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SCT On-detector VCSELs

SCT On-detector VCSELs. SCT On-detector VCSELs use older proton implant devices, not oxide implant (as in SCT/Pixel off-detector VCSELs and pixel on-detector). Slower and higher threshold (hence obsolete) Better reliability “Gold Standard for reliability”

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SCT On-detector VCSELs

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  1. SCT On-detector VCSELs • SCT On-detector VCSELs use older proton implant devices, not oxide implant (as in SCT/Pixel off-detector VCSELs and pixel on-detector). • Slower and higher threshold (hence obsolete) • Better reliability “Gold Standard for reliability” • Standard Truelight part with good reliability data • Safer packaging because • no glue used over VCSEL surface (fibre held above surface by plastic spacer). • no Infineon connector. • We performed accelerated aging test for irradiated VCSELs. Tony Weidberg ATLAS VCSEL Meeting

  2. Lifetime Studies (1) • Lifetime tests for the proton implant VCSELs: NIM A 497 (2003) 294. • 20 devices operated DC for 2534 hours at T=100C. • Use Weibull distribution for failure rates • If a=1 Poisson distribution. Use Truelight value a=1.7. • 90% c.l. MTTF = 8990 hours. Tony Weidberg ATLAS VCSEL Meeting

  3. Lifetime Studies (2) • Use Arrhenius equation: • Use Truelight measurement EA=1 eV. • Assume T~ 0C  AF = 88000  • MTTF ~9 104 years. • Don’t expect high failure rate over 10 years operation but need to monitor performance … Tony Weidberg ATLAS VCSEL Meeting

  4. VCSEL Power Measurements Monitor VCSEL power using p-i-n current in BOC (USA15). Tony Weidberg ATLAS VCSEL Meeting

  5. VCSEL Power Stability Higher temperature after cooling restart Good stability Stability in 2008/9 checked with Rxthresholds and was also ok. Tony Weidberg ATLAS VCSEL Meeting

  6. VCSEL Deaths • From May ’10 configuration: • Dead RX links 1.27% • Combination of electrical and optical failures. • Predominantly during installation ”delayed infant mortality” probably because burn-in could not be performed at sufficiently high temperature. • 1 death in 2010, none in 2009. • Live time of RX links • NRZ data so depends on L1 rate and occupancy. • Very limitted equivalent on-time so far. • Need more operational experience at higher L1 rate before we can conclude anything about the long term reliability of the on-detector VCSELs. Tony Weidberg ATLAS VCSEL Meeting

  7. Expected Data Rates • 3 months of testing would confirm survival up to 2015. Tony Weidberg ATLAS VCSEL Meeting

  8. Stress Tests • Need to perform stress tests at RT for long periods of time to detect any unexpected damage mechanism with a low value of EA • Plan to perform stress tests using harnesses on SR1 sector. • 47 barrel and 33 EC modules • Run in clk/2 mode  50% duty cycle • Operate continuously apart from when sector required for training. • Measure power • Use OSA for periodical checks for spectral narrowing. • Use 7 or 8 non-electrical functioning modules on detector in clk/2 for similar stress tests. Tony Weidberg ATLAS VCSEL Meeting

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