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GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 2B: Radiation Evaluation-Testing

Gamma-ray Large Area Space Telescope. GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 2B: Radiation Evaluation-Testing Hartmut F.-W. Sadrozinski Santa Cruz Institute for Particle Physics University of California at Santa Cruz Tracker Subsystem Scientist hartmut@scipp.ucsc.edu.

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GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 2B: Radiation Evaluation-Testing

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  1. Gamma-ray Large Area Space Telescope GLAST Large Area Telescope: Tracker Subsystem WBS 4.1.4 2B: Radiation Evaluation-Testing Hartmut F.-W. Sadrozinski Santa Cruz Institute for Particle Physics University of California at Santa Cruz Tracker Subsystem Scientist hartmut@scipp.ucsc.edu

  2. LAT TKR Radiation Overview • Radiation Levels are given in: • 433-SPEC-0001 GLAST Mission System Specification, CH 07 • LAT-SS-01165 TID Self-Shielding of the GLAST LAT TRK • Applicable LAT documents: • LAT-SS-00152 Level-4 Electronics requirements • LAT-DS-00011LAT SSD Technical Specifications • LAT-TD-00673 Constraints on the Temperature of TKR SSD • LAT-TD-00401 LAT EE Parts List • LAT-SS-00169 TKR Front-End (GTFE) Specification • LAT-SS-00170 TKR Readout Controller (GTRC)Specification

  3. LAT TKR Radiation Overview • Test plans: • LAT-CR-00082 LAT SSD Quality and Reliability Assurance • LAT-TD-00085 Testing Procedures for the GLAST LAT SSDs • LAT-PS-01325 Radiation Test Plan for the LAT TKR ASICs • Test Results • LAT-TD-00086 LAT Review of SSD RHA Test Results • LAT-TD-00128 Results from Heavy Ion Irradiation (SSD) • LAT-QR-01078 Q/A OF THE GLAST LAT SSD: RHA • LAT-TD-00333 SEE Test of the LAT TKR Front-End ASIC • LAT-TD-01172 LAT TKR Readout Controller ASIC SEE Test • LAT-TD-01632 LAT TKR Frontend ASIC SEE Test

  4. Radiation Levels: TID TID is caused by Charged Particles Trapped in SAA • Shielding helps! • Front: Heat blanket, ACD • Shielding 2 g/cm2eliminates all electrons • Back: Mass of LAT • Cuts TID by half • Expected 5Y TID < 0.8 kRad( low ! ) • Design 5Y TID = 4 kRad • (5x Engineering Margin) • Only in outer SSD layers • & for ASICS on outside • Majority of TKR much less • Testing TID = 10 kRad

  5. Radiation Levels: Heavy Ions SEE Effects due to Galactic Cosmic Rays and Solar Particle Events • High energy particles due to Geomagnetic cut-off: • Shielding less effective! • GCR: • For LET > 2 : F(5Y) ~ 5/cm2 • LET < 28 MeV/(mg/cm2) • SPE: • For LET > 5 : F(5Y) ~ 5/cm2 • (worst day/4) • LET < 100 MeV/(mg/cm2) • Rates very low, but SEE effects potentially destructive • GLAST Specs: • evaluate for LET < 37 MeV/(mg/cm2)

  6. Radiation Effects on TKR Parts • Use parts on the accepted parts list of GSFC as much as possible • New Part: Polyswitch re-settable device (3,456 in LAT) • Do ~ 100 kRad TID test ? NO (Parts are treated with 20 MRad during polymerization to enhance cross-linking!) • Mitigates SEL risk! • SSD: (9,216 in LAT) • SEE effects tested; no effects observed, as expected • TID (ionizing) tested with 60Co: part of Q/A at Hiroshima U. • Proton fluence generates leakage current and limits operating temperature • ASICs: (1,152 GTRC, 13,824 GTFE in LAT) • SEE effects important (SEU and SEL): test plan & results • TID (ionizing): test plan & results

  7. Radiation Effects on TKR SSD • Displacement damage due to trapped protons increases leakage current • DI ~ a*Vol*F • Noise in frontend amplifier increases with leakage current • ENC(DI) ~ (DI*t)0.5 • Exponential temperature dependence of DI limits operating temperature: Data apply to top TKR layers only

  8. Radiation Hardness Assurance on ASICs • Testing done by INFN Padova collaborators • SEE testing at INFN Legnaro tandem Van der Graff facility () • TID testing at INFN Legnaro 60Co source • We have done 2 SEE runs, 1 TID irradiation with fully functional pre-production prototype TKR ASICs • All LAT ASICs are fab’ed in epitaxial 0.5um Agilent CMOS • TID not a problem, SEL Threshold > 56 MeV/(mg/cm2) • TID Test Plan for each of the 5 lots of GTFE, 1 lot of GTRC • 7 parts each mounted on mini-MCM with 2 GTRC • TID = 10 kRad in 4 steps • Measure power, gain, noise rate and functionality • SEU Test Plan for of each of the 5 lots of GTFE, 1 lot of GTRC • 2 parts each mounted on mini-MCM with 2 GTRC • Heavy ions with LET from 8 (Si) to 83 (Au) MeV/(mg/cm2). • Measure Single Event Upset(SEU), Single Event Functional Interrupt (SEFI) and Single Event Latch-up (SEL) cross sections

  9. TID Test Results on TKR ASICs • Testing by INFN Padova (R. Rando, D. Bisello, J. Wyss et. al.) • Irradiate both GTRC and GTFE pre-production prototypes • Use mini-MCM and DAQ set-up: • After TID of 10 krad for GTFE, 20 krad for GTRC • Power dissipation did not change • Gain stable • Noise rate under control • GTRC and GTFE function at 20MHz

  10. SEE Test Results on TKR ASICs • Testing by INFN Padova (R. Rando, D. Bisello, J. Wyss et. al.) • Irradiate both GTRC and GTFE pre-production prototypes • Fluence from GTRC Test: • NO SEL observed  Upper limit on expected rate of Latch-up • SEU cross sections sensitive to layout details as expected • Rockett cell proves to be SEU hardened • No TID effects • Radiation Testing well in hand

  11. SEE Test Results on TKR ASICs cont. • Very consistent results wrt. to previous data on test chips • Cross sections different • for 0 —> 1 and 1 — > 0 etc • Cross section threshold: • ~ 5-8 MeV/(mg/cm2) • SEL Upper Limit • < 10-6 cm2 /GTRC

  12. SEE Test Results on TKR ASICs cont. • Communication errors and SEFI error cross sections and upper limits for SEL for the entire GTRC. • The Weibul fit s = S*(1-e-(LET-THR)/W) • gives S = 4*10-6, THR = 5 - 8, W = 40-48. • SEL Probability < 0.5 % for entire TKR in 5 years • SEU Probability ~ 1% for entire TKR in 5 years

  13. SEL Testing: Using the right H.I. Range • Single Event Upset (SEU) is essentially a surface phenomen: • Large charges in the gate flips the bit, no special H. I. range • Single Event Latch-up (SEL) • Caused by parasitic transistor inside the bulk • Epitaxial structures should reduce charge collection • Range of Heavy Ions has to exceed the charge collection distance • Collection Distance • A.H. Johnston “an ion range that is approximately twice the dimension of the epitaxial layer thickness is generally adequate”. • For our 6um epi process this means 17 um required range. • J. Howard et al. find charge collection distance of 26 um for high energy heavy ions in 7 um epitaxial structures. • ESA/SCC Basic Specification No. 25100: ion range > 30 um . • Heavy Ion Range for LET = 37 MeV/(mg/cm2) • LNL Legnaro (Br) 31um LAT TKR Preference • BNL (Br) 39um • TAMU (Ag) 130um GSFC Rad Branch Preference

  14. TKR Radiation Evaluation: Conclusions • SSD: • Radiation issues well understood; used to Q/A the lots (Hiroshima) • Increase in leakage current not expected to diminish TKR performance as long as the temperature is controlled to <30C • ASICs: • Require radiation testing for each of the lots (5 GTFE, 1 GTRC) • Radiation testing well in hand at INFN Padova • Expected TID and SEE risk very small • SEL mitigation from polyswitch resettable devices • Concern: • Schedule: ASIC radiation testing has to start in April, yet test plan has not been signed off by GSFC. • Cost: New requirements could introduce schedule, cost and man-power problems. We are talking with GSFC rad group …

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