Radiation Damage Studies for Solid State Sensors Subject to MRaD Doses [T506 2014 Follow-on]

1. Radiation Damage Studies for Solid State Sensors Subject to MRaD Doses [T506 2014 Follow-on] Bruce Schum UC Santa Cruz April 16 2014

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. 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 3

4. Hadronic Processes in EM Showers Up to 100W beam absorption; operate below freezing to avoid annealing Status: Thermal prototype under testing at SCIPP 4

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

6. Charge Collection Apparatus Sensors DAQ FPGA with Ethernet Sensor + FE ASIC Recently upgraded for multiple samples • P-type and N-type sensors • Float-zone and Magnetic Czochralski bulk • Will maintain 0-5o C during irradiation • Continue studies begin in 2013 6

7. Rastering Need uniform illumination over 0.25x0.75 cmregion (active area of SCIPP’s charge collection measurement apparatus). • Raster in 0.05cm steps over 1x1 cm, assuming fluence profile on prior slide (see next slide for result) Exposure rate: e.g. 1 MRad at 0.1 nA of 4 GeV e-  ~ 1.5 Hrs

8. Current Run Beam energy has been low: 3.0 GeV At these energies, exposure rate falls off faster than linearly due to migration of shower max. Exposure rate estimate: 125 rad per 150 pC pulse, or about 2.3 Mrad per hour  roughly 20 Mrad per shift

9. Irradiation Runs from 2013 Run of T506 (4 running periods in June and July 2013)

10. Results: PF sensors (un-annealed) 10

11. RUN ACTIVITY We 4/16 Began installation (open access) Th 4/17 Search and secure early afternoon; completed installation in controlled access. Alignment beam delivered and misalignments measured. Fr 4/18 Controlled access to raise platform; final alignment with magnet mover. Place PF sample, tungsten radiators and set up rastering and cooling. A-line set up. Accumulate 13:00 – 21:00.  16 Mrad Sa 4/19 Continue exposure 11:30 – 21:00  19 Mrad Su 4/20 Continue exposure 11:30 – 19:00  XXX Mrad Mo 4/21 Move apparatus off beamline for a few hours; return and accumulate until 21:00

12. Other 2013 T506 Goals  Continue high-fluence studies DUBNA (Russia) has developed bulk (non-diode) GaAs sensors as alternative for BeamCal  Explore radation hardness of DUBNA pad sensors (in hand; modifying charge-collection apparatus for single-panel pad sensors rather than strip sensors)

13. Results: NC sensors 13