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Project Scope

Development of an SiPM based multichannel array photon detector for the SciFi Tracker upgrade. The detector part includes also a flexible PCB and connectors together with a detector mounting structure that allows for a mechanical unit of typically 4 detector arrays. Attached to this project is also the development of a light injection system that allows to calibrate the gain of the SiPMs in situ.

Link the SciFi Tracker upgrade TDR:

Goals (SiPM)

Automated measurement of the detectors for the most important characteristics:

  • Breakdown voltage, gain and gain uniformity (multichannel) measurement
  • DCR at room temperature and at -40C for irradiated detectors (multichannel)
  • X-talk measurement (multichannel)
  • PDE (single channel)
  • LED light spectrum recording for super-module
  • Functional test (I-V) for series production acceptance test without soldering to flex
Possibility of measurement:
  • Temperature coefficient (T vs Gain) (single channel)
  • After-pulse (single channel)

Goals (Light injection system)

Development of a light injection system for gain calibration of the SiPM. The system needs to be sufficient uniform that the calibration by measuring the photon peaks (via threshold scan) is possible for all channels. Typical amount of light is 4 to 8 photons per pulse.


Optimization of the detectors for the requirements in the SciFi Tracker application includes:

A. Silicon optimisation

a) PDE optimization - maximal PDE is the most important requirement, further developments of the two providers Hamamatsu and KETEK need to be driven into this direction, higher fill-factor (FF) (Hamamatsu), green shifted or flat spectral response (KETEK), pixel size optimisation

b) X-talk optimization - trenches between pixels can redue x-talk but decrease the FF, larger pixels have higher x-talk

B. Silicon Packaging:

a) Low dead area between detectors is required to keep an overall high hit detection efficiency, tolerances regarding thermal expansion have to be defined. Thermal cycling of package to qualify resistivity against thermal stress

C. Flex and mounting:

a) Flex PCB needs to be optimized for low thermal conductivity and highest possible imunity for environmental electrical noise (RF) and good signal transmission between detector and FE ASIC.

b) Detector alignment and mounting to the Flex.

D. Detector characterisation:

a) Automated tests for production testing

b) Irradiation studies on latest generation of prototypes and final devices

c) Characterisation of devices in the lab for in depth understaning of certain parameters and characteristics

E. Develpoment of light injection system:

a) Test the leaking fibres with nothches or scratch and evaluate different fiber routing options. Evaluate the amount of light required.

b) Electronics for light injection - evaluate rad-hard electronics mezzanine pluggable on the FE card with fast LED driver.

Lab Facilities:


  • Automated test stand for non-soldered SiPM arrays for acceptance test
  • Warm and cold (-60C to +40C) characterisation box for arrays and single channel detectors (VATA64, FEMTO single channel amplifier), Gain, PDE (rel.), I-V, X-talk, after-pulse, automated threshold scan setup
  • Fiber module test stand with x-y table for laser, LED or e-gun injection tests
  • Neutron irradiation facility for irradiation of 2*10^10 neq/cm^2
  • Mulitchannel bias voltage power supply CAEN (32channels, 10mA, 10mV adj, current monitoring)
  • Liquid based circulating chiller for cooling large modules down to -80C



Presentation given in LHCb meetings

-- GuidoHaefeli - 15 Jul 2014
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Topic revision: r9 - 2015-11-18 - AxelKevinKuonen
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