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EUSO The E xtreme U niverse S pace O bservatory

EUSO The E xtreme U niverse S pace O bservatory. Marco Pallavicini INFN Genova, Italy. Talk Overview. Scientific case and Science Goals The observational approach The detector on the ISS The detector optics Detector expected performances. Euso. An Innovative Space Mission

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EUSO The E xtreme U niverse S pace O bservatory

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  1. EUSOThe Extreme Universe Space Observatory Marco Pallavicini INFN Genova, Italy

  2. Talk Overview • Scientific case and Science Goals • The observational approach • The detector on the ISS • The detector optics • Detector expected performances M. Pallavicini - INFN Genova

  3. Euso An Innovative Space Mission doing astronomy by looking downward from the Space Station at the Earth Atmosphere • Euso is devoted to the exploration from space of the highest energy processes present and accessible in the Universe: The extreme energy cosmic rays ( E > 4 1019 eV) • They are directly related to the extreme boundaries of the physical world. M. Pallavicini - INFN Genova

  4. Scientific motivations • Why should we study the Extreme Energy Cosmic Radiation (EECR) • From the Astroparticle Physics point of view, the EECRs have energies only a few decades below the Grand Unification Energy (1024 - 1025 eV), although still rather far from the Planck Mass of 1028 eV. • If protons, they show the highest Lorentz factor observed in nature (g ~ 1011). • What is the maximum Cosmic Ray energy, if there is any limit? • There is no compelling evidence for identification of EECR sources with objects known in any astronomical channel. • They may be a unique probe for Grand Unification theories and cosmological models • Neutrino astronomy from the deep space (no GZK cut off) M. Pallavicini - INFN Genova

  5. ICRC2001 Today’s knowledge: spectrum • Energy spectrum decreases like ~ E-3 • The spectrum extends above 1020 eV • At these extreme energies, flux is of the • order of Km-2 century-1 • Present data is interesting and challenging • Not consistent fluxes among measurements • GKZ cut off ? • Energy scales ? M. Pallavicini - INFN Genova

  6. Today’s knowledge: Direction Arrival direction of 59 events with energies above 4 1019 eV observed by AGASA No large scale anisotropy Indication of point like sources (1 triplet, 6 doublets, Prob. 0.07%) Triplet in the direction of interacting galaxy VV141 M. Pallavicini - INFN Genova

  7. Today’s knowledge: Direction (II) M. Pallavicini - INFN Genova

  8. Experimental problem ? • HiRes and AGASA measurements are barely compatible. Is there a problem ? • The number of events detected by AGASA above 1020 eV is quite larger than that detected by HiRES (10 events vs 2 events) for equivalent exposure. • The position of the “ankle” in the Cosmic Ray spectrum for AGASA is at energies a factor 2–3 larger than the one shown by HiRES ( 1019 eV vs 3x1018 eV). GZK:Is this a measurement of the effect or discovery of its non existence (AGASA, 2.6 s)? AGASA is almost complete HiRES will go on for 5 years M. Pallavicini - INFN Genova

  9. Today’s ignorance • How the cosmic rays reach such huge energies ? • Acceleration mechanisms ? • Decay from super-heavy relic particles ? • What are they ? • Protons ? • Nuclei ? • Neutrinos ? • If accelerated, from where ? • Galactic sources? • Extragalactic? Why GZK is not there (if AGASA is right) ? M. Pallavicini - INFN Genova

  10. Bottom - up Top - down Top-Down and Bottom-Up scenarios “Bottom-up”: with acceleration in rapidly evolving processes occurring in Astrophysical Objects with an extreme case in this class being represented by the Gamma Ray Bursts (GRBs). The observation of “direction of arrival and time coincidences” between the optical-radio transient and Extreme Energy Neutrinos could provide a crucial identification of the EECR sources. “Top-down”: processes with the cascading of ultrahigh energy particles from the decay of Topological Defects; these are predicted to be the fossil remnants of the Grand Unification phase in the vacuum of space. They go by designations, such as cosmic strings, monopoles, walls, necklaces and textures. Inside a topological defect the vestiges of the early Universe may be preserved to the present day. M. Pallavicini - INFN Genova

  11. Bottom-Up: Cosmic accelerators M. Pallavicini - INFN Genova

  12. Euso Scientific goals • Extension of the measurament of the energy spectrum of the Cosmic Radiation beyond the GZK conventional limit (EGZK 5 x 1019 eV). • How does the Cosmic Ray spectrum continues beyond the existing data? • Is there a maximum energy (Emax) ? • All sky survey of the arrival direction of EECRs. • Point sources? We want to identify their optical counter-part. • Observation of a possible flux of High Energy Cosmic Neutrinos. • Neutrinos can arrive from very distant sources! • Systematic sounding of the Atmosphere with respect to cloud distribution and UV light absorption/emission characteristics. • Investigation of Atmospheric Phenomena such as Meteors and Electrical Discharges. M. Pallavicini - INFN Genova

  13. To overcome these difficulties, an adequate solution is provided by observing the atmosphere UV induced fluorescence from space which allows to exploit up to millions Km2 /sr The Euso experiment • Experiments carried out by means of ground-based observatories, Auger (hybrid) and HiRes – Telescope Array (fluorescence), are limited by practical difficulties connected to the relatively small collecting area (up to 3000 Km2!!) still marginal for the extremely low flux involved (order of 1 particle/100 Km2/sr/year for a Primary of 1020 eV). M. Pallavicini - INFN Genova

  14. Columbus Nitrogen Spectrum Photons per m Euso Area vs Auger EUSO Pierre-Auger EUSO Euso observational approach M. Pallavicini - INFN Genova

  15. EUSO on ISS 30° 380 km 230 km Earth surface Geometry EUSO Geometry Detector distance 380 km Total field of view 60° Geometrical factor 5  105 km2sr Target air mass 2  1012 tons Pixel size (.8  .8) km2 M. Pallavicini - INFN Genova

  16. The instrument Monocular and Compact System electronics Focal surface support structure Focal surface Iris Fresnel lens M. Pallavicini - INFN Genova

  17. Field of View ± 30° around Nadir Lens Diameter 2.5 m Entrance Pupil Diameter ³ 2.0 m F/# < 1.25 Operating wavelengths 300-400 nm Angular resolution (for event direction of arrival) ~ 1° Pixel diameter (and spot size) ~ 5 mm Pixel size on ground ~0.8 x 0.8 km2 Number of pixels ~ 2.5 x 105 Track time sampling (Gate Time Unit) 833 ns (prog.) Operational Lifetime 3 years Euso parameters M. Pallavicini - INFN Genova

  18. Property ZEONEX TPX CYTOP PMMA Refractive index 1.525 1.463 1.346 1.49 Abbe’s number 56 90 55 Transmittance (400 nm) 3 mm 92% 92 ~ 93% 92% 86% Linear expansion coefficient /C 6.0E-5 1.17E-4 7.4E-5 8.0E-5 Water absorption rate (%) 60C <0.01 <0.01 <0.01 0.3 Requirements Density g/cm3 1.01 0.833 2.03 1.20 Total weight < 200 Kg Small chromatic aberration Space environment Small F/# < 1.25 Small point-spread function Mechanical strength for launch ±30° field of view Tensile strength kg/cm2 600 >235 (at yield) 400 490~770 Optics: Fresnel lenses 1.5 Fresnel lens prototype Possible materials M. Pallavicini - INFN Genova

  19. 10 mm 15 mm 6 mm 10 mm 50 mm 20 mm Optics: structure • Mass of each Lens • 20 mm PMMA 125 kg • 20 mm TPX 90 kg • 20 mm CYTOP 215 kg • 20 mm Zenoex 105 kg • 3 support rings, 24 ribs/lens, 20%Contingency 90 kg • Mass of Optical Structure • Graphite Fiber Re-enforced Polymer • 12 metering struts with 11 cross braces, 20% Contingency 60 kg struts and cross braces rings Ring and Rib Detail ribs Strut Detail M. Pallavicini - INFN Genova

  20. Optics: performance UV Filter De-focussing Acceptance M. Pallavicini - INFN Genova

  21. Focal surface design • Sensitivity to single photons in the wave length region between 300 nm and 400 nm • Fast response (  10 ns ), to be able count single photons and reconstruct the EAS direction from a single observation point by using photons time distribution • Each pixel must see roughly 1 Km2at ground level • 1 Km  3 ms; at 1021 eV you expect up to about 100 photons per ms on a single pixel • The system must be able to count photons at ( peak, max ) 100 MHz in a continuous background of about 1 MHz per pixel (from night glow 3 1011 photons m-2 s-1 sr-1) • A few mm2 spatial resolution on the focal plane • Optics point spread function size is a few mm2. • We do not want to be worse than that. M. Pallavicini - INFN Genova

  22. Focal surface “Macrocell” Focal surface is not a plane The FS is logically divided into macrocells Detailed structure is under study Trade off among efficiency, weight, feasibility, mechanichal stability Light Guide or Lens Hamamatsu R7600-M64 M. Pallavicini - INFN Genova

  23. Photodetectors Hamamatsu R7600-03-M64 Possible option: Weakly focused R8520 Better uniformity Need additional RD 5x5 maybe Pmts will be arranged in “microcells”, i.e. units of 4 pmts hold by a single PCB M. Pallavicini - INFN Genova

  24. Optical adaptors (I): Lens Problem: Hamamatsu R7600-M64 has a large dead area Option 1: Lens Features Good collection efficiency and angular acceptance Drawbacks Weight M. Pallavicini - INFN Genova

  25. Entrance Surface of Light Guide Surface of R7600-M16 0.3mm 4mm 7mm UV filter 2.57cm 2.8cm 2cm Light Guide 2cm 2.57cm Optical adaptors (II): Light guides M. Pallavicini - INFN Genova

  26. Optical adaptors: comparison M. Pallavicini - INFN Genova

  27. EUSO CONTROL & DATA HANDLING UNIT LEVEL Incoming UV photon PIXEL ASIC DIGITAL/ANALOG ELECTRONICS LEVEL MACROCELL DIGITAL ELECTRONICS LEVEL MC_TRIGGER From other pixels SAVE_FRAME PMT Enable ASIC M=M+1 Compare N=N+1 MC-level Dig. Thrsh M_thr SYSTEM TRIGGER Analog Threshold Compare N_thr X & Y+ PH_CNT RINGMEMORIES Y A X Y K Pixel-level Digital Thrsh MCell X ANALOG memories From other pixels From other MCs Electronics M. Pallavicini - INFN Genova

  28. The natural detector • The atmosphere is required to produce a shower. • Two source of signal for Euso: • Fluorescence • Cerenkov • The amount of light is proportional to the energy of the primary particle • The shape of the shower and the depth of its maximum gives information about primary particle type • Both signal intensity and shape are affected by atmospheric conditions • Rayleigh scattering • Aerosol (Mie scattering) • Ozone • Water vapor and cloud reflection and absorption • Ground albedo Euso needs night-time monitoring of these variables M. Pallavicini - INFN Genova

  29. Background Background is mostly due to: Nightglow (~400 m-1 s-1 sr-1 over sea) Man made Atmospheric phenomena M. Pallavicini - INFN Genova

  30. Yprojection TU X projection TU Event reconstruction to receiver CR C A  B M. Pallavicini - INFN Genova

  31. Neutrinos Protons & Nuclei Expected Performances Events in 1 year Proton vs neutrino separation Angular resolution vs energy M. Pallavicini - INFN Genova

  32. Schedule (a sort of) Phase A (preliminary study): 2002-2003 Phase B (project): 2003-2004 Phase C-D (construction): 2005-2008 Phase E (operation): 2009 ? M. Pallavicini - INFN Genova

  33. Conclusion • The study of EECR may lead to important discoveries in fundamental physics and astrophysics • EUSO is an innovative mission that will collect thousands of events above 1020 eV • The phase A has been approved by ESA and financial support has been provided by INFN and other institutions • Launch is foreseen in this decade M. Pallavicini - INFN Genova

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