CMOS sensors: a short introduction

1.What’s a CMOS sensor? A new technique for pixel detectors

A prototype on its test board support moi A sensor (1 million pixels) Sensors are produced on silicon wafers (30 to 50 units) 15 cm A single pixel 20  m A hair: microscopic view, same scale Zooming on the sensor makes the pixels visible 0.5 millimeters

2.How does that work?

The particle goes through Layer sensitive to particles Supporting bulk (insensitive) Charges collected are integrated to build an amplified electric signal moi Micro-circuits for signal treatment Collector Free charges are created, then collected by the diode (positively charged) Let’s cut a pixel. We see its composition and what happens when a particle goes through

Steering and analysis The particle goes through Information from each pixel are transmitted to PC Particle crossing position is identified precisely moi Particle crossing position is identified precisely Signal amplitude Column number Line number Hit pixel

Tracking particles 3. What’s for ?

Particles need to be tracked very near the collision point: this is the place for the thin and granular CMOS sensors moi 25 cm 10 cm Barrel type detector made of 5 sensor layers e-e- e+e+

Carbon fiber supporting ladder To build a tracking detector A. Individual sensor assembly on a ladder B. Ladders are arranged on a hermetic barrel moi

Barrel of ladders with sensors A tracking device Initial particle collision point. Newly created particles are emitted in all directions e-e- e+e+ moi 10 cm moi

Knowing the particle crossing point with a high accuracy, allows computerized algorithms to reconstruct the full trajectory of each particle. moi

Imaging 3. What’s for ?

Imaging versus tracking 3D space trajectory2D space + 1 time trajectory Particle physics tracks particles in space space Imaging camera tracks emission sources in time time Tracking sensors need to detect single particles Single particle sensitivity for imaging devices offers: Infinite dynamics Better image definition Noise reduction Cockroach head from synchrotron light source (5.2 keV X-rays) with a CMOS sensor

Accelerated electrons are individually detected by the CMOS sensor Detecting single photons from visible light Lilly root cell, through epi-fluorescence microscopy using an EB-CMOS camera Electrons are accelerated by the E- field Photons hit the photocathode and get converted into electrons

The pioneering group for particle tracking 4. CMOS sensor at IPHC

Charge collection & technology studies – simple demonstrators Production Real size prototype - yield studies Reticule 2x 2 cm 2006 Data compression - digitization Sara 2006Suze 2007 MIMOSA sensors: a coherent evolution Final circuits – sub-blocs integration Mimosa Pixel Array Discriminators Zero Suppression BiasReadout

More than 30 sensors designed & tested since 1999 ! Our CAD center Collaborations: The USA: Fermi Nat. Lab. Brookhaven Nat. Lab. L.Berkeley Nat. Lab. Europe: France: Lyon Uni., CEA Germany: DESY, GSI, Frankfurt Uni. Italian subatomic physics lab. (INFN) Switzerland: CERN, Geneva Uni. China: Dalian Uni. Xian Uni. Industry: SAGEM PHOTONIS

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