Transcript Space fluorescence detectors TUS/KLYPVE for study of UHECR

Space detectors TUS/KLYPVE for Study of
Cosmic Rays in Energy Range of
the GZK Energy Limit.
TUS/KLYPVE collaboration:
SINP 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
40 years old problem:
Is there the cut off in cosmic ray energy spectrum?
P+γ=P+hadrons Eγ=2Eph Ep /Mp c2
Eph =2.5 10-4 eV (T=2.75K)
In proton rest frame photon energy Eγ >100
MeV for Ep >1020 eV. ρph =500 cm-3
Cross-section of interaction is σ=10-28 cm2
Interaction free path L=1/ σ ρph =70 Mpc
G.T. Zatsepin, 1968
Greisen-Zatsepin-Kuzmin
made the first estimates of
the effect and find the energy
limit for protons
EGZK =5x1019 eV.
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 .
1980- J. Linsley- idea of looking on EAS from the space.
90’s-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.
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.
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 PeV<E<1 EeV (Khrenov&Panasyuk, 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,
EASTOP+Cherenkov
I(>3 PeV)=2.3±0.4 10-7 m-2
s-1 sr-1
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. AGASA+Yakutsk data (E>40EeV), HiRes data
in the Northern Hemisphere give evidence for correlation with
BL Lac sources (Gorbunov&Troitsky; HiRes collaboration)
Map of BL sources
Map of AGASA EECR events
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
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.
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 FD’s 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 .
In the TUS-type detector a simple mirror optics
with a comparatively narrow FOV is suggestedthe “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.
3. 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.
4. TUS detector as the pilot mirror telescope has to approve the
technology of large mirror telescopes for the EECR research.
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).
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
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
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.
The mechanism of mirror development
has been designed (Consortium Space Regatta)
A sample of the mirror segment.
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.
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
UV detector based on the pixel design of the TUS telescope is
measuring UV from the atmosphere on board the “UniversitetskyTatiana” satellite. Polar orbit height-950 km. Measurements started
from January 2005.
It is an educational satellite, see Web site
http://cosmos.msu.ru/universat2006/
UV light intensity, measured by the “Tatiana” detector- moonless night
side of the Earth. Peaks are lights from large cities (α-Mexico City,
β- Houston, γ- Los-Angeles.
UV intensity at the South High Latitudes. Moonless night.
The peak is Aurora lights.
UV intensity on the night side of the Earth at full moon.
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.
UV flashes registered by the “Tatiana” detector.
Oscilloscope trace 4 ms. UV energy in the atmosphere 10-100 kJ.
UV flashes registered by the “Tatiana” detector.
Oscilloscope trace- 64 ms. UV energy in the atmosphere 0.1-1MJ.
UV flash distribution over the world map. 50 of 83 registered flashes
are in the equatorial belt 10o N- 10o S.
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 (T=296K, sea level),
Open circles- winter atmosphere.
Recent data of Stanford group at sea
level give 4.4±0.7 ph/m electron
in agreement with the previous data.
At altitudes 6-15 km where EAS
maximum expected for EECR events
of zenith angle >60o the yield
5 ph/m±0.7 is a reliable value.
Simulation of EECR registration
Example of the EAS, “registered” by the KLYPVE detector
E0=100 ЕeV, θ0=75°, φ0=25°,
Moonless night; σE0/ E0 ~ 10 %,
σθ0 ~ 1.5°, σφ0 ~ 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.
Inclined EAS’s (zenith angles >50o)
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.
Expected temporal profile of EAS signal in TUS pixels.
Time samples 0.8 microsecond. Primary energy 100 EeV.
Zenith angle 75o .
The following features of the detector are taken into account in the
simulation:
1. Reflectivity of the aluminum mirror- 0.83 (could be done 0.9).
2. 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 RC=ts .
6. 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.
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.
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
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
The TUS/KLYPVE space detectors will be used for other
researches:
1. 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.
2. 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.
Development of the flash in video
(observed, left) and in TUS pixels
(expected).
Simulation of the micro meteor registration by
TUS
The meteor threshold kinetic energy – 100J. Expected rate- 100 per day.
Expected signal profile from the sub-relativistic
(velocity 1010 cm/s) dust grain. Energy 20J.
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)