Radiation Testing at KSU for the Run 2B Upgrade

1. Radiation Testing at KSU for the Run 2B Upgrade L0/L1/L2 sensors from both HPK and ELMA tested with 7-14 MeV proton beams at the James R. Macdonald Laboratory, a DOE national user facility for accelerator-related AMO physics. Many other detector components tested as well (hybrids, epoxy, cables, …).

2. Basic Setup • Beam from 7 MV tandem Van de Graaff (mostly 10 MeV protons). • Basic setup: • Samples are mounted in a vacuum target chamber un-powered. • Beam is rastered over sample using sawtooth pattern electric fields. • Current measured by Faraday cup/current integrator to 10 pC least count. • Runs are for fixed amount of charge, with beam currents 10-100 nA. • Sensors are annealed for 80 minutes at 60C, then electrically tested. • Multiple fluence points are taken on single sensor. • Long term storage is at -20C.

3. Layout

4. Fluence Checks • Fluence = integrated flux. • In L2 PRR, some issues arose over value of damage coefficient a (ILeak/volume = aF), which appeared ~3×too low when F was re-expressed in terms of 1 MeV neutron equivalent fluence assuming standard NIEL scaling arguments. • Issue now resolved. Simple plotting error (corrected) and unaccounted for physics effect: 10 MeV protons do not obey NIEL scaling. • Nevertheless motivated several checks of fluence. • See more extended write-ups in your “book” for details.

5. Current Integration Tests • Faraday cup is close behind target. • Only beam passing through sample in Al window is counted. • Efficiency corrections of ~1.01/1.02/1.1 for L0/L1/L2 are applied for MCS. • Efficiency checked to ~10% in special runs largest flux uncertainty. • Faraday cup cross-checked with other cup; current measurements checked against independent pico-ammeters to < 1%.

6. Copper Activation Analyses • 1.5 mil natural copper foils irradiated in same beam with protons to produce Zn-63(t1/2=38 min.) and Zn-65 (t1/2=244 days), which b+ or EC decay with accompanying g’s. • Zn-63 rates and Zn-65 rates measured at KSU Nuclear Reactor Lab using Ge well counter with NIST calibrated sources for efficiency and standard industry software inferred fluence agrees with direct measurement to 10%. • Zn-65 rate measured independently with NaI(Tl) counter by KSU AMO physicist same level of agreement. • Zn-65 samples measured independently at FNAL ES&H facility using Ge disk counter18% agreement with KSU. • Main uncertainty in activation analysis is Cu(p,n)Zn cross section (~10%), but many details need to be sorted out. • FNAL/KSU discrepancy not fully resolved, was converging.

7. Activation Summary • Activation analyses are consistent with direct fluence measurements. • No reason not to use more precise values from beam system.

8. Comparison with other proton data • We discovered belatedly that the best way to present our data is directly in terms of integrated proton fluence, rather than converting to 1 MeV neutron equivalence using the NIEL scaling hypothesis. • In doing this, we can compare directly with measurements taken with a similar setup at Montreal (RD48/ROSE Collaboration, D. Bechevet et al),Nucl. Instrum. Meth. A479: 487-497,2002). • NIEL scaling fails in this regime: this is well known to several members of this committee. • Our data is consistent with an aP value that is approximately independent of sensor type and geometry and which agrees with that measured by RD48/ROSE at both 10 MeV and 7 MeV.

9. 10 MeV Leakage Current Summary

10. 7 MeV Leakage Current Summary

11. Conclusions • We can reliably use proton beams from the KSU Macdonald Lab for radiation testing of all sensor types. • Beam current measurements are internally self-consistent. • Beam current and activation measurements are consistent. • Leakage current measurements agree with CERN results. • Our L1 data includes fluence to 1014 protons/cm2, well beyond anticipated Run 2 exposure. • We are beginning to irradiate production L2 test structures for QC/QA purposes.