIR, PC, EPRconcentrate on single material (MCz chosen with possibility of std. FZ for checking of unexpected results. Use only one type of irradiation, most readily available (TRIGA reactor at Ljubljana) and do limited number of F steps between 1E+12 and 3E+16 n/cm². WODEAN workshop, Vilnius 02/03 June 07

  11. 1st WODEAN batch sample list 150 samples n-MCz <100>1 kΩcm (OKMETIC, CiS):84 diodes, 48nude standard, 16 nude thick WODEAN workshop, Vilnius 02/03 June 07

  12. Irradiations Date: November 2006 Delivery to Hamburg: 8 January 2007 Distribution to WODEAN members: 9 February 2007 Important Info about irradiations: F≤ 1E+15 n/cm²: T ≈ 20°C, duration ≤ 10 min F ≥ 2E+15 n/cm²: high flux: dF/dt = 2E12 n/cm²sTemperature increase during irradiation3E+15: t ≈ 25 min, temp. rising to 70-80°C within 15 min (then saturating) 1E+16:t ≈ 80 min, temp. 70-80°C3E+16: t ≈ 4h, 10min, severe self anneal expected WODEAN workshop, Vilnius 02/03 June 07

  13. 2nd WODEAN batch sample list 90 samples n-FZ <111>, 2 kΩcm (Wacker, STM):67 diodes, 24 nude thick samples; WODEAN workshop, Vilnius 02/03 June 07

  14. Irradiations Date: EarlyApril 2007 Delivery to Hamburg: foreseen 11 June 2007 Distribution to WODEAN members: foreseen end June 2007 Important Info about irradiations (as for 1st batch): F≤ 1E+15 n/cm²: T ≈ 20°C, duration ≤ 10 min F ≥ 2E+15 n/cm²: high flux: dF/dt = 2E12 n/cm²sTemperature increase during irradiation3E+15: t ≈ 25 min, temp. rising to 70-80°C within 15 min (then saturating) 1E+16:t ≈ 80 min, temp. 70-80°C3E+16: t ≈ 4h, 10min, severe self anneal expected WODEAN workshop, Vilnius 02/03 June 07

  15. Hamburg, 08-May-2007 WORKSHOP ON DEFECT ANALYSIS WODEAN -RD50 internal project- I. Project Object The project is based on discussions during the first WODEAN meeting, which was proposed during the RD50 workshop at CERN, November 2005 and finally held in Hamburg, 24/25 August, 2006. The main object was to address the problem of defect generation in detector grade silicon using a variety of available techniques. By doing this in a correlated project it is hoped to get more insight in defect creation and a better understanding of their implications for the operability in extremely harsh radiation environments. Thus the main focus is set by the application of silicon detectors in the innermost tracking area of the future SLHC experiments, where accumulated hadron fluences of up to 1.5·1016 cm-2 (1 MeV neutron equivalent) have to be tolerated. Surveying the main effects of radiation damage for detector properties (reverse current increase, change of depletion voltage and reduction of the charge collection for traversing minmum ionizing particles), the latter effect was screened out to be most challenging. Indeed charge carrier trapping would ultimately limit the applicability of silicon detectors. WODEAN workshop, Vilnius 02/03 June 07

  16. II Project Outline Guide lines: Restrictions for the main objects such that results can be obtained within a reasonable time of 1 year with possible extension for a 2nd year. Common correlated project making optimum use of all available methods, intercomparability of obtained results (same material, identical irradiation, identical annealing steps etc.) As charge trapping is largely independent of the detector material, the project is restricted to MCz (magnetic Czochralski) and in a 2nd step to StFZ (standard float zone), both n-type As charge trapping after hadron irradiation is largely independent of particle type and energy (if fluence is NIEL normalised to 1 MeV neutrons), irradiations to be performed at the TRIGA reactor Ljubljana Maximum (1MeV neutron equivalent) hadron fluence expected in SLHC is 1.5·1016 cm-2. Irradiations should therefore cover a range from values usable for the most sensitive methods (DLTS) up to well above 1·1016 cm-2 in manageable steps.Methods for investigations: C-DLTS: Univ. Hamburg, Oslo, Minsk I-DLTS: Univ. Florence TSC: Univ. Hamburg, NIMP Bucharest PITS: ITME Warsaw PL: Kings College London, ITME Warsaw Lifetime: Univ. Vilnius FTIR: Univ. Oslo PC: Univ. Vilnius EPR: NIMP Bucharest, ITME Warsaw Detecor characteris. (C/V, I/V, TCT): CERN-PH, Univ HH, JSI Ljubljana WODEAN workshop, Vilnius 02/03 June 07

  17. Memberlist with affiliation: NIMP Bucharest: Sergiu Nistor, Ioana Pintilie (also guest in Hamburg Univ.) CERN-PH: Michael Moll Hamburg University: Eckhart Fretwurst, Gunnar Lindstroem, Ioana Pintilie (from NIMP) Florence University: Mara Bruzzi, David Menichelli JSI Ljubljana: Gregor Kramberger Kings College London: Gordon Davies Minsk University: Leonid Makarenko Oslo University: Bengt Gunnar Svensson, Leonid Murin (guest from Minsk) Vilnius University: Eugenius Gaubas, Juozas Vaitkus ITME Warsaw: Pawel Kaminski, Roman Kozlowski, Mariusz Pawlowski, Barbara Surma Needs to be updated!, Sergiu Nistor resigned, new members: Anfrey Aleev (ITEP)? III. Present Status A first batch of 120 different MCz samples (material from Okmetic; diodes and nude samples processed by CiS, 3 mm thick samples for FTIR and EPR from CERN) had been irradiated at the TRIGA reactor in November 2006 and distributed to the different collaborators. 11 irradiation fluences were chosen between 3·1011 and 3·1016 cm-2 with the smallest values for DLTS and the largest ones for EPR. A 2nd batch of FZ samples had been sent to Ljubljana and will be irradiated soon. First results on the measurements as well as an upgrade of the project program will be discussed in the 2nd WODEAN workshop scheduled on 2nd and 3rd June 2007 in Vilnius. A summary will then be presented on the following RD50 workshop. WODEAN workshop, Vilnius 02/03 June 07

  18. IV. Project Budget Proposal Total budget breakdown: Material-, processing, masks, special preparations: 35.000,- CHF Subcontracted analysis: 10.000,- CHF Total budget: 45.000,- CHF Requested support from RD50 common fund: MCz- and FZ material: 5.000,- CHF Processing 15.000,- CHF Analysis (SIMS, spreading resistance,…) 10.000,- CHF Total requested support from RD50: 30.000,- CHF Contributions from WODEAN members: CERN-EP: 2.000,- CHF Florence University: 2.000,- CHF Hamburg University: 8.000,- CHF Oslo University: 3.000,- CHF All other Institutes: contributions in kind: Total contribution from WODEAN members: 15.000,- CHF It is proposed that the finacial management for the RD50 support will be handled by the detector group, Institute for Experimental Physics, Hamburg University. WODEAN workshop, Vilnius 02/03 June 07

  19. Finally Last changes to the application as internal project: accepted as is what did we learn: this meeting discussion about overview report for RD50modifications for working program what else should be done with existing MCz samples, isochronal anneal! interchanging results inbetween workshops continuously next workshop date: end 2007 Changes to WODEAN member list: Diode characterisation: M. Moll (CERN-PH) included I-DLTS: D. Menichelli (Florence): observer (manpower problems) EPR: Sergiu Nistor (NIMP): observer (future participation possible) WODEAN workshop, Vilnius 02/03 June 07

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