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STUDY OF ULTRA HIGH ENERGY COSMIC RAYS: TOWARD THE SPACE-BASED DETECTORS

In memory of late Prof. John Linsley- a pioneer of the EAS investigation from space. STUDY OF ULTRA HIGH ENERGY COSMIC RAYS: TOWARD THE SPACE-BASED DETECTORS. TALK AT THE KOREAN PHYSICAL SOCIETY MEETING 22 OCTOBER 2004 B. A. KHRENOV Skobeltsyn Institute of Nuclear Physics

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STUDY OF ULTRA HIGH ENERGY COSMIC RAYS: TOWARD THE SPACE-BASED DETECTORS

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  1. In memory of late Prof. John Linsley- a pioneer of the EAS investigation from space STUDY OF ULTRA HIGH ENERGY COSMIC RAYS:TOWARD THE SPACE-BASED DETECTORS TALK AT THE KOREAN PHYSICAL SOCIETY MEETING 22 OCTOBER 2004B. A. KHRENOV Skobeltsyn Institute of Nuclear Physics of the Moscow State University, Moscow, Russia

  2. How Extensive Air Showers are measured EAS cascades for primary energy 1018 eV. Red curve- primary iron nuclei. Dotted blue- primary proton. Extensive Air Showers (EAS) give information on Cosmic Rays starting from energies 1014-1015 eV. At energies more than 1018 eV the EAS atmosphere fluorescence is measured along with the particle flux and the Cherenkov light. Fluorescence Particle or Cherenkov Detector detectors The isotropic fluorescence radiation could be measured from space- from the satellites. The innovative technology of space fluorescence detectors is in progress.

  3. Methods of the EAS primary energy measurement • Successfully working methods: • Charge particle (electron) size. Integral over the experimental lateral distribution. Core distances ~100 m. • Charge particle density at large core distance ~600-1000 m. • Air Cherenkov radiation flux. • Atmosphere fluorescence signals (cascade curve, signal at the EAS maximum). • Considered but unsuccessful yet methods: • Radio echo from the EAS core. • Radio signal, radiated by EAS (Cherenkov, geo-magnetic mechanisms) in air, in ice. • Acoustic signals in the ice and water, in the Moon ground.

  4. AGASAAkeno Giant Air Shower Array The particle detector EAS array, collected the record exposure of about 3000 km2 sr year . 111 scintillators + 27 muon det.

  5. The High Resolution Fly’s Eye (HiRes) The fluorescence detector array, collected the record exposure, close to the AGASA exposure (3000 km2 sr year), for the highest energy events (E>1020 eV). HiRes 1 HiRes 2

  6. Examples of EAS registration by the fluorescence detector. Note that results are presented for units of g/cm2 but measurements are done in meters. The atmosphere density (the height in atmosphere) for every point has to be known. The distance to the EAS track and signal absorption at this distance have to measured.

  7. Scientific Problem- Origin Of The Ultra High Energy Cosmic Rays (UHECR) Experimental data ofAGASA are against the GZK Cosmic Ray cut off. Data of HiRes confirm the cut off. Yakutsk data agree with the HiResdata. Detectors of the next generation should solve the problem.

  8. What is the cut off? T=2.75K Eph =2.5x10-4 eV Inverse photo nucleon interaction: P+γ=P+hadrons Photons of energy 2.5 10-4 eV in proton rest frame are of energy >100 MeV if Ep ~1020 eV. Density of photons is ρ=500 ph/cm3 Cross-section of interaction is σ=10-28 cm2 Interaction free path L=1/ σ ρ=100 Mpc Greisen-Zatsepin-Kuzmin made the first estimates of the effect and find the energy limit for protons EGZK =5x1019 eV.

  9. AGASA Results •     Highest Energy Event: •     Energy Spectrum: • Figure 2: AGASA Energy Spectrum [ EPS ] • The AGASA energy spectrum is shown in Figure 2 , multiplied by E3 in order to emphasize details of the steeply falling spectrum. Error bars represent the Poisson upper and lower limits at 68 % and arrows are 90 % C.L. upper limits. Numbers attached to points show the number of events in each energy bin. The dashed curve represents the spectrum expected for extragalactic sources distributed unifomly in the Universe, taking account of the energy determination error. Arrival direction of UHECR particles over the Northern hemisphere. Red squares- E>1020 eV, green points- E=4-10 1019 eV. Dublets and triplets (events from the same coordinates in sky in errors of 2.5o) are blue and violet circles. Galactic (red) and Supergalactic (blue) planes are presented as curves. Table 1: AGASA 1020eV Events • The number of events observed with AGASA and the Akeno 20km2 array are 886 above 1019eV and 72 above 4 x 1019eV with zenith angles smaller than 45o. •     Anisotropy above 4 x 1019eV: • Figure 3 shows arrival directions of cosmic rays with energies above 4 x 1019eV. Red squares and green circles represent cosmic rays with energies of > 1020eV , and (4 - 10) x 1019eV , respectively. • Figure 3: Arrival Directions [ EPS ] • Figure 4: Arrival Directions • Here is our paper on the 1018eV anisotropy. •     Muon Components: • We observed muon components in the detected air showers and studied their characteristics. Generally speaking, more muons in a shower cascade favors heavier primary hadrons and measurement of muons is one of the methods used to infer the chemical composition of the energetic cosmic rays. Our recent measurement indicates no systematic change in the mass composition from a predominantly heavy to a light composition above 3 x 1017eV claimed by the Fly's Eye group. • Here is our paper of the muon stuff. [ Back ]

  10. Possible sources: astrophysical accelerators, the objects with the relativistic shocks.

  11. The alternative sources of EECR are the massive particles (M~1024 eV) – relics of the Big Bang. They might be responsible for the Dark Matter. The EECR protons (or gamma quanta) are products of their decay. The EECR particles registered by AGASA in this interpretation indicate the Dark Matter of our Galaxy. Topological defects are the other theoretical source of the massive particles decaying to EECR particles. The experimental separation of photons from protons in EECR is the key point in a search for massive particles, producing mainly photons in final decay generation. AGASA data on the muon to electron ratio in EAS of the highest energies are against photon origin of primaries.

  12. Ground based fluorescence detector has a problem of fluorescence light absorption in a horizontal view. Absorption length La as a function of the fluorescence wavelength at sea level. La is the result of the Rayleigh scattering. Mie scattering (on aerozols) should be added so Lreal<La. Ratio of photon number registered in the view line to the EAS disc to the number of photons radiated by the EAS disc in the same line. Only Rayleigh scattering is taken into account.

  13. The space fluorescence detector looking through the vertical atmosphere layer has advantage of low absorption of EAS signals. Ratio of photon number registered in the view line to the EAS disc to the number of photons radiated by the EAS disc in the same line. EAS disc at the atmosphere depth X=130 g/cm2 Same ratio for EAS disc at sea level X=1030 g/cm2

  14. EUSO- the wide field of view (FOV) fluorescence detector (European Space Agency in cooperation with NASA). Two Fresnel lens optics is used for correction of aberration in wide FOV. Diameter of the lens is 2.5 m. Number of pixels 4x105. The energy threshold 4x1019 eV.

  15. Comparatively narrow FOV is used in the mirror optics: the “telescope” proposals KLYPVE and TUS • (Russian space agency). • A large area mirror- concentrator is easier to construct • than the lens. • Two main goals of this design: • Making the energy threshold low (~1019 eV, mirror area of • 10-100 m2), it will be possible to search for neutrinos- • products of the EECR protons interaction with CBMW photons • and to look beyond Greisen-Zatsepin-Kuzmin energy limit. • 2. Making the mirror area up to 1000 m2 , it will be possible • to cover a large area of the atmosphere with the telescope • on the geostationary orbit

  16. Telescope on the geostationary orbit. Mirror diameter 30 m, resolution 16’’ (3 km in the atmosphere). Energy threshold 1020 eV. Observed area 3x107 km2 .

  17. Illustration of the mirror telescope operation in orbit. The TUS (Tracking Ultraviolet Set Up) detector registers an EAS track from board of the Space Platform. The light collector and photo detector are notified by red color.

  18. TUS detector parameters • Area of mirror-concentrator- 1.4 m2 • Focal distance - 1.5 m • Pixel number - 256 • Pixel size (FOV) - 1.5 cm (0.01 rad) • Detector FOV - 0.16 rad • Time sampling from - 400 ns • Wave length range -300-420 nm

  19. The TUS Project Scientific Goals. 1. Approving of a new technology of observing EAS by the Space Detector with the geometrical factor not less than 3 000 кm2srper yearwith the EAS energy threshold of 3-5 1019eV. 2. Experimental study of the Cosmic Ray energy spectrum in the range of Greisen-Zatsepin-Kuzmin energy limit 5 1019 эВ. 3. Experimental estimates of the UHECR composition by observing the EAS maximum positions. 4. UHECR anisotropystudy. 5. Testing a possibility to measure meteors. Search for the ISM dust grains. 6. The TUS mirror-concentrator design is aimed for construction of large area mirrors in space (up to 100 m2 ).

  20. The 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.

  21. Example of the EAS, “registered” by the TUS detector Simulation of UHECR registration E0=100 ЕeV, θ0=75°, φ0=25°, Moonless night;σE0/ E0 ~ 10 %, σθ0 ~ 1.5°, σφ0 ~ 1°. In the space detector the Cherenkov light yield in the cascade curve is negligible, the Cherenkov is scattered only from the clouds or ground (sea).

  22. Two TUS detectors on board of the Resurs O. • The TUS detector on board of the Resurs DK1

  23. ТUS telescopes register an EAS track from board of the Resurs O. In the 1-st option two instruments observe the same area in atmosphere. It allows to measure twice the same event (errors in measured parameters are checked). In the 2-d option instruments observe twice larger area in atmosphere. The orbit height is 700 кm.

  24. Design of the segmented mirror- concentrator, consisted of 6 operating segmentsof the Fresnel mirror type. • The mirror- concentrator mass is less than 20 kg for the mirror area 1.4 m2. • Accuracy in mirror ring profiles 0.01 mm. • Stability of the mirror construction in the temperature rangefrom –80oto + 60oC. • The mirror development mechanism makes the mirror plane with the angular accuracy less than 1 mrad.

  25. Segmented mirror- concentrator of the KLYPVE project. Diameter of the mirror 3 m. Segments are similar to the TUS ones.

  26. Steel press-forms for production ofcarbon plastic mirror replicas (JINR).

  27. The first mirror segment sample- replica of the mold.

  28. The mechanism of mirror development is designed (Consortium Space Regatta) In this mechanism one electric motor moves the segments via axles and cardan joints.

  29. The TUS photo receiver prototype: 4x4=16 PM tubes. It was tested in the Puebla University (Mexico).

  30. TUS prototypes at the Mexican mountains Mexican Universities team with the first TUS prototype A view from the TUS mountain site

  31. The TUS type UV detector at the MSU micro satellite UV detector comprises 2 PM tubes (one tube measures the charge particle background) and electronics block. Detectors on the micro satellite. Goals in 2005: Testing the PM tubes and the TUS type electronics. Measurement of the atmosphere UV background in short time intervals (0.1 msec). Measurements of aurora lights, meteors, lightnings.

  32. New Ideaof the detector with a “tracking mirror” (EWHA Womans University, Seoul) New MEMS technology of the controlled micro mirror arrays allows to design a mirror, arranging its focus in direction of the EAS particle disc. The wide FOV detector using the tracking mirror will compete with the EUSO lens optics. Efficiency in collecting light and resolution of the tracking detector is expected to be higher than in EUSO.

  33. Meteor signal in the TUS detector. Entering the atmosphere velocity 30 km/s. A search for the extra solar meteors is effective.

  34. Temporal profile of the dust grain. The atmosphere entering velocity 109 cm/s. Such dust grains will indicate positions of the 104 year old SN’s (Khrenov&Tsytovich, 2004).

  35. Spectrum of the meteors over their kinetic energy. 1- average intensity of solar meteors. 2- expected spectrum of the extra- solar meteors. Bold lines- expected results from TUS telescope. Bold circle- the rate of fast grains from old SN’s. At the lowest intensity the rate in TUS is a hundred events per year.

  36. Conclusion • In phase A of the TUS project the segmented mirror- concentrator of area 1.4 m2 is designed. The first samples of the mirror segments are being tested. This design is aimed to construction of the large space mirrors with the area up to 10-100 m2 . • Electronics of the TUS photo receiver (256 pixels) is designed with a low power consumption. This design is aimed to the construction of the photo receiver of the next KLYPVE telescope with 2500 pixels.

  37. Conclusion (continued). • In process of the TUS design a new idea of the “tracking mirror” was elaborated. The tracking mirror will allow to design a wide angle detector with a high resolution (other advantages are small mass, low power consumption and economical number of pixels). • The TUS instrument is able to study other phenomena in atmosphere by measuring fluorescence in the range of 300-420 nm radiated by micro meteors, by space pollution dust etc. These other goals of the experiment could be reached by changing the TUS triggering conditions from the mission center. • The development of a large area mirror- concentrator is supported also by its potential use in solar energy generators.

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