Space%20detectors%20TUS/KLYPVE%20for%20Study%20of%20Cosmic%20Rays%20in%20Energy%20Range%20of%20the%20GZK%20Energy%20Limit.%20%20TUS/KLYPVE%20collaboration:%20SINP%20MSU,%20JINR%20(Dubna),%20CSCB%20

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Space detectors TUS/KLYPVE for Study of Cosmic
Rays in Energy Range of the GZK Energy Limit.
TUS/KLYPVE collaborationSINP MSU, JINR (Dubna),
CSCB Progress,RSC Energia, Universities of
Korea and Mexico
GZK40 Workshop 18 May 2006

• B.A. Khrenov
• D.V.Skobeltsyn Institute of Nuclear Physics of
  the Moscow State University

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40 years old problem Is there the cut off in
cosmic ray energy spectrum?
G.T. Zatsepin, 1968 Greisen-Zatsepin-Kuzmin made
the first estimates of the effect and find the
energy limit for protons EGZK 5x1019 eV.
P?Phadrons E?2Eph Ep /Mp c2 Eph 2.5 10-4
eV (T2.75K) In proton rest frame photon energy
E? gt100 MeV for Ep gt1020 eV. ?ph 500
cm-3 Cross-section of interaction is s10-28
cm2 Interaction free path L1/ s ?ph 70 Mpc
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When the GZK problem was formulated the best CR
experimentalists opened the new approach to
measuring of the highest energy EAS- by
registering fluorescence of the atmosphere.
1972-A.E. Chudakov and K. Suga- idea of the
fluorescence detector. 1975- K. Greisen and A.
Bunner- start to build the FD. Then the Utah
group made the Fly Eye .
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1980- J. Linsley- idea of looking on EAS from
the space. 90s-Development of space projects
OWL, KLYPVE 2000- L. Scarsi EUSO as a ESA
project. Meanwhile HiRes collaboration made
the new ground detector and has measured the CR
spectrum in the GZK region. In Argentina the
Pierre Auger hybrid array on the ground started
measurements in the GZK region. Telescope Array
collaboration is preparing the hybrid array in
the Northern Hemisphere.
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Recent experimental data on the energy spectrum
of Extreme Energy Cosmic Rays (EECR)
Pune ICRC, 2005 Today
Energy calibration is the main reason of
difference in spectra from different experiments.
The calorimetric data from the atmosphere
fluorescence light are decisive for surface
detector arrays.
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If we use only data of the arrays that measured
energy by the calorimetric method (Proton
satellite data and Cherenkov-TUNKA data) or at
least by the electron size method (MSU data) we
find steeper spectrum at energy 3 PeVltElt1 EeV
(KhrenovPanasyuk, 2006, Priroda, 2,p. 17-25)
which better meets the Auger spectrum.
Absolute energy and intensity is well measured at
the knee energy range. V. Prosin et al,
EASTOPCherenkov I(gt3 PeV)2.30.4 10-7 m-2 s-1
sr-1
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One of the most important issue in analysis of
the experimental data of EECR is a search for
correlation of EECR arriving direction with the
known astrophysical objects capable to accelerate
particles to extreme energies. AGASAYakutsk data
(Egt40EeV), HiRes data in the Northern Hemisphere
give evidence for correlation with BL Lac
sources (GorbunovTroitsky HiRes collaboration)
Map of BL sources Map of AGASA EECR events
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Today the Pierre Auger observatory in the
Southern hemisphere is the largest EECR array.
But it does not cover an important part of the
local source map available for observation by
the array in the Northern Hemisphere (inside the
green curve). J. Cronin
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The fluorescence probe space detectors (TUS and
KLYPVE) with integral aperture of the Auger scale
will look for EECR sources in a full sky
observation. Later (in 2015-2020) larger aperture
space detector will open the study of Cosmic Rays
beyond the GZK energy limit.
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Assets and difficulties of the space
experiment. 1. Looking down we have better
atmosphere transparence and a relatively constant
distance to EAS. 2. One detector covers a large
atmosphere area. 3. One and the same detector
collect data over the whole sky.
But 1. Average background UV light is higher
than in the special regions where the ground
FDs are operating. 2. UV background is
changing on-route of the orbital detector. 3.
Signal is much less than in the ground
measurements and the FD design meets new
technological problems .
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• In the TUS-type detector a simple mirror
  optics with a comparatively narrow FOV is
  suggested-
• the telescope option of the space detector.
• Advantages of this design
• 1. Simple optics has been already tested in
  several ground arrays.
• 2. A large mirror (area of 10 m2 ) will allow
  us to start measurements with a low energy
  threshold (1019 eV). With this threshold it will
  be possible to look for cosmological neutrinos-
  products of the EECR protons interaction with
  CBMW photons. It means that we will able to look
  beyond Greisen-Zatsepin-Kuzmin energy limit.
• In future the mirror area enlarged up to 1000 m2
  (adaptive optics has to be applied) will allow us
  to register EECR at very large area of the
  atmosphere (107 km2) with the help of a
  telescope at the geostationary orbit.
• TUS detector as the pilot mirror telescope has to
  approve the technology of large mirror telescopes
  for the EECR research.

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The TUS detector will be launched on a new
platform separated from the main body of the
Foton satellite (RosCosmos project, Samara
enterprise, launching in 2009-2010). Satellite
limits for the scientific instrument are mass 60
kg, electric power 60 Wt, orientation to nadir
3o . Preliminary TUS design 1- in the
transportation mode, 2 in operation.
1 2
Mirror area 1.5 m2 , pixels cover 4000 km2 of the
atmosphere (orbit height 400 km).
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Detector larger than TUS- with mirror area
10 m2 may be accommodated on the Russian
Segment of ISS (KLYPVE project).
Detector mass 200 kg, Electric power - 200 Wt
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Proposing large mirror in space we have to
consider the segmented mirror- concentrator
design.In the TUS telescope it consists of 7
Fresnel type mirror segments.

• The mirror- concentrator mass is less than 20 kg
  for the mirror area 2 m2.
• Accuracy in mirror ring profiles ? 0.005 mm.
• Stability of the mirror construction in the
  temperature range from 60o to 60o C.
• The mirror segments should make a plane with the
  angular accuracy less than 1 mrad.

Diameter of the mirror 1.8 m, focal distance- 1.5
m
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In the KLYPVE detector the mirror area is
planned equal to 10 m2 (diameter of the mirror
and focal distance is 3 m).
Number of Segments is 37.
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The mechanism of mirror development has been
designed (Consortium Space Regatta)
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A sample of the mirror segment.
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The TUS Photo Receiver , comprising 256 PM
tubes.
Photo receiver is consisted of 16 pixel rows and
columns. Every pixel is a PM tube (Hamamatsu
R1463, 13 mm diameter multialcali cathode) with a
square window mirror light guide. 16 PM tubes (a
row) has a common voltage supply and are
controlled by one data acquisition unit. UV
filter cover all pixel windows.
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Registration Electronics.
256 photo receiver pixels are grouped in 16
clusters. In every cluster the PM tube analog
signal is transmitted to one ADC with the help of
multiplexer (20 MHz frequency). Every 0.8 µsec
the digital signal is recorded in the FPGA
memory. The digital information is also coming to
the trigger system. The final trigger is worked
out in the TUS FPGA where the map of triggered
pixels is analyzed. Energy consumption per a
channel is 10 mWt. The TUS energy consumption is
less than 60 Wt.

16 channels module of the TUS electronics
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UV detector based on the pixel design of the TUS
telescope is measuring UV from the atmosphere on
board the Universitetsky-Tatiana satellite.
Polar orbit height-950 km. Measurements started
from January 2005.It is an educational
satellite, see Web sitehttp//cosmos.msu.ru/unive
rsat2006/
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UV light intensity, measured by the Tatiana
detector- moonless night side of the Earth. Peaks
are lights from large cities (a-Mexico City, ß-
Houston, ?- Los-Angeles.
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UV intensity at the South High Latitudes.
Moonless night. The peak is Aurora lights.
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UV intensity on the night side of the Earth at
full moon.
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Average UV intensity per circulation (at the
night side) during one moon month. Dashed line
is the moon phase. In 8 days of the moon month
the average UV intensity is more than 10 times
higher than at moonless night.
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UV flashes registered by the Tatiana
detector. Oscilloscope trace 4 ms. UV energy in
the atmosphere 10-100 kJ.
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UV flashes registered by the Tatiana
detector. Oscilloscope trace- 64 ms. UV energy in
the atmosphere 0.1-1MJ.
27
UV flash distribution over the world map. 50 of
83 registered flashes are in the equatorial belt
10o N- 10o S.
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Important issue is the absolute energy
calibration. Today several new experiments are
checking the fluorescence yield as a function of
atmosphere density, temperature, composition.
In Figure the data of Kakimoto et al are
presented, full circles-summer atmosphere
(T296K, sea level), Open circles- winter
atmosphere. Recent data of Stanford group at sea
level give 4.40.7 ph/m electron in agreement
with the previous data. At altitudes 6-15 km
where EAS maximum expected for EECR events of
zenith angle gt60o the yield 5 ph/m0.7 is a
reliable value.
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• Simulation of EECR registration

Example of the EAS, registered by the KLYPVE
detector
E0100 ?eV, ?075, f025, Moonless night sE0/
E0 10 , s?0 1.5, sf0 1.


In the near horizontal tracks the scattered
Cherenkov light from the atmosphere is negligible
to compare with fluorescence. The Cherenkov
scattered from the clouds or ground is a strong
signal.
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Inclined EASs (zenith angles gt50o) develop high
in atmosphere- above the clouds- and are
effectively registered by the space fluorescence
detector.
The Cherenkov light scattered from the clouds
gives the absolute scale of height in the
atmosphere in observation from the satellite. The
cloud height has to be measured by a special
device (Lidar) immediately after the EAS event
registration.
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Expected temporal profile of EAS signal in TUS
pixels. Time samples 0.8 microsecond. Primary
energy 100 EeV. Zenith angle 75o .
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• The following features of the detector are taken
  into account in the simulation
• Reflectivity of the aluminum mirror- 0.83 (could
  be done 0.9).
• Increasing of the focal spot with off- axis angle
  (in average 2 pixels are registering signal at
  the TUS detector FOV edge).
• 3. Light collection by the square pixel light
  guide (in average 0.75 of
• light coming to the pixel is guided to the PM
  tube).
• 4. Quantum efficiency of the PM tube- 0.2.
• 5. Efficiency of the registering signal in ADC
  time samples ts 0.8 µs by
• front- end electronics with RCts .
• Event selection system operating in 2 steps
  signal threshold in one pixel and n-fold
  coincidences of the neighbor pixels.
• Today an area and quality of mirror is a key
  technological point in
• getting a good S/N ratio. We should look
  also for a new photo detector
• with higher quantum efficiency.

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Unique feature of future space detectors might be
a possibility to register the residual shower
developing in the ocean. The light absorption in
ocean water is of the order of shower path (10 m)
and a fast (50 ns) ocean signal could be
selected from the longer EAS signal.
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Selected for TUS PM tubes and the pixel
electronics will allow to operate the detector at
moon nights (with higher energy
threshold). Energy threshold for TUS and KLYPVE
detectors as a function of the background UV
intensity is presented below. At the threshold
Ethr the signal in the shower maximum is equal
to 3sigma of the background and 3-fold
coincidence of pixels were taken. TUS KLYPVE
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Arrival equatorial coordinates of the isotropic
radiation for the range of zenith angles 60o -90o
. ISS orbit, one year of observation by TUS. Red
points are BL sources due to S. Troitsky (its N/S
assymetry might be due to poor knowledge of the
Southern sky).
P. Klimov and S. Sharakin
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• The TUS/KLYPVE space detectors will be used for
  other
• researches
• For observation of the UV atmosphere flashes with
  resolution
• in time 0.8 µs and in space 2-4 km. Due to
  large mirror
• aperture the sensitivity of the detector
  will allow to observe the
• beginning of the discharge in the atmosphere
  and to reveal
• the origin of the flashes.
• For observation of the micro meteors with the
  kinetic energy
• threshold of about 100J (solar system
  meteors of size mm).
• 3. For a search of sub-relativistic dust grains
  (velocity 109 -1010 cm/s)
• not observed yet by other methods.

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Development of the flash in video (observed,
left) and in TUS pixels (expected).
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Simulation of the micro meteor registration by TUS
The meteor threshold kinetic energy 100J.
Expected rate- 100 per day.
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Expected signal profile from the sub-relativistic
(velocity 1010 cm/s) dust grain. Energy 20J.
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Conclusion 1. The space experiments will give an
independent evidence for EECR particles and their
rate. The space observation has the advantage of
whole sky coverage by one and the same
detector. 2. The main goal of the first TUS
experiment is to approve the new method of space
observation of EECR and its techniques. 3. Other
phenomena of fluorescence light in the atmosphere
(UV flashes in the atmosphere electric
discharges, UV light from micro meteors and
sub-relativistic dust grains) could be studied by
the TUS- type detectors. 4. In international
collaboration the next more sophisticated
detectors could be developed with a major goal to
cover the atmosphere area up to 107 km2 needed
for exploring Cosmic Rays beyond the GZK energy
limit. International Workshop on June 19-21
(Italy)