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Early Work on Acoustic Detection of Neutrinos

Early Work on Acoustic Detection of Neutrinos. John G. Learned University of Hawaii at Stanford Workshop, 9/13/03. First Suggestions for Detection of High Energy Neutrinos. G. Askaryan, “Hydrodynamical emission of tracks of ionising particles in stable liquids” Atomic Energy 3 152 (1957).

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Early Work on Acoustic Detection of Neutrinos

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  1. Early Work on Acoustic Detection of Neutrinos John G. Learned University of Hawaii at Stanford Workshop, 9/13/03 John Learned at Stanford

  2. First Suggestions for Detectionof High Energy Neutrinos • G. Askaryan, “Hydrodynamical emission of tracks of ionising particles in stable liquids” Atomic Energy 3 152 (1957). • T. Bowen, at 1975 ICRC in Munich: first mention in terms of large neutrino detector • Dolgoshein, Bowen and soon others at 1976 DUMAND Workshop in Hawaii (including some calcs disagreeing by 6 orders of magnitude!) John G. Learned at Stanford

  3. Early Experimental Tests • Russian work includes some reports of large microbubble production (Volovik and Popov 1975). • Sulak and colleagues at Harvard with 185 MeV cyclotron (1977) test many media. • Experiments at Brookhaven (1976-1978) demonstrate thermo-acoustic mechanism. • Some hint of anomaly, though small. John G. Learned at Stanford

  4. A Bibliography (not finished) John G. Learned at Stanford

  5. Sound Propagation in Liquids • simple equations for most media John G. Learned at Stanford

  6. damping term • losses roll off spectrum ~ e-ω2 • non-dispersive John G. Learned at Stanford

  7. Basic Bipolar Pulse fromRapid Energy Deposition source size ‘damping’ or ‘smearing’ John G. Learned at Stanford

  8. Harvard Cyclotron Experiments • 150 MeV protons into vessel measured only leading pulse, zero crossing at 6o C John G. Learned at Stanford

  9. more Harvard tests • little pressure or salinity dependence John G. Learned at Stanford

  10. Brookhaven Experiments • Fast extracted 32 GeV proton beam John G. Learned at Stanford

  11. BNL Temperature Study John G. Learned at Stanford

  12. BNL Studies Bipolar pulse inverts at 4.2o C Tripolar pulse seems not to depend upon temperature John G. Learned at Stanford

  13. LBL Heavy Ion Experiment • Noise was a problem • Still, no large signal (order of magnitude larger than thermoacoustic) was seen John G. Learned at Stanford

  14. Acoustic Test Conclusions • simple theory works, mostly John G. Learned at Stanford

  15. Other Mechanisms? • Anything fast acting and relaxing will produce a tripolar pulse • Microbubbles – not normally, but what about clathrates in deep ice? • Molecular Dissociation – no, but what about in extreme energy cascades? • Electrostriction – maybe a little, but what about from charge excess in energetic cascades? Not much hope in water, but in deep ice? salt? We need studies, particularly in situ. There could be surprises! John G. Learned at Stanford

  16. Expected Distance Dependence Power Law, Not Exponential John G. Learned at Stanford

  17. LineRadiation • sqrt(ω) spectrum • total ocean noise due to muons not important John G. Learned at Stanford

  18. Pulse Due to a Cascade John G. Learned at Stanford

  19. The Real Ocean Noise: Near Deep Ocean Thermal Minimum Attenuation Length: Many Km in Ocean ~20-30 KHz signal 1/f wind noise thermal noise John G. Learned at Stanford G. Gratta astro-ph/0104033

  20. Real Ocean • Much noise due to surface… waves, rain… • Significant shielding at large depths, particularly below reciprocal depth John G. Learned at Stanford

  21. Power Law Dependences John G. Learned at Stanford

  22. High Threshold – Huge Volume There are limits on array gain and coherence due to distance per module distance limit per module gain limit John G. Learned at Stanford

  23. Something for Deep Ocean Arrays to Consider • Threshold very high and thus rate low. John G. Learned at Stanford

  24. Summary of Acoustic Neutrino Detection • Thermoacoustic mechanism explains results, mostly • Being revived after 25 years of little action • Advantages: • Power law behavior in far field • Potentially >> km3 effective volumes • Well developed sonar technology • If salt practical, could use shear waves too → range • Disadvantages: • Deep ocean and ice impulsive backgrounds still not yet well known • Ice and Salt properties not yet known (soon?) • Small Signals, Threshold >> PeV • Prospects: • Modest activity underway • Few years from dedicated experiment John G. Learned at Stanford

  25. Russian Acoustic Tests in Pacific and Black Sea Kamchatka AGAM Acoustic Array Some preliminary results at ICRC ‘01 Proposed Cable Buoyed in Black Sea Bottom Anchored 1500 hydrophones John G. Learned at Stanford

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