TUS/KLYPVE Program for Observation of Extreme Energy Cosmic Rays from Space B.A. Khrenov DV Skobeltsyn Institute of Nuclear Physics of MV Lomonosov Moscow State University Workshop “Cosmic Ray Large Scale Experiments in the Second Decade of the 21st Century” 17 May 2011

TUS/KLYPVE collaboration SINP MSU, JINR (Dubna), RSC “Energia”, Consortium “Space Regatta” EWHA University (Seoul, Korea) Puebla University (Mexico) Universities of Japan, RIKEN (Tokyo). TUS is pathfinder for JEM- EUSO.

Collaboration authors: (1) D.V. Skobeltsyn Institute of Nuclear Physics of Moscow State University, Moscow, Russia G. Garipov, N. Kalmykov, B. Khrenov, P. Klimov, M. Panasyuk, S. Sharakin, A. Shirokov, I. Yashin. (2) Joint Institute for Nuclear Research, Dubna, Moscow Region, Russia S. Biktemerova, A. Grinyuk, D. Naumov, L. Tkatchev, A. Tkachenko (3) Consortium "Space Regatta", Korolev, Moscow Region, Russia A.Puchkov, O. Saprykin (4) Physics Department, EWHA Woman University, Seoul, Korea I.H. Park, J. Lee, S. Nam, G. Na, J. Kim (5) University of Puebla, Puebla, Mexico J. Cotsomy, O. Martinez, E. Ponce, H. Salazar

Main results obtained by EAS ground-based arrays: 1.“Knee” in the energy spectrum at E= eV. 2.“Ankle” at E= eV. 3.Prediction of GZK cut-off at E= eV. Extreme low intensity of particles with energies E> eV makes the ground-based arrays inefficient for E>>10 20 eV.

Major scientific problem- the CR spectrum cut off. P+γ=P+hadrons E γ =2E ph E p /M p c 2 E ph = eV (T=2.75K) In proton rest frame photon energy E γ >100 MeV for E p >10 20 eV. ρ ph =500 cm -3 Cross-section of interaction is σ= cm 2 Interaction free path L=1/ σ ρ ph =70 Mpc G.T. Zatsepin, 1967 Greisen-Zatsepin-Kuzmin made the first estimates of the effect and find the energy limit for protons E GZK =5x10 19 eV.

In 1980 Prof. John Linsley suggested to put the fluorescence detector to space and look down to the Earth atmosphere. He called this experimental concept - “Airwatch”.

In line of “Airwatch” concept several projects were suggested: OWL, KLYPVE, EUSO. Today the most advanced are JEM- EUSO and KLYPVE with its prototype: the TUS detector. TUS is abreviation of “Track Ultraviolet Set-up”. It is prepared for launching in the end of 2011 on board of the “Mikhail Lomonosov” satellite. It is considered as “pathfinder” for JEM- EUSO and KLYPVE detectors which are planned for launching in the second decade of 21 century. Assets of the UHECR space experiment are: 1.One detector covers a large atmosphere area. 2. One and the same detector collects data over the whole sky. Difficulties are: 1. UV background average level on the satellite root is higher than in regions where the ground fluorescence detectors (FD) are operating. 2. Due to large distance between detector and EAS the space FD signal is much less than in ground measurements and FD design meets new technological problems.

The TUS detector is the main part of scientific instruments on board “Mikhail Lomonosov” satellite. TUS mass is 60 kg, electric power 60 Wt, orientation to nadir ±3 o. Two main parts of TUS are: 1. Mirror-concentrator and 2. Photo receiver. Mirror area is ~2 m 2, expected exposure factor km 2 sr in 3 years of operation at orbit height ~500 km (in the first 1.5 years) and ~ 400 km (in the next 1.5 years).

The main goal of the TUS experiment is a search for the UHECR energy spectrum in region of the GZK “cut-off” and a search for UHECR sources.

Ground-based detectors statistics still do not allow to distinguish difference in energy spectra expected for various models of Universe evolution (Berezinsky, 2006). Space based-detectors will do it.

Carbon plastic mirror-concentrator and its focal spots: 1- at FOV center 2- at the edge of FOV 12

Photo receiver contains 256 pixels. They are grouped in 16 clusters every of which contains 16 PMT’s with common HV and electronics.

The electronics is designed for a multi- purpose scientific program: time sampling starts from 0.8μs (needed for EAS measurements). Slower developed objects (atmospheric electric discharges, sub-relativistics dust grains, micrometeors) are observed with larger sampling 256 μs, 1 ms given by digital integration.

Operation of TUS pixels in EAS of E=200 EeV, zenith angle 80º. Noise at moonless night is negligable. TUS exposure factor: 4000 km 2 sr year Energy threshold: 70 EeV Statistics in a year: 20 In 3 years: 60 events

In two “Universitetsky-Tatiana” satellite missions the TUS pixel and electronics were tested in measurements of the atmosphere glow in near UV range (wavelengths nm). Polar orbits, heights km Important detector features: 1. Constant anode current, HV is controlled by UV intensity. 2. Digital oscilloscopes for UV flashes. FOV diameter in the atmosphere km

Map of the UV glow intensity. At moonless nights the UV intensity varies from to ph/cm 2 s sr. At full moon nights the intensity is ph/cm 2 s sr. This glow is the main source of background triggering rate of TUS tuned for EAS measurements.

Temporal profiles of the atmospheric flashes.

The short (1 ms) flashes with small photons numbers (<10 22 ) are uniformly distributed over the Earth. Their rate in the TUS FOV is estimated as 0.01 per minute.

Flashes with larger photons numbers (>10 22 ) are concentrated in the equatorial region (latitudes ±30°) over the continents. Their rate in TUS FOV is estimated as 0.1 per minute. Remember that EAS of E=100 EeV radiates photons.

The atmosphere glow and atmosphere flashes put a difficult problem of selection of EAS events and suppression of false triggering. The large photon flashes are easily distinguished as event with fully saturated pixels. The small photon flashes may accidently give imitation of EAS event at the early stage of a flash. Remember that EAS fluorescent photon number at E=100 EeV is four order of magnitude less than photon number in “small” flashes. For reliable distinction of flash events a pinhole camera with aperture four order of magnitude less than aperture of TUS is introduced to the detector.

The pinhole camera (camera obscura) is installed in the TUS detector in cooperation with JEM-EUSO group. It is placed in the receiver box, as shown below. Many-anode PM tube, selected for the JEM-EUSO photo receiver, will be used as the pinhole camera imaging detector. Many-anode tube of Hamamatsu.

Experience in construction of the TUS detector allows us to start the design and construction of larger scale detector KLYPVE. The aim of this work is to make measurements at energies below GZK limit. The mirror of 37 segments of the same size as in the TUS detector will increase mirror area to 10 m 2. The new photo sensors with quantum efficiency 50% and this larger mirror will allow to start measurements from energy threshold of 20 EeV (against 70 EeV in the TUS mission). KLYPVE in transportation mode KLYPVE in operation

Conclusions. 1.In near future ( ) the space detector TUS will start measurements of UHECR. 2.Experience of the TUS operation will be important for final design of the next space detectors: JEM-EUSO and KLYPVE. 3. It is plausible that in the next decade the technology of building much larger space mirror-concentrators (with area up to 100 m 2 ) will allow to start measurements of EAS fluorescent tracks in energy region E~3-50 EeV at unprecedented large atmosphere area (10 4 km 2 ) and collect reliable data on anisotropy and composition of cosmic rays.