The T506 Experiment: Electromagnetically-Induced Radiation Damage to Solid-State Sensors Test Facilities Users Workshop SLAC, September Bruce Schumm Santa Cruz Institute for Particle Physics

2 T-506 Motivation I: The ILC BeamCal ILC Detector BeamCal: accepts electrons (positrons) scattered between 5 and 50 MRad

3 T-506 Motivation II BeamCal maximum dose ~100 MRad/yr Beam Calorimeter is a sizable: ~2 m 2 of sensors. A number of ongoing studies with novel sensoers: GaAs, CVD diamond Are these sensors radiation-hard? Might mainstream Si sensors be of use? (some reasons for optimism…)

4 Departure from NIEL (non-ionizing energy-loss) scaling observed for electron irradiation NIELe - Energy 2x MeV 5x MeV 1x MeV 2x 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?

5 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 MeV (~E critical ) 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

2 X 0 pre-radiator; introduces a little divergence in shower Not shown: 4 X 0 and 8 X 0 radiators just before and after sensor Sensor sample

7 Detector Fluence Distribution (per incident e - ) Radius (cm) Fluence (particles per cm 2 ) For later charge collection measurement, must have ~1cm 2 uniformly illuminated area  Raster sensor across beam

8 Dose Rates (Including 1 cm 2 Rastering) Mean fluence per incident e - Maximum dose rate (10.6 GeV; 10 Hz; 150 pC per pulse; end of 2013): 28 Mrad per hour Confirmed with RADFET to within 10% Approximate dose rate: 1.7 Mrad per GeV-nA-Hour

LCLS and ESA Use pulsed magnets in the beam switchyard to send beam in ESA. Mauro Pivi SLAC, ESTB 2011 Workshop, Page 9

ESTB parameters 0.25 nC ParametersESA Energy15 GeV Repetition Rate5 Hz Charge per pulse0.35 nC Energy spread,  E  /E 0.02% Bunch length rms 100  m Emittance rms (  x  y ) (4, 1) m-rad Spot size at waist (  x,y  < 10  m Drift Space available for experimental apparatus 60 m Transverse space available for experimental apparatus 5 x 5 m (for now) Up to 10 Hz! ≤ 0.15 nC

11 T506 Doses for Si Diode Sensors “P” = p-type “N” = n-type “F” = float zone “C” = Czochralski

12 Sensor + FE ASIC DAQ FPGA with Ethernet Charge Collection Apparatus at SCIPP (UCSC Campus)

13 Results: NC sensors

14 Results: NF sensors high dose

15 Other T506 Exposures Two bulk GaAs sensors –5 Mrad –20 Mrad –Charge-collection evaluation underway LCLS Upgrade attachment samples T506 apparatus/infrastructure can be made available upon request

16 T506 Plans for 2015 Exposures must be at least 100 Mrad to be of use Low-energy/low-current running probably not of use Second kicker-magnet probably solves everything (T506 could make use of frequent high-energy running which is best for it anyway!)

17 T506 Wish List for 2015 “NC” sensor to 500 Mrad “NF” sensor to 250+ Mrad “PF”, “PC” sensors to 100 Mrad GaAs sensor to 100 Mrad 5 GeV, 0.75 nA  ~200 Hrs (20-25 shifts) 13 GeV, 1 nA  ~50 Hrs (5-7 shifts)

18 Summary and Conclusions The 2014 re-configuration of the T506 target has made it trustworthy and easy to use Running to date has shown promise for performance of “everyday” Si Diode sensors at ILC BeamCal dose rates With second kicker magnet, ESTB is up to the task of exploring full BeamCal dose rates T506 target also used for other exposures, including GaAs and LCLS upgrade samples T506 apparatus can be made available for controlled irradiation studies for any interested user

19 BACKUP

20 Results: NF sensors low dose

21 Results: PC sensors

22 Results: PF sensors

23 Channel-over- threshold profile Efficiency vs. threshold Median Collected Charge Charge Collection Measurement 2.3 MeV e - through sensor into scintillator