Post on 28-Dec-2015
EUSOThe Extreme Universe Space
Observatory
Marco PallaviciniINFN Genova, Italy
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 2
Talk Overview
Scientific case and Science Goals
The observational approach
The detector on the ISS
The detector optics
Detector expected performances
Nestor Insitute, Pilos, Jun. 05-10, 2002 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.
Nestor Insitute, Pilos, Jun. 05-10, 2002 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 ( ~ 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)
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 5
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
ICRC2001
•Present data is interesting and challenging•Not consistent fluxes among measurements•GKZ cut off ? •Energy scales ?
Nestor Insitute, Pilos, Jun. 05-10, 2002 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 anisotropyIndication of point like sources(1 triplet, 6 doublets, Prob. 0.07%)Triplet in the direction of interacting galaxy VV141
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 7
Today’s knowledge: Direction (II)
Nestor Insitute, Pilos, Jun. 05-10, 2002 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 )?
AGASA is almost completeHiRES will go on for 5 years
Nestor Insitute, Pilos, Jun. 05-10, 2002 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) ?
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 10
Top-Down and Bottom-Up scenarios
Bottom - upBottom - up
“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.
Top - downTop - down
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 11
Bottom-Up: Cosmic accelerators
Nestor Insitute, Pilos, Jun. 05-10, 2002 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.
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 13
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).
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
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 14
Euso observational approach
Nitrogen SpectrumPhotons per m
EUSO
Columbus
Euso Area vs Auger
EUSO
Pierre-Auger
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 15
Geometry
30°
EUSO on ISS
230 km
380
km
Earth surface
EUSO Geometry
Detector distance 380 km380 km
Total field of view 60°60°
Geometrical factor 5 5 10 1055 km km22srsr
Target air mass2 2 10 101212 tons tons
Pixel size(.8 (.8 .8) km .8) km22
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 16
The instrument
Fresnel lens Iris
Focal surface
Focal surface
support structure
System electronics
Monocular and Compact
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 17
Euso parameters
Field of View ± 30° around Nadir
Lens Diameter 2.5 m
Entrance Pupil Diameter 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
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 18
Optics: Fresnel lenses
1.5 Fresnel lens prototype
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 (%) 60C
<0.01 <0.01 <0.01 0.3
Density g/cm3 1.01 0.833 2.03 1.20
Tensile strength kg/cm2
600 >235 (at yield)
400 490~770
Total weight < 200 KgSmall chromatic aberrationSpace environmentSmall F/# < 1.25Small point-spread functionMechanical strength for launch±30° field of view
Requirements
Possible materials
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 19
Optics: structure16:16:09
f/1.25, 7mm pixel, 2.8m EPD, Dmax < 3.75 Scale: 0.03 DJL 06-Jan-00
735.29 MM
• 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
•
6 mm
10 mm
50 mm
10 mm
20 mm
15 mm
Ring and Rib Detail Strut Detail
rings
ribs
struts and cross braces
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 20
Optics: performance
De-focussing
Acceptance
UV Filter
Nestor Insitute, Pilos, Jun. 05-10, 2002 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 Km2 at 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.
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 22
Focal surface
Hamamatsu R7600-M64
Light Guide or Lens
Focal surface is not a planeThe FS is logically divided into macrocellsDetailed structure is under studyTrade off among efficiency, weight, feasibility, mechanichal stability
“Macrocell”
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 23
Photodetectors
Hamamatsu R7600-03-M64
Pmts will be arranged in “microcells”, i.e. units of 4 pmts hold by a single PCB
Possible option:Weakly focused R8520
Better uniformityNeed additional RD5x5 maybe
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 24
Optical adaptors (I): Lens
Problem: Hamamatsu R7600-M64 has a large dead area
Option 1: Lens
FeaturesGood collection efficiency and angular acceptance
DrawbacksWeight
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 25
Optical adaptors (II): Light guides
2.8cmUV filter
LightGuide
2cm
2.57cm
2cm
Entrance Surface of Light Guide
Surface of R7600-M16
7mm
4mm
2.57cm
0.3m
m
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 26
Optical adaptors: comparison
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 27
Electronics
MC
_TR
IGG
ER
From
other MCs
SYSTEM TRIGGER
SA
VE
_FR
AM
E
EUSO CONTROL &
DATA HANDLING
UNIT LEVEL
K A
PMT
PIXEL
Inco
min
g U
V
ph
oton
M=M+1
M_thr Co
mp
are
X &
Y+
PH
_C
NT
RIN
GM
EM
OR
IES
MCellX
Y
From other pixels
MACROCELL DIGITAL
ELECTRONICS LEVEL
MC-level Dig.
Thrsh
From other pixels
Analog Threshold
N=N+1
N_thr
Co
mp
are
Pixel-level Digital Thrsh
ASIC
X
Y
Enable
ASIC DIGITAL/ANALOG
ELECTRONICS LEVEL
ANALOGmemories
Nestor Insitute, Pilos, Jun. 05-10, 2002 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
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 29
Background
Background is mostly due to:
Nightglow (~400 m-1 s-1 sr-1 over sea)Man madeAtmospheric phenomena
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 30
Event reconstruction
X projection
TU
TU
Yprojection
A
B
C
to receiver
CR1
2 21
tan
2 tan
x
y
x y
c t
Nestor Insitute, Pilos, Jun. 05-10, 2002 M. Pallavicini - INFN Genova 31
NeutrinosProtons & Nuclei
Expected Performances
Angular resolution vs energy
Events in 1 yearProton vs neutrino separation
Nestor Insitute, Pilos, Jun. 05-10, 2002 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 ?
Nestor Insitute, Pilos, Jun. 05-10, 2002 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