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OPTICAL TUNING ALGORITHM FOR ATLAS PIXEL DETECTOR

OPTICAL TUNING ALGORITHM FOR ATLAS PIXEL DETECTOR. Ilaria Vergantini. ATLAS DETECTOR. Inner Detector. Pixel Detector. ATLAS PIXEL DETECTOR. Three disc endcap. Three layer barrel. Each Layer 13 modules. Each disc 48 modules.

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OPTICAL TUNING ALGORITHM FOR ATLAS PIXEL DETECTOR

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  1. OPTICAL TUNING ALGORITHM FOR ATLAS PIXEL DETECTOR Ilaria Vergantini

  2. ATLAS DETECTOR Inner Detector Pixel Detector

  3. ATLAS PIXEL DETECTOR Three disc endcap Three layer barrel Each Layer 13 modules. Each disc 48 modules. Pixel detector 1744 Modules. Each module 46080 Pixels. MODULE: smallest Pixel unit in terms of supply and readout. • PIXEL MODULE: • Silicon sensor material • 16 front end chips • One Module Controller Chip (MCC)

  4. ATLAS PIXEL OPTOLINK connects the on-detector components with the off-detector side. controller TTC Data DORIC FE VCSEL BPM On detector components Histogram & monitoring data PIN Off-detector side FE Hit formatter VCSEL VCSEL VDC PIN PIN Module Data DRX Event fragment builder module Optoboard BOC ROD Viset, Iset (0-20)mA OPTICALCOMMUNICATION NECESSARY: Procedure for tuning optical link parameters ESSENTIAL: Error free data transmission

  5. Optoboard DORIC (Digital Optical Receiver Integrated Circuit) • Receiver for TTC signals • Transmitter for module data VDC (VCSEL Driver Circuit) • Operation controlled by four voltage: • Vvdc : main supply voltage for DORIC and VDC (MAX: 2.5 V) • VPin : Pin voltage for the input pin diodes (MAX 20 V) • VIset : External control voltage for laser output power (MAX 2 V) • RESET : Optoboard Reset controlling clock-locking of the Doric. VCSEL array

  6. BOC(Back-of-Crate) • Three main purpose: • Timing of the on-detector components • Recovering and timing of returned signals • Stream decoding BPM VCSEL PIN PIN DRX RX-PLUGIN: • receives data from the optoboard • digitalize the signal with an adjustable threshold • determinates by a RX delaythe data sampling positions for the PIN signal

  7. Optical link tuning procedure Setting the best possible working points {RX delay, RX threshold, Viset} • Viset : external voltage for laser output power. Scanned in 50 mV steps ( 0.7 V  0.9 ) V • RX threshold : used to set the PIN signal discriminator value. Scanned in 7 steps (10 250) DACs. • RX delay : used to determine the data sampling positions for the PIN signal. Scanned in all 25 DAC(ns) steps. SUMMARY OF PARAMETERS:

  8. BOC SCAN HISTOGRAM {RX delay, RX threshold} Color-coded: amount of bit-flip errors White: error free regions BOC Scan histogram behaviour versus Viset :

  9. Plot of “threshold with minimal delay error band width” versus “Viset”

  10. Conclusion: • Communication between off-detector and on-detector needs to be tuned. • Parameters: { Viset, RX-threshold, RX-delay }. • For tuning: Boc scan. • Threshold set in correspondence of the minimal delay error band width. • Analysis algorithm fits the minimal delay error band threshold and determinates the best Viset when this threshold is around 210 DACs. • Connection of Pixel Detector is on-going and this tuning will probably be used in autumn.

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