1. June 27 th 2008ARENA 20081 Permafrost - An Alternative Target Material for Ultra High Energy Neutrino Detection ? R. Nahnhauer, A. Rostovtsev and D. Tosi

2. June 27 th 2008ARENA 20082 Motivation : All available options have certain problems water : large and unstable background operation over large distances difficult no radio detection possible (no hybrid detector at HE) ice: limited access to available location (South Pole) salt:hole drilling very expensive (prohibited real tests) Requirements: Large volume O(100 km 3 ) with reasonable depth must be available Homogeneity must be sufficient O(10cm) Elastic properties must be convenient Some infrastructure must be available Hole drilling should be not too expensive (or sponsored)

3. June 27 th 2008ARENA 20083 A New Option – Permafrost ? Advantages: - large and deep permafrost layers available in nature - density is ~2 times that of water and ice - drilling experience from gas and oil companies - deployment may be easy (freeze-in of detectors) Disadvantages: - homogeneity of permafrost in larger depth not known - no in-situ attenuation measurements for radio and acoustic signals available for interesting locations - bad infra-structure in most of the deep permafrost regions

4. June 27 th 2008ARENA 20084 Radio Signal Detection in Permafrost G. A. Askaryan JETP (48)988 (1965) “… possible working layers are: for internal radio detection – substances which absorb or scatter radio waves weakly (an ice layer, permafrost, very dry rock etc)…” Experimental verification:  in silica sand: D. Saltzberg et al., Phys. Rev. Lett. 86: 2806, 2001  in ice: P. W. Gorham et al., Phys. Rev. Lett. 99:171101, 2007  in permafrost: ???

5. June 27 th 2008ARENA 20085 Measurements and theoretical studies of seismic and ultrasonic properties of permafrost exist : Previous: e.g. I. N. Votjakov: Fisiko mechanicheskie svoistva merslych i ottoivajuschschich gruntov Jakutii Novosibirsk, Nauka 1975 Recent: e.g. J.M Carcione and G. Seriani, Seismic and ultrasonic velocities in permafrost Geophysical Prospecting, 1998,46,441-454 Acoustic Signal Detection in Permafrost

6. June 27 th 2008ARENA 20086 No clear picture for evolves from available papers  Study „artificial“ permafrost in laboratory Sand-water mixture Grain size ≤ 1mm T = -5 to -30 °C Measured density: ρ = 2 g/cm 3 Artificial Permafrost

7. June 27 th 2008ARENA 20087 Velocity of Sound artificial pmf natural pmf 21% 16% H 2 O 10% Temperature [ºC] v s = 3000 – 4000 m/s !  P ~ (v s ) 2 1% H 2 O 10% H 2 O 16% H 2 O 21% H 2 O

8. June 27 th 2008ARENA 20088 Signal Amplitude amplitude in permafrost about 10 times larger than in water at 25 kHz

9. June 27 th 2008ARENA 20089 Laser Signal Production laser Clear laser signal seen wavelength: 1056 nm pulse : 6ns x 1Hz energy : ~10mJ/pulse ~ 6*10 16 eV No strong temperature dependence of amplitude neither for piezo nor for laser excitation Distance dependence not measurable at short range laser

10. June 27 th 2008ARENA 200810 Natural Permafrost Appearance Permafrost covers ~20% of land on earth There are regions with > 500 m thick layers > 500 m depth Jakutia

11. June 27 th 2008ARENA 200811 Permafrost Experts I Permafrost Institute of the Siberian Division of the Russian Academy of Sciences, Yakutsk lans@imzran.yacc.yakutia.su lans@imzran.yacc.yakutia.su Sacha Republic (Yakutia) Size : 3.078.100 km 2 Inhabitians: 0.31/km 2 Earth cold pole

12. June 27 th 2008ARENA 200812 Homogeneity of Permafrost Layer near surface is rather inhomogeneous At larger depth homogeneity depends on kind of permafrost Best: big sediment layers in large river valleys

13. June 27 th 2008ARENA 200813 The Experts Advice ~400x200 km 2 region in Aldan valley has permafrost sediment layers of up to 1100 m depth

14. June 27 th 2008ARENA 200814 Permafrost Experts II Research Unit Potsdam: - terrestrial geoscience in the periglacial regionsterrestrial geoscience in the periglacial regions - atmospheric processes in the polar regionsatmospheric processes in the polar regions During last years several expeditions to central Yakutia (Lena and Aldan River region) Information from B. Dieckmann Aldan Lena

15. June 27 th 2008ARENA 200815 Summary Properties of artificial permafrost seem to be promising for radio and acoustic neutrino detection A location has been identified where natural permafrost of sediments reaches a depth of more than 1000 m A careful exploration of this quite large region would be necessary to decide if a ~100 km 2 area could be found, sufficiently homogeneous in depth In-situ attenuation length measurements would then show if a real detector of reasonable size could be built To do such investigation requires the common effort of a group of geophysicists and astro-particle physicists within a TAIGA * exploration study  go for a  T est A skaryan I nstallation for G eology and A strophysics