Tim Bolton, KSURun 2B L0/L1 PRRAug 7, 20031

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, …).

Tim Bolton, KSURun 2B L0/L1 PRRAug 7, 20032

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.

Tim Bolton, KSURun 2B L0/L1 PRRAug 7, 20033

Layout

Tim Bolton, KSURun 2B L0/L1 PRRAug 7, 20034

Fluence Checks

Fluence = integrated flux. In L2 PRR, some issues arose over value of

damage coefficient (ILeak/volume = ), which appeared ~3×too low when 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.

Tim Bolton, KSURun 2B L0/L1 PRRAug 7, 20035

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%.

Tim Bolton, KSURun 2B L0/L1 PRRAug 7, 20036

Copper Activation Analyses

1.5 mil natural copper foils irradiated in same beam with protons to produce Zn-63(1/2=38 min.) and Zn-65 (1/2=244 days), which + or EC decay with accompanying ’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 counter18% 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.

Tim Bolton, KSURun 2B L0/L1 PRRAug 7, 20037

Activation Summary

Activation analyses are consistent with direct fluence measurements.

No reason not to use more precise values from beam system.

0.75

0.80

0.85

0.90

0.95

1.00

1.05

1.10

1.15

1.20

1.25

0 5 10 15 20

sample number

acti

vati

on

flu

ence

/dir

ect

flu

ence

Zn-63 (669+961 keV lines)-- KSU Gedet.

Zn-65 (1115 keV line)-- KSU Ge det.

Zn-65 (1115 keV line)-- KSU NaI(Tl)det.

Zn-65 (1115 keV line)-- FNAL Ge det.

Tim Bolton, KSURun 2B L0/L1 PRRAug 7, 20038

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 P 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.

Tim Bolton, KSURun 2B L0/L1 PRRAug 7, 20039

10 MeV Leakage Current Summary

Tim Bolton, KSURun 2B L0/L1 PRRAug 7, 200310

7 MeV Leakage Current Summary

Tim Bolton, KSURun 2B L0/L1 PRRAug 7, 200311

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.