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Plans for Radiation Damage Studies for Si Diode Sensors Subject to 1 GRaD Doses

Detailed plans for radiation damage studies on Si diode sensors exposed to 1 GRaD doses at the FCAL Workshop in Belgrade. The focus is on understanding the impact of electromagnetic and hadronic radiation on sensors used in the ILC BeamCal, with proposed irradiation plans, sensor types, and assessment methods.

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Plans for Radiation Damage Studies for Si Diode Sensors Subject to 1 GRaD Doses

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  1. Plans for Radiation Damage Studies for Si Diode Sensors Subject to 1 GRaD Doses FCAL Workshop, Belgrade 14 September 2011

  2. The Issue: ILC BeamCal Radiation Exposure ILC BeamCal: Covers between 5 and 40 miliradians Radiation doses up to 100 MRad per year Radiation initiated by electromagnetic particles (most extant studies for hadron –induced) EM particles do little damage; might damage be come from small hadronic component of shower? 2

  3. 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? 3

  4. 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 •  These are largely isotropic; must have most of hadronic component develop near sample 4

  5. Post-radiator and sample Pre-radiator

  6. Hadronic Processes in EM Showers 6

  7. 5.5 GeV Shower Profile e+e- (x10) All  “Post” “Pre” Remember: nuclear component is from photons in 10-500 MeV range. Fluence (particles per cm2) E > 100 MeV (x20) E > 10 MeV (x2) 7 Radius (cm)

  8. Proposed split radiator configuration 3mm Tungsten “pre” 18mm Tungsten “post” Separated by 1m Fluence (particles per cm2) 1.0 2.0 3.0 8 Radius (cm)

  9. Rastering • Need uniform illumination over 0.25x0.75 cmregion (active area of SCIPP’s charge collection measurement apparatus). • Raster in 0.05cm steps over 0.6x1.5 cm, assuming fluence profile on prior slide (see next slide for result) Exposure rate: e.g. 1 GRad at 1 nA 13.6 GeV e-  ~ 48 Hours

  10. Illumination Profile Uniform to  10% over (3x6)mm area 1.0 2.0 3.0 10

  11. Irradiation Plan • Intend to use existing sensors from ATLAS R&D (made at Micron). Both n- and p- type, Magnetic Czochralski and Oxygenated 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 11

  12. OTHER ISSUES/CONSIDERATIONS • Will want to run with all of radiator upstream to determine if damage is from EM or hadronic radiation (nuclear production is isotropic)  working on optimixing radiator configuration, but is likely to be x5 slower. • Upgrading charge-collection measurement apparatus for quick turn-around with many samples (~5 PC boards & lithographic elements) • Will result in greater modularity  will allow easy collaboration with groups interested in other sensor technologies

  13. LOOKING FORWARD • Proposing first run at SLAC • Should be able to reach 100 MRad level for several samples • Plan to have cooling in place at SLAC, and to transport cooled sensors to SCIPP for assessment (avoid spurious annealing effects) • May be able to offer to do study for sensor samples others will provide, if interested (please contact me to discuss).

  14. SUMMARY ILC BeamCal demands materials hardened for unprecedented levels of electromagnetic-induced radiation 10-year doses will approach 1 GRad. Not clear if hadrons in EM shower will play significant role  need to explore this Propose to start study at 100 MRad level at SLAC Hoping to offer as generic facility for high-level EM radiation damage studies (please contact if interested)

  15. Backup

  16. Parameters required for Beam Tests To the presenter at the ESTB 2011 Workshop: please, fill in the table (at best) with the important parameters needed for your tests

  17. Shower Max Results Photons with E > 100 MeV per electron, x 100 Photons with E > 10 MeV per electron, x10 Photons per electron Electrons, per GeV incident energy 1.0 2.0 3.0 17  Photon production ~independent of incident energy!

  18. 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? 18

  19. 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) 19 Radius (cm)

  20. 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)

  21. 5.5 GeV Electrons After 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) 21 Radius (cm)

  22. 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/positrons) • NIEL rises quickly with decreasing (proton) energy, and fragments would likely be low energy •  Might small hadronic fractions dominate damage? 22

  23. BeamCal Incident Energy Distribution 2 4 6 8 10 e+/e- ENERGY (GEV) 23

  24. Wrap-up Worth exploring Si sensors (n-type, Czochralski?) Need to be conscious of possible hadronic content of EM showers Energy of e- beam not critical, but intensity is; for one week run require Ebeam(GeV) x Ibeam(nA) > 50 SLAC: Summer-fall 2011 ESA test beam with Ebeam(GeV) x Ibeam(nA) 17 – is it feasible to wait for this? 24

  25. Rates (Current) and Energy • Basic Idea: • Direct electron beam of moderate energy on Tungsten radiator; insert silicon sensor at shower max • For Si, 1 GRad is about 3 x 1016/cm2, or about 5 mili-Coulomb/cm2 • Reasonably intense moderate-energy electron or photon beam necessary What energy…? 25

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