Initial Results from SLAC ESTB T-506 Irradiation study FCAL Workshop, DESY-Zeuthen

1. Initial Results from SLAC ESTB T-506 Irradiation study FCAL Workshop, DESY-Zeuthen 7-8 October 2013 Bruce Schumm UC Santa Cruz Institute for Particle Physics

2. T-506 Motivation • BeamCal maximum dose ~100 MRad/yr • Beam Calorimeter is a sizable: ~2 m2 of sensors. • A number of ongoing studies with novel sensoers: GaAs, CVD diamond • Might mainstream Si sensors be of use? • Some reasons for optimism… • 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 polished by decades of technical development. • There is some evidence that p-type Si may be particularly resilient: • Neutron flux does not seem to be a problem for Si (RD50 findings). • There are very few e+/e- radiation hardness studies: • S. Dittongo et al (2005); n/p-type Si;160 MRad of 900 MeV e- • J.M. Rafi et al (2009); n-type Si; 1.7 GRad of 2 MeV e- • Our region of interest is ~100 MeV (incident) and lower (shower max)

3. Departure from NIEL (non-ionizing energy-loss) scaling observed for electron irradiation NIELe- Energy 2x10-2 0.5 MeV 5x10-2 2 MeV 1x10-1 10 MeV 2x10-1 200 MeV G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 (1993) Also: for ~50 MRad illumination of 900 MeV electrons, little loss of charge collection seen for wide variety of sensors (S. Dittongo et al., NIM A 530, 110 (2004) But what about the hadronic component of EM shower? 3

4. G.P. Summers et al., IEEE Trans Nucl Sci 40, 1372 (1993) 4

5. More notes: • Neutron flux does not seem to be a problem for Si (RD50 findings). • There are very few e+/e- radiation hardness studies: • S. Dittongo et al (2005); n/p-type Si;160 MRad of 900 MeV e- • J.M. Rafi et al (2009); n-type Si; 1.7 GRad of 2 MeV e- • Our region of interest is 100 MeV – 10 GeV (incidence) and lower (shower max) 5

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

7. NIEL (Non-Ionizing Energy Loss) • Conventional wisdom: Damage proportional 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? 7

8. Hadronic Processes in EM Showers • From what we have seen, there are three main processes for generating hadrons in EM showers: • Nuclear (“giant dipole”) resonances • Photoproduction • Nuclear Compton scattering • Rates, CBAF, Vitaliy’s picture… 8

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14. Sensor + FE ASIC DAQ FPGA with Ethernet 14

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17. Irradiation Plan • Intend on using left-over sensors from ATLAS sensor R&D (made at Micron). Both n- and p- type, Magnetic Czochralski and Oxigenated Float Zone. • Plan to use NL-CTA beam at 120 MeV (with degrader). • Will assess the bulk damage effects. This will further assess the breakdown on NIEL scaling (x50 at 2 MeV and x4 at 900 MeV) in the energy range of interest. • An interesting possibility is to mimic the expected radiation tail with an absorber, to be less dependent on radiation damage modeling. • Want to also characterize the charge collection efficiency. Sensors Sensor + FE ASIC DAQ FPGA with Ethernet