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

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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

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)

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

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

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

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

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

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

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