1. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Muon Telescopes at Basic Environmental Observatory Moussala and South-West University - Blagoevgrad I. Angelov, E. Malamova, J. Stamenov INRNE – BAS, SWU “N. Rilski” Presenter : I. Angelov

2. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Institute for Nuclear Research and Nuclear Energy, BAS Basic Environmental Observatory – Moussala 42°11’N, 23° 35’E, 2925 m a.s.l. South West University “N. Rilski” Blagoevgrad Department of Physics 42°01’N, 23° 06’E, 383 m a.s.l. Observation sites

3. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Outline 1) Description of the instruments. 2) Main characteristics of the telescopes. 3) Examples of experimental data. 4)Summary 5)Future plans.

4. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Detectors setup Moussala – 1 m 2, 2x2 configuration, 1m between detectors planes Blagoevgrad – 2.25 m 2, 3x3 configuration, 1.5 m between detectors planes Both telescopes use water cherenkov detectors

5. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Detectors setup Mirror container 50x50x12.5 cm 10 cm distilled water as radiator 2.5”, 12 dynodes photomultiplier FEU-110, FEU-139 PMT in single electron counting 300 Ohm anode load 90 MHz bandwidth amplifier with gain x50 discriminator threshold 15 – 50 mV 60 ns ( 45 ns ) TTL pulses formed

6. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Coincidence circuits and data acquisition system

7. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Detectors adjustment : plateau in the counting characteristics fixed thresholds are selected – 28 mV for Moussala – 22 mV for Blagoevgrad optimal HV is chosen for each detector Dependance of the count rate – vertical coincidences on the HV for the four pairs of detectors of the telescope at BEO Detectors adjustment

8. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria DirectionAngular interval, deg Number detector pairs Count-rate, min -1 Statistical error for 1h Vertical+18.4 -18.498780.44% NS0 - 33.764380.61% SN0 - 33.764380.61% WE0 - 33.764550.6% EW0 - 33.764550.6% DirectionAngular interval, deg. Number detector pairs Count-rate, min -1 Statistical error for 1h Vertical+25.6 -25.6423870.27% NS0 - 4528140.45 SN0 - 4527040.49% WE0 - 4527560.47% EW0 - 4527340.48% Angular directions and count rates SWU telescope count rates => BEO telescope count rates =>

9. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria BEO telescope : 40 cm concrete above the detectors; 5 cm Pb ; ~ 0.45 GeV energy threshold for CR muons SWU telescope : 160 cm concrete above the detectors; 5 cm Pb ; ~ 1 GeV energy threshold for CR muons the MMC (Muon propagation Monte Carlo) software was used for calculation (Chirkin and Rhode, 2004, 2005) Energy thresholds and response to primary protons BESS spectrometer at mount Norikura – 2770 m a.s.l., Rc=11.2 GV. (Sanuki et al., 2003) kinetic energies ~ 0.48 – 106 GeV I 0  0.0105 cm -2 s -1 ster -1 Count rate  580 min -1 - Moussala telescope 2925 m a.s.l., Rc=6.3 Gv, corresponds to I 0  0.0188 cm -2 s -1 ster -1

10. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Energy thresholds and response to primary protons Results from simulations with PLANETOCOSMICS code Response to primary protons generated muons – BEO telescope 90% of the counted muons generated from protons with energies above 10 GeV Response to primary protons generated muons – SWU telescope 90% of the counted muons generated from protons with energies above 15-20 GeV Rc  6.34 GV Rc  6.24 GV

11. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Meteorological corrections Barometric effect for CR muons SWU muon telescope  = -0.1245 / % hPa Barometric effect for CR muons BEO muon telescope  = -0.2845% / hPa

12. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Forbush decrease October – November 2003, SWU telescope FD in october – november 2003 (HALLOWEEN SPACE WEATHER STORMS OF 2003) <= SWU telescope, pressure corrected 1h data. <= Athens NM data

13. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Forbush decrease December 2006, BEO telescope FD in December 2006 (after the GLE of 13 December) <= BEO telescope, pressure corrected 1h data. <= Athens NM data

14. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Summary Two operational muon telescopes in BG ( Rc  6.3 GV )  at ~380 m. a.s.l., 2.25m 2 detectors, 1 GeV energy threshold, 0.45% statistical error for 1h intervals (after reconstruction since November 2007)  at ~2925 m. a.s.l., 1m 2 detectors, 0.45 GeV energy threshold, 0.27% statistical error for 1h intervals, (since August 2006) Detectors of original construction, easy to build and cost effective.

15. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Future plans Coincidence circuits and counters controller upgrade, using FPGA - all combinations of UP and Down detectors A possibility to upgrade to higher number of detectors at South West University exists – enough room space ;

16. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Thanks for the attention ! The BEO muon telescope was constructed and funded as a part of the FP6 BEOBAL project - BEO Centre of Excellence Research Capacity Improvement for Sustainable Environment and Advanced Integration into ERA. Questions, comments and ideas are WELCOME.

17. I. Angelov UN/ESA/NASA/JAXA Workshop on the International Heliophysical Year 2007 and Basic Space Science 2-6 June 2008, Sozopol, Bulgaria Basic references Hamamatsu Photonics K. K. Photon counting using photomultiplier tubes, 2005 http://sales.hamamatsu.com/assets/applications/ETD/PhotonCounting_TPHO 9001E04.pdf Chirkin D., Rhode W., All Lepton Propagation Monte Carlo, Proceedings of the 29th ICRC, Pune, 2005, http://icrc2005.tifr.res.in/htm/Vol- Web/Vol-19/19093-usa-chirkin-D-abs2-he21-poster.pdf Chirkin D., Rhode W., Muon Monte Carlo: a high-precision tool for muon propagation through matter, 2004, http://arxiv.org/PS_cache/hep- ph/pdf/0407/0407075v1.pdf Sanuki T., Fujikawa M., Abe K. et al, Measurements of atmospheric muon spectra at mountain altitude, 2003, http://arxiv.org/PS_cache/astro- ph/pdf/0205/0205427v3.pdf Desorgher L., PLANETOCOSMICS Software User Manual, 2005,