Initial Results from SLAC ESTB T-506 Irradiation study

FCAL Workshop, DESY-Zeuthen7-8 October 2013

Bruce SchummUC Santa Cruz Institute for Particle Physics

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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)

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Departure from NIEL (non-ionizing energy-loss) scaling observed for electron irradiation

NIEL e- 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?

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

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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)

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e+/e- ENERGY (GEV)

BUT: Most fluence is at shower max, dominated by ~10 MeV e-, e+ and . Why might (?) incident energy matter?

BeamCal Incident Energy Distribution

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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?

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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…

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Sensor +FE ASIC

DAQ FPGA with Ethernet

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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

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