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SiPM current status

SiPM current status. LHCb Week – 15.09.2014 Presented by Brice Maurin EPFL, Lausanne - Switzerland. Overview of current studies. Hamamatsu (H) and KETEK (K) devices received in August New x-y table for I-V scan (before and after soldering)

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SiPM current status

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  1. SiPM current status LHCb Week – 15.09.2014 Presented by Brice Maurin EPFL, Lausanne - Switzerland

  2. Overview of currentstudies • Hamamatsu (H) and KETEK (K) devices received in August • New x-y table for I-V scan (before and after soldering) • New flex without ground plane to reduce copper (thermal conductivity) • eGun and x-y table for test of fiber mats (modules)

  3. x-y table for I-V scan Production test installation: • I-V scan with and without light • I-V scan test before (no flex) and after soldering (with flex), allows to evaluate influence of soldering and temperature cycling • Allows to determine Vbd and RQ for each channel!

  4. New Hamamatsu status • Batch with out of specs RQ partially tested • All tested detectors (20 out of 50) fully working • 15 devices mounted on flex • 8 sent to Heidelberg • 5 devices to be mounted at CERN for mounting in reflow soldering process • New batch (55 pces) arrived and tests start today

  5. New multichannelarraysfrom Hamamatsu • Pixel size 50 x 50 μm2 → 57.5 x 62.5 μm2 (surface +44%) • Lower x-talk than expected; 7% @3.5V for old CB02 and 5% @3.5V for new arrays (expected 10% with gain increase), trench technology is new (CB03) but latest technology from H is CB04 with even lower x-talk • Difficulties are encountered with the gain measurement (for PDE manufacturer specification is used): • Fast signals are attenuated due to limited bandwidth so VATA system readout is excluded • Counting pulses (Current and DCR ratio) method 25% wrong, shows strong temperature dependence • Integral (V over time) with oscilloscope has to be used but precision not yet satisfactory Work in progress: • RQ distribution (homogeneity) • Vbd distribution

  6. PDE comparison • At 3.5 V (overvoltage), max PDE is: • 34-36% for CB02 • 38% for new arrays H • Large increase (still) with higher overvoltage, but overvoltage increase is prohibited by noise increase, DCR, x-talk (still some hope) • Values as expected or slightly higher

  7. Pulse shape Hamamatsu (wrong RQ) τshort=1 ns, dominated by oscilloscope bandwidth (1GHz) τlong=62 ns, willbe 2.5x lower for new batch Ringing due to impedance mismatch on the flex, connector and amplifier (50 Ohm), has to be reduced with copper GND plates since same frequency as signal. • Slower signal desired for: • Less ringing • Limited bandwidth of amplifier

  8. New Ketek detectors (package) • 12 detectors with different specs • All of them have broken channels (up to 30-40%) best devices with4-5 channels broken • Difficult to be used in testbeam, we will use the best devices with fibre mats to evaluate the light • Problems on package with glass plate seen • Air bubbles trapped under the glass • Glue of wire protection on glass plate • Glass plate too large (stand over the edge)

  9. Nextsteps • I-V scan and characterisation of RQ, Vbd distribution • Test H and K detectors with fibre mats and eGun • Temperature cycling for stress test of H and K • Irradiation test in Ljubljana with H and K • Resolve problems with K of package and dead channels (next iteration) • Preparation of new flex with thin GND plates

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