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A. Nepomuk Otte Max-Planck-Institut für Physik München

Prospects to Use Silicon Photomultipliers for the Astroparticle Physics Experiments EUSO and MAGIC . A. Nepomuk Otte Max-Planck-Institut für Physik München. Outline. EUSO & MAGIC Why new photon detectors? Photon detector requirements The SiPM principle Development @ MEPhI and Pulsar

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A. Nepomuk Otte Max-Planck-Institut für Physik München

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  1. Prospects to Use Silicon Photomultipliers for the Astroparticle Physics Experiments EUSO and MAGIC  A. Nepomuk Otte Max-Planck-Institut für Physik München

  2. Outline • EUSO & MAGIC • Why new photon detectors? • Photon detector requirements • The SiPM principle • Development @ MEPhI and Pulsar • Development @ HLL in Munich MPI für Physik

  3. Extreme Universe Space Observatory http://www.euso-mission.org/ MPI für Physik

  4. Gamma ray Particle shower ~ 10 km ~ 1o Cherenkov light ~ 120 m Major Atmospheric Gamma Imaging Cherenkov Telescope http://hegra1.mppmu.mpg.de/MAGICWeb/ MPI für Physik

  5. Motivation for new Photon Sensors Photon detection efficiency (PDE) of state of the art photomultiplier tubes ≈20% A higher PDE results in a better signal to noise ratio (SNR) ≈ 80% PDE improves SNR by a factor 2…3 Same effect as increasing the MAGIC mirror from 17m diameter to 70m Both experiments can lower their energy threshold with more sensitive sensors MPI für Physik

  6. access to lower γ-energies deeper look into the universe (higher redshifts) new sources Egret 280 sources with 0.1m² active detector area (<10GeV) ACT‘s 15 sources with 5•104m² active detector area (>300GeV) extend accessible energy range overlap with existing experiments AUGER, AGASA, HIRES detailed study of GZK cutoff improved energy resolution What is gained by a lower Threshold? MAGIC EUSO MPI für Physik

  7. Photon Detector Requirements most requirements are similar large differences in sensitive range and pixel size challenging: detection efficiency MPI für Physik

  8. The Silicon Photomultiplier An avalanche photodiode (APD) in Geiger mode is a high efficient single photon counting device MPI für Physik

  9. The Silicon Photomultiplier An avalanche photodiode (APD) in Geiger mode is a high efficient single photon counting device BUT: Output signal of a single Geiger APD is independent of number of photoelectrons MPI für Physik

  10. The Silicon Photomultiplier An avalanche photodiode (APD) in Geiger mode is a high efficient single photon counting device … BUT: Output signal of a single Geiger APD is independent of number of photoelectrons Solution: Combine an array of small Geiger APDs onto the same substrate (less then 1 photon per cell) MPI für Physik

  11. 1 mm 1 mm Development @ MEPhI and Pulsar Enterprize P. Buzhan et al. http://www.slac-stanford.edu/pubs/icfa/fall01.html about 20% active area limits photon detection efficiency MPI für Physik

  12. characteristics of current prototypes: geometry: 24 x 24 pixels = 576 pixels within 1mm2 available up to 1024 pixels / mm² Operating voltage: 50 V to 58 V Gain: 105 up to ~ 5•106 single pixel time resolution: 570 ps FWHM single pixel recovery time: 1μs dark count rate: 106 counts per second at room temperature Characteristics MPI für Physik

  13. R&D Goals to improve existing MEPhI-Pulsar Prototypes • Luminescence of hot avalanche electrons gives rise to crosstalk with neighboring APD cells (40% @ Gain 106) • Counter measures: • grooves between pixels to absorb photons • reduce gain (4% Crosstalk @ Gain 105) • Photon detection efficiency determined by: • Intrinsic QE • packing density of pixels • Geiger breakdown probability • transmittance of entrance window • work on: • reduction of dead area • improve blue sensitivity • optimization of entrance window P. Buzhan et al. NIM A 504 (2003) 48-52 MPI für Physik

  14. photon path of the photo electron depleted bulk avalanche regions Si 50µm … 450µm output Blow up of one “micro pixel” Development @ MPI Semiconductor Laboratory in Munich Different approach to increase photon detection efficiency use of back illumination principle → no dead area MPI für Physik

  15. Development @ MPI Semiconductor Laboratory in Munich drift path of a photo electron photon shallow p+ n bulk drift rings p+ deep n avalanche region quench resistor output line • Simulations are in final stage: • Operating voltage of avalanche region 50V • Geiger breakdown probability 60%...90% • average drift time differences < 1ns MPI für Physik

  16. Summary and Outlook • We investigate the SiPM as photon detector in MAGIC and EUSO • First SiPM prototypes are very promising • SiPM prototypes already usable for some applications (e.g. PET, TileCal for Tesla) • The development is pursued in two different ways • front illumination @ MEPhI and Pulsar • back illumination @ HLL in Munich • A lot of R&D ahead: • increase effective QE up to 70% • increase UV sensitivity • reduce crosstalk • increase SiPM size MPI für Physik

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