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Charge Division and Radiation Hardness of Si μstrip Sensors

This seminar focuses on the charge division and radiation hardness of silicon μstrip sensors. Topics include reconstructing tracks in jets, electromagnetic radiation hardness, and the design of the Beam Calorimeter. The seminar also discusses the rates and energy involved, as well as the hadronic processes in electromagnetic showers.

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Charge Division and Radiation Hardness of Si μstrip Sensors

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  1. ILC R&D Sampling: Charge Division and Radiation Hardness of Si strip Sensors SCIPP Seminar Sept 14 2010

  2. Charge Division for Silicon Strip Sensors Jerome Carman, Vitaliy Fadayev, Rich Partridge (SLAC), Ned Spencer, B.S.

  3. Reconstructing Tracks in Jets at Ecm= 500 GeV (e.g. Non-prompt Tracks)

  4. Final step: practical detectors are not isolated strips. Include two nearest-neighbors in simulation: Network effects lead to ~5% reduction in longitudinal resolution.

  5. Electromagnetic Radiation Hardness of Si strip Sensors

  6. The SCIPP/UCSC Beam Calorimeter Group Faculty/Senior Vitaliy Fadeyev Bruce Schumm Collaborators Takashi Maruyama Tom Markiewicz (SLAC) Students Joey Gomez Spencer Key Donish Khan Fergus Noble* *(Cambridge) Beam Calorimeter: surrounds the beam pipe several meters downstream of the IP. Expected to receive greater than 100 MRad per year  ~ 1Grad dose must be withstood.

  7. Some notes: • Beam Calorimeter is a sizable project, ~2 m2 of sensors. • Sensors are in unusual regime: ~ 1 GRad of e+/e-; 1014 n/cm2 after several years. • There are on-going studies with GaAs, Diamond, Sapphire materials (FCAL report, Nov 2009). • We’ll concentrate on mainstream Si technology proven by decades of technical development. • There is some evidence that p-type Si may be particularly resilient… 15

  8. Rates (Current) and Energy • Basic Idea: • Direct electron beam of moderate energy on Tungsten radiator; follow with silicon sensor at shower max • For Si, 1 GRad is about 3 x 1016/cm2, or about 5 mili-Coulomb • Current scale is A, which points to the 1-5 GeV beam at CBAF (Jefferson Lab, Virginia, USA) 16

  9. G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 (1993) NIELe- Energy 2x10-2 0.5 MeV 5x10-2 2 MeV 1x10-1 10 MeV 2x10-1 200 MeV Damage coefficients less for p-type for Ee- < ~1GeV (two groups); note critical energy in W is ~10 MeV But: Are electrons the entire picture? 17

  10. Hadronic Processes in EM Showers • There seem to be three main processes for generating hadrons in EM showers (all induced by photons): • Nuclear (“giant dipole”) resonances • Resonance at 10-20 MeV (~Ecritical) • Photoproduction • Threshold seems to be about 200 MeV • Nuclear Compton scattering • Threshold at about 10 MeV;  resonance at 340 MeV •  Flux through silicon sensor should be ~10 MeV e/, but also must appropriately represent hadronic component 18

  11. 1mm Downstream of 18mm Tungsten Block Not amenable for uniform illumination of detector. Instead: split 18mm W between “pre” and “post” radiator separated by large distance Caution:nuclear production is ~isotropic  must happen dominantly in “post” radiator! Boundary of 1cm detector Fluence (particles per cm2) 19 Radius (cm)

  12. 5.5 GeV Shower Profile “Pre” “Post” e+e- (x10) All  Remember: nuclear component is from photons in 10-500 MeV range. Fluence (particles per cm2) E > 100 MeV (x20) E > 10 MeV (x2) 20 Radius (cm)

  13. Proposed split radiator configuration 5mm Tungsten “pre” 13mm Tungsten “post” Separated by 1m Fluence (particles per cm2) 1.0 2.0 3.0 21 Radius (cm)

  14. JLAB Hall B Beam Dump (Plans to run 0.05 A through next May)  Total power in beam ~250W.

  15. Rastering Need to achieve uniform illumination over region of size 0.25x0.75 cm (active area of SCIPP’s charge collection measurement apparatus). To be safe (alignment), raster in 0.05cm steps over 0.6x1.5 cm, assuming fluence profile on prior slide (see next slide for result) ~x10 fluence enhancement from shower very helpful  2-3 hours per GRad.

  16. Fluence (e- and e+ per cm2) per incident 5.5 GeV electron (5cm pre-radiator 13 cm post-radiator with 1m separation) Center of irradiated area ¼ of area to be measured ¼ of rastoring area (0.5mm steps)

  17. Irradiation Plan • Intend to use existing sensors from ATLAS R&D (made at Micron). Both n- and p- type, Magnetic Czochralski and standard Float Zone. • Plan to assess the bulk damage effects, charge collection efficiency. This will further assess the breakdown on NIEL scaling (x50 at 2 MeV and x4 at 900 MeV) in the energy range of interest. Sensors Sensor + FE ASIC DAQ FPGA with Ethernet 25

  18. Nominal Run Plan (not yet proposed to JLAB) Current thinking: Four groups of sensors available and qualified: (Float zone, Czochralksi) x (p bulk, n bulk) Run each at 0.1, 0.5, 2.0 GRad) Also, run one of each at 2.0 Grad with all 18mm of tungsten 1m away (no hadronic component). Total of 16 runs, about 15 hours of accumulated beam time. 26

  19. Concluding Remarks • Broad array of generic and specific tracking R&D: • Optimized Si strip readout (LSTFE) • SiD baseline concept development (KPIX/2Metal) • Generic study of strip noise sources • Radiation hardness • Exploring use of charge division for strip z coord • Sid tracking performance benchmarking • Non-prompt signature from GMSB • Excellent training ground for undergraduate physics/engineering majors (9 currently working on project) • Schumm also on LC Steering Group of the Americas, ALCPG EXEC Committee

  20. BeamCal Incident Energy Distribution 2 4 6 8 10 e+/e- ENERGY (GEV) BUT: Most fluence is at shower max, dominated by ~10 MeV e-, e+ and . Why might (?) incident energy matter? 28

  21. NIEL (Non-Ionizing Energy Loss) • Conventional wisdom: Damage proportional to Non- Ionizing Energy Loss (NIEL) of traversing particle • NIEL can be calculated (e.g. G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 [1993]) • At EcTungsten ~ 10 MeV, NIEL is 80 times worse for protons than electrons and • NIEL scaling may break down (even less damage from electrons/psistrons) • NIEL rises quickly with decreasing (proton) energy, and fragments would likely be low energy •  Might small hadronic fractions dominate damage? 29

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