1. Feasibility of acoustic neutrino detection in ice: First results from the South Pole Acoustic Test Setup (SPATS) Justin Vandenbroucke (UC Berkeley) for the SPATS group International Cosmic Ray Conference, Mérida, Mexico, July 7, 2007

2. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 The SPATS Group DESY Zeuthen: Sebastian Böser, Jan Fischer, Reiner Heller, Kevin Krieger, Rolf Nahnhauer, Mario Pohl, Karl-Heinz Sulanke, Delia Tosi University of Ghent: Freija Descamps University of Stockholm: Stephan Hundertmark, Christian Bohm UC Berkeley: Buford Price, Justin Vandenbroucke University of Uppsala: Allan Hallgren

3. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Neutrino-induced cascades produce 3 detectable signals air dense medium interaction  particle shower (1)optical Cherenkov cone ~100 m (2) Askaryan radio cone ~1 km radio and acoustic (?) travel farther than optical in ice (3) Askaryan acoustic pancake ~few km?

4. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Goal: Detector for >10 EHE (GZK) per year First characterize South Pole ice acoustic properties: Attenuation, noise, refraction Similar to initial AMANDA (optical) and RICE (radio) activities theoretical Showers  10-60 kHz acoustic waves Theorized attenuation length ~few km Hybrid acoustic/radio/optical array extending IceCube: >10 GZK per year? (astro-ph/0512604)

5. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 SPATS array design IceCube holes, separate strings 3 strings 7 stages per string surface digitization IceCube surface cables

6. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 SPATS stage design transmitter 3-channel sensor

7. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 3 strings successfully deployed January 2007 SPATS B, hole 72, Jan. 11 SPATS A, hole 78, Jan. 14 SPATS C, hole 47, Jan. 22 first hybrid optical/radio/acoustic string

8. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 SPATS Geometry 400 320 250 190 140 100 80 m Horizontal Vertical

9. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Commissioning and running - All transmitters working - 53 of 63 sensor channels working normally - Continuous running since Feb., except 3 power outages - 3 string-PC’s running smoothly 2 m under -50° C snow

10. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Gaussian noise floor -60 stable very Gaussian RMS ~1.5x lake tests decrease with depth sample amplitude (V) counts

11. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Typical noise spectra Swedish lake (water) South Pole (ice) bumps: acoustic? spike: EMI?

12. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Background transients Rate: ~1/minute/channelLoud examples: 12 ms 5 V

13. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Inter-string transmitter pulses recorded through ≥125 m of South Pole ice 19 pulses from A6 to B6  t = 55 ms width ~1 ms 1 pulse signals detected from every string to every other string amplitude ~10x lower than in lake: why?

14. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Attenuation analysis: work in progress Ln(amplitude*distance) vs. distance preliminary Missing many pairs in noise: overcome with pulse averaging

15. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Conclusion Thanks to the IceCube Collaboration for its support! SPATS deployment + commissioning + running all smooth First hybrid string deployed Analysis begun with first 4 months data Noise floor Gaussian and stable; decreases with depth Spike + bumps in spectra Transmitter events ~10x lower amplitude than expected Attenuation analysis underway 4th string to be deployed Dec. ‘07 / Jan. ‘08 More details: F. Descamps poster #1142 (Posters 3, Mon/Tue)

16. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 extra slides

17. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Theoretical attenuation vs. frequency (P. B. Price 2006)

18. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Overcoming module to module variation with ratios 2 T’s + 2 S’s  couplings divide out: One remaining unknown: TATA TBTB SASA SBSB Model: Assumes S, T independent of angle

19. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Ratio method (Monte Carlo) Assume  measure = 100 m Treats angular variation (~40%) as uncorrelated variation in amplitudes

20. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 astro-ph/0512604 Simulated hybrid array geometry

21. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007 Simulated hybrid array sensitivity astro-ph/0512604

22. 30th ICRC, Mérida, Mexico Justin Vandenbroucke July 7, 2007